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Discussion Starter #1
Hi,
I had a bit of work done on the head of my 1968 Triumph Daytona due to a stuck intake valve. I put it all back together, adjusted the tappet clearances and went for about a 40 minute first ride. All went well, but when I checked everything over when I got back I found the intake clearances were now a lot slacker (though the exhaust side was still good). Is this sort of change normal or does it mean I have might have further problems to investigate?
 

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Hello,
Presumably the chage in valve clearance was measured when it had cooled down again? Depending on how much change we are talking about, any time the head has been off it takes a while for things to settle down. The usual reason for change is caused by the head gasket settling; did you do a first heat cycle and then re-torque it after it cooled down? Did you change the position of the push rods? If they have been moved from their original positions when the head was off it may take a while for them to settle into the cup of a different tappet block. Apart from adjusters coming loose which could increase the play, watch out for clearances decreasing which can be caused by the inlet valve settling in the seat a little, especially if the lapping of the valve seat with grinding paste was not perfect.
 
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Discussion Starter #3
Hello,
Presumably the chage in valve clearance was measured when it had cooled down again? Depending on how much change we are talking about, any time the head has been off it takes a while for things to settle down. The usual reason for change is caused by the head gasket settling; did you do a first heat cycle and then re-torque it after it cooled down? Did you change the position of the push rods? If they have been moved from their original positions when the head was off it may take a while for them to settle into the cup of a different tappet block. Apart from adjusters coming loose which could increase the play, watch out for clearances decreasing which can be caused by the inlet valve settling in the seat a little, especially if the lapping of the valve seat with grinding paste was not perfect.
Thanks Brian,
no, I didn't do any of the re-torquing procedure (I had no idea - still a bit new to this), will do that next. Good point about the push rods though as they both dislodged themselves when the valve stuck, so like you say they could still be settling into the cup. The adjusters aren't loose - I have made that mistake previously so am careful about that now ;-)
 

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Hi
How much was a "Lot slacker" when measured with a feeler gauge.
knowing the amount in thousandths of an inch might help to differentiate the difference between ‘settling down’ and ‘something amis’
regards
Peg.
 

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I'm puzzled by this thread.. The OP assembled, adjusted, went for a ride and when they got back "valve clearance" had opened up.

I hope someone will correct me if I'm confused, but aren't tappet clearance and "valve clearance" inversely proportional? (if adjusters are loosened all the way then the valves will never open, and conversely if adjusters are screwed down until there is negative lash then the valves might not ever close).

But assuming that by "valve clearance" the OP was actually referring to tappet clearance, then no. Not normal. Not unless perhaps tightening the head bolts was overlooked.

In my experience, which admittedly is limited to one T120R, tappet clearance has always closed up on first run after initial torquing of headbolts. Never saw it open up.

Do I need more coffee?
 

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Bruce,
Valve clearance and tappet clearance are effectively the same thing. Ignoring the mechanical advantage of the rocker arm, as you can't actually get to the tappets to measure any clearance there, the clearance in the valve train can only be measured at the valve stem in the usual way with feeler gauges (or a DTI onto the adjuster head if you are really keen).
 

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Bruce,
Valve clearance and tappet clearance are effectively the same thing. Ignoring the mechanical advantage of the rocker arm, as you can't actually get to the tappets to measure any clearance there, the clearance in the valve train can only be measured at the valve stem in the usual way with feeler gauges (or a DTI onto the adjuster head if you are really keen).
Brian - thanks for that - confirms that we're all talking about the same thing. The notion that it's normal for tappet clearance to increase after first post-torquing ride made me wonder.
So my response to the OP would be no, it's not normal.

I'm guessing that more settling down results from compression of the rocker box gaskets than the copper head gasket. But, compression of the either head gasket or rocker box gaskets results in less tappet clearance, not more.

As you suggested in your first post, a displaced pushrod could account for increased tappet clearance. But wouldn't that result in an inoperative valve and much more evidence of engine problems than the OP suggests?

You also pointed to another variable, i.e. head temperature. But doesn't tappet clearance decrease as temperature rises? So if the OP measured greater clearance on a hot engine then when it was cold, that would also be abnormal.

I'm still mystified by how the clearance could increase in a normal way. But life is full of little mysteries I guess.

Grove188, after you readjusted the clearances has the engine run ok and with everything seemingly normal?
 

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Discussion Starter #10
Hi Hermit47,
yes, Iike you say intuitively we would assume tappet clearance tends to decrease as temperature rises, hence my confusion. I found the intake tappet clearance decreased as the engine cooled down, but by the time the engine cooled down completely was still bigger than the clearance I originally set.

I have not yet gone for another ride as the weather has been bad - will post again whether the engine ran ok the second time once the weather improves.
 

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As you suggested in your first post, a displaced pushrod could account for increased tappet clearance. But wouldn't that result in an inoperative valve and much more evidence of engine problems than the OP suggests?
Hi Bruce,
To avoid any confusion, what I was saying was a swapped over pushrod, not displaced. Clearly, as you say, a displaced pushrod would not operate the valve. The 500s have pushrods with plain duralumin lower ends, not steel caps like the 650s. If a pushrod gets swapped over a slightly different wear pattern may exist which could cause the "wrong" pushrod to settle once it has re-seated itself in the cup on the end of the tappet. Hence the reason to mark pushrod positions when doing work on the engine.
 

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Brian - sorry man - if I'd read your original post more carefully it would have avoided the confusion. All makes sense to me now.
Depending on how great the clearance difference was, another possibility could be that the condition of the valve tip or rocker surface created an anomalous reading either during the initial adjustment or the subsequent check.

Best case would be the engine runs normally and all's good!
 

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I've seen it go both ways. Threaded jam nut adjusters can reset into the threads during initial run opening the clearance. Thick oil or debris/varnish can disperse opening the clearance. Over a longer period the valves can recede into the seats reducing clearance but I have also seen wear on the tappet mechanism open the clearances.
 

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Discussion Starter #14
In any case, the weather cleared and I went for a similar half hour ride today and all was well. Clearance only increased slightly in one intake valve so things seem to be settling down. Leaking oil from both rocker covers though - is this normal too? They were new gaskets.
 

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Leaks are not “normal” but they’re a common problem.

The mating surface of the cover can be trued with abrasive paper on a sheet of glass and sealant can be used.
 

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Yes, as TT says the mating surfaces must be clean, flat and smooth. Also, common leaks close to the same area are at the top of the pushrod tubes. Those leaks sometimes disguise themselves as rocker cover leaks, head gasket leaks and exhaust pipe leaks because the oil will flow all over along the fins. Clean the area up and take some pics too to help. Throwing some baby powder on the cleaned area sometimes helps to detect exactly where the leaks are. Careful not to overtighten rocker cover bolts. It is common to strip the threads of the covers.
 
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