427 BBC cylinder head choice and options

Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
mikeB said:
Mortec.com shows the 3904390 heads as having 98cc closed chambers. Since I'm fairly new to BBCs, I need advice on pistons that will keep compression low enough to run on pump gas, if that's even possible with small chambers.
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Block is a 427.

The heads have been sitting the shelf since the 1980s, but the first thing we'll do, of course, is have them magnafluxed. Then move on from there.
My buddy ended up getting 3 sets of heads that have been sitting on the shelf for 20-30 years. The 390 ports looked like they've been opened up quite a bit, so it's hard to know the actual port volume.

He also got a set of bare 290 oval port heads that are totally untouched (casting flash still in the ports). They are dusty, but so clean they may even be new.

Finally, a set of rectangular port 291 heads that have been ported big-time. A small pet could get lost in one of the intake ports!

Which set would be our best bet here for street performance?

Car is a 69 Camaro and will have a 4.11 or 4.56 axle and Tremec 5-speed with 2.87 first gear.

Oh, yeah, block is 71-79 454 with a 427 crank.

prctool.png


SOME ROLLER ROCKERS CAN AND DO BIND ON ROCKER STUDS, or rocker adjustment nuts, youll need to check carefully
rpo1x.JPG

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


496bbcfgh.jpg

BEEHIVE SPRINGS GIVE A GOOD DEAL MORE ROCKER TO RETAINER CLEARANCE

rectvsoval.jpg

the upper closed chamber head is bath tube shaped to provide dual opposed quench areas that squish against the piston deck,
forcing the fuel air mix toward the central cylinder bore, the lower open chamber head combustion chamber was found to un-shroud the valves,\
thus increasing the cylinder fill efficiency especially at upper rpms.
the dome higher compression ratio pistons for both combustion chambers are similar in shape to the combustion chambers they are designed too be used with.
the closed chamber piston can be used with the larger open chamber combustion chamber , but its reduced volume results in less effective compression and the dome,
of the closed chamber dome is marginally restrictive to the flame front propagation.

bbchead1.jpg

opench1.jpg

opench2.jpg

bbcbolt4.png

bbcbolt5.png

bbcbolt6.png

bbcbolt7.png


markV1.jpg


0704ch_17_z+chevy_big_block.jpg

mark iv blocks
mrkiv.jpg

mark v blocks
markv.jpg

(keep in mind that ALL '91 and later Gen.V and Gen.VI big blocks come with 4-bolt main caps. The two-bolt big blocks are no longer in production
MANY BUT NOT ALL aftermarket head designs have been modified to work on both the early MARK IV 1965-90 and later MARK V & VI blocks 1991-later.)

BTW, , on BIG BLOCKS the oil pumps and oil filter adapters are different due to the block oil filter recess and rear seals being different
GEN 4 or MARK IV
bbcmk4.jpg


GEN V and VI
bbcmkv.jpg

coolant holes in factory heads match factory blocks of similar version, aftermarket heads usually tend to have a universal coolant passage design that will function on most blocks but you need to verify and use the correct head gaskets
markvcool.jpg

found this gasket over at summit..
using the correct head gasket too match the heads and cylinder heads your using on any big block chevy engine, is critical to prevent coolant loss, and maintain proper cooling
be aware that head bolts enter the block coolant passages,
so if you failed to dip the bolt threads in sealant when they were assembled,
through the heads coolant can seep up along the head bolts,
into the area under the valve cover
btw read this



80057.jpg

80063.jpg


both of these work great at sealing head bolt threads,IF you forgot to use thread sealant on the head bolt threads, why, not try to eliminate one potential area of concern,why not pull each head bolt one at a time and clean its threads dip the clean bolt in the can of sealant and re-install and re-tighten the individual bolt to the required torque, before removing the next bolt, I've done this in the past when guys failed too seal the bolt threads and its worked and there was no head gasket issues later, the only thing you have to loose by trying this is the cost of a can of thread sealant and an hour or two of your time, and of course you'll more than likely need to re-adjust valves as the rockers will need to be removed at some point in the process..

http://www.summitracing.com/parts/FE...2/?image=large

fel-8180pt-2.jpg

you,ll want to place a head gasket you,ll use on the heads and mark the area inside the opening as the only areas you can change,
(notice the gasket fire ring is NOT a perfect circle like many people assume)
ideally you,ll want to un-shroud the valves while opening up the combustion chamber volume, but not extend the combustion chamber past the front edge of the gasket fire ring as that usually causes gasket failure

laying a head gasket on the head and use machinist blue dye to show the areas inside the gasket fire-ring
8c3cd11a-b277-4018-b98a-b5648e0314be_1.74e42cf0e55dcba325d8cd403b5783b9.jpeg

http://www.skygeek.com/dymon-8000-s...MI8vPS24jm1gIVBolpCh2pnAoWEAQYAiABEgL2ZPD_BwE


gasketsh.png

BlackoutSteve posted these pictures
What cylinder head?
With my 4.280" bore and AFR head, I am forced to use a 4.540" bore gasket because the chambers are wide and would otherwise allow the gasket to "hang" in the chamber.

