[tbirdtbird]

of course the bores will expand with too much heat. that is what bores do. everyone knows that.
But everyone also knows that aluminum expands more than steel degree for degree.
It is the expansion of the piston that is the culprit. If this were not the case the required clearance would be ZERO, think about it.

It is not complicated. we need not know any more physics than that.

I was taught years and years ago what Purdy just said: .001 per inch diameter. If the old timers knew this, why can't we?

By the time I am done honing, some clearances do come out at .004 instead of .0035. Big deal.

Agree totally with Purdy. And look at where the coolant intake is on the motor. Between cyls 2&3. And the pump sucks from there. So why in God's name is the same amount of coolant gonna magically bathe cyls 3&4 when it is all being sucked up front.

Buy a cheapo HF IR thermometer and shoot the sides of the cyls like we have and see the temp diff for yourself!!!! Get some simple instruments, watch, and learn. Listen to a guy like Purdy with 8 zillion miles under his belt on 6 diff. Model As for 50 years. Nah, what does a guy like that know anyway.

Users have 2 options and let's keep it simple:
1. set it up tight like a modern engine and have it score and seize and bring it to me for repair
2. set it at .0035-.004 and have a good strong motor. Seriously, you can't live with that much clearance? It will keep you up at night? WHY? Tell me what can go wrong with .0035-.004 clearance. I need to know

Listen again...we are trying to save you money and aggravation......any takers?

and the valve clearly wasn't straight when it was new; there is no other explanation....but that would have been hard to know at that point