Tappet adjustment query

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spegru
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Tappet adjustment query

Post by spegru » Mon Sep 09, 2019 9:47 pm

well it turned out that my dial guage, or rather its very simple stand would not allow be to attach it anywhere useful - so I bought another one of ebay that has a multi position arm. It has a magnetic base and I attached it in various places on the side of the cylinder heads and exhaust manifold. Th pic shows just one of many of these positions.
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The arm is the red thing, the magnet base is the black box and the dial guage is the dial wit the probe (which works sideways rather than in and out as some do).
So i've been able to fine tune the rocker clearances i using actual rocker movement so that it takes out any non flatness in the wearing surfaces. I moved the arms by hand while reading the dial movement. I was surprised to be able to measure changes resulting from adjustments that were no more than about one flat on the adjuster
Actually I took one of the rockers right off to examine it. There is certainly some wear but hard to say whether it's excessive (more pics) - but on some rockers I could feel movement in the clearance with a little bit of sideways movement of the rocker
2019-09-05 18.43.43.jpg
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2019-09-05 18.43.35.jpg
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2019-09-05 17.25.14.jpg
2019-09-05 17.25.14.jpg (83.1 KiB) Viewed 340 times
Anyway I am pleased to say that by doing it this way my tappet noise is GONE! A bit of a fiddle but perhaps not that more difficult than a feeler guage.

Regards
S


PS. I'm just slightly concerned about variations in the reading coming from unevenness on the top surface of the rocker whether guage was touching - that could distort the reading considering the possibility of sideways rocker movement. However I could definitely feel the movement with my fingers so I hope I measured it righ



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Tappet adjustment query

Post by Coupe Racing » Tue Sep 10, 2019 4:28 am

Im no engineer but i take it you now have an even side to side measurement but what is the clearance between the valve and the rocker arm?
Must admit i did read this very quickly so be gentle :D


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Tappet adjustment query

Post by b.c.flat hat » Tue Sep 10, 2019 7:59 am

If the round tip of the moving DTIs arm is centred above the valve stem, then this is very well liked by an ex-steam loco and airframe fitter.



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Tappet adjustment query

Post by scimjim » Tue Sep 10, 2019 8:10 am

The wear on those rockers looks fine - they end up with a definite hollow with ridged edges when they’re worn.

What gaps did you set in the end?


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spegru
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Tappet adjustment query

Post by spegru » Tue Sep 10, 2019 9:29 am

Sideways movement can cause a big change in the reading (say 0.3mm) caused I think by the the uneven top surface plus the fact that the rockers can also rock sideways a bit - which not only alters the reading if the guage is not centred but i think also changes due to the way the rocker sits on the push rod. If I've got it right then it's because of a manual 'feel' judgement as to where the bottom and top of the normal clearance actually are.
I was aware that I needed the tip over the guage to be over the top of the valve stem (in order to a get a reading that is not distorted by distance along the lever) so I think I got that right
I was very struck by the sensitivity of the measurement in terms of the detectable clearance change with a very small turn of the adjuster - probably more sensitive than a feeler guage would be
I would say that the feeler guage is quite likely more reliable - as long as there is not wear on the surfaces. What I should have done of course was to measure the clearance with a feeler guage after using the dial guage - to compare and note the difference for next time...
I went for the clearances of 0.3 and 0.51 inlet/exhaust (cold)
Bottom line for me though is that the engine is transformed with that rattle gone and interestingly the idle speed has increased, which i suppose is due to changes in valve opening and indeed valve timing.



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Tappet adjustment query

Post by spegru » Thu Sep 12, 2019 4:08 pm

I managed to upload a video of me using the dial guage and some of the troubles I had with it to begin with. I got better at it later on!
https://www.youtube.com/watch?v=ikciQpZC8cI

I think hope this is showing 0.30mm on an inlet!



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Tappet adjustment query

Post by spegru » Thu Sep 26, 2019 9:29 am

just by way of completeness, I thought I'd remeasure with a feeler guage while changing the cork gaskets.
Perhaps oddly they all measured up fine albeit very tight on the guage. Just one seemed a bit too tight - seemed to be 0.2 vs 0.3mm (Inlet on No2) so I loosened that a bit. Hard to say whether the noise reduction had changed at all as I had been away for a week but does seem alot quieter than before.
So the moral seems to be use a feeler guage but make sure that it is really very tight - or perhaps compensate for wear by going down by say .01mm
I also noticed that the side to side rocker wobble effect affects the feeler almost as as much as the dial - so I can see that leading to inaccuracy in setting the clearance. Perhaps that is what my original problem was
Overall though the dial gauge is indeed more fiddly to use than the feeler but one can be pretty confident that wear will be taken account of (as will subtracting a bit from the specified setting)



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