installing a BIG BLOCK CHEVY IN A C4


Staff member
theres no way a c-4 will exactly match the weight distribution and handling of a C6,

BUT the strait line acceleration CAN be equaled or exceeded with a decent well thought thru and executed BBC swap,and you might be amazed at how well a properly set-up C4 with a big block engine handles in the road race style driving, and handling will not be so adversely effected that it makes the car handle a great deal differently than the original engine configuration.
obviously if you use aluminum cylinder heads, water pump and intake manifold on a big block swap the weight difference is almost negligable from its original SMALL BLOCK config.
Ive helped start and/or worked on several of these big block engine swaps in the c4 vettes these big block swaps have all been a bit different because every time different components were selected to be used by the cars owners over the last 25 years in c4 vettes. plus the years of the cars varied from 1984 cross fires to 1996 LT1 so a great many of the connections , sensors, and suspension components and clearances are slightly different.
but in every case the result was a car with a good deal more torque than the original engines provided, Ive seen guys use 427-540 big blocks and while obviously the power levels varied wildly the net result was a rather unique swap and almost every car was a vette I would have liked to own, personally, but obviously the condition of the body, suspension, interior electronics, in the base car your starting with and the skill and care thats applied to the drive train swap effects the end result.
I honestly think chevy made a HUGE mistake by not offering a big block option in these cars and if you ever visit the corvette museum , you might see the factory proto type, big block c4 corvette, they built that was on display there.
The typical problem you eventually run up against is not installing the engine or getting it installed or running correctly ,its the fact that the owners of the cars eventually get used to the significantly increased power and occasionally start doing stuff like drag racing the cars, and the stock differential, suspension and transmissions were not designed to handle what can easily be 500ft lbs to 600 ft lbs of torque these engines can supply, Id strongly suggest a 4L80E trans and a stronger rear differential, and bigger brakes and a much bigger radiator and a transmission cooler be considered almost mandatory for the swap. the stock 700r4 and a dana 36 rear differential will not last long under the stress of a driver with a big block that insists on jack rabbit launches.
btw Id suggest checking your fuel pressure at W.O.T. if you experience any tendency for the power to plateau or nose over at near peak rpms once you install a big block in a c4 if you retain the stock fuel lines (not ideal) as a few of the builds Ive helped on found that the original fuel lines, even with a fuel pump designed for carb use were not adequate for a big blocks flow requirements, Id suggest a fuel line upgrade to AN #8 or 1/2" inside diameter fuel lines and a fuel pump that supplies at least 120 GPH at 6 psi as a MINIMUM
the most important and effective performance asset you have is simply your ability to ask yourself questions, the ability to think logically isolate and test components carefully and doing the research if its required to find the best answer's you'll need.


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the headman tight tubes shorty headers are reported too fit the big block C4 engine swap ,with out modifications"
yeah your correct they can,t be really effective at scavenging but if they fit its obviously one option some guys will take rather than pay for custom headers


headman 68090 header can be modified to fit the C4 corvette, the pass side fits the drivers side need mods

- use stock small block engine mounts/brackets ok" />>>

- use GM oil pan 14091356 with Mark IV big block >>

use a small gear reduction starter to allow more header clearance

- use as-delivered pan with Gen 5 crate engines, they come with pan 10240721. No mention of Gen 6.>>

- use '65-'70 big block Vette short water pump and corresponding accessory brackets (factory serpentine system won't fit), modify as required >>

- clearance is especially tight between crank pulley and steering rack >>

- use a '91-'95 LT5 heater core case (passenger side valve cover hits stock heater core case) >>

- driver's side valve cover hits firewall inboard throttle cable pass
through, modify VC as required >>

- use small distributor cap >>

- use '70-'74 big-block Vette exhaust manifolds or custom headers
1963-1967 Hedman bbc corvette headers. Pass side had to be hammered on one tube,rather extensively,to the point it was almost useless, its better if you fabricate and re-weld a new tube like this guy did in the picture below
below you can see the mods one guy made to those headers






read thru these links and sub links theres a ton of related info you need.
well one minor "plus" too this process is that, if your starting from scratch,
or taking over a partly done and abandoned BIG BLOCK CHEVY ENGINE INSTALL in a C4 corvette,
by the time youve corrected a bunch of these issues the previous owner ,
(who obviously was not all that knowledgeable or skilled or even all that concerned with doing the engine conversion correctly,
is that you can,t help but be guided (almost forced") into learning the how, and why and basic mechanics of how a proper engine swap is accomplished,
this may not have been the initial expectation, but in the long term, if you stick with it to the end youll have vastly increased your skills ,
knowledge and significantly increased your appreciation for what is required in a proper performance car build.
youll also by default have gained the increased skills, tools and intuition, due to the process, to find and rapidly test isolate ind repair most of the sub-systems in the car!.
in most of those BBC engine swaps,
its engine & transmission COOLING,
fuel delivery, proper ignition, advance curve and spark delivery,
engine lubrication, enhanced suspension, better and larger surface area tires
and better , larger and more fade resistant brakes,
a larger and less restrictive exhaust,connecting the sensors and gauges
and cosmetics like the seating interior and paint,
that become the areas that need up=grades
thus by the time your done youll be dragged kicking and screaming into a vast knowledge base based on the c4 corvette plat-form. ... %2FHeaders


viewtopic.php?f=57&t=176&p=210#p210 ... index.html



and at about less than 1/2 the price of a new Zo6, and its no trick to easily exceed the hp of the stock Zo6, depending on the extent of the mods you want, and your fabricating and shopping skills somewhere between 15K and 35K should get you one very fast BBC C4 and that price COULD easily include the car itself, if youve already go the car you can knock a good chunk like 5K-15K of the cost off the total.
PLUS if your like me, having built or modified most of the car yourself, and owning something rather unique, has a strong draw to my pride of ownership vs paying huge bucks for a Z06 that anyone with a fat wallet can own.
plus theres nothing that sounds like the rumble and rolling lope of a high compression, BBC with over 500 cubic inch displacement.
personally opening the hood to display a nice BBC in a c4 seems to me to be the better option and it shows more hot rodding skills than paying $70K plus for a Zo6, and I like the looks of the C4 better

LINGINFELTER sold several c4 corvettes with fuel injected 540 BBC engines in the late 1990s , but by now those cars are close to 20 years old , you won,t know how badly they were maintained or abused by previous owners over the last 20 years so you might want to clone the cars with a new 502-540-572-632 BBC and upgrade the transmission to a new 4l80E-6L80E





yes it can and IS regularly DONE! no its not a TRUE drop in, but its not that difficult either! and its a reasonable way to get 500hp PLUS in a c4

first, having done a few swaps,I can point out,a BBC with aluminum water pump,heads and intake only adds about 75-80 lbs over the front wheels compared to a standard sbc, Id bet your girl friend in the pass seat adds more weight,youll never notice if your the average driver, and adding a stiffer front sway bar can easily make up the difference for street use.

