Main Motorcycle: Triton 650
Join Date: Nov 2012
Location: Isle of Wight, UK
T120 8-stud cylinder head flange depth
Been using my 8-stud (~1960 ish) T120 cylinder head for 32 years.
I've had it skimmed twice in that time, and it was probably skimmed once or more in the 20 years before I got it.
The result of this is that there is almost no flange remaining, in places the gasket face almost blends into the bottom of the lowest fin.
When running it over the last 5 years with 8.5 pistons 40 thou oversize, on the best (crap) modern petrol, though it went like a rocket, it was very "on edge" and fussy with plugs/carbs etc.
Compression gauge readings typically 185+psi.
Very rough calculations suggest that skimming 1mm would raise CR by approx 1/1, another 1mm by another 1/1 (not quite so much in fact, just roughly)
I wish to "soften" it somewhat, by using a thicker head gasket to replace some of the skimmed head flange.
As a starting point to judge how thick a gasket to use, I would like to know deep the head flange was to begin with.
Any of you who have an 8-stud (or even early 9-stud may help)head, could you give me an idea of the depth of the flange relative to the bottom fin, or from the rockerbox surface? Would be much appreciated.
Anyone with experience of thicker head gaskets, or even the merits of stacking gaskets together?
From the amount of squash I have on the pushrod tube rubbers, I reckon my head flange has lost 1-2 or more mm.
Many thanks Dave