my current corvettes 383 combo


Staff member
I was asked "whats your current engine, combo, Ive listed it below,
KEEP in mind the whole concept of the build, a dual personality engine that, the idea was too build an engine combo that would work well N/A, for cruising on highways, with a bit over 440 hp (NA) yet primarily designed too still kick butt with a healthy boost of a wet nitrous,plate on the plenum, the question always comes up about the drive train and gearing, thats always critical, and a good question with several answers and limitations on what you can do based on what rear differential you have and what your willing to do or can afford to do.
most guys feel its a two step process and a first step is a high stall torque converter , ideally matching your engines power curve, generally allowing you to jump in where your torque curve starts to pick up strongly at about 3300rpm-3500rpm stall speed and with a 3.73 rear gear ratio, this usually fits or at least works fairly well with most performance engines built for street/strip use, used on the street, as it allows a fairly long duration cam that will allow a 383-406 sbc engine most guys build with about 10:1-10.5:1 compression ratio to maximize the engines potential,your limited by the cars tire diameter on a c4 corvette is about 24"-24.5" so thats not likely to be changed due to rear wheel well clearance limitations, if you have a dana 36 rear differential youll be limited to a 3.73 rear gear set , some dana 44 rear differentials will accept a 4.11 rear gear set.
yes I have to admit that when I personally swapped from a stock stall speed converter
,in my 383 sbc corvette and a 3200 rpm stall speed converter the difference in performance was amazingly better.
swap too a 3.73:1 rear gear and you've noticeably further enhanced that seat of the pants and slam in the back acceleration.
people tend to not fully appreciate the fact that the performance cars drive train gearing, power to weight ratio and the converter stall
(in the case of automatic transmission) must match the engine torque curve if the car is to perform to anything close to its best potential.

obviously knowing your engines effective operational power band and matching the drive train gear ratios to operate most of the time well with in that power band makes sense.
your over drive 700r4 or 4l60 you may have replaced it with has an over drive top gear in the .70 range, a trans like that has limited strength, upgrading to the larger / strong 4l80E takes fabrication and modifications but pays off in a much stronger platform

yes a couple different parts could have been selected that would have easily boosted the power level significantly higher , but it would have resulted in a trade-off that reduced the street drive-ability,in exchange for peak power numbers that were seldom used on the street
"yes IM fully aware it will take hours to read all the sub linked info, youll save weeks of work and thousands of dollars if you take the effort, theres not much sense in not taking advantage of several decades of research and dozens of engines built and finding out what did or didn,t work correctly is there?"
Im always amazed at the number of guys who jump into modifying something like an intake without doing the first basic test to find out what the stock runners flow, or to establish a base line for the mods they intend to do. guys fail to test, or measure what parts of the intake ,like runners,cross sectional area, plenum volume or look at port matching needed to be modified to make it flow better , and theres a huge number that never bother to test the results of the mods they do, so they may not be getting the expected improvements or they may stumble on a significant way to improve flow rates.
(you might be amazed to find some mods make a very noticeable improvement while others have minimal effect.)
Id also point out that cam timing matched to the exhaust scavenging has a huge effect on potential intake flow rates


but keep in mind its not peak hp but ease of effective nitrous use and decent driving characteristics when not using nitrous that were the main goals in the parts selection, OF MY PERSONAL 383, but theres a TON of related info you can benefit from in the links that has zero to do with use of nitrous,and yes I need to run 92-93 octane fuel and have a slow advance curve and keep the coolant and oil temps at the lower edge of the average range to prevent detonation from being a problem ,running that much compression, and let me state that the component choices were made over 12 years ago, today there are much better component choices available especially in cylinder heads. if they were available at that time I would have selected some of the newer heads, the trickflows are good but certainly not state of the art now.
even without mild porting these TWISTED WEDGE TRICKFLOW heads have exceptionally good exhaust flow numbers, once ported they are easily able to run with the more expensive 195 AFR heads

keep in mind the engine combo in my corvette was designed primarily to maximize the results of a nitrous system NOT to run great hp numbers running N/A. but theres dozens of engines in the links, and the sub-links in those threads, posted that were designed to run without nitrous
yes the rules at most race tracks are there mostly to improve the car and driver safety,
but it also greatly increases cost, and reduces participation.
I rather enjoy the , local Saturday night "run what your brought"
racing, yes your limited to about a 13 second car,
but its still fun to watch because its mostly guys in street driven cars
what screws it up is theres always some guy that could run low 10 seconds with $5000 plus in computer controlled equipment,
that basically lets the car run the race, and click off boringly consistent runs
making the guys with basic street driven cars at a huge disadvantage in the long term.
when I first got my 1985 corvette it would consistently run about 14.5 seconds in its O.E.M. condition,
once I tweaked a few things and added a few parts .
consistent 13.3 second runs.
at this point I had a great deal of fun with the corvette.
yeah I decided to tweak the combo a bit, changed cams, several times, ported heads,
swapped to a custom ported and significantly modified stealth-ram,much larger injectors, a new ignition,
added a better 3" full length and well designed low restriction,exhaust ,
and low 11 second runs, with a 250 hp, wet nitrous kit ,
and getting told I could no longer race the car was a huge P.I.T.A.