next. yeah you can get 500hp and 500 ft lbs very easily from an N/A sbc, but it won,t be traffic friendly to drive, hey throw a turbo on and 700 plus ft lbs and 700 hps plus easily with in reach, but with the mandatory intercooler, bigger radiator ETC.,ETC, your at the same weight and more complex than the BBC swap, and yes the turbo will allow the car to be faster than the average c5-c6 but it costs a bunch. look theres lots of options, each has its benefits and flaws, you could even just install a new C6 engine, or add a centrifical supercharger to your stroker SBC.
but the fact remains, you can buy a decent c4 for under $7K-$15K and throw a $9K-$13K BBC engine in it and for under $22-$30K have a faster car (at least for 1/4 mile accelleration) than a zo6.....each of us has a choice and if your not into BBC engines you may not like that option, that doesn,t make it non-workable for the more mechanically inclined engine swap crowd!
personally opening the hood to display a nice BBC in a c4 seems to me to be the better option and it shows more hot rodding skills than paying $70K plus for a Zo6

how do you install a 454-502 in a C-4

if you put a bbc with aluminum heads, intake and water pump in , in place of the standard iron small block you only gain about 50-70 lbs, not enough differance to cause any problems at all, , I have worked on several of these swaps now and Im in the process of getting ready to do another one,heres whats needed
steering rack mounts cut and rewelded 3/4"-1" farther forward (that of course means the power steering pump lines/steering shaft, need to be extended 3/4" also)

small notch (starting at rear and going 3" forward from rear edge X 3/4"deep X 5" wide works well in rear top surface of (K) frame cross member to clear damper and pulley)(if you use an internally balanced big block with the 6.75" diam. damper you can most likely skip the notch but with the 8" diam damper its necessary, and some oil pans will also require the back 1 1/2 of the (K) frame to be notched at an angle sloping to the rear to clear them so you'll probably need the notch of some kind anyway)(and yes before you ask you could shim/modify the motor mounts up to get the clearance, but that would slightly raise the weight center and slightly effect the handling, and that also makes the windshield motor and distributor clearance a bigger problem)

air conditioner shrouding fiber glass on pass side foot well around the air conditioning on the firewall needs to be modified for clearance, (the fiber glass cover from a LT5 makes this easy)(evaporator housing cover)

1971 bbc vette exhaust manifolds (or custom headers) and all brackets/pulleys (mods needed here)
(see the post on building your own headers)
oil pan needs to be only 7.5" deep max

3" hood scoop unless you run a low rise intake and carb or a low height efi system

for a step by step instructions with pictures get a copy of the august 1998 vette magizine article( starts on page 34)it helped quite a bit the first time

front/back adjustable location motor mount

otherwise its almost a drop in deal, but keep in mind that youll need a bigger radiator, the trans will not last to long with that amount of torque and it may not pass emission testing and a small size starter is needed, and your windshield wiper motor needs to be replaced with a much smaller one,(I don,t remember where we got them but a little measuring and a trip to the salvage yard took care of that problem, and no tall valve covers don,t work well!

btw install the short block then add the heads with it in the car its FAR EASIER THAT WAY than trying to install the long block

BTW the earlier cars like the 1984-86 (Im not sure what years exactly)don't have the heavier forward frame bracing above the steering rack that makes this swap more difficult to do! I have worked on this swap on the 84, 85, and 86 cars so I know they work fine, the later cars like the 1992 with the heavier forward frame braces above the steering rack look like they will be more difficult but still do-able with some extra work, btw theres a guy at ARIZONA SPEED AND MARINE that has one you might want to talk to .just a few points
an aluminum head, intake and water pump bring a bbc engines weight to within 70 lbs of the stock iron small block, so handling is almost unchanged

any un-supercharged small block not using nitrous or some other power adder that makes over 550 hp is highly likely to be at least somewhat un-streetable as a daily driver and your not likely to build a small block that makes "764 HP & 695 lb/ft at the flywheel" likely costs as much or more than a big block makeing similar power, look, good engine choice

it will of course depend on the engine combo you chose , and traction is usually a problem but low 12 second to mid 11 seconds is not at all hard for the cars Ive worked on. now you could build a kick butt engine and get into the 10s with ease but at that hp level the rear suspension and rear end itself tends to need work! the strong point here is that unlike a high hp sbc engine with nitrous and a huge cam, these cars are relatively easy to drive as daily drivers and the passing power with just part throttle is necessary to feel to be believed. plus the viper guys get really upset when you pull next to them at 50mph and pull away like they have a dead cylinder with the better chevy bbc engine combos, but you really are better off with aluminum heads/water pump and intake. btw getting a kick butt bbc is very easy, and far cheaper than a viper engine. btw the 700r4 trans or the manual trans that comes in the corvettes won,t handle a 550hp plus engine for long, but the 4L80E OVERDRIVE automatic TRANSMISSION chevy installs in the larger trucks can be used (EXPENSIVE BUT THATS WHAT I BOUGHT FOR MY FUTURE SWAP) ... &xid=42186 &V1=30014126&V2=30014126&V3=1&V5=1100018 5&V4=10&S1=&S2=&S3=&S4=&S5=&DSP=0&CUR=84 0&PGRP=0&CACHE_ID=0

keep in mind the cost versus performance ratio, a nice C-4 vette can be purchased for $6000-$20,000 add that $9000-$15,000 BBC drive train and you'll have a car that kicks 99% of the cars on the roads butts (INCLUDING MOST VIPERS) for about $16,000-$35,000

the rear ends hold up fairly well until you use slicks, street tires won,t normally get enough traction to break things unless you use nitrous
both the 4 plus 3 manual and the 700r4 trans will work for awhile especially if your not trying 3000rpm launches all the time, the 700r4 trans can be built fairly tough but if your intent is to get 10 second 1/4 mile drag times then no! youll need to upgrade the trans to a 4L80E or TH400 with a serious big block or one of the sturdier manual transmissions
heres a few links
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Staff member
4l80E trans set up for full manual control with that kit and all the best internal parts will cost in the $4500-$5300 range

I've driven a couple of those c4 BBC engine cars and I've helped build or work on 8 different c4 bbc engine cars, each was totally different , some had mild 427 BBC engine one was a 572 with a centrifugal supercharger , some carbed, most were EFI.
I would suggest the 4l80E transmission and a dana 60 or ford 9" non-independent rear differential and a minimal roll cage to increase chassis stiffness
when your in the process of custom building a car you obviously have the option to make the upgrades YOU feel are warranted, but think things through and you'll want big brakes a higher amp alternator, a larger aluminum radiator, and a trans fluid and oil cooler will be mandatory

SOME ROLLER ROCKERS CAN AND DO BIND ON ROCKER STUDS, or rocker adjustment nuts, youll need to check carefully

some roller rocker too retainer combo clearance issues cause problems easily solved with beehive springs and smaller retainer diameters



"4L80E in C4 Corvette Adapter (1984 - 1996). Swap your 700R4 / 4L60E transmission to the much stronger 4L80E transmission with our new double strength case hardened output shaft and adapter kit. At this time we have in development an adapter kit for the C4 Corvette to replace your 700R4 / 4L60E transmission with the much stronger 4L80E transmission. This 4L80E transmission will be the same length as your 700R4 / 4L60E transmission making it possible to reuse your existing 27 spline driveshaft and C-beam. This is the worlds first 700R4 / 4L60E to 4L80E swap direct replacement. All that needs to be changed on the 4L80E transmission is the tail housing and output shaft. The full manual shift model works without a computer.'






if your reading this and are not familiar with the c4 corvette drive train configuration or what a c-beam is this may help


add one of these aluminum big blocks and LOOSE 100LBS off the front end compared to a small block, and more than double the power, even with the 4L80E the car will weight about the same but the center of gravity will be lower and further back

you can use a computer to control the trans

BUT the 4L80E can BE converted TO FULL MANUAL CONTROL

THESE THREADs may give you some info

mark iv blocks

mark v blocks


MARK V- coolant passages


MARK IV- coolant passages
I think it is 80 & up mark IV big block engines that has the later improved cooling with the three extra holes.
(look at the gasket info below)
ITS Real easy to drill the holes in the earlier blocks if you don,t have then with a 3/8" drill , using the gasket as a pattern as it was found to increase cooling.

BTW fritz1990 posted this info

Top gasket pic is one with the extra cooling holes. Can use this gasket as a template to drill these 1/2" holes in the deck of the block. All heads already have these holes just some blocks don't.

The holes are the three on the bottom side of the gasket right below the ones between the cyls. The ends of the gasket are also different.

Just don't use the top gasket on your block without drilling the holes. I have to run to work and I can explain the difference later. The top setup is suppose to give you a lil' better cooling but there are many like yours running around, not a real big issue, just better to do it now.

If you have the three holes in the block you can run either gasket.

