compression for a 1.4 with 1.3 head

[LUV2XLR8]

just wondering if anyone else with a 1.4 with a 1.3 head could tell me what compression their engine is showing?
im ihn two minds of doing the head again or selling it :(

[mikey14sr]

The 1.3 head on mine has been skimmed a couple or three times, never worked out the C/R, but on a bad day it shows 175psi.

[LUV2XLR8]

i see, would 200 psi be too much?

[mikey14sr]

Think it might be,lol.

[LUV2XLR8]

how would i go about lowering compression? i have a vernia, would timeing help? or thicker gaskets?

[Stuart]

you could retard the cam a bit so that the intake valve closes later, but you then run into other issues like the exhaust opening too soon.

imho 200psi is "fine" since dans freak engine does way more than that iirc.

[Welsh Dan]

My 1.2 reads around 200psi, but the average compression tester wont be completely accurate anyway, stuarts compression calculator will be much more accurate.

[Stuart]

yea but my calc is only for static compression (no you cant just take the test result and divide by atmospheric pressure as its not that simple lol)

[Welsh Dan]

True, but considering that most petrol engines have an 8-12 (ish) compression ratio, and the fact that you'll never get a completely full cylinder on an NA engine unless you crank it over by hand, and that the atmosphere is 14psi give or take, then a full cylinder compressed at 12:1 is only 170psi.

I'm not saying that LUV2XLR8's results are wrong, but I know mine are, and therefore that compression testers dont always tell the truth :).

[Stuart]

the thing with comrpession testers is that you want the same (ish) numbers all the way across and you can tell if theya re very low.... thats all that matters really.

[LUV2XLR8]

so what psi should i be looking for? about 170- 185psi ?

[craig green]

That would show a reasonable healthy set of rings tbh, not much else.

Sameish results on all 4 would indicate the bores are OK. As for the compression ratio of the cylinders, it doesnt help at all.