Stupid question maybe, Valve lash

[mustangguy289]

When setting valve lash when the engine is cold you go with a smaller gap than when the engine is warm correct?

My valve card tells me .016 Intake and .018 Exhaust. Talking with ShaunT, he led me to believe this was the "warm" lash given by comp cams.

He told me for aluminum heads to subtract .005 to set them cold.

(.011 int, .013 exh).

After reading that other thread it got me thinking.

[greenbullitt]

set lash loose (cold) so it doesnt hang the valve open when warm.

ie, cold figures are larger than warm

[mustangguy289]

set lash loose (cold) so it doesnt hang the valve open when warm.

ie, cold figures are larger than warm

So I have been doing it backwards then. It seems to run great as I have been doing it this way for years now. Hmm wonder how much better it would run setting them looser.

So I should be doing .021 and .023.

[mustangguy289]

set lash loose (cold) so it doesnt hang the valve open when warm.

ie, cold figures are larger than warm

That is what always had me confused... because metal expands when warm... the lash should get tighter as it warms up... I guess I was a fool for believing him.

[greenbullitt]

since i sped read your original post, to elaborate since heads do affect figures, heres something for you


Here's a blurb from the Crane website:

Compensating for a Cold Engine when Adjusting Valve Lash

When installing a new cam, the engine will be cold but the lash specifications are for a hot engine. What are you to do? There is a correction factor that can be used to get close. We mentioned that the alloy of the engine parts can be affected by thermal expansion in different ways, therefore the amount of correction factor to the lash setting depends on whether the cylinder heads and block is made out of cast iron or aluminum. You can take the “hot” setting given to you in the catalog or cam specification card and alter it by the following amount to get a “cold” lash setting.

With iron block and iron heads, add .002”

With iron block and aluminum heads, subtract .006”

With both aluminum block and heads, subtract .012”.

[mustangguy289]

since i sped read your original post, to elaborate since heads do affect figures, heres something for you


Here's a blurb from the Crane website:

Compensating for a Cold Engine when Adjusting Valve Lash

When installing a new cam, the engine will be cold but the lash specifications are for a hot engine. What are you to do? There is a correction factor that can be used to get close. We mentioned that the alloy of the engine parts can be affected by thermal expansion in different ways, therefore the amount of correction factor to the lash setting depends on whether the cylinder heads and block is made out of cast iron or aluminum. You can take the “hot” setting given to you in the catalog or cam specification card and alter it by the following amount to get a “cold” lash setting.

With iron block and iron heads, add .002”

With iron block and aluminum heads, subtract .006”

With both aluminum block and heads, subtract .012”.

That is pretty much what he told me. Ive been subtracting .005 for iron block and alum heads.

[greenbullitt]

That is pretty much what he told me. Ive been subtracting .005 for iron block and alum heads.

If they were iron, it would be different...obviously

[Broncojohnny]

Get you a dry erase board for your garage. Heat the engine up, set the lash on each valve to the correct setting. Let it cool off. Remeasure the lash when it is cold and write those settings on the dry erase board so you know where to set them at when the engine is cold. Each valve will be slightly different, plus minus a few thousandths but generally the numbers quoted above are correct.

[slow55]

On the all aluminum motors I was running it called for 28 hot so I would set them at 15 cold and they would be right on after warming up.

On iron block/alum head motors I just set them right at what it said to and just re-checked them after it got hot. Not one single time did every valve need re-adjusting, just a few here and there and they were usually just a few thousands off at that.

[slow55]

Also if you're not familiar with setting valve lash I would recomend getting someone to help show you the first time you do it.
I know there are charts that tell which valves to set while a certian valve is open etc.
I just fly through each one in order, when intake starts to close check the exh and when exh starts to open check int.

[mustangguy289]

Also if you're not familiar with setting valve lash I would recomend getting someone to help show you the first time you do it.
I know there are charts that tell which valves to set while a certian valve is open etc.
I just fly through each one in order, when intake starts to close check the exh and when exh starts to open check int.

Yea I have done it numerous times. I will be getting one of those valve setting tools from Summit though. Setting poly locks with a wrench in one hand and an alan wrench in the other can really get frustrating.

The thing with doing them hot is by the time I get to the 4th cylinder on each side there has been quite a bit of heat dissapation compared to when doing the 1st cyl. on each side.

[slow55]

Yea I have done it numerous times. I will be getting one of those valve setting tools from Summit though. Setting poly locks with a wrench in one hand and an alan wrench in the other can really get frustrating.

The thing with doing them hot is by the time I get to the 4th cylinder on each side there has been quite a bit of heat dissapation compared to when doing the 1st cyl. on each side.

Once it's hot you have a little while to get it done. Unless it takes you more than 30 minutes to set them I wouldn't worry about how much it cools off.

It might seem like it's cooled off a lot just to the touch but the inside of the motor will still be hot and expanded to where it needs to be