Tappet clearaces, Perfect or acceptable?

[peterrc]

Hi Guys, greetings from the frozen North. I am starting to rebuild my cylinder heads after a skim/valve grind and would like some advice please. The tappet clearances on one head (LH) are within tolerances but on the other head 5 clearances (4 inlet 1 exhaust) are below minimum. My question is, should I try to get all clearances the same, either Max, Min, or middle, or should I just be happy that they are within tolerance.
Peter, Cupar

[jbuckl]

Tightest :-

Exhaust .016
Intake .008

Aim for these values.
The feelers should not be sliding/gliding in but a positive push-in...... not too hard or you could be opening the valve.

Its worth taking your time to get them spot on.

018 / 010 will give too much clicking until really hot imho.

[V Mad]

I agree, I think its worth getting them all spot on (middle) as it will make the engine smoother and run better, and anything that is under the lower limit might end up burning a valve. Dont forget different clearances also means different valve timing.

[peterrc]

Hi Julian & Chris, thank you for your advice. It's back to the arithmetic then, I thought I only had to do it on the 5 low ones but now there are another 8 need doing. Looking on the bright that means 3 that are spot on.
Peter, Cupar

[V Mad]

I have just done it on mine and its quite tedious sometimes. I carefully check everything, then fit the new shim, refit cam, measure and sometimes its wrong again! So I repeat until its just right. I hope its worth the effort!!

[peterrc]

I have just done it on mine and its quite tedious sometimes. I carefully check everything, then fit the new shim, refit cam, measure and sometimes its wrong again! So I repeat until its just right. I hope its worth the effort!!

Hi Chris, I appreciate that it is a time consuming process. But as the heads are off I can bring them into the house it is warmer than the garage and the initial measurements were taken in the house. I did take measurements in the garage and there was a very slight difference.
Peter, Cupar

[KOY 23]

I agree, I think its worth getting them all spot on (middle) as it will make the engine smoother and run better, and anything that is under the lower limit might end up burning a valve. Dont forget different clearances also means different valve timing.

Hi Chris.

I would be interested to know what effect on the timing, a thou clearance makes?

John

[dasadrew]

Hi Chris.

I would be interested to know what effect on the timing, a thou clearance makes?

John

~ 0.03° ??

[flying farmer]

I always aim for the middle of the tolerance, but provided it is within the max/min it won't give any trouble. watch out for the wear dimples on the shims, if the clearance is a bit big flipping it over to the unworn side can make a difference.
Regarding the cam timing and valve clearances, I once tried measuring the cam timing of a standard cam and found over 20 degrees difference between lobes, at the point where the valve opened/closed and it had no visible signs of wear. Probably just BL's appalling machining. Had to measure them at 1mm open as that got rid of the worst errors
Neil

[dasadrew]

Neil, do you have any cam timing data for the standard cams?

Do you know if anyone does a vernier camwheel set up? (I know you can file elongated holes!)

Drew

[redstag]

http://www.sprintparts.triumphowners.com/news.cgi?articleID=480303

Pete

[dasadrew]

Thanks for the link - never thought to look under Sprint. Will arrange an appointment with the bank manager!

[Tdm]

I have just done it on mine and its quite tedious sometimes. I carefully check everything, then fit the new shim, refit cam, measure and sometimes its wrong again! So I repeat until its just right. I hope its worth the effort!!

When I did mine some years ago I noticed that the thickness of the buckets themselves varied considerably, so that it was important when fitting a new shim you were using the same bucket you took the measurements from in the first place. Mix the buckets up and the clearances become totally different.

[KOY 23]

~ 0.03° ??

As much as that..

[flying farmer]

Drew, I have never come across any cam timing data, though someone on this forum (Stagmatt)? said it was IIRC 18 58 58 18 which is common to some of the four cylinder engines
Due to the timing discrepancies at the start and finish of valve lift, I used a dial gauge on the cam bucket of inlet and exhaust so that at 1mm of valve lift I could get symetrical timing either side of TDC. True TDC needs to be measured first as I have known timing marks to be 4 degrees out. If the timing marks didn't line up, I prefer to redrill the sprocket at almost 90 degrees using the basis that one third of a tooth is three degrees, and if I can get it within that I am happy. If in doubt I prefer timing to be advanced by a degree or two and never retarded. This is because wear on the timing chain and tensioners will retard the cam timing with mileage anyway, if it starts retarded it will get worse, if it starts advanced it will get better
Neil