What is my compression ratio? I have an l33 5.3 aluminum engine with factory flat top pistons. The heads are texas speed tage 2.5 (243 casting) heads that have a 65cc cc, and a .060" cometic head gasket. Can someone tell me the correct compression ratio?

 

I get 9.4:1. Why such a thick head gasket ? Whats the bore size of the gasket ?

 

Well if that is the truth, i need to call and cancel the gasket. Texas speed figured up 9.7:1. My goal is 9.5:1 compression. I am going to be running 10-15 lbs of boost one e85. I am not sure on the bore size. I just called into texas speed and ordered those heads and cometic gaskets. I told me my target compression ratio. I was just questioning it because i had called them once before and they told me a different compression ratio with the same heads.

 

Are you going to drive this on the street ? If so I would keep the compression around the 10:1 mark. 15#'s on e-85 will be just fine on 10:1 compression.

I used 3.90 bore on your gaskets when doing the compression ratio calculator so if that value is bigger it will drop the # some. If Texas speed told you 9.7:1 that's going to be very close.

 

Yes it is a street strip build. I'll keep it there then. So if you came up with 9.4:1 then who is right?

 

It was 9.47:1 so 9.5:1 is what I got, .2 isn't going to make or brake any thing. Again I guessed at the gasket bore because I cant find the .060 thick gasket on tsp web sight, it might be smaller than the 3.90" bore I used in the calculator.

You might want to drop it down to a cometic .040 gasket or a GM MLS .051 gasket.

 

http://www.csgnetwork.com/compcalc.html

3.622 Stroke
3.77 Bore
.060 gasket thickness
65cc Heads
0 for flat top pistons
.008 piston out of hole

 

Ok so texas speed was off a bit then .

 

The factory 4.8/5.3 bore size is 3.78

And you have to enter -.008 if the piston is above the deck surface.

I get about 9.8:1 to 9.7:1 with a .060 gasket.

 

9.88 is what I get with my calculator - .030" bore gasket will lower it .1 point usually. Pistons on stock motors are generally .006" out of the hole, not .008".

 

Do you guys think .060 gasket will be a problem?

 

The .060 gaskets are fine to use , you could also go with a GM MLS gasket @ .051 thick and save a few bucks VS cometics. Either way you should be just fine to feed that thing 10-15 psi with e-85 and a good tune.

 

Thanks guys