The bottom gasket is the one you will need to use if you don't drill the holes.




Three types of gasket materials are generally available, steel shim, composition and copper gaskets. Cast iron heads can use all three types of gasket materials. Aluminum cylinder heads require the use of composition or copper gaskets. Various compressed gasket thicknesses are offered. Remember that you should have a minimum clearance of .035"-.040" between the top of the piston deck and the deck of the cylinder head when using steel rods. Aluminum connecting rods typically require a larger clearance.
Fel-Pro composition head gasket (PN-8180-PT) for 4.250" bore Mark IV engines. It has two additional holes for head bolts that go into the lifter valley found on some high performance Bowtie and aftermarket blocks.

Different head gasket bore sizes are offered. Mark IV head gaskets have different coolant core hole passages than gaskets for Gen.V engines, blocking some passages and opening other coolant passages. Some block deck coolant core holes are round, while on Gen.V production blocks the holes are irregularly shaped on the block deck. Mark IV heads and head gaskets should be used on Mark IV blocks. Likewise Gen.V style cylinder heads and gaskets should be used on Gen.V blocks. There are exceptions. Mark IV heads can be used on Gen.V "Bowtie" and on Gen.VI HO blocks because the core holes in these block decks will seal the water core holes found on Mark IV heads. If you build this combination then use a Mark IV style head gasket and plug the core hole in the Gen.V "Bowtie" block deck located near the front head dowel pin location (see photo). Otherwise coolant entering the front of the block can bypass the rest of the block and exit out thru the head and intake manifold.

Steel shim gaskets and copper gaskets require the use of head gasket sealant. Composition gaskets do not require sealant.

Head bolts should be completely cleaned and then torqued down in the proper sequence and to the correct torque values. Head bolts or studs, used on aluminum heads, need to have a hardened steel flat washer (PN-3899696) under each bolt head or nut, to prevent damage to the aluminum head surface. Head bolt threads going into water passages should be coated with sealant and head bolts going into blocks with "blind" holes should be coated with moly lube or oil. Some head gaskets do not need retorquing, but it is a good practice to retorque all of the head bolts after the motor has been heated up the first time and allowed to cool down. Remember, do not try to put Mark IV heads on a production Gen.V block and visa versa. You can use Mark IV heads on the new Gen.VI 454 and 502 HO blocks or on "Bowtie" blocks.
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Staff member
I was asked "why would you go thru the effort to swap to a BBC vs a SBC
after all. you can make 400 plus hp with a SBC?"
well if I was only after 400 hp Id agree
heres a few advantages the BBC has...
theres EXCEPTIONS but generally.....
LARGE VALVES=more flow at any lift
MORE EFFICIENT PORTS=more total flow per port
SPLAYED VALVES= better low lift flow/better exhast flow
LESS CYLINDER WALL SHOUDING=due to slightly larger bore on average
LARGER DIA CAM=LESS stress on lifter
LARGER SPRINGS=less pressure needed in some cases
STRONGER BLOCK,=Less distortion under higher pressures
WIDER BORE CENTERS= better cooling
LARGER DIA. BEARINGS=more load capacity
STRONGER PUSH RODS=SBC generally 5/16", BBC 3/8 or 7/16"
EXHAUST PORTS equally spaced=better cooling

getting 500hp from your average 350,383 sbc takes a good deal more effort than from a 427-454BBC
ONCE you exceed about 600hp the BBC combo tends to be CHEAPER at any hp level

AND YEAH! Im fully aware that the SBC can easily have a larger valve IN RELATION to cylinder displacement
but theres PLENTY of BBC heads flowing close to or even well in excess of 400cfm, a few over 500cfm and darn few SBC heads flowing over 310-320 cfm

another way to look at this, the most common stroker for a SBC is a 383, for a BBC its a 496, if each makes 1.25 hp per cubic inch the 383 makes 480hp
the 496 will make 620hp
youll have a hard time making 600hp from a SBC with no power adders for 7K like this crate engine

or 900HP for 11K
there ARE several suppliers of adapter tail housings for the conversion of a much stronger 4l80E transmission to the C4 corvettes C-beam support

like this 620BBC


sometimes you need to fabricate adapters, if you want to install a transmission that was not originally designed for the application
careful measurement, a drill press and a welder in even limited skilled hands can fabricate a decent adapter

some more welding grinding and some paint can do a lot for the looks


I know its frustrating as all get out!,
(building a car with an engine that can easily shred the drive train behind it)

(just a bit of history) and yes its a all too common mistake, and one reason I like to post both my successes and screw ups so we can all learn, as we are much more likely to think things thru if we hear about what worked and what did not work on other guys car builds
If you have been reading the threads on the site you might have noticed I HAD ADDED A NITROUS KIT TO MY 383 SMALL BLOCK ,
and even without the nitrous the engine (that was designed and built specifically for nitrous use) makes decent power.

well the 383 sbc engine alone , that I built mostly because I wanted to have something to drive with a bit of performance while I worked on building my big block engine I intended to swap into the car, at a later date, even, without the nitrous easily trashed the stock original 700r4 trans in short order, I got good at replacing U-joints and even replaced the half shafts. the original 700r4 was replaced with a upgraded 700r4 from an 87 corvette,while the original 700r4 trans was rebuilt with much stronger internal components as a spare.
Then I found a 4L80E and purchased that to be used for the intended big block swap as it was obvious that the 700r4 trans design was never going to hold up to the power levels a properly built big block could easily produce which would easily double the torque levels the 383 N/A produced.
I eventually resigned myself to just not putting slicks on the car or drag racing as the launches were just too hard on the existing drive train and a huge bottomless money pit! all of which too what very limited cash I have occasionally that is originally intended for the big block swap just to keep the small block running
I have come too see building the small block as a stop gap measure as a huge financial mistake, I should have spent that money on the true main goal of installing the big block upgrade, but at the time I had a great many of the small block components handy, the cost like most projects looked like it would be far lower than it eventually was, and it seemed logical, yet thinking back it turned out to be a bottomless money pit that slowed the big block swap to a near stop, and I regret that decision.
If I had spent the cash I spent on that 383 build and the re-builds of both 700r4 transmissions plus the half shafts and u-joints on the intended dana 60 4 link rear upgrade and 4l80e full manual control upgrades along with the big block engine I still may not have completed the process but i would surely have progressed further toward the goal than I have currently, on the up-side I learned a great deal , helping several friends build their big block powered c4 engine swap corvettes , and learned about how too build,a better big block swap watching the successes and mistakes made on those cars, being rebuild and learned more about how too repair u-joints , acquired a shop hydraulic press, and gained some learned knowledge points on tweaking MPFI small blocks,and acquired a good many more tools, and a new shop, with a lift and several welders,etc. so I guess its not a total loss

The Time GM Almost Offered a 454-Powered C4 Corvette
Alex Sommers
Sep 17, 2020

Photo Credit:

The experimental V12 Falconer C4 Corvette, known as “Conan,” has been having a bit of a moment lately since being highlighted by YouTube channel, Rockstar Rides. The 686 HP monster’s rekindled celebrity is well-deserved, but in the world of hopped-up C4 prototypes, there is another!

Behind the scenes, at General Motors in the late ’80s and early ’90s, there were several differing opinions about which direction to steer the C4 Corvette program. The King of the Hill was hitting showrooms, and there were teams fully dedicated to bettering the DOHC heart of the beast. Another group was focused on out Viper’ing the Viper with Conan’s twelve cylinders. Then there was Scott Leon, project coordinator at GM’s Arizona Proving Ground, and his dream of seeing big-block power return to America’s sports car.

While the former two groups ended up getting kneecapped by a three-headed monster of dwindling C4 sales (after moving 51,547 ‘Vettes in ’84, nearly 40k in ’85, and over 35,000 in ’86, the C4 only broke into the thirties one more time, just barely in 1987, before falling to 22 and change for ’88 and bottoming out at just over 20k in ’91 and ’92), high expensive bespoke engines, and a parent company in financial disarray; the latter faction, behind the leadership of Leon, could have delivered ZR-1 performance at a fraction of the cost.

