Does anyone know what is a good starting cold mechanical valve lash should be for a 350? I know the hot measurement is .020in and .024 ex.

Thanks

Add .004 inch to each hot lash setting, adjust cold. Bring engine to operating temperature, re-adjust to hot lash. Let cool overnight, measure cold lash to see/feel where it ends up.

Crane's website has good recommendations. The fudge factor varies depending on the type of head/block material.

I SUBTRACT .004" from the recommended hot lash setting when checking cold on an ALUMINUM head SBC. On an IRON head engine I subtract .002".

So . . . if recommended lash is .022" hot, I set to .018" cold on an aluminum head engine. On an iron head engine I would set lash for the same cam to .020" cold.

I've done this several times on several different cars and have verified that it will get you close . . . within .002" for sure on a SBC . . .

Good to know, Eric. Crane says add .002 for iron head and subtract.006 for aluminum. Gotta go with real-world experience.

I'm kind of confussed. I thought one would need to add so when the metal gets hot and expands,you would end up at your hot lash setting. I have aluminum heads.

your aluminum heads "grow" taller when they get hot which will cause the lash to increse.

You would think that iron heads would grow too when hotter . . . just not as much as aluminum. crane's recommendation is interesting . . . I wonder why they are saying that iron would shrink .002" :confused:

I'll tell ya what . . . I just set up a friend's solid FT cam last weekend at .020" cold. It has iron heads, I'll check lash hot now and see what we got. We're shooting for .022" hot . . .

Thanks all. I was just thinking about the valves stems and push rods, not the head themselves. Maybe thats the difference between the iron vs. aluminum. The aluminum grows more than the iron heads, but the valve stems and rods out grow the iron heads so you must subtract. Just thinking out loud.

Maybe I mis-read his question, but, I thought I read he was asking for a figure to adjust the valves so he can start the engine to get the engine to operating temperature to set hot lash.

Once he's at hot temp, then he can set hot lash and life goes on.

Alum does expand more then iron and steel and at a faster rate. But hot lash will take this event into consideration.