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a second options the aftermarket FIRST TPI intake with larger runners



stock un-ported runner entrances

porting the stealth ram, adds noticeably to the intakes flow potential, of course the extent and quality of the porting work varies but its well worth the effort



be sure to accurately calculate the injector flow rate needed at the delivered fuel rail pressure
example on my corvette a 470cc in each runner port injector is approximately a 44 lb injector

below is a picture I took about 9 years ago, a very early proto type version on my test mule corvette 383 engine where I was testing cams with versions of the custom intake during research.


don,t forget all that potential extra air flow from a correctly ported stealth ram intake and matching heads that can flow in excess of 300cfm per runner, requires 36lb -44lb injectors and a cam with enough lift and duration to allow that air flow rate to be effectively used if you expect the intake to perform to near its full potential, and remember if the cylinder heads you select, at the cam lift and duration you select and the low restriction headers and exhaust system behind the headers can,t flow similar CFM flow rates the extra intake flow potential is wasted to some extent.
POSTED ABOVE theres a picture of a TEST MULE engine,in my corvette, itS nothing fancy to look at, for sure, but it put out over 500 hp,AND IT GETS TESTED WITH NEW CAMS , INJECTORS ETC. CONSTANTLY. Ive built/fabricated and tested dozens of custom plenums and several stealth ram, runner modifications and about 20 cams now, so I have a good grasp on whats required to boost power levels, this early plenum custom built mod, easily out flowed the stock plenum, but the current versions even better. once you own a TIG welder and a MILLING MACHINE this type of fabrication is far easier to do and your no longer limited to stock part modifications.
keep in mind the basic stealth ram intake is a modified tunnel ram designed to operate in the 3500rpm-6500rpm range, so a cam matching that power band in the 230-245 duration at .050 lift range on a fairly tight 106-110 lsa , and enough lift to allow the heads to flow at the max rate, (usually .550-.630 lift) with the proper intake mods to allow the heads to reach max flow rates would maximize the results on a 383-406 displacement with a matching required compression ration and heads matching the intake and exhaust flow requirements.
Correctly done porting helps air flow significantly, just keep in mind its part of a complete system, so the injector size, fuel pressure, and air cleaner restriction to air flow, the cams lift, duration,LSA, intended power band, cylinder head flow rates and exhaust restriction, & scavenging , all play a major roll in your results

HOLLEY changed the STEALTHRAM casting to a thicker flange a few years ago , notice the lower intake is marginally thicker allowing larger ports to be cut when porting
."yeah! didn,t take long after I built my first 383 for the 1985 corvette, to find out that the 700r4 and the dana 36 rear u-joints were not up to even the rebuilt engine let alone the wet nitrous once you mounted decent tires, if you use stock tires they spin and loose traction acting like a fuse and preventing drive train failures, but once your making 500 ft lbs plus of torque both the u-joints and stock trans are on borrowed time

comparing this to the super ram, after having run both Im telling you guys at least on a highly modified engine the STEALTH RAMS THE WAY TO GO! YEAH I KNOW THE STOCK STEALTH RAMS PLENUM IS 3/4" too tall to shut the hood , HOOD CLEARANCE sucks but the powers great if you can use the air flow potential which is quite a bit better that the super ram and the more I tweak the EFI tuneing the better the STEALTH RAM runs


some of you may have missed the pics of a stealth ram installed in a c-4 corvette(one of mine, the 85) this is installed on a full roller 383 with ported trickflow heads and a #119661 crane roller cam ,yeah it ain,t much for looks but it can go slightly faster than it appears, and I have not reinstalled the giggle gas throttle plate yet,I figured on tuning the stealth ram EFI first,
compare this to the super ram, after having run both Im telling you guys at least on a highly modified engine the STEALTH RAMS THE WAY TO GO! YEAH I KNOW THE STEALTH RAMS IS 3/4" too tall to shut the hood , HOOD CLEARANCE sucks but the powers great if you can use the air flow potential which is quite a bit better that the super ram and the more I tweak the EFI tuning the better the STEALTH RAM runs

ok here, I got my kid to take pics, this is how far the stock hood will close on a stock hood with the stealth ram installed



before you go jumping into building any engine take the time to read thru these threads and sub links ,it may seem tedious and wasted time but I assure you it can save you hundreds of dollars and weeks of work






viewtopic.php?f=69&t=8540&p=35051#p35051 ... aders.html
















BTW this info and software a good tool, but understand theres not a single original Chevy part in my engine and I'm constantly changing components (part of the HOBBY/RESEARCH)and that just because this combo fits my needs doesn,t mean its going to be ideal in your car!
THE combo I choose was NOT designed to maximize N/A hp, but too maximize BOTH the drive ability when I was off the giggle gas and to get a reasonable boost once the nitrous was used, with durability and trouble free operation as a main concern.

