Compression with 302 heads??

[dodgefreak8]

I am building an 86 318 with 302 heads and I was wondering what my compression would be with the 302 heads and the keith black 167 pistons if I didn't zero deck my block??? also what octane should I run with this combo?? thanks

 

[BJR Racing]

What are the head cc's going to end up at? We have to know this before we can give you a answer.

 

[dodgefreak8]

I'm not really sure my book lists them at 56-65 cc's but that's a BIG area. I guess without that exact piece of info I won't know will I. I'm not going to mill them unless I have to in order to get a good flat surface.

 

[AdamR]

Bobby, what do stock 302s CC at ?

I think the 167s are close to zero deck and the 302s are around 62 to 64ccs so with a .039" gasket you will be around 9.5:1

 

[dodgefreak8]

that's what I was looking for! That high of a compression ratio will probably demand 91 octane fuel won't it?? I'm trying to stay somewhat street-able but have a good running engine for my daily driver as well. thanks for the answers

 

[AdamR]

Octane requirement will depend on a number of things, Altitude, Cam timing, trans and gearing.

The 302s have a closed chamber which is more efficiant and wont be as prone to detonation. You may very well be ok on 89oct.

 

[BJR Racing]

Adam,
Your right they are 62-64 cc's from the factory, I just thought that they had been milled and thats why I asked what they were.

 

[AdamR]

Im guessing Moper milled mine down to 58cc, he said he thinks it was a .060" cut.

 

[C130 Chief]

A good chamber finish helps with detonation resistance a lot. Polish the cast surface with something like a brown scotchbrite disk, knock off all sharp edges, and keep the quench height down to .035 to .040. Run the coldest plugs you can and you should be fine.

Polish the chambers, and do any porting BEFORE you have the final cut on the seats for obvious reasons.