[TR] Compression Ratio

diggle at clear.net.nz diggle at clear.net.nz
Wed Jul 18 02:10:45 MDT 2012


Its been a long while but I am slowly getting back into
getting my TR4 back on the road.
The engine has been recond, everything that might have been
worn was replaced, including the bearings that were in
excellent condition.
After all I thought that if I was going to all that expense
why save a few dollars.

My head needed rewelding between 2 and 3 cylinders and thus
was skimmed.
Prior to the recond it pinked if I ran anything less than 98
octane.
I have calculated the comp ratio using a burette.
My volumes are:
54.8 - 56ml in each cylinder.
Stroke 92mm
I assumed head gasket thickness 50thou
piston tops in line with the deck
Standard gasket diameter 88mm
87mm pistons
Gives me a ratio of 9.6. which I am very happy with.
Which I would not have thought would cause pinking with
96octane.
My engine reconditioner (a friend) says that it more likely
because of a tired dizzy, ie weak springs.

Jim and the stationary 1962 TR4


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