What is cold? (Valve Adjustment Question)

[whc03grady]

Webster's tells us cold means "marked by a lack of the warmth of normal human emotion, friendliness, or compassion <a cold stare> <got a cold reception>; also : not moved to enthusiasm <the movie leaves me cold>", but that's not what I'm interested in.

Back in my salad days St. John the Muir beat it into my head that valves are to be adjusted cold, sea-oh-ell-dee. Like "sat all night" cold. Now I've got someone telling me that during engine break-in I'm to run the engine at 2,000rpm (maybe he said 3,000; I don't have my notes with me) for x minutes, let it cool down a little while, and then adjust the valves. It was implied that "a little while" was significantly less than the overnight Muir recommends. Like a few hours'd do it.

I've been bit by Muir before (see: 009s in all my non-f.i. VWs), so I'm prepared to think that while I obviously shouldn't turn off the key and then race around back to do the valves, it might not be the case that a full night's sleep is necessarily indicated.

What do we make of these conflicting bits of advice? Does Muir loudly preach "overnight!" just so us mopes'll be damn sure they're cold?

[Bleyseng]

After the initial 20 mins of CAM/Lifter run in...then let the engine cold down..to the ambient temp. Use a fan to blow on the motor if you are in a hurry..so if its 80F out then the motor will be about 80F-90f if you have a CHT gauge.
More important is that you check the valve clearance as after the run in you could have some changes in clearances. If you are a perfectionist then also change the oil , Raby approved Brad Penn 30w break in oil to run for 500 miles. I like to change the oil as it gets all the bits of crap out then.

[RSorak 71Westy]

I concur, ambient temp....Also breakin should be done at varying RPM's between 2 and 3 thousand....never staying at 1 rpm long.

[Amskeptic]

Muir beat it into my head that valves are to be adjusted "sat all night" cold.
Now I've got someone telling me that during engine break-in I'm to run the engine at 2,000rpm (maybe he said 3,000; I don't have my notes with me) for x minutes, let it cool down a little while, and then adjust the valves.

You do both of the above situations.

When performing a maintenance valve adjustment, you better best had do them stone-cold overnight cold.

When doing a break-in, you can be much more casual because you WILL be doing them the next morning regardless and in another 100 miles and dimensions are shifting all over the place as it is. The clearance check after the initial 20 minute cam/lifter break-in is mostly to see if anyone has loosened grossly or tightened insidiously. It is a judgment call too, if the exhaust note is steady and smooth, I would not waste my time until the next morning.
Colin