Cold Lash

[dirtdevil]

I know it seems to always be asked, but:

Aluminum heads, aluminum rockers, aluminum intake. Cam card calls for .020 lash HOT on both valves. What is a good start cold, untill the motor can be warmed up ?? I am guessing .019?

[fast_crew]

I would start with about .016 then recheck when hot, and adjust accordingly.

[dirtdevil]

Thanks that is what I will do.

[usafracer]

I would go 22. Metal expands when heated.

[sj valley dave]

fast_crew is correct, usafracer has got it backwards...he is correct that all metal expands with temperature, but aluminum expands at roughly twice the rate of steel...the valve train is steel, the cylinder heat is aluminum...the head expands more than the valvetrain, thus opening up your lash, NOT tightening...On our all aluminum engine, the lash is .000/.002 cold and at 205* it is .018/.020....

[dirtdevil]

Thanks Dave, as always good and trusted advice from you.

[fast_crew]

fast_crew is correct, usafracer has got it backwards...he is correct that all metal expands with temperature, but aluminum expands at roughly twice the rate of steel...the valve train is steel, the cylinder heat is aluminum...the head expands more than the valvetrain, thus opening up your lash, NOT tightening...On our all aluminum engine, the lash is .000/.002 cold and at 205* it is .018/.020....

We see the same thing on our all alum. engine (410 sprint). We run .000/.000 on one and .004/.006 on the other, cold.