Late after work one night, using a 1984 test mule that they had just laying around, Leon and his team set out to see if they could wedge a 454 cubic-inch Rat motor under the C4’s clamshell hood. It took some slight chassis mods along with the addition of a rigged-up tuned-port fuel-injection unit, an aftermarket tunnel-ram manifold, and Buick Grand National fuel injectors but, eventually, they were successful, and the “Big Doggie” was born.


Photo Credit: Remarkable Corvettes

Once the makeshift proof of concept was running, Leon presented it to GM brass and got the green light to build a pair of 454-prototypes. One used an automatic transmission 1986 coupe as a foundation and the second was a 1989 Z51 Convertible equipped with a six-speed and a clutch.

The Big Doggies made use of Chevrolet marine 454 short-block with L88 heads. To complete the build, the hood dome was raised slightly, the floorpan and frame rail were slightly modified, the convertible top mechanism was removed, and the hardtop was bolted to the body (a trick that would later be implemented on the C5 FRC and Z06). The completed feasibility studies were given the ZR-2 moniker, a name that had only seen the light of day on twelve individual 1971 Corvettes with the incredibly appropriate, special big-block handling package. The new ZR-2s were never put on a dyno, but engineers said that not only were they making LT5 levels of power, but they could also embarrass the fancy Lotus-designed eight with massive levels of low-end twist.

In the end, another three-pronged attack doomed the ZR-2 project. It was thought that offering similar performance with a desirable big-block powerplant at a much lower price would undermine GM’s sizeable investment in Lotus, the LT5, and the ZR-1. There were also emissions requirements and the same financial problems that initially got the C5 program canceled to consider. Offering the ZR-2’s 454 in the performance parts catalog as an engine swap kit was also briefly considered, but it never came to fruition.

An alternate universe where the fourth rendition of the crossed flags featured a 32-Valve masterpiece, a 12-cylinder supercar fighter, and the return of the big-block V8 is a place all Corvette fans would love to visit but, here in our present; we can take solace in the fact that a classic displacement did fight its way back from the dead in the C6 Z06 and there are some truly unique and magical things on the horizon for an eighth-generation car that likely wouldn’t have happened with any other series of events than the one we got.
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Staff member
LD85 said:
Grumpy, lets say I pic up a 454, with iron heads etc. what kind of HP can I expect, if I port the stock heads, new cam and bore it out, no strokeing?

now I know few cars with less room to mount an efficient oil cooler with a fan than a c4 corvette

theres certainly not much room under the hood and ground clearance is a huge issue

read the links

I first calculated the size of cooler I wanted , then realized there was no place it would easily fit, until I thought about replacing the rear spare tire with the cooler by purchasing a second spare tire carrier cover and a sheet of thin perforated steel plate so I could cut out a decent size area of the surface and cover it with the of thin perforated steel plate tpo protect the fins on the cooler yet allow a good deal of easy access to the airflow under the car, and mounting the cooler in place of the spare tire allows easy servicing,from behind the car nothing obvios shows or hangs down as i painted the perforated screen flat black, just like the spare tires carrier cover,and since the trans cooler is mounted inside the spare tire cover its up out of the way of road trash, yes you'll need to run the lines from the transmission back to the oil cooler but after careful measuring I had a local hydraulic shop fabricate two 5/8" inside diam trans fluid lines that are designed to work at up to 300 psi and 300f temp, to fit the cooler with the correct end adapters

17" & 18" rim size slicks are available




200f -230f temps on trans fluid are very common on stock transmissions when your beating the hell out of the trans racing, but 190f-210f on the street while cruising is more common using the stock in the lower radiator trans fluid cooler.
I had a larger than original capacity aluminum aftermarket radiator most of the time , in my corvette and if I ran a 180f T-stat both the coolant and trans fluid tended to run about 190f UNTIL I swapped to a 3200 stall converter , where the temps jumped noticeably by about 20f if I pushed the car but those temps dropped rapidly if I was just cruising in O.D. but I felt I needed a better system, to cool the trans fluid, adding the additional rear mount aux cooler drops temps to 150f-160f with the fan on and about 170f=180f with it off even if Im pushing the car so I wired a switch to the fan, and a sensor that turns the fan on at 175F
this is well written info

then look at (tech)....(Oval Port vs. Rect. Port - BBC cylinder head info. )
here are now 17" slicks available ....but a serious power level and a dana 36 combined won,t be a good combo with slicks

17" & 18" rim size slicks are available ... s_id=12401


now we didn,t always do things the best way in the old days , YET WE DID HAVE FAST BBC MUSCLE CARS , a decent machine shop can add longer valves,back cut the valves, add a 3 angle valve job, do a pocket port job , add beehive springs and clearance the heads for a .650-.700 lift, you then swap to pistons that give a decent cpr in the 10.5-12:1 RANGE ,(THE RADICAL CAMS REQUIRE MORE COMPRESSION) IF YOU NEED TOO, if the heads you have are open chamber designs ,TO GET THAT cpr, ADD A NITROUS KIT UNDER THE CARB,AND and add a good solid flat tappet cam, some 4.11-4.56 rear gears and a 3500 stall converter or a manual trans, A DECENT INTAKE LIKE THE rpm AIR GAP WITH A 780-850 CFM CARB, DECENT HEADERS, and you get an old school muscle car that kicks butt!


Chevrolet Performance Camshaft; Part Number SS4242
Chevrolet Performance Camshaft; Part Number SS4254
Chevrolet Performance Camshaft; Part Number SS4265

BUT WE EXCEEDED 500 HP VERY EASILY WITH A 427-468 bbc, and with the right parts 600hp plus is do-able


Airflow Chart for PowerOval Street Cylinder Heads
Lift Value Intake Flow CFM Exhaust Flow CFM
0.100" 74 64
0.200" 160 113
0.300" 231 146
0.400" 275 178
0.500" 316 209
0.600" 336 240
0.700" 347 264
Tests conducted at 28" of water (pressure). Intake with CNC-bowl blend and
CNC-inlet with Fel-Pro 1212 gasket; exhaust with 2" pipe.

BTW ,when I post answers its to a broad audiance, where I need to cover most applications, you can get that 500-600hp/tq from a 468 BBC but it will require some compromises in the driveability if your not useing a super charger,turbo or nitrous,and theres always guys that suggest that you can get 500hp from a SBC and thats true enought! but in any case the extra displacement and bigger valves and ports allow you to better any sbc results in almost any case where your not throwing huge buckets of cash at the project, and even then once you try to exceed about 500hp youll soon see the BBC has advantages and tends to be cheaper to build at some point

550 Urban Assault Engine

The goal was not top horsepower, although 600 is pretty good, but a broad torque curve. This engine had 625 ft. lb. of torque at 2800 RPM and still was above 625 at 4800. Based on the brand new Merlin III block and featuring Merlin iron heads and aluminum intake the new 550 has produced some phenomenal numbers on the dyno. The engine was designed for daily street use and starts great and idles at a smooth 700 RPM. On the dyno, 18 pulls were made to optimize timing, jetting, etc. Different rocker ratios and carb spacers were also tested.

The engine features all premium components including 4340 steel crank, H-beam rods, forged SRP pistons, Sealed Power plasma moly rings, race bearings parts that will take a good shot of nitrous. A complete Comp Cams valve train is used including the latest technology hydraulic roller cam. Top line brands like MSD, Manley, Holley, and Moroso finish the package.

for aluminum heads add $800
many options available Complete engine carb to pan

youll have a hard time building an HONEST 600hp/625 tq in a small block for $9K

This is a special project for the Super class, and serious bracket racer, that needs power and torque, but also has to make rounds all day without motor maintenance. This engine now makes 900 HP at 6400 RPM with 830 lb. ft. of torque at 4800 running 33 degrees of timing. The cam lift is only .748 and the rockers are Jesel shaft mount. No need to check valve springs and lash between rounds. Engines are built with Merlin III blocks, Brodix BB3X, or Dart 345 heads, Merlin X intake, Ohio Crankshaft 4340 forged 4.75" stroke crank, H-beam rods with ARP 2000 bolts, Canton pan, Comp cam, Felpro gaskets, and Melling oil system.