Ive got that software ,at first, its a P.I.T.A. to fill in all the necessary requested data "CORRECTLY" and fill the necessary data banks the basic program needs , but the more you use it the easier it becomes to use as it holds previous data in memory,but its an excellent program that gives good advice and reasonably dependable answers, unlike some of the cheaper
that and YEARS OF experience and testing assist in finding a decent combo
keep in mind the rpm band your car REALLY spends MOST of its time in, most guys seem mesmerized and glued to the peak power results, it does little or no good to make huge peak power numbers at an rpm that you'll spend only fractions of seconds at during occasional race use vs the rpm band where your car spends 99% of its time, I could easily have built a killer race combo with huge peak hp numbers but I wanted something that was reasonably easy to drive on the street and still be fast on the track on the rare occasions I get there. I drive My corvette and its NOT a trailer queen!

my comb changes almost every month as I play with it, but heres My current 383 combo, (which Im currently refreshing for a spare)I built the engine SPECIFICALLY to run nitrous , but still be marginally easy to drive on the street, Its certainly NOT a race car but its fast enough to be marginally scary at times

splayed 4 bolt block,4.030 bore ARP studs
.020 copper head gaskets
6" cat 7/16" rod bolt (H) connecting rods
SCAT 3.75" stroke FORGED internally balanced ,4340 crank
CRANE 119661 roller cam & kit (better springs added, its installed retarded 4 degrees)
air pump eliminator
jackson gear cam drive
smaller crank pullie
BBK 58mm throttle body
ERSON 1.6:1 BILLET roller rockers
gapless rings
TRICKFLOW twisted wedge heads (ported extensively)
STEALTH RAM(direct strait shot from back of valve to plenum) (ported and modified extensively)plus adjustable fuel pressure regulator
SFI 168 tooth flex plate
10 qt custom oil pan/high volume oil pump
windage screen/crank scraper /oil cooler
3000 rpm stall converter
44 LB injectors (soon to be 46 lb)
hooker 1 3/4" headers, 3" exhaust
taylor 10.4 mm wires
MDS ignition with manual retard dial
3.73:1 rear gears
aftermaket EFI fuel pump
larger fuel lines
trans cooler with powered fan
1.5"deeper aluminum trans pan
175 hp wet nitrous kit (EXTENSIVELY MODIFYED and re-jetted) similar to this


be damn sure you get a WET nitrous system, and retard the ignition advance curve,
the OEM TPI computer processor speed is way too slow,
and sensors won,t keep up and you,ll burn valves or pistons,
with a dry nitrous system on a TPI engine


Im currently collecting parts to upgrade to a BBC in the vette, after running various combos/ components and testing over a dozen cams and almost that many intakes based on this basic 383 design
several 700r4 transmission, and a couple rear suspension, parts,
and more replaced U-joints , tires and brakes ETC. than you would believe
(being retired hurts the spare cash budget flow rates)

here just for grins is what DD2000 makes its wild guess at my current corvettes combo, RUNNING WITHOUT THE NITROUS,notice torque peaks before the hp peak, and I must shift at 6300rpm because its starting to drop off by that point in the power curve (AS I DESIGNED IT TOO)as the engine combos designed to run nitrous from 3500rpm-6000rpm, if required but thats rarely been necessary for brisk performance on the street


heres the resulting power band, of my corvettes 383 with an extensively ported custom stealthram intake and other mods like ported trickflow twisted wedge heads, erson roller rockers and a crane 119661 roller cam, with a 3200 stall converter stall and shifting at about 6350rpm N/A

keep in mind that from planing to finish product this engine was designed to run nitrous, up too 200 hp shot, the dyno below is with only a 120 shot, and gives you some indication why I get good at replacing u-joints frequently and don,t use slicks to preserve the rear differential , and yes u-joints and 1/2 shafts have a limited life expectancy

I have tried over a dozen hydraulic roller cams in my corvettes 383 sbc so far, I was using a 3200 stall in my trans at the time I used most of them in my corvette , and had ERSON 1.6:1 roller rockers on my 11:1 cpr 383 and the crower 00471 certainly was fun to drive if you were only concerned with performance.
the only reason I swapped back to the crane 119661 was that the crane cams a bit easier to drive in traffic and cruise with, but the crower has a bit brisker performance.
ideally youll want a fairly tight LSA of close to 106 in a cam for a 383, but the difference between a 106-to a- 110 LSA,is not going to make or brake the combo, it simply changes the volumetric efficiency slightly and its only ONE of dozens of factors that will effect your results.
going with a slightly wider LSA tends to broaden the power band and smooth out the idle SLIGHTLY but the difference is not huge on cams with the same lift and duration.
yes the more factors that you calculate and take the time to maximize the better, but don,t think that one change will destroy the engines power curve.
I tried the CROWER 00471 in my cars 383 and then settled on the CRANE 119661, there was no question the crower 00471 made better peak power, than the crane 119661 , but being a bit older and less impressed with "POWER" than over all day to day drive-ability, and having installed a 200 hp wet nitrous system on that car that provided more than enough EXTRA kick when I needed it I felt I could compromise and loose a few PEAK N/A hp with ZERO NET LOSS
every choice you make is a compromise in some area!




THIS MAKES A GOOD STREET/STRIP CAM with a 3200 stall converter and 3.73:1 rear gears and 44 lb injectors

this is the cam I selected for street use in my 383
119661.png ... tId=749110


keep in mind the current BASIC combos 12 years old and theres been a bunch of better parts come on line...It was a great combo at the time but it can be improved on now...

