357 c.i.
stock replacement flat top piston w/4 valve reliefs
72 cc 202 heads
steel shim gasket

How can I figure my C.R. with this info or can I?

 

Yes. You will need to look at manufacturers data for heads and pistions. Here are links to online calculator with data you need for equation.
http://www.csgnetwork.com/compcalc.html
http://www.greatplainsas.com/icompratio.html

Only true way is to measure all the parts you plan on putting together. Advertised volumes for relief pistons and heads will vary compared to actual. Difference may be negligable though - maybe somebody else can chime in.

Stock 350 bore is 4 inches. Was your block bored to get 357 cubic inches? How much overbore? You will need to enter this larger bore diameter.

Any reason for going with steel shim? Composite gaskets fit better to slight deck uneveness with block and heads. You also need to determine quench area. Ideal is 0.04 inches. I believe composite gasket helps here too as you can get different thickness gaskets for ideal quench. Links below on quench and compression.

https://www.thirdgen.org/forums/tech...45-quench.html
https://www.thirdgen.org/forums/tech...-question.html

Keep us updated.

Btw - nice car color combination. One of my favorites. Why didn't chevy make it for the thirdgens...

 

you will need to find out how far below the deck the pistons sit and the valve relief volume but i wouldnt count on anything more than 9.0:1 with those heads and say 7-12CC pistons and

 

Thanks,my wife actually picked the color combo,and I like it alot.

I bought the motor the way it is.He said the steel shim was to raise the C.R.

I am currently looking to replace my torque converter and C.R. is about the only thing I'm not sure of.

I was told it should be approx. 9.5:1,just wanted to check it.

Thanks
Mike T

 

okay say you have a 72cc head
12cc piston dish
a .015 x4.100 gasket
4.04 bore

to even run that engine i would bet the pistons are sitting at least .035+ in the hole

but say they are only .026 below the deck pretty risky but just for illustration 8.8:1
now the .036 comes out to be 8.7:1

 

flat top, 4VR pistons are never more than 7cc, and can be as low as 4cc, so you're probably over 9.2:1.

 

Thanks for the help guys.
The guy I bought it from said it should be around 9.5:1.

I don't know how far down the pistons are and won't till I'm ready to replace the heads.

Using the calculator blackdog sent me it comes out to 10.69:1

4.04 bore
3.5 stroke
72cc head
7cc piston?
.015x4.1 gasket
.036 in the hole?

 

stroke is 3.48

and your right attilla most of the 4 valve relief flat tops add 6cc or less

how ever every stock replacement with 4 valve reliefs also only have a compression distance of 1.540 instead of 1.560/1.565 so six of one half dozen of the other

adding the "extra" .020 to the distance below deck brings you back to 8.8:1 with 6cc valve reliefs

 

Thanks

This is why I asked becuse even with the calculator I was way off.

So my new heads should be 64cc to bump up my compression correct?

Then I will figure out what converter I need.

What would CR be with the 64cc heads if nothing else changes?

 

This is NOT true. I handle a half dozen sets of these every week, and I do have to check some sets, but the Silv-O-Lites and the SpeedPros are all 1.560", even their cheapest "claimer" versions. So these are what I push, and I imagine most other reputable shops do the same.

 

If your pistons aren't too far in the hole, and you can get your piston-to-head to around .040", where it should be, you should then be around 10.3:1. That's fine with aluminum heads.

 

yeah so silv-o-lite really all at 1.56+ your sure...
http://www.summitracing.com/parts/UEM-1436-030/
so that is a miss print?
http://www.summitracing.com/parts/UEM-1436-STD/

i could continue STOCK REPLACEMENT mean CAST not HYPER which mean 1.540 COMP HEIGHT

oh and speedpro
http://www.summitracing.com/parts/STL-345NP80/
http://www.summitracing.com/parts/STL-345NP/
http://www.summitracing.com/parts/STL-345NP60/

all 1.540 stock replacement cast 4 valve reliefs and 1.540 comp height

stop trying to use your job to prove your right because you "handle half a dozen sets of these every week" doesn't mean you have a clue about what your saying

 

Typo's are common. My own measurements are all I care about. And on every single set of Silv-O-Lite hypers, including their "claimer" s, and every single set of H345NCPs, I've found at least 1.559". You want to argue and become famous and respected, this guy just wants info he can use, you dumb armchair warrior, hiding behind your keyboard. Go away. To the OP: Here's the info you can use: Pull the head, and measure how far down your pistons are at TDC. Then we can go from there.

 

Engine was built by a reputable local shop.

I bought it from the guy who bought it from the guy who had the short block re-built so I apparently do not have all the info I need to figure this out.

I won't be pulling the heads till the season is over.

At least now I now I can go with the 64cc and still be around 10:1,I don't want to go higher than 11:1.

And the converter will have to wait till I figure this out.

Thanks again

 

apparently reading comprehension is a problem...

STOCK REPLACEMENT IS CAST NOT HYPER!!!