'65 L78 Engine Components

[Mark S. Lovejoy]

It's time for engine work on the 396ci, 425hp motor we are building for the '65. Right now the block and heads are bare, no internal components at all.

Ideally I would like to purchase a balanced rotating assembly with 10.5 to 10.75 static compression (pump gas), stock camshaft profile and stock valve train (using GM valve covers).

Heads: Stock GM components or aftermarket?

Camshaft: Flat tappet or roller lifters?

Block: Need recommendations for internal components.

Is there a good source for GM parts other than my local GM dealer (who has no interest in this project).

Thanks,

Mark
#27152

[Joe L.]

Re: '65 L78 Engine Components

Mark-----

A lot depends upon what you want the engine to be. If you want absolutely strict adherence to originality in every detail (except, possibly, compression ratio), then that's one thing. If you want strict adherence to EXTERNAL configuration, but are less concerned about internal configuration, that's another thing. If you are not too concerned about EXTERNAL or INTERNAL configuration, that's yet another thing.

[Mark S. Lovejoy]

Re: '65 L78 Engine Components

Hi Joe,

My concerns are only for judging purposes, so it must look correct. I was going basically stock because I think the GM engineers know a little more engines than I. At least I hope so. I'm sure there are modern improvements to the internals that I would want to take advantage of. This will my first GM BB, any and all advice appreciated.

Thanks,

Mark

[Mark #28455]

for street use

Consider the KB160 piston by Keith Black. It is a hypereutectic alloy which allows very tight piston to bore clearances for a long service life, is strong like a forged piston, and provides somewhere around 9.5 or 10:1 compression for easy street use on pump gas. While there are more modern camshaft designs out there, most performance type cams do NOT work well with a stock Corvette exhaust system and the stock 425 HP solid lifter cam does. In fact, with the stock solid lifter cam and 9.5:1 compression and a reasonable spark curve, you may even be able to run 89 octane gas - hey, that extra 20 cents per gallon adds up when the car only gets 8 MPG!

Mark

[Duke W.]

Re: '65 L78 Engine Components

The best thing you can do is massage the heads and go with everything else OE or OE equivalent inside. If you want to get the block sonic tested bore it out as much as you can if you're looking for the best possible power across the rev range.

Your compression ratio target is optimistic for pump premium. A SB with a SHP cam is on the ragged edge of detonation at 10.5, which can usually be eliminated with a little initial timing reduction and/or slowing of the centrifugal curve.

For a SHP BB I would limit CR to no more than 10.25:1, and as with any precision engine build, you need to take all the measurements to compute actual CR with the installed components. The OE type forged pistons are pretty bulletproof and their loose fit clearance will help maintain the engine's orignal acoustic character, and the CR can probably be brought in within the range of 10-10.25 with proper head gasket compressed thickness selection depending on deck actual measured height/clearance.

These vintage Corvette engines were very well designed and the SHP versions have a lot of premium parts. The best you can do is "blueprint stock" which includes judicious head work to include pocket porting/port matching and multiangle valve seats.

Such a configuration will maintain the visceral characteristics of the OE engine, have acceptable low end torque, and pull useable power beyond the original 6500 redline.

Duke

[Clem Z.]

bore it to 427 size,4.250 if it is a orignal

396 corvette block. with a little work inside you can sneek in a 454 crank. that will help with the lazy bottom end of the 396 with rectanglar big port heads. use a 143 cam with lifters that have the .025 hole EDM into the lifter bottom for better cam lobe to lifter interface oiling or grind a .003 deep flat on the side of the lifter from the center recess band down to about 1/8" from the lifter bottom..

[Mark S. Lovejoy]

Thank You Gentlemen....

you have comfirmed my initial thoughts about staying as close to OE as possible.

Duke,
I'm not sure I understand what pocket-porting is exactly, could you elaborate?

[Mark S. Lovejoy]

Re: bore it to 427 size,4.250 if it is a orignal

Hey Clem,

What is the complete part number for a '143 cam?

Why is cam to lifter lubrication an issue with the 3855962 block?

[Clem Z.]

Re: bore it to 427 size,4.250 if it is a orignal

the cam and lifter kit from GM is part# 12364057. there should not be a oiling problem if you use the GM cam and lifter kit and the GM part# 12371061 valve spring kit. just make sure they install the correct rear cam bearing and the cams rear journal is grooved. this groove may have to be done by the machine shop