Valve lash-cold vs. hot adjustment

patiolant · Jun 5, 2013

Adjusting the valve lash on my MF65 gas. Problem is that the spec"s call for hot measurements of .016 intake and .018 exhaust, but it took me several hours to get to the valves by the time I removed the gas tank, etc., and other things interrupted the job. So, is the best approach to add .002 to the measurements if the valves are cold? What do you guys do in this situation?

Nebraska Cowman · Jun 5, 2013

When I was younger I liked to adjust them running. I had a quart can for gasoline with a nipple soldered into for a temp fuel tank.

Bob Bancroft · Jun 5, 2013

That should be fine. Even .001". Those seem like fairly high numbers to begin with.

Whichester1 · Jun 5, 2013

I would not worry about it, I worked as an engineer in the engine industry for over 25 years. When all the tolerances in all of the machined parts are calculated it could change the adjustment far more than the hot or cold adjustments.

It has been 15 years since I left Cummins but when I was there manufacturing tolerances could change the compression ratio one point one way or another.

Don't worry about hot or cold adjustments.

rustred · Jun 5, 2013

very easy, just add .002 to the spec if doing it cold. another thing is hot does not mean"hot". so get it to operating temp and by the time you are ready to adjust all is good.

RodinNS · Jun 5, 2013

An extra 2 thou sounds fine to me. I'd be more concerned about getting them set accurately at that or even hot spec than I would be worried over a couple thou tho...

Rod

ben there · Jun 5, 2013

any spec sheet i've seen says cold as in overnight cold...if engine was up to operating temp the hot setting can still be used if 4-5 hours later.

JRSutton · Jun 6, 2013

If I were in doubt I'd just split the difference and consider it "warm".

Instead of .002, I'd add .001

I'd do that even though I knew in the back of my head that it REALLY doesn't matter - this isn't an indy car, it's an old tractor that's going to be just fine even if I just gapped them by eye.

patiolant · Jun 6, 2013

So I guess I could just use my fingernail for gapping the intake and thumbnail for the exhaust.

My only concern was for valves being too tight-when I bought it 20 years ago it started to run very poorly and the issue was tight valves on the number 4 cylinder. It has been running poorly again, and I was doing the valves again as a matter of principle. It turns out that they were still within 0.001-0.002 of expected.

I was also able to measure within 30 minutes of running, and again the next morning. All measurements were within 0.001 of eachother. So hot vs cold doesn"t seem to matter much on this engine.

Thanks for all the replies.

Valve lash-cold vs. hot adjustment

patiolant

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Nebraska Cowman

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Bob Bancroft

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Whichester1

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rustred

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RodinNS

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ben there

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JRSutton

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patiolant

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