The following is for a 302.

here are some numbers that I got from a dyno program on the computer.

I inputed a given comp ration and recorded the chamber sze in cc's that was given. Can someone tell me if this is correct.

12:1 56.22 cc
11.5:1 58.90 cc
11:1 61.84 cc
10.5:1 65.09 cc
10:1 68.71 cc
9.5:1 72.75 cc
9:1 77.30 cc
8.5:1 82.45:1


If this is not correct, then can someone give me the comp ration that I would end up with, using origional pistons, with aftermarket heads of a popular chamber size.

64 cc chamber seems to be a popular size for 5.0 heads.

if this is right (aprox 10.5:1), will I be able to run a 10.5:1 302 on 91 octane gas???

 

Thats completely wrong unless you have domed pistons. 58cc's will give you 9.5:1 on average and 69cc's will give about 8:1. its about .13/.14 Comp ratio points per chamber CC. You do the math.

 

O.k. so the 64's are about 8.5:1. What is the stock comp ratio from a mid 80's 302?

Anybody ever run a set of 58cc chamber heads? any specific brand or type, and how do they work?

 

Also, do I have to change pistons, or anything else internal to use large valve heads? Just going by memory here, I think that a standard large intake velve is 2.02".

 

Standard valves Int. 1.78in
Exh. 1.45in

mid 70s truck heads had 58.2cc chambers giving a 9.3:1 cr on a newer engine.
casting no.s C9TE or D1TZ

 

c9te or d1tz from a mid 70's truck with a 302. This will give me a 9.3:1 ratioi. This is sounding good. What size of valves do they have?

 

1.78/1.46 are the size of all 302 valves accept the boss 302 which had cleveland heads.

 

Awsome. Not that the small valves are awsome, but now I know where to find a set of higher comp. heads at a low cost. A potring job and I should be set. Thanks.

By the way, what should I pay for a porting job, and new valves, springs, etc. from a machine shop?

 

too much, it will cost you as much as a new set of aftermarket heads, unless you do it yourself.

 

would it be worth a try to get a set from the wreckers and juts throw them on?