Piston dome height

WOT !!!!!!
Don't get all Prima-Donna

0.3mm off a top of a DOME isnt the same as 0.3mm x 91mm gasket diameter

See I knew that ,,,,,,,,,,,,,,,,,,,,It's so precise this GTA tuning

I bet it'll still go bang whatever

0.3mm off the head gasket means the whole head is 0.3mm closer to the piston. The top of the piston isn't flat so you'd be taking 0.3mm off the diameter of the top of the dome, not the whole diameter of the piston.

0.3mm is such a tiny fraction that you'll lose that in a worn set of chains (inlet valve will close later as the chain stretches thereby lowering the dynamic compression ratio - yes I've been learnin'!)

And lowering the compression ratio is not a "good thing" per se. You want to keep the compression ratio as high as possible in order to keep off-boost performance reasonable, if nothing else.

I will come out of my box now and say that I built the TT DeLorean engine with Volvo gaskets and have had no trouble with knocking at 1.2 bar and inlet temps in excess of 80 degrees C.

Use them and don't worry about it. I would

Who rattled your chains

I's never runnnin off boost innit

0.3 isnt alot agreed, IF you had a brand new engine with no carbon build up on the heads or pistons ,brand new cams that had full original lift and lower dynamic ratio, and 100% original height un-machined heads....

But we ain't....

0.3mm off the head gasket means the whole head is 0.3mm closer to the piston. The top of the piston isn't flat so you'd be taking 0.3mm off the diameter of the top of the dome, not the whole diameter of the piston.

Im not talking about clearance issue, there are no clearance issues on the Z7U even if you skim mm's off the heads.... more the volume in CCs you would remove from the dome to make it the equivalent of losing 0.3mm x 91mm (by a thinner gasket) so you'd need to remove more that 0.3mm of the 'top' of the dome

I have measured the far end of the fart and where the smell goes to ............................ The carbon on the pistons was a good 0.25 in isolated areas .The carbon's off and the heads have been skimmed previous and will be again due to me being careless with a nail in the bench I'm just trying to put it back together in a better condition than it came out .

0.3mm off the head gasket means the whole head is 0.3mm closer to the piston. The top of the piston isn't flat so you'd be taking 0.3mm off the diameter of the top of the dome, not the whole diameter of the piston.

Im not talking about clearance issue, there are no clearance issues on the Z7U even if you skim mm's off the heads.... more the volume in CCs you would remove from the dome to make it the equivalent of losing 0.3mm x 91mm (by a thinner gasket) so you'd need to remove more that 0.3mm of the 'top' of the dome

WE KNOW

: The carbon on the pistons was a good 0.25 in isolated areas ..

Quite so.. so most GTA are running well over 9:1 on virgin heads...

WE KNOW

I know you do...

WE KNOW

I know you do...

I know you know I know ya know ,but it's a small victory so let me have it please

Im not talking about clearance issue, there are no clearance issues on the Z7U even if you skim mm's off the heads.... more the volume in CCs you would remove from the dome to make it the equivalent of losing 0.3mm x 91mm (by a thinner gasket) so you'd need to remove more that 0.3mm of the 'top' of the dome

That's what I said.......

Who rattled your chains

I's never runnnin off boost innit

Call it throttle response then

Having played with the TT DeLorean's map, adding in quite a bit of advance to the sub 100kpa ignition map gave it a much livelier off-the-line snap.

One day we'll get back on that car and finish it......

Im not talking about clearance issue, there are no clearance issues on the Z7U even if you skim mm's off the heads.... more the volume in CCs you would remove from the dome to make it the equivalent of losing 0.3mm x 91mm (by a thinner gasket) so you'd need to remove more that 0.3mm of the 'top' of the dome

That's what I said.......

You said 'The top of the piston isn't flat so you'd be taking 0.3mm off the diameter of the top of the dome'

You need to take roughly 1.5mm of the top of the dome to compensate (if possible)..

Okay, okay, so for once I'm the one being ambiguous I meant "...so you'd be taking 0.3mm off the diameter of the top of the dome, rather than across the entire diameter of the piston, which WOULD have the same effect as skimming the heads or using a thinner head gasket, cam timing and DCR notwithstanding"

Clear?