IF I was to build the combo today and select current parts with a goal of PEAK HP, and was willing to put up with a less streetable engine combo,Id swap to the 66cc AFR 210cc heads,with L98 angle plugs and ID BUILD/WELD up a CUSTOM EFI intake , similar to the STEALTHRAM,
BUT,BASED on the

ID swap to this cam, and a 3500 rpm stall converter and a set of 42 lb injectors ... il&p=24183
crane 119581

one of the cams I tried after listening to a friend give it rave reviews was the Erson 119824 WITH 1.6:1 ratio roller rockers and a TPI intake, on my 383 and it worked rather well ,having good off idle torque and good power all the way to the peak rpm where the stock auto transmission shifts at, I must admit, but it lacked power above about 5000rpm, ESPECIALLY after I swapped to the ported holley stealth ram intake

if you have a 3.90-4.11 rear gear and a 3200rpm-3500rpm stall converter, an 10.5:1-11.5:1 cpr and are willing to put up with fairly bad street manors to maximize the hp of your 383-427 sbc this HYDRAULIC ROLLER CAM listed below is a good selection

a crane 119651

or maybe even a crane 119591

this thread and its related links and its contained sub links contain a huge amount of related useful info you can use

or lunati 40120732 and this being a solid roller cam as it would have a theoretical 500 rpm advantage over the hydraulic rollers
Lunati 40120732, but then if I went that route Id use 210cc AFR heads with that cam selection ... ffca829bad

this would probably boost my hp 50-70 hp and raise both ends the useful rpm band about 600rpm, but make it even LESS street friendly to drive, and require a different set of valve springs

but I'm currently collecting parts to upgrade to a BBC in the vette, after running various combos/ components and testing over a dozen cams and almost that many intakes based on this basic 383 design
several 700r4 transmission, a couple rear suspension,
and more replaced U-joints , tires and brakes ETC. than you would believe
(being retired hurts the spare cash budget flow rates)

If your afraid to experiment, or too modify parts or try new things..... YOUR PROBABLY in the wrong HOBBY, you need too research your choices and ideas carefully, see if someone else tried it first and see what results they got,but do the research, theres lots of guys who could not melt ice without instructions and they could still screw it up with a video guide, do the research, or you'll find yourself in a never ending and bottomless money pit with little hope of building a killer combo at a near reasonable cost.
you DON,T NEED the absolute fastest car, what you need is a very dependable car thats far faster than most.
its no huge trick to exceed 450hp/450 ft lbs with a properly thought thru and assembled 383, and 500hp PLUS and 500ft lbs PLUS is certainly achievable WITHOUT & before you use nitrous
If your thinking of building a TPI intake based engine,your almost racing a horse wearing hobbles here!
the stock heads flow about 200 cfm , they are very restrictive, it makes very little sense to use an intake that once ported can flow more than 275cfm matched to heads that flow 200-220 cfm, or restrict an engine with a cam that won,t allow air flow much past 5500rpm, matched to an intake that flows well past 6500rpm.
your wasting your time with the stock cams designed to meet the TPI flow characteristics and peaks at about 5500rpm,
the stealth rams designed to flow a good deal more air at a much higher rpm than a TPI, a stock or even mildly ported TPI basically post stalls by 5500rpm,the stealth ram can easily allow 6500rpm or more with the correct cam and heads, gearing etc.
youll want a 3.73:1 rear gear, a 3000 stall converter with a decent trans cooler, or manual trans, or a combo like this won,t work correctly

stealthram base


a properly ported stealth ram, matched to decent heads
heads that can actually use the potential intake flow rates, 30lb-40 lb injectors to supply the required fuel to match the air flow..


and it would sure help if you build a 383 -406 SBC to use the extra air flow potential,with 10.5:1 COMPRESSION OR AT LEAST SELECT HEADS FOR YOUR 350 THAT FLOW AT LEAST 250 CFM AT .500 LIFT AND GET TO 10:1 COMPRESSION MINIMUM
obviously what goes in needs to exit so a decent set of headers and a low restriction exhaust is mandatory



calculate horse power from intake port flow rates

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Great site,I see you are running a gear drive on the cam on this combo,do you like it better than chains and I guess there is no knock sensor in the system anymore.
Thanks DPC


Staff member
Yes your correct ,IM running a gear drive currently, but your correct, also,that it does occasionally drive the knock sensor nuts.
when I take that engine apart the next time,for a refresh(bearings and fresh rings and a detailed inspection) Ill temporarily replace the Jackson gear drive with a cloyes roller chain drive just to see it theres any worth while improvements.
The last time I did that I found zero improvement , but IM curious if the last 30K miles have resulted in enough wear, on the gear drive to change the results

btw heres a little tip,
I run a serious shot of nitrous on my 383 roller engine and its destroyed u-joints and a few built 700r4 transmissions,but you can aid the longevity a good deal by not using slicks as spinning street tires acts like a (TORQUE FUSE)preventing drive line failures provided you add the shot of nitrous rater gradually and only at or above about 50mph and 4000rpm, in the top couple of gears, as it tends to soften the impact forces on the drive line

BTW any suggested areas of improvement on the site??


if you want serious power from a corvettes SBC,
and your engine has a manifold design that will allow its install,
a direct port wet nitrous system (IDEALLY HIDDEN) can make impressive power




porting the runners on a stealth ram is mandatory for maximizing flow rates, leaving the runner entrance like this creates a restriction and turbulence,and if your significantly increasing the air flow rates your obviously going to need a longer duration cam, better flowing cylinder heads a low restriction exhaust, efficient headers and larger injectors to supply more fuel, ETC.
porting helps flow significantly, but the walls should be smoothed and opened up carefully down 3" or more into the runner entrance and exits


theres some rather significant advantages in ordering a cam that closely matches the engines
requirements, and after building dozens of similar engines youll notice some trends and you may want to tweak the cam timing, this of course requires both a good understanding of what your trying to change or accomplish and what the changes you intend to make are likely to do to engine performance.