For example..
428gaga.jpg

454gaga.jpg

Brand Fel-Pro
Manufacturer's Part Number Q8180PT2
Part Type Head Gaskets
Product Line Fel-Pro Head Gaskets
Summit Racing Part Number FEL-8180PT-2

Bore (in) 4.370 in.
Bore (mm) 110.998mm
Gasket Material PermaTorqueMLS
Compressed Thickness (in) 0.039 in.
Compressed Volume (cc) 9.700cc
Lock Wire No
Quantity Sold individually.




According to summits apps page


The gasket your have fits

http://www.summitracing.com/parts/FP...ET&prefilter=1

Make CHEVROLET
Engine Type V8
Liter 6.5
CID 396
Engine Size 6.5L/396
Beginning Year 1966
Ending Year 1970
Engine Family Chevy big block Mark IV


Make CHEVROLET
Engine Type V8
Liter 6.6
CID 402
Engine Size 6.6L/402
Beginning Year 1970
Ending Year 1972
Engine Family Chevy big block Mark IV


Make CHEVROLET
Engine Type V8
Liter 7.4
CID 454
Engine Size 7.4L/454
Beginning Year 1970
Ending Year 1990
Engine Family Chevy big block Mark IV


http://www.superchevy.com/how-to/en...-big-block-casting-changes-through-the-years/

it may be the result of a crack in the head or block or just an intake or head gasket leaking, issue, as stated change oil and filter ,
and if the problem returns you darn sure better track down the source before repairs get exponentially more expensive
some cracks won,t leak until the engine heat of the engine thats been running for awhile expands the metal.
if its not up too operating temp, theres no leak.
its not un-common for intake gaskets to leak coolant,
into the lifter gallery if they were not correctly installed or damaged, or intake manifolds to leak coolant,
if the coolant passages are corroded or improperly machined,
or too find coolant leaks if the wrong head gaskets were used.
454Parallelflowgasket.jpg
454Seriesflowgasket.jpg


Quote:
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.

I'd assume the intake gaskets are the source until proven otherwise.
but be aware that miss matched head gaskets, to the heads and block combo in use, can cause several issues

don,t assume the worst, just logically and step by step track down and correct the issue using FACTS.
The Gen V was first installed in the 1991 year models.
The earliest casting I've decoded was a very late (Nov/Dec?) 1989 date.

The Gen VI was first installed in the 1996 year models.

The cams for the Mark IV and Gen V are interchangable for flat tappet lifters.
The Gen VI where the first equiped with Roller Lifters, but the main difference is the machined flats on the lifter bores of this block - you can still install an earlier cam without rollers.
The cam retainer plate holes are verticle on a Gen V~VI, rotated 90deg from the Mark IV's horizontal orientation.
The '91 on trucks with Gen V's had manual transmissions and use a bracket for the pivot, the later medium duty trucks have a hydraulic clutch.
The Gen blocks use longer main cap bolts than the Mark blocks.
The crank on the Gen engines uses one long key in the keyway slot for the cam drive gear and the damper - the Mark cranks have two short keyway slots and two seperate keys, one for the cam gear one for the damper.
As he stated, Gen cranks are one-piece seal, Mark are two-piece.
The Flex plates are interchangeable - but Flywheels, for truck and marine applications, are not interchangeable on Mark and Gen engines.

FAILING TO READ THE LINKS WOULD BE A BIG MISTAKE HERE!

http://www.chevydiy.com/gaskets-fasteners-guide-big-block-chevy-engines/

http://www.superchevy.com/how-to/4567-chevrolet-big-block-engine-generations/

http://hotrodenginetech.com/top-10-reasons-to-build-gen-vi-based-big-blocks/

http://garage.grumpysperformance.co...-brief-big-block-chevy-history.951/#post-5878
http://www.csgnetwork.com/compcalc.html

do the math, with flat top pistons and 98cc heads and your typical .031 thick head gasket your near 8.8:1-9.0:1, static compression, well in side the typical pump gas octane range

a cam like this , with the correct clearances and valve springs and a 3.54:1-3.73:1 rear gear and a good dual plane intake
https://www.summitracing.com/parts/wnd-8019
would match and wake it up!.
http://www.cranecams.com/product/cart.php?m=product_detail&p=24010


ID take the oval port 390 heads to a local reputable cylinder head re-builder and ask for a detailed written estimate a detailed inspection, a 3 angle valve job and general refresh

obviously you have options here, but with only 427 displacement oval port heads work great if properly set up and matched to the correct components

read the links
http://www.maliburacing.com/patrick_budd_article.htm

http://garage.grumpysperformance.co...ig-block-heads-and-casting-s.3960/#post-10599

http://garage.grumpysperformance.co...ig-block-heads-and-casting-s.3960/#post-10599

http://garage.grumpysperformance.com/index.php?threads/big-block-chevy-info.710/#post-60299

http://www.chevytalk.org/fusionbb/showtopic.php?tid/343253/

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