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View Full Version : What cc pistons? (calculating compression)


charlie
11-20-2006, 06:09 PM
What cc piston dish do I need to get 8.9:1 compression with Romeo heads?

I'm assuming the Romeo heads are 42 cc chambers.

OR..... Some one can tell me how to calculate this my self!

Thanks
Charlie
Mark #2
11-20-2006, 07:27 PM
What cc piston dish do I need to get 8.9:1 compression with Romeo heads?

I'm assuming the Romeo heads are 42 cc chambers.

OR..... Some one can tell me how to calculate this my self!

Thanks
Charlie
http://www.csgnetwork.com/compcalc.html
charlie
11-20-2006, 07:38 PM
http://www.csgnetwork.com/compcalc.html


:rll: :rll: :rll: Oh the irony of it all.... Man that sight is exactly what I ask for... thank you. Now if I just knew the #'s to plug into it.

No worries. I'll let the machine shop figure it out tomorrow.

Thanks Mark


Charlie
BigBobsL
11-20-2006, 08:18 PM
:rll: :rll: :rll: Oh the irony of it all.... Man that sight is exactly what I ask for... thank you. Now if I just knew the #'s to plug into it.

No worries. I'll let the machine shop figure it out tomorrow.

Thanks Mark


Charlie


If you assume stock 42 cc for coumbustion chamber and use 0.042" thick x 3.65" diameter bore for stock head gasket), 3.572" bore (0.020" over), 4.165" stroke, and -.120" deck height, the stock (-18 cc) pistons will get you there. With 46 cc "Patriot ported head chamber, you will need -14 cc piston.
charlie
11-20-2006, 08:29 PM
Wow thanks BOB. The heads I'm thinking about getting is from JDM, along with the stage 3 cams.


Man I'm glad i joined this site.


Charlie
BigBobsL
11-22-2006, 05:41 PM
Wow thanks BOB. The heads I'm thinking about getting is from JDM, along with the stage 3 cams.


Man I'm glad i joined this site.


Charlie

Jim's heads will have a 46 cc chamber as well. If you buy aftermarket head gaskets, a few of them are only 0.030" thick and will slightly increase compression, but may not seal as well.
charlie
11-22-2006, 08:08 PM
Jim's heads will have a 46 cc chamber as well. If you buy aftermarket head gaskets, a few of them are only 0.030" thick and will slightly increase compression, but may not seal as well.

Why would they not seal? I was getting the fel-pro 1141 head gaskets.

Charlie
BigBobsL
11-24-2006, 01:35 AM
Why would they not seal? I was getting the fel-pro 1141 head gaskets.

Charlie

The FelPro's are one of the better aftermarket MLS head gaskets and will likely work OK. Ford increased the thickness to better address leaks oil and water leaks. Some people have better luck coating the gaskets with copper coat before installation; this is particularly helpful if heads or block are not machined to optimum finish.