adjusting valves hot.

[lolcantturn]

Yep I'm going to adjust my valves again. This time while the engine's warm. Now I already know how to do it, but how warm should my engine be? Unfortunately I don't get up to operating temperature (the halfway point on the gauge). but my engine at its highest temperature is untouchable. This would be ok, correct? And when adjusting it hot, should I keep it a little "loose," where the feeler gauge has a loose amount of play, or "tight" where it's somewhat difficult to pull out? Or keep it in the middle between those? Because I know some people prefer different ways of setting the play.

[rThor432]

You shouldn't adjust the valves when the engine is hot.. ever. Who gave you that idea?

[otto325e]

People say the valve lash is tighter when hot because metal expands at higher temperatures but they are always tighter cold..


I've done mine a few times now and usually I'll adjust them warm(20-30C) and when I go to check them, afterwords when the engine cooled down, they are tighter. Yesterday, at near freezing weather, I went to adjust/check them to replace a few stripped screws and they were super tight...when I purposely set them a bit loose last time when it was around 15C or so..

[lolcantturn]

You shouldn't adjust the valves when the engine is hot.. ever. Who gave you that idea?

The Bentley Manual + various older threads on forums of people adjusting them hot.

People say the valve lash is tighter when hot because metal expands at higher temperatures but they are always tighter cold..


I've done mine a few times now and usually I'll adjust them warm(20-30C) and when I go to check them, afterwords when the engine cooled down, they are tighter. Yesterday, at near freezing weather, I went to adjust/check them to replace a few stripped screws and they were super tight...when I purposely set them a bit loose last time when it was around 15C or so..

Did the engine run smoother when you adjusted them hot and tightened up?

[jlevie]

Seems to me I remember reading that a hot adjustment is to 0.012", vs 0.010" cold. It is best to adjust the valves cold since that is an easily condition to reach.

[lolcantturn]

Seems to me I remember reading that a hot adjustment is to 0.012", vs 0.010" cold. It is best to adjust the valves cold since that is an easily condition to reach.

Yep that's what the bentley recommends.. I'd just figure it would be better to adjust it hotter? Or it wouldn't make any difference?

[call me jack]

Yep that's what the bentley recommends.. I'd just figure it would be better to adjust it hotter? Or it wouldn't make any difference?

since the hot and cold specs differ from one another, i would assume they are accounting for different metal expansion rates, and it wouldn't make a difference if you did it hot or cold... frankly though, when i finally adjusted my valves, i couldn't accurately get a feeler gauge under my rockers, so i just did it by feel. worked fine

[u3b3rg33k]

I'd suggest you adjust them cold, with a herring can lid.

Very simple to do:
1: Misplace your feeler gauges
2: get angry
3: find micrometer
4: measure stuff until you find a .010" object
5: cut the herring can tab into a rectangle
6: adjust valves

[jlevie]

Yep that's what the bentley recommends.. I'd just figure it would be better to adjust it hotter? Or it wouldn't make any difference?

The problem with adjusting the valves hot lies in defining what "hot' is. The only condition that would yield repeatable results would be to run the engine to get it to operating temperature, shut it down, and immediately adjust the valves. If you can complete the job quickly and the ambient temperature is at least warm, the head won't cool down much.

[NigelStu]

I've heard of cutting down trees with a herring, but never adjusting valves! Kudo's to you sir!

[lolcantturn]

The problem with adjusting the valves hot lies in defining what "hot' is. The only condition that would yield repeatable results would be to run the engine to get it to operating temperature, shut it down, and immediately adjust the valves. If you can complete the job quickly and the ambient temperature is at least warm, the head won't cool down much.

Well shucks. I see no point in doing it then if I'm not going to get any "Real" results.

My engine is very rough sounding, like a diesel engine litterally. When I pull up at gas stations they ask "Diesel?" But the idle is as smooth as butter and so is everything else. The engine noise bothers the heck out of me though. I reduced it with my previous valve adjustment, but it's still pretty damn rough sounding, even though M20's are supposed to sound like "sewing" machines and arent the quietest of engines, this is not like it.

[otto325e]

Valve chatter is actually much quieter than piston slap, which is what the diesel sound is. You can't really hear valve chatter unless the hood is open anyways. Completely normal for e30s

[lolcantturn]

ah alright. I guess I'm going to fill her up with 20W-50 and hope for it to smoothen out

[nando]

You shouldn't adjust the valves when the engine is hot.. ever. Who gave you that idea?

really? then why is there a hot adjustment spec? :roll:

adjust them to .012" hot. the valve clearance actually gets bigger as the engine heats up. And hey, you actually get a better adjustment since you are changing the operating clearance and not the cold one.

[DÌEGØ]

when I went to do my adjustment [hot] by the time I was on the 3rd cylinder I noticed my head had cooled down quite a bit [it was like 40F tho] so I just waited a bit for it to cool down some more and started over doing the cold adj