Guys - please cofirm for me what is being said here.
Are you saying that you have gained 300 kw from a set of cams that are only marginly bigger ?
With everything else being the same ?
Is this correct or have I missed something ?
with the head gasket - I am referring to graphite gaskets. So when u meausre it on the bench, it will definately be less when compressed. A laminated steel one should theoretically be what it is advertised at. So like u said a 1.2mm should be 1.2mm when compressed. But never take it for granted, it is easy to measure with a small piece of malleable lead or similar.
sorry I was working on acl rb30et piston
which has -4.5cc dome, 0 deck height , a compressed gasket usually works out at 1mm compressed, 88.8 mm gasket bore size ( the last few Ive had measured this )
and the more oversize you go the higher comp ratio you end up with as your swept volume increases.
So with the ACL RB30ET piston with a R33 RB25 head you end up with close enough to 8.0:1 comp - plus or minus as every engine differes a little, depending on actual comb chamber volumes, compressed head gaskets ( depending on brand etc )
Its a very precise calculation.
with a 1mm gasket, 62 cc combustion chamber ( that would be a non reco'd head ) 87mm bore ( 40 thou over ) - it works out to 8.0:1 ( rounded )
as mine has a 57cc comb chamber it worked out at 8.5 with the above specs
The ACL piston is a 8.5:1 not like the OEM piston in the RB30ET - so they actually work ok with the RB25 head. As they come in around ( cant remember exactly ) 8.0:1, and with a slight surface you can bumo it up a little. As Im using the R34 GTT head mine came in at 8.4:1 as they have a smaller combustion chamber than the R33 head.
Ive used Performance springs in the RB25 VCT head, they are a direct fit - you can not use Rb26 springs in the VCT head for the reasons you have already mentioned. From memory the R32 RB25DE head ( non VCT ) has the same springs ( or can use ) RB26 springs.
RB26 head with valves, springs, retainers, lifters, shims, std cams, tappet covers, centre cover and cam gear covers. ( what you read is what you get, nothing else )
$1100 plus freight