Compression drop from larger cc heads?

[g356gear]

Hey guys,
Looking at changing from a 109cc head to a 118cc head. I am currently at around 10.0:1. Any idea how much compression I would drop by going to the larger combustion chamber?

[Carver67]

Hi G,
If you can supply a little more info that would really help.
Bore & stroke of your engine
Piston dish/dome volume
Expected head gasket thickness
Is the block zero decked to the pistons or does it sit down in the cylinder (if so, how much)
Without this info all you'll get is a very uneducated guess.

If you're talking a 454 with a 4.00 stroke and 4.25 bore with flat tops, a 0 deck height and 109 chambers you've got about 9.5:1.
When you bump the chamber size to 118 your compression drops to 8.9:1
These are just rough numbers using an engine calculator I found online.
I highly recommend you determine your exact combo if possible. Remember that some cams don't like to run as well at certain CRs so you may lower it enough to have a negative effect on performance.
Good luck on your project.
-Mike

[Jims68]

Not trying to jack this tread, but i've been looking at changing my heads aswell. I have a 236/242 @.050 cam and factory 109cc retangle port heads. The block is bored .030 over and has standard deck. The compression now is around 9.5:1 with Speed Pro pistons.
My question is that if I just change the heads with a 122cc head, I will drop compression down to around 8.5:1 and what effect would it do to the cam performance?
Since I don't want to redue the motor, I could buy edelbrock 110cc oval port heads and just change my intake. But is that head any better than the one I have and how much performance gain would I get?

[Pro Stock]

Don't go with the Edlebarks, Find a Brodix or Dart head that meets your chamber volume requirements, these are of higher quality and more powerful heads, also stick as close to 10:1 as possible

Dale

[MonzaRacer]

Well as far as Brodix go i wouldnt walk across the street for them, 2engines I worked on had severe issues just wouldnt flow, they had poor castings and and even worse flow characteristics.
We got a set of Edelbrocks and had them ported by a professional hand porter , the other set we tried were AFRs and both made great power, awesome torque and the engine never had made that much power.
Now Dart does make some good heads as do World Products.