heres a cam thats rather well known for producing good power in a 10.7:1 compression 406 SBC combo.
(use mostly for racing in a light weight car like a cobra replica)
Ive built several times in the past, it really requires the following matched components
210-230cc port heads, 5" scat rods on a forged crank, a 3600-3800rpm stall converter, a 4.11:1-4.56:1 rear gear and an automatic trans that shifts at 6300rpm under full load race acceleration.
a good single plane intake like the edelbrock VIC series, an 850 cfm carb, long tube 1 3/4" headers 1.6:1 roller rockers and a rocker stud girdle

heres the came basic cam, but with a few mods that provide about 20 extra horse power, but at the cost of a noticeably rougher lope in the idle
notice the tighter LSA and its a 4/7 swap cam version on a smaller base circle

btw, if your using a stealth ram it requires a small base distributor for clearance
if your replacing a TPI intake with a tunnel ram, HOLLEY STEALTH RAM or other intake requiring a small base diam. distributor, a gen 1 sbc distributor that fits physically, into the intake can be used in most cases, it can be made to function, most guys use aftermarket remote coil distributors, but the small diam. camaro distributor works,I used a HOLLEY 890-160 distributor

Stealth ram /msd 6A /Holley # 890-160 distributor
Ignition wireing

First Two wire connector
Small orange----------coil positive
Small black------------coil negative

Magnetic pickup (NOT USED)

Single Heavy red----------battery positive +

Single Heavy black------- battery NEGATIVE/GROUND

Second Two wire connector
Small white---------small white from two pin plug on holley 890-160 AND splice in small tan Chevy tach pick-up from harness
Small red------------small red on Holley two pin plug and splice in heavy pink from Chevy harness

HOLLEY 890-160 distributor
Smaller Four pin plug on distributor plugs to ( Holley #534-138 adapter* ) then large plug on adapter plugs to larger 4 pin factory harness

HOLLEY 890-160 distributor

*these adapters are very easy to make from salvage yard parts(wire plug connectors)

viewtopic.php?f=55&t=583&p=754&hilit=j%26b+weld#p754 ... 77161.html ... l/corvette ... l/corvette ... l/corvette
keep in mind youll need a small base distributor to clear a holley stealth ram based intake, or several other similar aftermarket intakes that won,t allow the large cap hei distributor to fit and function

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Staff member
If your looking for a basic HOT STREET TPI combo, ID suggest you read these threads/links for basic concepts


BTW if you run a high stall speed converter youll need a decent trans cooler, every trans and converter builder Ive ever talked with suggests 170F-180F is the preferred trans fluid temp range




go step by step, on a basic hot street TPI combo
heads , cam and intake are critical, to making a tpi combo breath, but what goes in needs to go out so a low restitution, and effective scavenging exhaust is mandatory to have the intake reach its full flow potential

IF I was building an engine as a HOT STREET combo, with easy to assemble components

you might want to consider that, brodix has good product support, and good heads those would be my choice for that application. ID ask brodix if theres an option you can order for springs that will clear a .575 lift, which I thinks a minor optional extra

1.470 Hydraulic Roller Valve Spring - CC 987,
125 lb Closed, 325 lb Open,
1.900 Installed Height,
.575 Maximum Lift
(IK 180, IK 200)

youll want the quench distance to be between .039-.043 and the compression ratio to be about 9.5:1 -9.7:1 for street use, so select the larger combustion chamber option and dished pistons

roller rockers


if youve got an auto transmission a 2800rpm-3000rpm stall converter is mandatory

oil pan
get a decent 7qt baffled oil pan like the canton ... 88bb985ecf

dart 406 short block

crane hydraulic roller cam ... vl=2&prt=5

use a 3.54- 3.73:1 rear gear, and any decent full length header with a 3" exhaust, and (X) pipe to lower flow Resistance behind it, ID SUGGEST something similar to this
c_4_system.jpg ... ms/c-4.php


Staff member
Ive had rather extensive experience trying to improve the performance on the 1985-1991 TPI engines and it helps a good deal if you understand the limitations and restrictions that need to be over come to get the performance most of us would like to have, originally both the cylinder heads and intake manifold were designed to maximize the low and mid range torque on the 305 displacement engine NOT the 350, so while those components work reasonably well to produce impressive torque both components become hopelessly restrictive on a 350 displacement engine by the time rpms reach the 5000rpm range as does the low lift cam the stock engines were supplied with.
Years: 1985–1992

The new 1985 L98 350" added tuned-port fuel injection "TPI", which was standard on all 1985–1991 Corvettes. It was rated at 230 bhp for 1985-1986, 240 bhp for 1987-1989 (245 bhp with 3.07:1 rear axle ratio (1988-1989 only)), and 245 bhp in 1990-1991 (250 bhp with 3.07:1 rear axle). Aluminum cylinder heads (Corvette only) were released part way through the 1986 model run, modified for 1987 with D-ports, and continued through the end of L98 Corvette production in 1991(still used on ZZx 350 crate engines).[10] The L98 V8 was optional on Jan.87–92 Chevrolet Camaro & Pontiac Firebird models (rated at 225 hp (168 kW)-245 hp (183 kW) and 330 lb·ft (447 N·m)-345 lb·ft (468 N·m)) 1987 versions had 10 hp (7 kW) and 15 lb·ft (20 N·m) more and a change to hydraulic roller camshaft. Compression was up again in 1990 to 9.5:1 Camaro/Firebird and 10:1 Corvettes, but rated output stayed the same.
cranes gold roller rockers are decent quality rockers for a small or big block chevy,Ive used those, ERSON, CROWER and COMP CAMS ROLLER ROCKERS, many of them come with jam nuts that require a 3/16" allen key
and look a great deal like these posted here below


