Compression

[nivvy]

I am currently running 906's with about 9.8 ot 1...I believe the 906's are 88cc
I am going to aluminum and want to get my compression up to about 11 to 1?
I dont need to change my pistons do I? or is the compression gonna come up to 11 to 1 because of the aluminum 78cc chamber?? Im sure gasket thickness matters as well...I dont know the formulas to figure this out

[moper]

http://kb-silvolite.com/calc.php?action=comp

It's fun to play with...

For piston dome ccs, you need to know the size (volume) of the valve releifs you have. This can be gotten from catalogs or websites.

I'd venture to gues your 906s are much larger than 88 ccs, unless they were CCd at one time and it's measured smaller. Most open chamber heads are in the 90-94cc range.

Also, most gasket bore sizes are for a .060 over 400 bore..which is 4.410"
And speaking of gaskets, you will want to figure what you need when running a composite gasket..most are .040-.045" compressed thickness.
  have fun...

[Chryco Psycho]

basically yes with the 10 cc smaller chamber the compression will jump approx 1 point of compression , gasket thickness will affect the exact result 

[nivvy]

I just read an article in one of my car mags and it says stroking a motor will raise the compression as well.....I think I read entirely to much and get confused all the time....

I think CHYRCO should start his own Mopar Tech Magazine.....

[Chryco Psycho]

yeah more than a few people have suggested me writing a book I was thinking about setting like a service manual using the same sections

[moper]

Changin nothing but adding stroke will raise it. But you change the pistons too..so that's out the window.

[Chryco Psycho]

once you stroke an engine everything changes & needs to be recalculated , the stroke increases & the rod lenght can go shorter , longer or stay the same & then the piston has to be adjusted to correct for shape & height to give specific quench & compression ratio 

[Aussie Challenger]

Goimg down a couple of cc's, 360 with approx .010" flat top piston down the bore, felpro head gasket and either a 302 or 308 head standard or just cleaned up give in the way of compression?? I am hoping to achive an end result of around 9.2:1.

 Dave   

[moper]

For that 360, you are close to 9.5:1 with .010 down in the hole flat tops, a .043 (fel pro) gasket, and a typical 74-75cc stock 308 chamber. Maybe higher with a good (meaning the small end of the factory 68-72cc spec) chamber.