Every component is available off the shelf, the bore size will allow two rebores, and the compression is 14.3:1 which does not require the ultra expensive gas, or could be run on alcohol. The Best part is the price at $10995, less carb, ignition and valve covers, this is a really great deal.

Holley 1250 Carb $975
MSD Ignition $695
Valve Covers $295
Aluminum Block $2350
E85 Carb $1300

Complete Engine

900hp/830tq from any sbc without a turbo is almost unheard of

heres 675 HP for $9K

ripper;14288 said:
1976 all iron engine, except intake and water pump. hit a massive brick wall with the ac install, condenser will take up valuable radiator room and evaporator housing needs massive mods to clear exhaust, still scratching back of head. i'm thinking about leaving it out for now. still waiting for that water pump.

maybe I can help just a bit

if you can locate one thats been wrected or the components the firewall pieces for the LT5 give a great deal more room for headers, than the stock LT1 or L98 firewall parts. a large COMBO OIL /trans fluid cooler mounted where the spare tire normally is reduces the engines need for a huge radiator


Perma-Cool 13318 $209 (summit)

Hedman Hedders 68090 $181.95 fit on one side without mods and on the other one side need one tube re routed to get them to work
if the header flange is strait and flat and your useing a decent gasket (personally I prefer the copper ones) and youve coated the bolt threads in ANTI-SEIZE like you should have almost any decent 6"-8" box end wrench can be used to snug the bolts up firmly



and YEAH! the windshield wiper motor needs to be relocated swapped for a differant ,smaller one,or removed

396588 = BB or Caddy
3965589 = 168 tooth SB '66-'91
354353 = 153 tooth '66-'91
3851294 = '64-'69 Vette
3816511 = '62-'68 SB

Attachment: brackets.jpg (53.42 KB) 4 View(s)
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Staff member
Early std cars (84/85 at least ) never had the extra frame braces.
It and the 2 braces from X -member to frame under engine were part of the Z51 handling option to support
the frame rails, and to tie them together.
All became std on all later cars

you can temporarily do away with the solid brace in the front, to gain extra swap access room by making the upper front brave removable, so that it unbolts. ID suggest (4) 5/16" end plates welded in place and bolted with at least (4) grade 8 3/8" bolts on each end plate.
yes you can make a custom brace that bolts in place, obviously the cuts must be vertical and parallel and carefully measured and youll need 4 matched end plates welded and drilled correctly but any decent fabrication shop should be able to easily do it once you explain whats needed



I have seen it done (having a car with a welded removable brace) I know it was tig welded and its been driving several years and even raced occasionally so I doubt its highly stressed or subjected to stress levels that cause problems , keep in mind all most all the potential stress on that upper cross brace is in compression not tension or torsion so its not a highly stressed application ... E_Swap.htm

swapping to a MUCH STRONGER 4L80E trans in a c4 vette


most chevy first gen v8 motor mounts, on both the sbc and bbc engines come in one of two sizes, youll want to measure the mounts your replacing and order POLY motor mounts that are similar, because they could be ether type in most applications


early style "short and wide" motor mount that measures 2 5/8 in. between the ears and 1 3/4 in. tall to the center of the through bolt hole


early style "tall and narrow" motor mount that measures 2 3/8 in. between the ears and 2 3/16 in. tall to the center of the through bolt hole

there are now 17" slicks available ....but a serious power level and a dana 36 combined won,t be a good combo with slicks ... s_id=12401

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Staff member
just some info youll need to make an informed choice

a big block chevy CAN be assembled from readily available parts that weights close to or even less than a small block using expensive options like an aluminum block and heads,intake,water pump, etc.......but lets look at the more comon style combo with an IRON block and aluminum heads, intake, water pump. youll be about 80lbs-90lbs heavier than an iron small block combo, but what do you gain for that extra weight?
first you gain much better flowing heads,larger stronger rotateing assembly and potentially at least a larger displacement, and better engine cooling, a wider head gasket seal area between the cylinders, and generally significantly more hp at the rear wheels if both engines are built to a similar hp per cubic inch level of power.
lets look at that!
lets assume your sbc corvette weights 3500 lbs and has a 383 stroker based on the comon 350 block, producing 470hp
a similar big block stroker would be a 496, this gives you a 113 more cubic inches, if both engines make about the same 1.23 hp per cubic inch that small block makes the big block will make about 608hp but the car would weight aproximately 120 lbs more, yet the small block with 470hp is pushing 7.44 lbs for each hp, the big block combo even thought its 120 lbs heavier(engine plus accessories) has only 5.95 lbs per pound to accellerate...........approximately a 20% advantage, now both engines can be made larger, or more powerfull but the ratio and potential advantages only get slanted even more in the bbc favor



Staff member
use of aluminum HEADS, INTAKE MANIFOLD and WATER PUMP is advised to make the total increase in engine weight almost meaningless as a handling factor, BUT most guys Ive seen do the swap or Ive helped do the swap have used iron head engines simply because thats what they had when they started,(most used aluminum intakes,) theres no huge loss in handling unless your doing autocross type driving and even then the extra tq provided from the larger engine with a change in your driving style tends to make it a minor problem at most.

keep in mind theres dozens of different T-stat housings for clearance issues
remember the lower radiator hose has an internal spring to prevent it collapsing under suction from the water pump,
failure to use a re-enforced lower can cause a flow restriction and potential over heating issues

IF your going to need to fabricate a custom lower radiator hose, you might want to install a convenient drain

lowdrain1.jpg ... ator+drain
btw, Im reasonably sure your aware that theres heavier sway bars and springs and shocks that can be swapped in IF you really want to maximize the handling, but Id spend more effort in a larger radiator, oil cooler, trans cooler and large baffled oil pan than even thinking about what an extra 120 lbs on the nose of the car does to the handling, think about it,do you feel a huge decrease in handling with your girl friend in the car?


personal opinion and some field experience, here no doubt ,
yet having built and modified several dozen c4 corvette engines,
and having done several transmission swaps , related ,too various power levels
, theres a balance to be striven for in a rational street/strip car.
I am personally not all that impressed with the 700 hp dodge cars,
yes power is obviously impressive
but in my opinion styling and handling leave a great deal on the table.
now I also am not impressed with the c5-c6 styling,
but with minor upgrades, handling in both is in my opinion superior to the much heavier dodges,
I like the c7 corvette styling and the drive train suspension and engines have a good deal of potential.
the C8 is yet to be fully revealed so its an unknown.
most of us can,t afford to buy or modify a C7 corvette but the c4 and c5 are in a reasonable price range.
personally as Im sure youve deduced I prefer the 1996 C4 corvette looks and you can very VERY easily ,
modify a C4 with a dozen options like a BBC,4l80E or a turbo an verious ls engines,
and a few suspension and brake and cooling mods,
to run with the dodges for a considerable reduction in cost from the $50K-60K plus the new or year or so old dodge costs.

heres pictures of a guys engine swap, bbc c4
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Staff member
your engine installation check list


(1)verify why the orriginal engine needs replacing and that any deffective components or acessories or sub systems, are in pecfect order, especially the cooling and electrical systems.

(2)If the transmission failed verify the clutch or torque converter is in great shape , clean and CAREFULLY INSPECT THEM,BEFORE even thinking of re-using them. verify the oil pump pick-up is brazed to the oil pump and its got a 1/2" clearance from the oil pan floor.