but these are NOT locking jam nuts designed to work with a rocker stud girdle
TFS-30400700_xl.jpg ... /overview/

brodix ph# 1-479-394-1075 (ALWAYS VERIFY PART NUMBERS SEVERAL,

the brodix rock stud girdle is part # BR-6435 and LIST price is about $230 you can get it for less if you shop carefully
BE AWARE that the I.K. 200 heads were shipped with BOTH 3/8" and 7/16" rocker studs ,
and the poly locks for the 7/16" rocker studs ONLY fit that rocker stud girdle
obviously you need to verify what your heads have before you order the matching rocker stud girdle
Verifying your engines clearances, and rocker geometry, and use of A rocker stud girdle and high quality roller rockers go a long way towards maintaining valve train durability


rocker stud girdles require significantly longer shank jam nuts , but you need to mount the rocker stud girdle up out of the way so the upper surface of the rockers can,t touch the lower surface of the stud girdle at full lift

those are rather PATHETIC NUMBERS compared to what can be accomplished with a few component upgrades, heres a few links to get you thinking along the lines of whats required
you might want to read thru these links

ID strongly suggest you keep firmly in mind that doing your math home work and selecting and correctly installing a few high quality well matched components , goes a long way towards building a durable high performance engine and its best to concentrate on maximizing the engines torque curve in the mid rpm range, up to the engines useful rpm red-line, and gearing the drive train to match that intended power band!
If your building a high performance street driven cars engine, ID try hard to build a combo that allows you to stay under about 4200 feet per minute in piston speed, maximizing the engines displacement, getting the dynamic compression close to 8:1 and carefully checking valve train clearances, and geometry.
building an engine with a Quench distance that falls in the .038-.044" range, and matching the cam duration, lift and LSA to the intended power band, and having headers that are designed to amplify cylinder scavenging in that power band, and carefully thinking through and installing a 7-8 quart baffled oil pan and windage screen along with use of high quality bearings, and valve train components, with carefully verified clearances ,goes a long way towards maintaining better long term durability!
YOU'LL tend to get what you pay for! in both parts quality and machine work precision, You'll almost never regret buying and carefully installing a few better quality forged rotating assembly parts or double or triple checking clearances, but you'll frequently wonder "W.T.F. WAS I THINKING"
if you buy cheap components or fail to verify clearances , if your bargain priced parts fail under stress!
do your reading and research home work before you buy parts!
if your not 110% sure of what you need stop and ask questions and get answers from several sources before proceeding on! ... index.html









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I was asked what components ID select if I was building a NEW SBC engine for my corvette with the parts currently available,
since The current corvette engines at least 13 years old now, Ive learned a great deal of what makes a good combo is the ability to jump into an be able to drive the car without needing to be concerned with, its function or durability, or if its likely to break down or over heat or run like crap in traffic, so you should concentrate more on how it runs, and functions than on the potential peak power it can produce.
yes you can select parts that will allow you to make impressive power but giving a great deal of thought into how it will run, or what components are likely to break under stress well before it might happen. is not wasted effort.
but if I was going to build it to produce more power than the current engine, and was to use the better parts now available.
well giving it some thought Id concentrate on the drive train, gearing converter stall, transmission strength and engine cooling and lubrication, systems ,a bit more than just the engine itself, to start, as Ive learned a good deal about what makes a decent running car, and its not all related to the engines potential power curve.
but given the option of todays better parts if I was to build a replacement power plant.

ID start with a 406 displacement DART SHORT BLOCK probably purchased from these guys as a short block assembly., and get the components to make a 10.5:1 static compression and a .042 quench.
ID get a 0.100 intake and 0.120 exhaust valve clearance machined
ID select the newer forged steel comp cams roller rockers , use a matched rocker stud girdle and tall dart cast valve covers.
ID USE CLEVITE (H) series bearings
ID use the same holley ignition

Id start with decent cylinder heads

and a decent crane hydraulic roller cam, while this is not the cam that would produce the max power its a cam that would come close without being a total P.I.T.A. to drive on the street , but only if the correct drive train was used as it would be miserable in a car with a stock drive train.

ID select a 3.73:1 rear gear ratio, installed in a DANA 60 rear differential with a 4 link rear suspension,Id use a front coil suspension and a 3300 stall converter stall speed.


ID select 44 lb injectors and re-use the current heavily ported Holley stealth ram intake with its 58mm throttle body,
ID use the new HOLLEY EFI controller and use a full manually control modified 4L80E transmission
ID use the same custom modified high capacity baffled oil pan.

ID use the melrose headers and exhaust ... ms/c-4.php


ID use a 3-4 core aluminum radiator , with much higher coolant capacity , a high amp (200 amp alternator, and a separate trans fluid cooler, and a high flow capacity water pump.


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1963SS said:
Thanks for your informative website Grumpy and I've read a lot of great info on there. I didn't want to post his in an open forum in case you had something bad to say so here goes.

