Triumphrat

RetroRod

Hi all,

Never was any good at IQ tests that included engineering type tests so I really need to pick someone's brain on this.

Rebuilt my '72 650 engine with .020, 9:1 pistons. The head was shaved .004". I do not know the previous history on the head, viz, whether a previous owner had the head shaved also.

Achieved .060" sqeeze on the PRTs using the the smallest thickness neoprene seal, and a standard .040" copper gasket.

I am really wondering whether any of these changes from standard are likely to alter the piston:valve clearance. I am guessing it would not make any appreciable difference, but like I said, I'm a dunce when trying to work these things out. RR

Caulky

The standard copper head gaskets are .048".
It is very unlikely that your pistons and valves will touch.
See:
http://www.triumphrat.net/classic-vi...-kickover.html
(page 10)
The plasticine in the piston recess confirmed I had 1/8" or so clearance, but I had fitted a .070" `extra thick` gasket. (There`s reasons for using this gasket, 9.5:1 pistons, etc).
This was a rather extreme situation, I think.
Refurbished head with new valves and seats, new barrels and pistons and no idea how much had been skimmed off.

Plewsy

Hi RetroRod I run 11.1's on my Bonnie and have had the head skimmed, and had no contact problems If you are worried and want to check use Caulky's idea and stick some plasticine on the pistons.

RetroRod

Hi guys,

It occurred to my non-mechanical brain last night, that this is most probably more of an issue where vavle timing and lift are changed.

I am a worry wart for sure, but we all know these Triumphs have a capacity to let us have it in the neck if we drop our guard. Thanks again. RR