1stgenboy

Just curious, what does putting the 20R head raise the compresson ratio to?

kyle_22r

i think the ratio will bump to about 9.4:1. don't quote me on that though

1stgenboy

Thanx for the response. I was hoping for more than that....Does anybody know if you can use pre '85 donut top pistons with the later lazer block and a 20R head?

kyle_22r

they won't work too well with the lazer block -- it's 3mm higher than the '81-84 block so they lower part of the pistons won't go all the way to the top.

talk to the guys at LC engineering. i know they can mill 20R heads and do some necessary reworking of an oil passage so you can run the head on a lazer block with flat top pistons -- i think that bumps the compression to over 10:1

Phssthpok

I dunno if this will help or not, but this is the most complete listing of 'specs' regarding the 20/22r that I have found (so far.. I'm still searching).

While it doesn't give the specification of the chamber volume for the head, there is a formula about 2/3 down the page that spells out how to work out the EXACT CR you will have with any given set of specifications.

1stgenboy

Thanx for the info. I also found a site that states that your compression test #'s should be 17-20 times your compression ratio. This allows for an estimation on CR cause if your compression averages 200psi then that would equal ~10:1 CR. Now if only my bro did not steal my compression tester...doh!