I'm building another LT4 engine for my Vette and have just about got myself talked into a Holley Stealth Ram. I currently have the AFR 1039 heads and they flow 293/224 @ .500 and 308/233 @ .600 lift. I've talked to Mike Stark at CFM Performance and he seems to think the HSR can be opened up enough to support that head flow. He's talking about adding some material to get the ports to match, removing the thermostat housing and porting the whole thing. I have the Toledo Pro 2 3/4" rise hood on my 1995 Vette. In your experience, will the HSR fit under that hood? Can it be opened up enough to get to 310 CFM of thereabouts.

The primary use of the car is going to be a waste. ALthough I have the Jesel shaft mounts and a solid roller cam, I'll primarily be using this as my street car playing around machine. I drive my Impala SS about 15000 miles a year and it runs the 1/2 at 11.78 @ 116 MPH. I like power AND reliability. I want to be qable to get in the ole' Vette and take off on a thousand mile road trip.

It seems that the HSR does a great job according to some stuff you've got on your website. I've got a 3600 Stall converter (9 1/2") from Vigilante that I'd like to use and it seems as though it's right according to your dyno charts. I know that I could use other manifold combinations that would give me more torque but I'd rather have everything start to come together at a reasonable 6500 RPM or so.

It appears that I'll have about $1000.00 in the manifold and the conversion work not counting fuel rails and the such. Mike wants $600 for the welding, milling and porting. Is there anything that you'd do differently for about the same money to get equivalent power. I really don't care as much about the low end torque as I do the higher RPM horsepower. I don't want to destroy my Dana 44 stuff if I can help it and how much torque does a 3300# car need anyways?

If you know of anyone that does this type of work that you'd rather recommend please let me know. I just want to ship my heads, the intake and stuff to someone and get them all back knowing that everything is matched as closely as possible. Thanks again for your help and I don't think you're that "Grumpy" at all. Of course, I'm not married to you either. Have a great day and I'm looking forward to your suggestions/recommendations.

"did you get my previous reply? any questions/, discussion? "

Thanks Grumpy, I do have some questions and some comments. Sorry about being late getting back to you but I've been really busy on a "hurry up and build it" job. I've also been trying to put a carbon fiber wrap on my nephews hood and scoop and spoiler. On a 2005 Impala of all things.That stuff is a pain in the ass to get right. Well at least I assume it is because I haven't got it right yet. Anyhow...........
back to the HSR vs TPI or even the Single plane with a throttle body. I looked at the LT1 setup for the TPI and that looks real good. I have a 9 1/2" 3600 stall torque converter that I'd like to use on this setup. The only problem that I have with the neat TPI is that I'm afraid it will make "too much" torque......if there is such a thing. The engine in my 4300# Impala could use all of the torque but does the Vette really need it. I'd be more inclined to have the Vette engine more of a RPM machine than a torque monster. I'd like to see around 525-550 Horsepower at about 65-6800 RPM and torque come in around the 3600 converter sweet spot. (Cost savings. I already own the converter). Although the TPI looks good I don't know if it will allow the RPM's I'd like and it appears that it would make a ton of it's torque below the 3600 converters threshold. The reason for the lower torque is the Dana 36 that I have now. I've got a 3.42 D-44 that I can use but hopefully not right away. I do imagine that the first really good shift will grenade the D-36 but I'd like to try for a while. Stupid, I know but it's just a time issue. I want to drive the Vette this summer, not work on it.

I also think that a 3.73 gear in the D-44 would be better but I do want primarily a street cruising, road trip machine and I think a 3.42 would be a better gear. My Impala has a 4L60E and 3.73 gears and I'm turning about 2300 RPM at 65-70 MPH and that is OK too. I have no problem with the 3.73 gears and although I'm not sure of the Impala's torque I don't think the 3300 pound Vette will need as much as my 4400 # hogmobile. I'm not a drag racer by any stretch of the imagination but I have road raced SCCA and IMSA most of my adult life.

What are your thoughts on the best manifold for getting some RPM's while holding the torque down a fuzz. Maybe I'll not be able to SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START but I still should be plenty fast.

Here's my best timeslip from the Impala at 4400#'s. I don't know the horsepower or torque but I don't need quite that much for the ole Vette. I drove the Impala 500 miles to a meet, ran my first ever drag race on borrowed slicks and drove it home. I got 21 MPG on the trip......not counting the dragstrip, autocross and playing in the parking lot. Weight was 4340 pounds.

Thanks again for all the help. I do want something different and good looking under the hood. I was even thinking about converting an old Kinsler or Enderle fuelie setup under a plenum similar to the Holley Stealth Ram with a 1/2" Lexan top so the runners are visible. I may wind up with that this winter but for now what are your ideas. Have a great day.

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

look at the bottom of this page these guys make a much improved larger runner TPI style intake, they make an LT1/4 version, its larger runners and ports would be a very good option
by the time you modify the holley stealth ram to fit the LT1 youll have more cash and time into the holley stealth ram and I think this is a better option

grumpyvetteAdministratorStaff Member
there have been guys that have the financial resources or connections and or skills to have built an independent rear differential , based on the far stronger DANA 60 vs the factory supplied dana 36 or dana 44 , which are comparable to the G.M. 10 bolt rears, hardly impressive or known for strength or durability, to fit the corvette frame, obviously this takes a good deal of time,effort and money but it also can result in an exceptionally strong rear differential











yes its very unfortunate that there's no commonly, available, and reasonably priced, independent rear differential,available to the performance car enthusiasts,with large disc brakes in the compatible width, and easily retro fitted suspension mounts that I'm aware of, in most local salvage yards , similar to the corvette rear suspension, that has the strength of the dana 60 rear differential.
yes there are custom fabricated solutions, if you have a very healthy bank balance , but nothing based on a dana 60-70- or ford 9" or heavier duty independent G.M. differential

yes, if you can weld, machine and port the holley stealth ram and then extensively port it, it can easily support 550 plus hp.but I don,t think that the results vs the cost on a lt4 WOULD BE WORTH IT.

