Cold Engine Valve Tappet Clearance

[Jethrow]

I'm replacing worn valves and guides on an Hercules IXB-3 motor.  Manual calls for hot clearances of .006 intake and .008 exhaust.

The magneto has been swapped out for a distributor on this engine making it impossible to access all the tappets.   Anyone know what the clearances can be set to while the engine is apart.

Thanks

[ObsoElitist]

On some OHV enginss I heard to set them .002 loose, but this is not the same. It is a small engine, could you put it in an oven at 180 degrees for a couple of hours?

[Jethrow]

That's a thought;

When the new valves arrive, I will mic a few cold and then pop them in the oven.  The cam followers or "push rods" aren't that long so the greatest gain from expansion would be in the valve.

[ObsoElitist]

The iron block expands with heat too. I cant say how much, but when making casting patterns for iron I asssume 1/8 inch per foot shrinkage when cooled. Hence my idea of hearing up the whole thing to operating temperature. It couldmalso be done by running hot water throught it.

[Blake Malkamaki]

There is a rule of thumb, but I can't remember what my gramps told me. It should not be too much different for a flat head as you don't have a lot of linear expansion. Check with another flat head engine of the same size, such as an Allis-Chalmers B or Continental.