How would an ambient temperature increase of 50 degree (F) effect valve lash. It doesn't seem like it should make much of a difference, but it is 25% of what total average run temp and it would seem significant if the same 50* swing was from 150*-200*, rather than 50*-100* directly related to ambient.

I don't have a direct comparison, as there was 400 miles and several 1/4 mile runs on the engine between lash inspections. My lash was set at .018", say a month ago, give or take, done late at night and during a cold spell. I'm guessing it to have been somewhere in the low 50's.

Yesterday, with temps easily over a 100*, lash across the board had increased .001", a couple bordering on .0015" (would not easily accept .020" feeler guage). I don't consider there to be anything to be concerned with. It just got me thinking, how much could actually be attributed to heat expansion alone? Does expansion directly corespond to temp increase or is it subject to a progressive rate {i.e.: spec cold (100*).024, hot (200*) .028, direct would see 150* being .026" and 250* .030" / progessive would be something like 150* only .025, 200* still .028, but 250 something like .034}.

These are theoretical figures, but do you see what I'm trying to get at.

Rowdy,

I don't believe ambient temp will change the settings enough for us to measure, but I remember reading on here that if the engine is cold you can close the setting .004 with aluminum heads and .002 with iron heads. Do a search on this as I am not sure on the specs.

Bill

got more to do with the temp of the iron, steel, aluminum and oil than the ambiemt temp of outside air. did you warm it up the same amount of time both times?

Rowdy,

I don't believe ambient temp will change the settings enough for us to measure, but I remember reading on here that if the engine is cold you can close the setting .004 with aluminum heads and .002 with iron heads. Do a search on this as I am not sure on the specs.

Bill

Actually it is .005-.006 on a Rat with aluminum
With steel you would set them .002 looser

Rowdy's numbers are within reason assuming the head temp raised buy 50°
If you raise the temp of the aluminum by 50° .001-.0015 is pretty a pretty reasonable number.

Aluminum expands at a rate of .00001244/deg
http://www.p1m.com/expansion.htm

Thanks Mike,
Did you already have the reference or did I get you wondering after my last email?

Tom,
No warm up, hence, "cold" lash. The metal (steel, aluminum, etc...) would/should be fairly consistent to the ambient temp, unless, of course, it's exposed to direct sunlight, in which case, it sould be considerably warmer. Especially in Vegas. I've been working under a car and grabbed a wrench that's laying in the driveway (out of the car's shadow). It's like a branding iron.

If you notice the time that the thread was posted, 3am, that should say a good deal about the inquiry. This is when insignificant things like this can find time to fester in the back of your mind. Plus, I don't think anyone considers anything as "hot", unless they burn themselves touching it. Although relative, hardly scientific in the physics of metal expansion. Steel has a pretty wide temperarure span within it's state as a "solid" matter. There has to be somewhat of a progressive nature to it. I would think that the rate of expansion would have to slow as it reaches it's melting point (2500*), as well as on the opposite end of the spectrum. It can only contract so much. It would make sense that the rate would slow prior to reaching it critical shattering point.

The likely reason that it is the best suitable material, is that we use it within the temperature range that it is the most forgiving or "flexible" (not to be confused with pliable).

Unnecessary thoughts can be hazardous to your health, mental anyway.

Bear with me while I ponder the validity of the expansion chart that Mike has linked. It appears that these figures are formulated. In my mind, it seems that the vastly different physical values of the various metals would result in an equally diverse ability of maximum expansion.

However, calculating the rates of expansion, to each metals melting point, universally results in a maximum linear expansion of .010". It just does not seem reasonable that EVERY metal listed, physically melts after expanding exactly .010". UNLESS, this is a property that actually qualifies an atom as a hard metal, or any metal, for that matter.

Know what I mean?

Thanks Mike,
Did you already have the reference or did I get you wondering after my last email?

Tom,
No warm up, hence, "cold" lash. The metal (steel, aluminum, etc...) would/should be fairly consistent to the ambient temp, unless, of course, it's exposed to direct sunlight, in which case, it sould be considerably warmer. Especially in Vegas. I've been working under a car and grabbed a wrench that's laying in the driveway (out of the car's shadow). It's like a branding iron.

If you notice the time that the thread was posted, 3am, that should say a good deal about the inquiry. This is when insignificant things like this can find time to fester in the back of your mind. Plus, I don't think anyone considers anything as "hot", unless they burn themselves touching it. Although relative, hardly scientific in the physics of metal expansion. Steel has a pretty wide temperarure span within it's state as a "solid" matter. There has to be somewhat of a progressive nature to it. I would think that the rate of expansion would have to slow as it reaches it's melting point (2500*), as well as on the opposite end of the spectrum. It can only contract so much. It would make sense that the rate would slow prior to reaching it critical shattering point.

The likely reason that it is the best suitable material, is that we use it within the temperature range that it is the most forgiving or "flexible" (not to be confused with pliable).

Unnecessary thoughts can be hazardous to your health, mental anyway.
=
I knew it was about 2.5 steel but got curious about the real number over time so,,,, I looked it up.

Or,,, at 40° would you use .006 & at 80° .005,,,,,,
would I even worry about it seeing as my .018 is someone else's .016 or .020,,,
I guess as long as you are reasonably consistent in how you do things it is all academic as valve lash is very subjective & if you really want to know what is correct for your engine you spend a lot of extra time on the dyno playing with it,,
Deal is with 750HP in a street car do you really think you will notice ± 10 or 20HP ;)

My head hurts,,,, :confused:

Mike,
I'm way past the lash part of it now. I agree that consistency is the key to monitoring for developing problems, as all lobes and/or rollers are highly unlikely to deteriorate equally, even if subjected to identical catestrophic circumstances.

Now I'm hung up on the fact that supposedly ALL metals are limited to .010" inches of linear expansion before universally melting.

See what you did.

Mike,
I'm way past the lash part of it now. I agree that consistency is the key to monitoring for developing problems, as all lobes and/or rollers are highly unlikely to deteriorate equally, even if subjected to identical catestrophic circumstances.

Now I'm hung up on the fact that supposedly ALL metals are limited to .010" inches of linear expansion before universally melting.

See what you did.
=
You gotta quit somokin them funny cigarettes :D