(3)carefully inspect the old and new engine placed side by side to verify the accessories and bolt on components will fit correctly,things like the fuel pump,fly wheel,brackets,clutch, damper, pullies, starters,water pumps,intake manifolds,exhaust manifolds, verify the dip stick and the amount of oil in the engine match,etc MAY OR MAY NOT DIRRECTLY INTERCHANGE

(4)verify theres OIL YOU PUT INTO THE ENGINE and an oil filter in/on the engine, after checking the oil pump clearance to the oil pan floor and that theres a plug in the oil pan, the oil pan and valve cover gaskets etc, don,t leak, the water pump spins, the transmission has new fluid and a new transmission filter, etc., prime the oil system, with the correct tool to look for oil leaks and slowly rotate the engine by hand to verify oil comes out of each rocker assembly.

(5)verify that all reused parts are totally clean and free of old gasket materials , broken components,and the bolts and threads are clean and crud free.

(6)have the radiator, radiator hoses and transmission lines checked and ideally pressure tested. visually inspect the belts and pullies and brackets.
its always a good idea to put in a new, 180F T-stat and I generally drill 8 1/8" holes in the outer edge flange, so coolant flows even when its closed.

(7)install a new oil filter, and in a chevy v8 at least 6 qts of good brand name 10w 30 oil, once the engines installed verify all sensors are correctly connected, the coolant lines, fuel, transmission cooler lines and all electrical connectors and gauges are connected, verify the throttle linkage operates smoothly without binding and the springs are connectede, if theres a transmission TV cable ADJUST it correctly, if theres vacuum lines connect them, see that the PVC is connected, verify the motor and transmission mounts are in good condition and connected(BOLTED) correctly, verify the exhaust is connected.verify the engine ground strap is connected, verify the driveshaft is connected at both ends.

(8) verify the radiator has a full level of coolant,and transmission fluid is correctly filled, verify the ignition timing is correct, verify youve got fuel pressure at the carb or injectors, verify the fuel is water free and new,check the air filter is new, verify the cats on the exhaust are not clogged, set the float levels and idle screws if its a carb, set the valve lash/preload, Check distributor, advance controls and distributor cap for cracks, check the coil for voltage and set the spark plug gap to at .045, use a vom meter to verify theres no open plug wires or excessive ohms readings.

(9) verify the fan turns freely, verify the oil pressure sendng gauge is connected, verify the clutch pressure plate or torque converter is bolted on correctly. verify the dash gauges light up and move when the keys turned., once the engine starts watch for coolant flow in the radiator, and any air trapped is released and the coolant levels correct, before replacing the cap. Start engine, check oil pressure, adjust ignition timing with the timing light to the manufacturers specifications and adjust carburetor after engine has warmed up fully.

(10) take the car for a road test but stay close to your garage or shop and bring an extinguisher and a cell phone with you, look for leaks and verify oil pressure remains consistant, listen to the valve train and test for vacuum leaks, watch the engine temp. carefully.


Staff member
-the real basics, (off ebays site)-------------------- ------------------------- ------------------------- ---------
This guide is intended to help you sort out the more major differences among Big Block Chevrolet engines produced since 1958. Chevrolet has designed and produced several different "big block" engine families. Within each family, there can be evolutionary changes, and special parts designed for competition use which may not be directly interchangeable with the regular production items. I don't intend to cover every possible variation. For practical purposes, all big block Chevrolet engines use a cylinder bore spacing of 4.84 inches although note the one exception below.

Early engines were designated as Mark I, (Mk I) Mk II, Mk III, and Mk IV. Later engines continued the numbering system as Generation 5 (Gen 5), Gen 6, Gen 7. There are some conflicting theories as to the reason for the change from "Mark" to "Generation". My first guess: "Gen 5" sounds much more modern, hi-tech, and trendy than "Mk V".

Mark I: The original "Big Block Chevy", also called the "W" engine perhaps because of the layout of the valves and therefore the shape of the valve covers--although another possibility is that GM chose the "W" prototype for production rather than the competing "X" or "Y" prototypes, and therefore it's a convenient coincidence that the valve layout is in the shape of a "W". It should be noted that this engine became "Mark I" only after the Mark II was being designed years after the "W" was introduced. Whatever the origin of the name, this engine family was installed in vehicles beginning in 1958, as a 348. In 1961, it went to 409 cubic inches, (as immortalized in the Beach Boys song "She's so fine, my 409") and for one year only (1963) a few well-connected racers could buy a car with a 427 cubic inch version called the Z-11. The 427 version was all about performance, and had special parts which were not directly interchangeable with the 348/409. While production of the 427 was severely limited, both the 348 and 409 were offered in passenger cars and light- and medium-duty trucks. The truck blocks were somewhat different from the passenger car blocks, having slightly different water jackets and of course, lower compression achieved by changes in the piston in addition to more machining of the top of the cylinder. A novel feature of this engine is that the top of the cylinders are not machined at a 90 degree angle to the bore centerline. The top of the cylinder block is machined at a 16 degree angle, and the cylinder head has almost no "combustion chamber" cast into it. The combustion chamber is the top wedge-shaped section of the cylinder. Ford also introduced an engine family like that in '58--the Mercury/Edsel/Lincoln "MEL" 383/410/430/462. The "W" engine ended it's automotive production life part way through the 1965 model year, when the 409 Mk I was superseded by the 396 Mk IV engine.

Mark II: This is more of a prototype than a production engine. It is the 1963-only "Mystery Engine" several of which ran the Daytona 500 race, and in fact won the 100-mile qualifier setting a new record. It is largely the result of engineering work by Dick Keinath. Produced mainly as a 427 but with a few 396 and 409 cubic inch versions, all in VERY limited numbers. Even though it was intended as a NASCAR-capable engine, it had 2-bolt main caps. This engine was never installed in a production-line vehicle by GM, it only went to racers. And even though it was available in 1963, it has very little resemblance to the 427 Mark I "W" engine of the same year. The Mark II was a "breakthrough" design using intake and exhaust valves that are tilted in two planes--a canted-valve cylinder head, nicknamed the "Semi-Hemi" or "Porcupine" because it is "almost" a hemi head, and the valve stems stick out of the head casting at seemingly random angles. The engine was the subject of an extensive article in the May, 1963 Hot Rod Magazine. Because of NASCAR politics, Chevrolet was forced to sell two 427 Mark II engines to Ford after the '63 Daytona race, (to "prove" that it was a production engine, and therefore eligible to race in NASCAR events) and so this engine is not only the grandfather of the Mark IV and later big block Chevies, it's also the grandfather of the canted-valve Ford engines: Boss 302, 351 Cleveland and variants, and the 429/460 big block Ford. The bore and stroke of the 427 MK II is not the same as the 427 MK IV.

Mark III: Never released for production. This was rumored to be the result of GM/Chevrolet's proposed buyout of the tooling and rights to the Packard V-8 engine of the mid-to-late '50's. The Packard engine was truly huge, having 5" bore centers. The former president of Packard wound up at Ford after Packard folded, perhaps because of that, Ford was also interested in this engine. Ford wanted to make a V-12 variant from it just as Packard had once envisioned. One way or another, neither GM nor Ford actually went forward with the purchase.

Mark IV: The engine that most people think of as the "big block Chevy". Released partway into the 1965 model year as a 396, superseding the older 409. It is a development of the Mark II and using similar but not identical canted valve (semi-hemi/porcupine) cylinder heads. It was later expanded to 402 (often still labeled as a 396, or even a 400,) a 427, a 454, and a few "special" engines were produced in the late '60's for offshore boat racing as a 482. There was a 366 and a 427 version that each had a .400 taller deck height to accommodate .400 taller pistons using four rings instead of the more usual three rings. These tall-deck engines were used only in medium-duty trucks (NOT in pickup trucks--think in terms of big farm trucks, garbage trucks, dump trucks, school busses, etc.) The tall-deck blocks all had 4-bolt main caps, forged crankshafts, and the strongest of the 3/8 bolt connecting rods. All-out performance engines used 7/16 bolt connecting rods, along with other changes. This engine family was discontinued in 1990, with the Gen 5 appearing in 1991.

