T140 pushrod tubes

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Oct 28, 2014
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I realize this topic has been beaten to death but I have come up with a solution AT LAST.
I wanted to get a squeeze of .030 on the top oring and bottom square oring COMBINED.
Extremely difficult or impossible to do given the prior history of each motor. And that head gaskets are of different thickness. I like to use the composite head gasket which I have seen in 2 or 3 different thicknesses. Yes I know some people swear by the solid copper head gasket..use what you want.
I discovered in a previous attempt that it is actually possible to seal compression between the cylinders even though it is a razor thin area between left and right. I surfaced the head and cylinder to insure flatness. Then I removed the lifter blocks and machined off .060 from the flange where the square o ring sits.
Do a dry run fitting the head gasket, pushrod tube, top o ring.
Carefully measure with feeler gauges the gap between the tube and the lifter block.
The thinnest square o ring should measure about .125 - .129. It is possible that even after removing .060 from the lifter block the square o ring is still being compressed. It turned out that on the exhaust side I only needed to add .013 to achieve the .030 squeeze I was looking for. I had shims made up in three thicknesses so I could adjust accordingly. After reassembly and the usual several rounds of re-torquing the head bolts it was ridden for an hour on the freeway without leaking a drop from the tubes.
I consider this a repeatable method. It took work and a lot of calculating but I think this is the most accurate way. Anything else requires guesswork. The results are the best I've ever done with Triumph top ends.
 
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Jul 25, 2010
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One generally puts the head on with a used gasket , and no seals on the pushrods , to check gap .

Pushing the tubes up & down gets a few ideas going .

A straight edge between the fins , and a marker pen . Or masking tape on the tube & a ball point or sharp pencil
and you get a pretty accurate measurement .
 
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Oct 28, 2014
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The new head gasket was thicker than the old gasket, both composite. There are quite a few variables. I install the new top oring because that is the one I will be using. The o ring inside the pushrod tube I leave out while measuring just so the tube will go up and down with no interference. No gasket goop on the final assembly.
 
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