what diameter would you make the cylinders for oversize pistons 006?
Do you mean .060"? (Sixty Thousands of an Inch)
You do not show a decimal point.
Nominal value would be 3.750" plus .060" plus the desired clearance, say .004". However you would need to have the actual pistons that are to be used before you would final hone the cylinders because some pistons vary in manufacturing specs, particularly when you are talking about oversizes.
So the nominal answer is 3.814" but don't cut the bores until you have pistons in front of you. Then you need to simply make the bores .004 - .005 larger than the piston.
Educate me. Don't the piston manufacturers figure in the clearance when they make the pistons?
Yes no and maybe. For example I bought a set of oversize pistons for a 427 Ford from Ross last year. I ordered .017" oversize pistons which would mean nominally 4.23" (stock piston diameter) + .017" = 4.250". Again this is a nominal, not an actual value.
When the pistons arrived they were 4.255" diameter - because Ross figures the oversize on top of the original bore + clearance value. Again, the key is to bore the cylinder after you have the pistons sitting in front of you, so you can maintain the proper clearance value desired.
That is part of the beauty of the aircooled VW/Porsche, (and Corvair?). The piston, pin, rings and cyl come as a set; no honing or other fitting needed. I was taken aback the first time I saw the ritual for iron block engines.
Do you remember all the color codes for the sets in 0.0005 increments? Quite different than the piston diameter plus 4-5 thou....
Yes I have a chart at home for the 427 piston oversize specs. The cylinder bores on a new block were color coded from the factory to match the oversize needed.
Renault, Peugeot, Triumph sports cars, some Alfas and maybe a few others that are water cooled have wet sleeves and pistons with rings & pins in a set.
An engine can be sleeved and running in the same day without removing the engine. I miss that.
No worry about cracked cylinders or if a certain oversize is available.