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The block casting no. is 10066036, which is Goodwrench crate motor with two-piece rear seal made in Mexico. The date code is 25th week of 1995. Its a four-bolt, the heads are casting no. 3932441, 76cc chambers with 1.94 int and 1.50 exh valves. Casting date 1970. The motor has an Edelbrock Performer RPM on it, Summit camshaft installed. But the prev. owner only remebers it is a dual-pattern with about .530" lift and .050 duration in the 230's. Heres the Question change to 58cc or 64 cc heads to get the compresson up ?and about what will either get it up to? I would like to run mid grade or premium at the most.Also if it were you would change the cam ? The new/rebuilt heads are casting 416 or434 with 2.02/1.60 ss valves
 

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Carl,

Without knowing more details on the engine these numbers are a estimate. Going from 76cc to 58cc can increase compression 1.5 to 2 points higher. Your engine is around 8:1 so going to 58cc could raise it to 10:1

If those cam specs are true, the cam is too big for the compression ratio you have now.

Here is a link so you can see how different cc heads effect comp ratio
http://www.wiseco.com/Catalogs/Automotive/Chevrolet.pdf
 

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354434.....75-79...262/267/305...60cc chambers

14014416...80-86...305..........1.84"/1.5" valves, 58cc chambers

these heads are tiny, the 416s are tiny and a lightweight casting prone to cracking.

keep the heads, change the cam.
 
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