Okay i just bought a stroker kit last week that have JE pistons that are -5cc flat tops and yeild 10.8:1 CR with 64cc heads. I found some heads and they are 54cc. How much would that bump up the compression? Would it be around 12.1:1 and what is the highest CR you could run considering 91-pump gas and daily driving? I appreciate any info to see where i would stand....

 

what cam? block decked? what gaskets (if you know)?

You did right by getting -5cc pistons IMO.

 

http://car.race-cars.net/calculators...alculator.html

 

if it's a 383 and you have 10.8:1 with 64cc chambers then
54cc would give 12.2 : 1

91 octane and that static compression ratio? Has anyone been able to tune a heavy street car for that?

Karl

 

does scr even matter without knowing dcr?

 

Uh, yeah. Maybe you have it backwards?

 

backwards? I don't think so, but I'm no engine builder. Why don't you show us otherwise?

 

The way I've done it you need SCR to find DCR, not the other way around. I think the DCR is a more accurate description of what is actually going on inside the cylinder, but both should be used to build an engine.

Isn't the SCR more important on boosted applications?

 

Me too, and for me, I adjusted the piston volume get the scr to dcr resultant I want. Depending on a few factors, one shouldn't be too concerned if a scr result of 12.4:1 comes up as long as the dcr value is within a pump gas limit (i.e. no greater than ~8.7:1 for our crappy 91 octane fuel). Like I said, I'm no expert and use the calculators for what they are worth, but also consult guys who build engines to make sure what I'm ordering is correct for my application.

 

I think I read that, when building an engine, you should get a cam spec'd for your needs and maybe heads, and then build the shortblock around that. I may be getting that backwards.

 

I read that too...we're saying the same thing

 

that one is not accurate..it doesnt take into account the deck height...mine was off .4 use this one its a little more accurate.



http://www.rbracing-rsr.com/compstaticcalc.html

 

well..assuming you get your block milled .010 and you use felpro 1074's for headgaskets...your compression ratio would be 12.15:1 with the 54cc heads...a little too high for pump gas... even if you leave stock deck height...(.020) it would be 11.98:1..your better off with 64cc heads

 

As far as camshaft i have the CCA-08-470-8 and head gasket i have FEL-9966PT. The heads are actually 56cc and it still standard deck height. And yes its a 383 kit with 6" rods and piston height 1.125.

Would 12.2:1 be ok CR for a street car? I thought with aluminum heads it kinda like knocking off a point compared to cast stell heads.

Im looking for 400+RWHP so hopefully i would be able to make the numbers with my setup

 

with the right heads/cam you can make well over that..I still think 12.2 is a little too high for the street..unless you plan on running 100 octane