Gen 5: General Motors made substantial revisions to the Mark IV engine, and the result was christened "Gen 5" when it was released for the 1991 model year as a 454. There were 502 cu. in. versions, but never installed in a production vehicle, the 502s were over-the-parts-counter only. Changes to the Gen 5 as compared to the Mk IV included, but are not limited to: rear main seal (and therefore the crankshaft and block) were changed to accept a one-piece seal, oiling passages were moved, the mechanical fuel pump provisions were removed from the block casting, the machined boss for a clutch bracket was eliminated, the cylinder heads lost the ability to adjust the valve lash, and the coolant passages at the top of the cylinder block were revised. The changes to the coolant passage openings meant that installing Mk IV cylinder heads on a Gen 5 block could result in coolant seepage into the lifter valley. Frankly, the changes (except for the one-piece rear main seal) were all easily recognized as cost-cutting measures which also removed some quality and/or utility. All told, the Gen 5 engine was not well regarded by the Chevy enthusiasts because of the changes to the coolant passages and the lack of an adjustable valvetrain. As always, the aftermarket has provided reasonable fixes for the problems. The Gen 5 lasted only until 1995.

Gen 6: GM recognized that it did not make any friends when it designed the Gen 5, and so they chose to revise the coolant passages again when designing the Gen 6, allowing the older heads to be used without coolant seepage problems. The boss for the clutch bracket returned, but was generally not drilled and tapped. The non-adjustable valvetrain remained, as did the one-piece rear main seal. Some but not all Gen 6 454 (and not 502) blocks regained a mechanical fuel pump provision. Production engines installed in pickup trucks got a high-efficiency cylinder head, still canted-valve, but with a modern heart-shaped combustion chamber of about 100cc. The intake port has a "ski jump" cast into it to promote swirling of the intake air flow. All production vehicles with a Gen 6 used a 454 version, but over-the-counter 502s are available. The Gen 6 is sometimes referred to as the "Gen Fix" because it fixed a number of issues that disappointed enthusiasts when the Gen 5 was released. As an added bonus, most if not all Gen 6 engines use hydraulic roller lifters.

Gen 7: A very major revision of the previous engines resulted in the 8.1 liter/ 8100/ 496 cubic inch Gen 7 in 2001. The block gained .400 in deck height so it is the same height as the previous "Tall Deck" truck blocks, wider oil pan rails, and the cylinder heads have symmetrical port layouts instead of the previous 4 long/4 short port layout. Very little interchanges between the 8.1 liter engine and the previous Mark IV/Gen 5/Gen 6 engines. The head bolt pattern and even the firing order of the cylinders has been changed. There are some things that remained true to the previous Mk IV/Gen 5/Gen 6--the bellhousing bolt pattern, the side motor mount bolt pattern, the flywheel bolt pattern, and the exhaust manifold bolt pattern are the same. Note that the bolt holes are threaded for metric fasteners. The 8.1 is internally balanced, so you could install a flywheel/flexplate from a 396/427 Mk IV provided you use the correct bolts to suit the 8.1 crankshaft.

I have had a chance to compare Mark IV, Gen 5/6 and Gen 7 head gaskets. It seems to be possible--but very difficult--to install IV/5/6 heads on the Gen 7 block. GM did this on one show vehicle, it IS possible. You must move three head bolt holes in the block; and as the holes only move about 1/2 their diameter it would be difficult to plug the existing holes, re-drill the new holes, and still have enough strength in the deck surface. There are cooling system differences as well that must be addressed. I have NOT done this conversion; but I do have comparison photos of the head gaskets.

(sorry if this table loses it's formatting: I don't know how to fix it. It looks "ok" at full screen width on my computer)

Engine family Displacement Bore Stroke Rod length

MK I 348 4.125 3.25 6.135

MK I 409 4.31 3.5 6.010

MK I 427 4.31 3.65 6.135

MK II 427 4.31 3.65 6.135

MK IV 366 3.938 3.76 6.135 (Only offered as a medium duty truck engine)

MK IV 396 4.094 3.76 6.135

MK IV 402 4.125 3.76 6.135

MK IV 427 4.250 3.76 6.135 (Offered in passenger car and medium duty truck versions)

MK IV/Gen 5/6 454 4.250 4.0 6.135

MK IV 482 4.250 4.25 6.405 (very rare, made only for offshore boat races. Used tall-deck block)

Gen 5/6 502 4.466 4.0 6.135 (Over the parts-counter only; not installed in production vehicles)

Gen 7 496/8.1 4.25 4.37

Specials: GM has sold many special-purpose engines, partial engines, blocks, cylinder heads, etc., "over the parts counter" that were never installed in production line vehicles. It is very difficult to track all the various items--suffice to say that heavy-duty "Bowtie" blocks and cylinder heads in various configurations--Mark IV, Gen 5, etc, have been produced. Oldsmobile used the Big Block Chevy as a baseline when designing the first of the Drag Race Competition Engines (DRCE) so that the early DRCE engines have an Olds Rocket emblem cast into the block, but it's Chevy parts that fit inside. There are special high performance blocks and heads, in either iron or aluminum, produced by GM and by aftermarket suppliers to suit almost any racing need.

Coolant Routing Mk IV/Gen 5/Gen 6
There are two different ways that coolant can be routed through the engine: series flow and parallel flow. Both ways work just fine. There may be a slight preference for parallel flow, but it is not a big deal. Series flow has the water exiting the water pump, flowing through the block to the rear, it then transfers through the head gasket and into the cylinder head through two large passages on each cylinder bank at the rear of the block. The coolant then travels from the rear of the head, forward to the front of the head, into the intake manifold water passage and out past the thermostat and thermostat housing. The water cools the block first, then it cools the head. The coldest water (coming out of the water pump) is directly below the hottest water (having already picked up the heat of the block and the head) as the hot water transfers into the intake manifold. By contrast, parallel flow has the water exiting from the water pump into the block, where a portion "geysers" up into the head between the first and second cylinder, another portion "geysers" up to the head between the second and third cylinders, another portion geysers up to the head between the third and fourth cylinder, and the remainder transfers to the head at the rear of the block. The coolant temperature inside the engine is more even that way. The differences in coolant routing is having (or not having) the three additional coolant transfer holes in each block deck, and three matching holes in the head gasket. The heads have passages for either system, and are not different based on coolant flow.

Be aware that gaskets that DO have the three extra holes between the cylinders often have restricted coolant flow at the rear--instead of having two large coolant transfer holes at the rear, there is only one, and it's the smaller of the two holes that remains. This is important because if you use a parallel flow head gasket on a series flow block, you can have massive overheating and there's NOTHING that will cure the problem except to replace the head gaskets with ones that don't restrict flow at the rear of the block, or to drill the block decks to allow the coolant to flow into the head between the cylinders. Here's why they can overheat: A series-flow block doesn't have the openings between the cylinders, no coolant can flow up to the head there. The gasket may only have the single, smaller opening at the rear, so the amount of water that gets through that opening is greatly reduced from what the block designers intended. The result is that the coolant flow through the engine is only a fraction of what is needed.

Most, but NOT all Mk IV engines are Series Flow. ALL Gen 5 and Gen 6 engines are Parallel Flow. A series flow block can be converted to parallel flow by drilling 3 holes in each deck surface, and then use parallel flow head gaskets. You can use the parallel flow gaskets as templates for locating the additional holes. It's really easy: Put the parallel flow gaskets on the block, mark the location and size of the three extra holes. Remove the gasket. Grab a 1/2" drill and a drill bit of the correct size, and pop the extra holes in the block. There is NO modification needed on the head castings. Some blocks have one of the holes already, but it needs to be ground oblong to properly match the gasket. Again, very easy with a hand held die grinder and rotary file.