its always been my experience that you can NEVER have to much torque, but its sure possible to have too LITTLE traction, not enough tire or the wrong suspension. as too porting the stealth ram, its going to be limited to about 300 cfm per runner after extensive porting and that flow rate easily exceeds your power goals,


stock un-ported runner entrances


but you also have other options and adding injector bungs and fuel rail mounts to a good high flow tunnel ram base, and modifying it to fit the LT1 heads, is one ID think is better, as it potentially adds a bit more flow. if you want to spin that engine to 6500rpm, that lower restriction and higher flow might help.

a discontinued holley 300-44 or edelbrock tunnel ram base would be my first choices as both have larger runners, but each is designed for the first gen small block and will require extensive mods to work with the LT1-4 and reverse flow heads.
youll also need an oil pump drive





these threads may interest you also




adding a high rise hood allows a much larger choice in intake designs that will fit under the hood, but does little to reduce engine heat trapped under the hood, keep in mind that if you can increase the radiator fans efficiency "and thats done partially by reducing and resistance to air flow exiting the engine compartment" you can increase the air flow mass absorbing heat as air passes over the radiator fin surface.
remember the c4 corvette sucks air from under the car, so at lower travel speeds the electrical fans are responsible for the vast majority of the air flowing thru the radiator, as vehicle speeds increase a increased air pressure builds under the cars nose increasing air flow rates thru the radiator.

adding hood vents like these pictured above are mostly for show, but will help lower engine heat (MARGINALLY) they are to small to be ideal
adding a larger area hood vent to each rear panel thats about 9" x 12" increased air flow rates enough to lower engine temps a measurable amount, especially at track speeds larger like these will help lower engine heat and they are to large enough to be closer too ideal

the rear panels are almost designed as a good location for heat to exit the engine compartment if the proper vents are added







I was asked what combo of parts ID use if I was going to build a tuned port intake based small block chevy engine.

well the first step would in my mind to select the currently best flowing TPI style intake which is the FIRST DESIGN,(keep in mind the basic TPI intake design is set up to maximize mid rpm range torque,with its longer ram tube intake runners, so Id build it based on a DART BLOCK,built to be a 427 displacement with rods with 7/16" ARP rod bolts and an internally balanced 4340 forged crank, forged pistons and 10.5:1 compression.

THE larger 1.75" of the FIRST intake design, vs the STOCK 1.47" diameter runner cross section , of the stock G.M. tpi, intake adds at least 1200 rpm to the engines potential IF properly matched to the correct components, like 42lb injectors,
Id select decent flowing heads like these
these 1.6:1 ratio roller rockers
a cam like this
a good quality 7-8 quart oil pan with windage tray
these valve covers ... ory_id/249
a high flow water pump
and a vertex magneto ignition
Id match that with a 3.73:1 rear gear, 4l80E transmission and 3300rpm stall speed converter

before you go starting to buy the components, to build this or any other combo, price it out, think it thru, keep in mind theres other options, something like a 570hp/570 ft lb TPI combo could be built, but its much easier to build a 496-540 BBC if thats your goal, or add a centrifugal supercharger to your engine build plans, (OR BOTH)
why not call the tech dept at all five cam manufacturers linked below, and get their input,
(without discussing or letting anyone know you talked to other sources
.what any other cam manufacturer might have said in any way)
write down the cam specs they suggest,

then average the results and
select the cam thats the closest match, to that average , of the 5 cams that were suggested.

crane (386)310-4875

crower 619.661.6477

erson 800-641-7920


ISKY 323.770.0930

what your basically trying to do is to maximize operational compression,
over the useful rpm range
(this maximizes the torque curve efficiency,)
but, while keeping that cylinder pressure under the detonation threshold
ID suggest you select from heads from these sources
Jegs; 800/345-4545;

Summit Racing; 800/230-3030;

Scoggin-Dickey Parts Center; 800/456-0211;

TRICKFLOW ... 4294867081
1-330-630-1555 • 1-888-841-6556


Dart Machinery; 248/362-1188;

toll free: 877-892-8844
tel: 661-257-8124

Patriot Performance
Patriot Performance; 888/462-8276;

Toll Free: 877-776-4323
Local: 901-259-1134

EDELBROCK ... main.shtml
Edelbrock; 310/781-2222;

BMP (world products)
Tel: 631-737-0372
Fax: 631-737-0467




“Quality means doing it right when no one is looking.”
Henry Ford

“Quality is like buying oats. If you want nice, clean, fresh oats, you must pay a fair price. However, if you can be satisfied with oats that have already been through the horse ... that comes a little cheaper.”

an hour to a week spent in careful research,
before you buy or install parts,
can save you months or frustration
and easily 300%-to 500% of the eventually,
cost incurred in buying cheaper parts,in this hobby!

good quality parts tend to cost more, so expect to pay a fair price, remember the sweetness of low price tends to be forgotten long before the bitterness of living with low quality, that remains forever!

but your could exceed those numbers easily with a turbo LS engine or 496-572 big block swap


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