Engine compression

[rota_nation]

hey i just did a reading on my engine compression and i was wondering how to read the compression numbers and put them into proper readings like 8:1 etc. the readings i got from my 4cylinders from the front of my 5k 2 the bak were.. 150, 150, 150, 140, it was in lb/in2 im sure. and i want to kno the compression reading so i kno if its low enough to put my supercharger on or change the head cos i am going to put bigger valves in my engine head but wana chek compresion it incase i need to change the head to lower the compression.

cheers

[vegie]

i've wondered if you can do this too. i guess you need to know the bore/stroke and piston dish/dome as well as the head cc's to work out the static compression...which means pulling it down anyway.

you could alway look at other k series engine to see if the have different chambers around the valves i.e. larger or smaller. i know l series nissan 16/18/20 heads do. or space the head to decompress it with adjustable cam gear to compensate.

[SYKOV6]

get a workshop manual, it will have what comp ratio your engine will be. most stock engines are around 8.5-9.25 ratio just enough to get some alright throttle responce but not enough to make any real power. with a forced induction engine it all depends how much boost u intend to run 7-8 to 1 prolly good for most applications up to 12lbs boost the less comp the more gutless it is off boost. the more comp the better it is off boost but will suffer from detonation at higher settings. RT can prolly explain it much better than me as he has lots of experiance in these areas