we are building a 2.0l zvh and i need to know how much to dec the pistons by to get the desired 7.8.1 comp ratio
bore is 84.7 mm
head is 129mm thik
pistons are accralite blanks so machining is necessary

thanks for any help given

 

how thick is your head gasket going to be

 

No one can just tell you how much to take off it depends on lots of things its best to take it all to an engine builder who can measure things, for example the measurement might be different form centre of gudgin pin to top of crown than what someone else has used so they tell you to take 1mm off like they did and it could be miles out, better to be safe than sorry.

 

thats why i said what type of pistons they where

 

The pistons are just one example of what needs checking but you carry on.

 

i aint taking the piss mate just thought that some one might have done the same thing with same pistons and some wher around the same thikness head or i could just check the pistons against the oe ones as they need .5 taken off to get them where they need to be so thats one way ore i could mesure the fluid way the head chambers and work it out from that

 

Well i personally havnt used the accralite ones but i took 1mm off some others that where an unmachined crown to lower the comp and i run a bar of boost with that, but the only trouble im having is pinking due to the fueling as its still running the s2 mfi injection system soon to be changed to cossie managment, what you going to be running ?

 

what pistons didi u use coswurv?

 

I really cant remember i think they where mahle .5 oversize, They arnt forged so they wernt as strong as the accralite ones but they've lasted for years just skimmed a mm off and fitted them, it depends on what you want out the engine power wise i settled for a bar of boost and it goes well alot more low down torque but then i spose thats down to it being a 2ltr, im having it dyno'd when the managment has been changed and ill post what she done if its still in one piece !!

 

its cos l6 mate so fueling aint a problem

 

Yeah thats what im going for, just on standard cossie yellows at the mo and see what the dyno guy's reccomend.