head gasket thickness for SC use

exmantaa

OK, need some facts on this:

Might need a slightly thicker head gasket to lower the compression a bit on a SC-ed 2,2 ((2,2 + eagle rods + standard pistons)
Courtenay said somewhere that the 10:1 OEM compression might be a tad too high for the small pulley on premium gas => knock => spark retard => no power.
(Also in the 2.0 LSJ world they need some decent timing advance to make power: add meth/E85 => no knock => lots of timing => Lots of power!!)

So, how much thicker do I need to lower compression to say ₉.5+ :1?
Thickness of the OEM 2,2 gasket? Saab B207 gasket? Make a "hybrid layer"of 2 gaskets? What compression had the old sc's with decompression plate? (1mm + 2 gaskets??)

Or stay OEM , use good mapping and stay efficient... :think:

JohnnyN

Mine was the last 8.5:1 back in May 2008. S/S decompression plate sandwiched with 2 gaskets.

😉

exmantaa

That 8,5:1 was with a 1mm sandwich plate and 2 regular headgaskets?
To low. Thinking about making a 5 layer MLS gasket from 2 Saab B207's...

Need accurate thickness from different head gaskets...

vocky

I recommend the saab/z20net head gasket for sc use

exmantaa

Because off??

vocky

purely because the saab/z20net is a thicker head gasket than the z22se and z22yh :thumbup:

I think forced induction is safer with a lower compression dunno..

exmantaa

I posted that before I read your answer in the other thread.
Same thoughts here; think 10:1 on a forced Ecotec is a tad too much for the higher boost pressures/smaller pulleys. => To counter knock you then are retarding the power through the exhaust.
Maybe the Dr. knows...

ATOM_X

Z22yh gasket 0.37mm
Z22se gasket 0.49mm
Z20net gasket 0.98mm

1mm roughly equates to 1.00 CR on 86mm bore with 53cc of combustion chamber

Therefore If one were to replace standard SE gasket with NET/B207 gasket
then CR would drop 0.5 CR

original (SE) CR = 10.00:1
replacement (NET) CR = 9.50:1 approx

I do not recommend using two gasket together

exmantaa

Thank you for this usefull info!!

9,5:1 is my target compression, so a NET/B207 gasket will be perfect ! :thumbup:

cavaddict

Sooo...what you're saying is...if i skim 0.5mm off my Saab head, i should be using a B207 gasket then?
Hope so.....cos i've picked a couple up for £12 each!!

exmantaa

A couple for £12 each?? :wtf:

How did you manage that?? (I can use 2...)

vocky

cavaddict said:
Sooo...what you're saying is...if i skim 0.5mm off my Saab head, i should be using a B207 gasket then?
Hope so.....cos i've picked a couple up for £12 each!!

if you want to keep the standard CR then skim 0.5mm off the head and use a saab head gasket.

if you want to raise the CR then skim 0.5mm and use the z22yh gasket :thumbup:

if you want to lower the CR then use a saab gasket and don't skim the head

2-20

Thank you for the gaskets thickness ! :thumbup:
What about the Cometic's ones.
What do .027" (0.7 mm) and .040" (1mm) stand for ?? :eh: Is this before being compressed or are they really that thick ?

vocky

cometic are basically identical to the saab :thumbup:

the saab gasket is made of three layers

cavaddict

A couple for £12 each??

How did you manage that?? (I can use 2...)

Yeah found a site online selling off genuine parts cos they're old stock....cant see how a head gasket goes outta date though lol