I'm looking at fitting some Comitec head gaskets when I plonk a 2.5 semi-closed shortblock, fitted with forged CP Pistons and Eagle Rods onto my Sti 8 heads, but I haven't got a clue as to which thickness of gasket to fit to maintain the correct compression ratio!

Don't ask me what compression I want to run as I haven't got a clue with that either!!

Am I correct in assuming that I should be aiming to retain the same standard ratio that my 2.0 Sti is running now? (is this 8:2:1?)

Praying for a quick simple answer as block is on its way


Thanks for any help

Dave.

 

Mine are 1.6mm

 

1.6

 

Must of beat me 30secs

 

Where these on the same engine as what I'm knocking together?


WOW, that was some quick answering from you lads

 

Mine were on a 2.5 bottom end with STI V5 2.0L heads.

 

Might they need to be different for my STi 8 heads then

 

I wouldn't imagine so. The STI 8 still ad the same bore size.

 

was told 1.6 for mine also

 

Have your heads been machined for the 2.5 bore? De-shrouded at all?

If so you head cc size will of increased and will lower you CR

 

Getting the CR right is critical to the future performance of your engine so do it properly first time.
To do this you need to know the combustion bowl capacity for your heads and as Frayz points out, this will vary if the heads have been machined in any way. You also need to confirm the deck height and what is the CP Piston bowl capacity? I assume it is O/E 2.5l bore. At that point the head gasket thickness can be calculated for your choosen C.R.

 

Thanks, 1.6mm ordered


Been unable to post reply due to SN technical issues........

 

bought the cometic ones myself and when the paperwork came, it said they were 1.5mm i think?

they are specced, just for fitting 2.5blocks to 2.0 heads