How much can I raise compression by shaving/thin HG? (4agze)

[~SlideWays~]

Im looking at options for my new engine build, it is a bigport 4agze. I am looking into getting a smallport head and either using 8.9 comp pistons or re-using the 8:0's I have.

My question is can I get close to 8.9:1 comp by shaving/machining the head and/or a thinner headgasket (when still using 8:1 pistons). ie can I shave enough off the head without causing problems with valves etc.

Also if I use a redtop block and my 8:1 pistons, will there be a problem with the oil squirters?


Cheers

[IH8TEC]

the 8:1 pistons will not clear the oil squirters whichever block you use. if you wanna use those pistons you'll have to get grooves cut out of the piston skirt to clear. it's a hassle and time consuming job, but worthwhile.

probably be cheaper just to get the 8.9 pistons

[~SlideWays~]

Yeah I think I'll get a set from revhead. Hopefully this engine doesn't fall through like the last one I wanted!

[~SlideWays~]

New question:

Assuming I use a redtop small port head and 8.9:1 forged pistons plus bluetop cams; can someone tell me what compression ratio I would have if the head has been machined?

Problem is that the guy doesn't know how much has been shaved off the head so I am worried that the compression will be too high and I might need to use a thick gasket ie 2 trd metal ones, as suggested by Revhead, which would give a 1.6mm HG.

Can anyone give me some possible figures depending on the upper and lower limits of how much could have been machined off the head?

Probably an improssible ask due to the variables!

[4age_rage]

A while ago i came across a calculator sort of thing that calculates compression ratio and a couple of other things using different variables, I'll see if i can find it