340 Cold Valve Lash Unknown Cam

As above check the lash COLD now. Write it down. Fire it up and drive it. It’s not good enough to just warm it up. Get it to temperature and put a few miles on it.

Then pop a valve cover off while it’s hot. Check several valves and write down what it is.

Compare results. They should be looser hot.

If that hot number is somewhere between .014 and .028 for the intake and .016 and .032 on the exhaust you are golden.

If you like the way it runs with that lash drive the wheels off it. Then you can play with lash a little bit and see how it feels.

I always set the valve cold. Always. Because A) I hate working on hot, oily stuff and B) even if you can set valves like Jack the Bear (meaning lickety split) the temperature change while setting the valves can affect your actual lash.

That’s why I said check several valves hot. Three maybe four and then the engine cools off.

When the engine is cold at least everything is the same temperature.

The rule of thumb is if you have iron heads and block the lash will grow about .002-.004.

Iron block and aluminum heads will be about .004-.006.

An aluminum block and head will grow .012 to about .024 or a bit more.

I’ve only seen the high number with a blown alcohol deal. You could sit there and watch the blower belt tighten up while it was warming up.