The pistons we pulled out of my friends documented 60 HP sunliners original engine were flat top with no valve relief,and the original cam that we checked for lift was not .500 lift,it was roughly .480 with no indication of excessive wear. We had seen conflicting references of listed cam lift figures some saying .500 and others listing .479,based on our observations I tend to believe the .479 figure. It appeared to be an early engine as it had a B9AE block,still had the stamped timing cover with timing pointer that matched the HP balancer and had the earlier C0AE dual point distributor they had 2 C0AE DP dist. with different suffixes,the K suffix dist.was the later one and his had the earlier one but I can't remember what the suffix was on it.It also had the earlier narrow beam rods,the later ones supposedly switched to a wide beam rod.
Did you check the piston compression height on those original pistons or how far down the hole were they?
I'm guessing maybe .038 - .040 in the hole then?
Now, how thick was the original gasket, a .020 shim?
OK then with no valve reliefs, would they HIT? Probably not - but how much piston-to-valve clearance would that leave?
It doesnt depend so much on the max lift, since the piston is way down the hole by then.
Piston-Valve clearance depends more on Overlap, ie valve events at .020 or .050 lobe lift.
Do you still have that cam by chance?
The .480 net lift vs .500 net lift mystery seems to linger, but doesnt make much difference - about 3 hp or so.
Mainly though, if there is a .480 net lift cam (new, unworn), are its DURATIONS the same as the 228-228-114.5 cam used on the 390HP, 406, 427-4v?
The only way to know that would be to degree it.
Either way - I dont know what the piston-valve clearance would be. Maybe they cut it kind of close!