Ok, I am all mixed up trying to figure out my compression ratio...

I have a 5.3L block and HO 5.3L pistons....

I can't find the CR for the HO 5.3L engines so I'm stuck here....


Then once I figure that out I need to see if I can calculate the CR with my GTP heads on without knowing what the CCs of the heads is.

I do know that on a stock compression LS1 motor these heads would bring me to 11.4:1 CR. The heads have been milled (not sure how much) and the chambers welded up to simulate 5.3L heads..


So my questions are these:

#1 What is the CR of a stock HO 5.3L motor?
#2 What would my CR be with these GTP S2+ heads on it?



Misc. info that might help.
Stock LS1 CR is 10.1:1.. Stock LS1 heads are 66cc.

Stock 5.3L heads are 61cc

 

Im pretty sure the 5.3HO is 9.95:1 and its identified as the LH6.

 

Ok, I was thinking it was 10:1 or close to it..

So then my question is this.

If I say started with 10:1 on this motor, with it's smaller bore than the 5.7L, would my CR increase or stay the same with these heads?

 

Ok, getting closer..

For every 1. in CC you change CR by .1 so the difference in stock 5.3L heads and stock 5.7L heads is 5cc. This will make for a diff. of .5CR

So could I assume that if my motor is 10:1 just like the 5.7L then by putting these heads on the truck I would be at about 11:1 if the 5.7L motor is 11.4 or 11.5:1 with these heads??

Someone give me and Advil please?

 

Not that we don't have the knowledge here, but have you checked with the freaks in the Engine Internals section? Those guys live and breath this stuff, and would probably love to sink their mental-motor-teeth into this question....

 

I thought about asking there. I just like to post in here to so we can all learn from the question

I'll make a post in the internal section and post any results in here as well. Thanks Naked

 

You have no idea what the dome size is on your new heads? Really need to know that to accurately figure your CR.

 

No, I have tried to get GTP to email me another spec sheet on the heads the last time they were in there but they never come through with it. I got a fax copy once but expected to get a copy with the heads but never got it.

 

Its gonna be hard to tell teh CR then IMO. Head CC's contribute big time. Not sure what to say man.

 

a birdy told me that 1cc roughly = .1 compression point as you stated., unfortunetly he was not a real drag racer