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A curious valve question

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A curious coincidence?

3 weeks ago, (due to a moving inlet valve), I completed a full top end re-build, high comp piston, SS inlet valves, hot cam, cam chain, gaskets etc.....

Whilst torquing the head down, one of the cylinder studs (hold the barrel down onto the crank case) snapped.

Oh-well, they're only cheap (£5 / $10) so I replaced all 4 with new studs.

Last week, whilst on a hare & hound, my bottom radiator hose cam off (probably my fault, not tightening the rad hose up properly).

This dumped all my water & cooked the engine. So back to the workshop. Luckily, only the piston rings looked scorched, so I changed them.

Whilst re-building the cylinder (for the second time in 2 weeks) I managed to snap another cylinder stud!!! And this time they are only 2 hours old!

[before you ask, there is nothing wrong with the torque wrench]

Now, was this just bad luck, or is there more to it than luck, because both of the studs that snapped were adjacent to the right inlet valve, the very same valve that is well known for deforming.

Is there a cooling problem in this area I ask myself?

Is it just a coincidence that the two snapped studs & a deformed valve are in the same location????

Is this a localised heat problem?

WR G

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That same thing almost happened to me, I almost snapped off or twisted one the studs as I torqued the nut when I did my top end rebuild, but I stopped before anything happened. What I think was happening as I torqued one of the rear nuts(I cant remember which rear one it was) the nut was not turning on the washer. I had used brake clean to clean the nuts and washers and installed the washers dry, and of course the head surface where the washer goes was clean and dry also. I think if I had put some oil or small amount of grease on the washer or bottom of the nut it would have turned smoothly or normally when it was being torqued, instead it bound up or stuck. When you broke the stud(s) where did it break at?

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Always oil studs,washers,nuts etc at assembly & make sure you tighten in a crisscross pattern to seat everything properly.

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Always oil studs,washers,nuts etc at assembly & make sure you tighten in a crisscross pattern to seat everything properly.

Believe it or not, torquing the nuts wet applies more force to the threads then dry using the same setting on the torque wrench. Less friction (lubed) makes it go tighter. Same torque, more force. Not saying this is the way to go on the head nuts, just saying....

It is always good to know if the torque values are wet or dry. Not sure on the CRF. And I generally torque in 3 steps to make sure one nut doesn't apply more force than another.

Check out this site if you are interested:

http://www.raskcycle.com/techtip/webdoc14.html

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Believe it or not, torquing the nuts wet applies more force to the threads then dry using the same setting on the torque wrench. Less friction (lubed) makes it go tighter. Same torque, more force.

The first statement is false. The second and third are true. The amount of torque you are applying IS the amount of force (measured in ft./lbs, in/lbs or newton meters) being applied to the threads. 10 foot/lbs dry is the same amount of force on the threads as 10 foot/lbs wet -it's still 10 foot/pounds. But reducing friction on the threads increases the amount of clamping force by reducing the amount of friction generated between the threads and by the twist the body of the bolt or stud is subjected to. Force goes straight down as clamping pressure rather than friction induced damage to the fasteners. I'm guessing these cylinder studs are ultra-low quality grade 2 or 3 (like the rest of Honda bolts) and MUST be lubricated to prevent damage. In fact, I believe Honda ALWAYS gives wet torque values.

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The first statement is false. The second and third are true. The amount of torque you are applying IS the amount of force (measured in ft./lbs, in/lbs or newton meters) being applied to the threads. 10 foot/lbs dry is the same amount of force on the threads as 10 foot/lbs wet -it's still 10 foot/pounds. But reducing friction on the threads increases the amount of clamping force by reducing the amount of friction generated between the threads and by the twist the body of the bolt or stud is subjected to. Force goes straight down as clamping pressure rather than friction induced damage to the fasteners. I'm guessing these cylinder studs are ultra-low quality grade 2 or 3 (like the rest of Honda bolts) and MUST be lubricated to prevent damage. In fact, I believe Honda ALWAYS gives wet torque values.
One is basically correct and here is why: Even though the torque wrench will click off at the same setting, the wet installed bolt will fail at a lower setting due to less friction.

Throwing friction into the mix causes the torque wrench to click at a different time then when lubed. This is why a wet installed bolt torqued to a giving setting will give up the ghost before a dry installed bolt. You actually were correct when you said, "But reducing friction on the threads increases the amount of clamping force". This is what I was trying to say.

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Well, I torqued them by the book, IE with a dab of grease on the nut's & washers.

Fact is, that bolts & studs snap, but my theory is that these snapped studs (both in the same location) could be related to the left inlet valve issue, and could be due to a localised poor cooling issue???

WR G

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That same thing almost happened to me, I almost snapped off or twisted one the studs as I torqued the nut when I did my top end rebuild, but I stopped before anything happened. What I think was happening as I torqued one of the rear nuts(I cant remember which rear one it was) the nut was not turning on the washer. I had used brake clean to clean the nuts and washers and installed the washers dry, and of course the head surface where the washer goes was clean and dry also. I think if I had put some oil or small amount of grease on the washer or bottom of the nut it would have turned smoothly or normally when it was being torqued, instead it bound up or stuck. When you broke the stud(s) where did it break at?

It would be interesting to know if it was the right rear??

WR G

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When I read your first post it sounded very similar to the same situation I experienced when torqueing down the cyl head on my bike, as I tightened one of the rear nuts it stuck tight and did not turn and had I kept going something would have probably snapped off, at the time I was more concerned that I would pull the threads out of the case on the bottom when it finally did turn, because of how tight it was stuck it would have required way too much force to make it turn.:thumbsup: Only other possibility I could think of is that maybe the nut was bottomed out on the top of the stud.

WR Geezer where did the studs break? Top, middle or bottom-not which stud position. I dont think the studs are going to be affected by heat.

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When I read your first post it sounded very similar to the same situation I experienced when torqueing down the cyl head on my bike, as I tightened one of the rear nuts it stuck tight and did not turn and had I kept going something would have probably snapped off, at the time I was more concerned that I would pull the threads out of the case on the bottom when it finally did turn, because of how tight it was stuck it would have required way too much force to make it turn.:thumbsup: Only other possibility I could think of is that maybe the nut was bottomed out on the top of the stud.

WR Geezer where did the studs break? Top, middle or bottom-not which stud position. I dont think the studs are going to be affected by heat.

The stud snapped approx 2 inch up from the crank case.

WR G.

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