ls6 heads
 

A freind of mine has a set of big block heads,cast numbers 3964291. are these ls6 454 heads? If so what application,he believes the valves are 2.25 and 1.88, closed chamber. if so what is the chamber cc and intake runner cc?

Re: ls6 heads
 

3964291 1969-70 396/402 375 L-78, Intake Port 325cc
427 425, 435 L-71/L-72
454 450 LS-6,
Closed 108.0cc

I beleive the valves should be 2.19 and 1.88. Chevy didn't use 2.25 valves in any heads.
James

Re: ls6 heads
 

Good deal James ,I think Im going to try and talk him out of these heads and use them on my gen v 454 Im putting in my 70 chevelle SS( reproduction ls6454 4 spd ) car. Thanks a lot for the great info.
David.

Re: ls6 heads
 

Can you put Gen IV heads on a Gen 5? I thought there were coolant passage changes on the Gen V's? Also, no fuel pump boss on a Gen V...

Re: ls6 heads
 

I think you can use a diff head gasket set up on one of those combos and make it work https://www.yenko.net/ubbthreads/imag...mlins/hmmm.gif....have to check one of GMPP dealer's sites to be sure.

wilma https://www.yenko.net/ubbthreads/imag...ins/3gears.gif

Re: ls6 heads
 

Yea, please check on that I'd hate to make a deal with him and not be able to use them,Im running an edelbrock two four set up on the gen v so an electric fuel pump is needed.
under the hood two fours, but if the ls6 heads will not work then i will go with edelbrok rpm heads.

Re: ls6 heads
 

Be sure and check the exhaust valve sizes. My 291s had 2.19 and 1.72 valves.

BCD

Re: ls6 heads
 

I have a set of early 1970 291's that have 2.19-1.72 valves as well.

I've been told, but I have yet to verify, that the L78 engines got the heads with 1.72 valves, and only the true LS6 engines got the heads with 1.88 valves.

Can anyone confirm this?

Eric

Re: ls6 heads
 

We did measure these valves and the exhaust measure 1.88 and intake measure 2.19 , they date dec 7,1969.I had mentioned earlier that I thought the intake was 2.25 but I had a senior moment I guess, no punt intended.

David

Re: ls6 heads
 

FYI found info in my yearone chevelle book, mark IV cylinder heads will not work on gen V block as well as the crank, balancer ,flexplate or flywheel however will work on genVI block due to chevrolet changed back to prev. coolant passage design.Iguess Ill be purchasing some edelbrock heads after all.