Please check out my guides to GM small block engines , and Olds, Pontiac, and Buick big block engines, Mopar V-8 engine families, Ford V-8 engine families since 1932 or HEI distributors , too.


Staff member
IF your looking at the choice between an LS series and a BBC swap...ITS all a matter of what you want as a finished product,its going to be reasonably easy to get into the 500hp range with either choice,

the best bang for your bucks if your on a strict budget will most likely be building a 482-496 BBC.

youll be hard pressed to beat this price
near 600hp for about $6k

a decent LS series engine can get into the 500-550hp range with the correct parts reasonably easily but parts are just as or more expensive than the BBC parts. and theres no way a stock LS series engine will have the low rpm torque of a BBC.
In most cases you need to look at the total cost, and the results and yes the LS weights less so its bound to handle a bit better, but once your goal is over about 550hp , especially over about 650hp, those extra cubic inches of the BBC and larger ports will be a significant advantage.
YES youll need aftermarket performance parts to get to those upper hp levels,
look you can turbo either engine and hit 1000hp, a bbc could easily reach 1600 plus hp, but all thats totally meaningless.and the cost gets crazy.
once you exceed about 600hp with either engine the rear suspension and transmission needs to be upgraded, so thats not a factor, the BBC under the hood in my opinion LOOKS a hell of alot more impressive with tall chrome valve covers and being able to say your running a 454,496,540,572 displacements alot more impressive even if the power was identical.......which its NOT LIKELY TO BE!
THE BBC has the advantage of lots of used parts, lower cost intakes cams heads etc., and increased displacement, which if correctly set up will result in ALOT MORE HP/TQ, but your results will depend on YOUR COMBO and YOUR SKILLS, personally IM going BBC/swap as soon as my finances allow, mostly because IVE done the swap like 9-`10 times on other guys cars and loved the results.

want to get CRAZY?????

This is a special project for the Super class, and serious bracket racer, that needs power and torque, but also has to make rounds all day without motor maintenance. This engine now makes 900 HP at 6400 RPM with 830 lb. ft. of torque at 4800 running 33 degrees of timing. The cam lift is only .748 and the rockers are Jesel shaft mount. No need to check valve springs and lash between rounds. Engines are built with Merlin III blocks, Brodix BB3X, or Dart 345 heads, Merlin X intake, Ohio Crankshaft 4340 forged 4.75" stroke crank, H-beam rods with ARP 2000 bolts, Canton pan, Comp cam, Felpro gaskets, and Melling oil system.

Every component is available off the shelf, the bore size will allow two rebores, and the compression is 14.3:1 which does not require the ultra expensive gas, or could be run on alcohol. The Best part is the price at $10995, less carb, ignition and valve covers, this is a really great deal.

Holley 1250 Carb $975
MSD Ignition $695
Valve Covers $295
Aluminum Block $2350
E85 Carb $1300

Complete Engine





another option is a floating solid rear differential
SKI DOWN IT sells these







Staff member
This 1989 Corvette ZR-2 was a factory engineering concept that answered that age old question: What would happen if we dropped a 454 in a C4 Corvette? In additional to the high horsepower engine, the concept was treated with a special orange exterior, ZR-2 badges and has been signed by GM development engineer/driver John Heinricy. This GM Heritage Collection Corvette sold at the 2009 Barrett-Jackson Collector Car Auction for $65,000.


2006 – 4L80E in C4 Corvette Adapter Kit (1984 – 1996). Swap your 700R4 / 4L60E transmission to the much stronger 4L80E transmission with our new double strength case hardened output shaft and adapter kit. At this time we have in development an adapter kit for the C4 Corvette to replace your 700R4 / 4L60E transmission with the much stronger 4L80E transmission. This 4L80E transmission will be the same length as your 700R4 / 4L60E transmission making it possible to reuse your existing 27 spline driveshaft and C-beam. This is the worlds first 700R4 / 4L60E to 4L80E swap direct replacement. All that needs to be changed on the 4L80E transmission is the tail housing and output shaft. The full manual shift model works without a computer. We are also working on a C4 Corvette 4l80e ... ettJackson

heres a nice option ... ngine.aspx


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Staff member
"Hey Grumpy i just got my BBC from the machine shop and Im starting to line up parts for my swap. the water pump i need to use is it a short or long?"

we have used both,length water pumps in the past,but short is preferred as it allows less movement on the rack/pinion being moved forward for clearance welding and k member mods,as the belt pulleys sit a bit closer to the engine remember you'll be using electric fans not manual belt driven,so have the correct matching belts and accessory drive brackets and pulleys, and youll need to find or fabricate brackets, salvage yards are a good source at times

heres a few links with info that may help










Staff member
now this is a modification done on an earlier c3 big block c3 corvette but I could easily see some similar mod being done on a C4 with a big block engine install being done
Mooser said:
Another cross post as requested

Decided to install a spreader bar since I switched over to electric fans, mainly because I now have room

Orders a un-welded kit from VBP and couldn't quite get the location I wanted without dropping the bar lower than I liked so ended up machining a set of brackets out of some 1x2 tubing (inside dim = 3/4 which is the same as the ball-ends on the bar.

Couldn't get enough clearance to the water pump pulley when trying to mount it behind the front stud so I moved it forward, maybe not ideal but it should still work better than dropping the mount point below the axis of the control arm rod.

The 7/16 mounting holes are slightly slotted to allow for the alignment shims to angle everything around.


Drivers side has the belt from the P/S running up to the Alt so some additional clearance got added to that side



Good clearance on the bottom, a little close on the top, so I took another 1/4" off on the top only. Should be plenty of room for some belt flexing, plus it's on the "tight" side of the belt Will have to double check once everything is running.

Lots of room in front (might even be able to change a belt if I needed to)


Tucks up but clears nicely the SPAL fans


I needed to use 12-pts nuts to fit inside the tube so I ordered a set of ARP nuts which worked out perfectly, added a little lipstick and done is done



And a final check






solid fixture here in the forum
Grumpy what did you do exact to the Heater AC Box on the C4 Corvettes you swapped a Big Block Chevy Into ?
Finding a C4 ZR1 HVAC fiberglass box will be near impossible in 2018.
And expensive if found.
C4s can be miserable to drive with no Heater or Defrost.
AC not working in my 87 Roadster no longer.
Dont need AC.

I have that Wonder Bar on my 87 Vette.
Does it need to be cut out ?
Like to keep it.
Z52 car I have.


The Grumpy Grease Monkey mechanical engineer.
Staff member
most people I have helped install a big block engine in a c4 corvette have,
either totally removed the heater/air-conditioner components forward of the firewall,


or they modified the components. a modified thin, fiberglass cover can be made with a dent,
or concave in the area the pass side valve cover and spark plug access requires to gain better clearance.
this area is mostly but certainly not all open empty air flow duct
modified evaporator cover in pass side engine compartment to get clearance for big block engine install


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solid fixture here in the forum
most people I have helped install a big block engine in a c4 corvette have,
either totally removed the heater/air-conditioner components forward of the firewall,
or they modified the components. a modified thin, fiberglass cover can be made with a dent,
or concave in the area the pass side valve cover and spark plug access requires to gain better clearance.
this area is mostly but certainly not all open empty air flow duct
OK. That makes sense.
I could Pop rivet an aluminum cover in place or use some of that 3M Super adhesive.


solid fixture here in the forum
Its Been a Month since I visited this Thread Grumpy.
I see you added a few pictures.

What about a working wiper motor with a BBC Swap ?
Its a must have for me.
Often have to drive in rainstorms.
The Jet Stream weather pattern runs right through here.
What works with carburated induction and the stock hood ?
Rainstorms again the issue.
427 Tall Deck is like a 572 BBC Crate engine.
Tall deck also.