Small valve clearances

The pushrod is also the same length as the distance between the cam and the rocker, no?

Valve clearances decrease with temperature. Accept it.

Steve

I've never heard of that happening. Care to specify this stressed engine?

Steve

It does.

And incidentally where the barrels and/or heads are alloy, giving as you say the uneven expansion rate, what are the holding down bolts made of?

Steve

Usually, yes. Always? No.

Accept it.

Chris

So which engine(s) are you referring to?

Steve

Ford York

Air-cooled OHV motorcycle engines :-)

Chris

This is how I did it:

1. Removed head cover.
2. Measured valve clearance, got 0.00 mm.
3. Specification says 0.15 mm clearance.
4. Removed 2.60 mm shim.
5. Fitted 2.45 mm shim.
6. Measured valve clearance, got 0.10 mm.
7. Removed 2.45 mm shim.
8. Fitted 2.40 mm shim.
9. Measured valve clearance, got 0.15 mm. Done.

I argue there was a -0.05 mm clearance. I'm sorry if that ruins your sleep.

Which ones?

Steve

So the valve clearances for the york inlet valve is 0 or thereabouts is it, to allow for increased clearance due to contraction when hot?

Steve

Nope, the noise from the valve train on a Ford Yorks pretty irrelevant.

Tuned pre-unit Triumph twins using E3134 camshafts.

Chris

For which the valve clearance settings are ?

Steve

And the valve clearances are?

Steve

Well, there won't be any "official" settings, because it was a tuned engine using lost of non-standard parts.

I spent a long time trying to get the valve timing exactly right. An engineer friend came up with a very accurate way of doing this. (No, not by using vernier gear wheels!)

ISTR that the inlet valve clearances were 0.002", and the exhaust 0.004" cold. Apologies for non-metric values - it was a long time ago!

The valve seats were *very* narrow. Not wanting to burn them out, I used to recheck the clearances when fully warmed up. The exhausts were always as set or smaller. The inlets were always wider.

I don't have a clear reason for this happening. I just know it did.

Chris

Which is physically impossible assuming the valve was fully closed. You DID take account of a layer of oil plus inherent inaccuracies in measuring?

An odd assumption to make, since (as you said) it makes the observed measurements physically impossible.

Perhaps if you were attempting to understand what was happening, rather than score points off people, you would make more sensible assumptions? (for example, that the valve wasn't fully closed, and that 0.05mm of additional "clearance" was required to get

What difference would the layer of oil make?

And _all_ measurements are inherently inaccurate, to some extent, I don't think the point was that there was exactly -0.05010002mm clearance, but that the clearance can be usefully described negative in the first place, which you appear to deny.

Hopefully nice springy steel to keep the tension between the head, barrel and crankcase roughly constant over temperature and time.

thing

Now if you actually quoted the rest of my reply where I gave the possible scenarios...

What was that about point scoring?

Err...it has a thickness?

When it is 0.05mm I do. Unless you are using a load guage on the feelers to judge how much resistance there is when sliding it in and out of the gap or using a micrometer, you can just make a "best guess".