questions about big block heads
Thread Starter
Instructor
Joined: Jun 2003
Posts: 114
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From: Sydney NSW
questions about big block heads
Hello I would to know if closed chamber heads off a 390 hp. 1970 /454ci eng. can be used on a 365 hp. 1971 /454 ci. eng. which had open chamber heads would I have less comp. than the factory 8.5 ?as the 1970 /454ci had 10.25 comp/ with the closed chamber heads? thank-you 
Le Mans Master
Joined: Apr 2006
Posts: 5,403
Likes: 95
Hello I would to know if closed chamber heads off a 390 hp. 1970 /454ci eng. can be used on a 365 hp. 1971 /454 ci. eng. which had open chamber heads would I have less comp. than the factory 8.5 ?as the 1970 /454ci had 10.25 comp/ with the closed chamber heads? thank-you
69/70 oval closed chamber head 3964290 casting number shows to have one of the smallest closed chamber sizes 101 cc. your 71 would have more like a 113 to 119 open chamber size.
Last edited by Little Mouse; Oct 5, 2008 at 03:17 PM.
Burning Brakes
Joined: Dec 2003
Posts: 1,150
Likes: 154
as far as I know you can put open chamber heads on a car that came with closed chamber heads(piston dome height)most of the time. but putting closed chamber heads on a car that came with open chamber heads could be a problem.check it out with some engine builders.
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
Open chamber pistons will hit closed chamber heads because of the different shape of the piston dome. OC heads on closed chamber pistons will reduce the CR due to the extra volume.
Le Mans Master
Joined: Apr 2006
Posts: 5,403
Likes: 95
Thats right lol, 71 LS5 flat top piston you can use closed or open chamber oval port head, just bolt the closed chamber on enjoy the extra compression. With the extra compression gained you can get rid of the low duration low lift factory cam use something more realistic for a 454 cu in engine.
Last edited by Little Mouse; Oct 5, 2008 at 10:41 PM.
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