What compression ratio would be best for my motor? I've heard anywhere from 9-9.5. It'll be 95% street driven on 91 octane, although I haven't ruled out E85 or meth.

Here are my specs.

383 cubic inches
4.030" bore
3.75" stroke
-24cc piston(dished)
-.0185" down in the cylinder deck height
-67cc combustion chamber
Head gasket anywhere from .040-.029-undecided-depends on where the compression ratio needs to be

Big FMIC.

I can have the heads milled, but they would have to be angle milled and that's around $200 and I would like to leave the deck as thick as possible.

 

do 9 - 9.5

I'm having my heads milled from 64 to 58cc on my 383 with 28cc dishpistons and using a .040" gasket for 9:1

 

^^ I agree.
I'm going to end up closer to 8.5 but that is just how the cards fell. If you are closer to my range I would not worry too much. The 383 and a good flowing top end will spool that 76 almost instantly. Torque will not be an issue.

 

So would 9.5 be too much for pump gas and say 15 psi? Or should I stay closer to 9. If I do 9.5 and end up getting ping or knock can I just back the timing off a little and still be good. I don't want this motor to feel like a dog when its not in boost, but I also don't want to do any damage.

 

Also I just measured the deck height and the pistons are about .0185" down.

 

One more thing, would it be better to mill the heads a little and use a .029 compressed gasket, or just milled the heads more and use a .040 compressed gasket.

 

For 15psi on pump gas I'd shoot for 9 rather than 9.5; that's exactly what I'm doing.

A thinner gasket is better than a thicker one. If you run a .040" gasket with your pistons .018" in the hole, your quench is .058", less is better but you need to keep your pistons at least .035" to .040" away from the heads.

 

This motor will not really have anytime out of boost

 

The porter wants $200 to mill the heads down to a more reasonable compression ratio, they are at a 67cc now and would need to be milled to about a 60 or so. He stated something about having to angle mill or roll them. Does that sound about right? A local guy wants $60 but the porter, who currently has the heads, is very reputable, especially with these heads. I think he said it would make them about a 22º or a 22.5º heads. Is that going to cause any problems with my intake or headers?

 

I'm having my heads flat milled down 6cc. Changes in the block deck height, head deck, or gasket thickness will effect the intake manifold fitment. As you remove material in these places the heads sit lower and the intake manifold bolt holes in the heads get closer together, and the manifold no longer bolts on. It also opens up a gap on the front and rear flat spots where the manifold seals to the block.

I'm going to have my manifold milled to fit depending on what is required when I get the heads back. Milliing the heads is about $65 each and the manifold is about $80.

 

Ditto... especially if you are gonna run 91 octane

 

im goin from 8.5 to 9.5 but im running 110, and jackin the boost up! we shall see. i think 9.5 could be pushing it! your tune would have to be right on! id go 9.0, dont think the extra .5 would be worth the risk!

 

A lot of the vette guys run much higher CR. 9.5 up to 10 and 10.5-1 and make great power with little issues. They all have a meth kit so I guess 94 plus meth can get into the high 9 to low 10 to 1 range.

 

See this thread:

https://www.camaroz28.com/forums/sho...d.php?t=743139

 

8 or 8.5 should be your goal if you plan on running any decent amount of boost. As Rich said, more boost and less compression will always make more power.

It's no coincidence that the vast majority of OEM forced induction engines run around 8.5/1 compression and 8-12 psi reliably. With the turbo, you won't be limited to X amount of boost because of drive problems with the supercharger.