txhokie4life

I have a 84 944 with 9.5:1 pistons.

According to the rules it looks like I can take 1.38mm off an otherwise original head.
I have 9.5:1 pistons.

"0.891in (22.62mm) for 9.5:1 pistons and 0.927in (23.54mm) for 10.2:1 pistons as measured in factory specified location and assume use of a stock 1.1 mm (.043in) head gasket. Factory repair 1.4mm (0.055in) head gaskets may also be used and their extra thickness must be taken into account if a head is inspected after being removed from the engine. For reference the factory specified head thickness is 24.0mm +/- 0.1 (.945 in +/- .004)."

Shaving the heads will change the camshaft timing?

Is this compensated for?

It also mentioned using the 2mm offset camshaft key. Is this cumulative?

thanks,

Mike

V2Rocket

Hopefully M758 can come chime in about the cam key.
My understanding is they limit the cutting of the head to cap static CR at 10.5:1 or thereabouts to put everyone on a level playing field. No more "88 motors are better than 83-87".

If you can use the offset key you want to ADVANCE the 944 cam as much as you can.
Truly amazing what that does to driving feel.

Dave951

The amount of timing difference that will be a result of the material reduction from the head will be extremely minor.

Van

At the RPM ranges I see on the track, advancing the cam actually hurts.

This chart is a throttle and RPM histogram. I'm under 4,400 RPM for only 8.5% of a lap. And 56% of a lap is at WOT.

V2Rocket

Van,
Advancing the cam makes more power from 5000-6000 than straight up.
I admit I have not tried dynoing with retarded cam but Joshua said the gains were very minor.

944 stock cam is "all done" before 6000rpm anyways, but I guess a flat HP line at high RPM still gets you accelerating.