8.75, yes, on the race gas.

Everyone has a different way of building a motor... I know of one builder her in Los Angeles that SWEARS oil should be cold and thick. Useing that advice I saw bearing scuffing and distruction never witnessed in a BBC engine before... and then was told by the builder that it was "normal". I've argued that oil should reach at least 200 degrees and be the thinnest you can run without it being squeezed off the bearing surfaces. Most people running big block chevs run Crane roller cam lifters. Crane recommends 10-40 oil for best flow through the lifter and lubrication of the rocker and cooling for the spring.

Piston expansion, size, and design are a product of several factors.
1. Ultimate compression ratio.Blown motors are higher.
2. Duty cycle. I know race engines are stressed highly... but there are periods of deceleration where cylinder vacuum draws oil up onto the upper cylinder and piston. This helps with the transfer of heat and lubrication.
3. Lubrication. Oil helps keep the pistons from scuffing along the cylinder walls... but it also acts as a medium to transfer heat out of the piston top (from the underside) and also into the cylinder wall. A lot of high performance rods have a port that squirts oil onto the underside of the piston crown and down the major thrust side of the cylinder wall. This is great for cooling a piston... but it makes oil control a problem. 4.Pistons aren't just "cam ground", they also have a taper.That taper is there to compensate for the expansion of the crown from heat . Ideally the piston when running at operating temps will be almost straight up and down. That is one reason engines are noisy when cold. There is also another aspect about forged pistons that most people don't know or understand why. That is an offset wrist pin. Most hiperf pistons don't have an offset because people don't care about the noise. JE will offset the pin of you ask them.
5.Automotive racing engines are designed to run at higher temps because of thermal efficiency. You can't run raw sea water at high temps through an engine block and heads unless you want to see your engine dissolve from the inside.
So... if you want to cool your engine with superheated corrosive salt water, go right ahead. The other option is a huge intercooler, and it's going to suffer also from the corrosive effects of the salt water. That is the reason the Viper motors that have been marinized by Ilmor have heat exchangers and are naturally aspirated. They can't stand having salt water flowing through an aluminum block. Ilmor runs bigger piston clearances when they marinize the engines... Do you want to tell me you more know about racing engines than Ilmor?
6. Most people are trying to run supercharged engines using pump gas.. not racing fuel. Everything is a compromise.

"It's one of the reasons you don't just buy GM crate motors and stuff them in a boat with brass freeze plugs."

BADKACHINA - Actually, I stuffed a ZZ502/502 crate in my boat and have run it for 4 seasons now. Brass freeze plugs and all Lots of WOT. Including a hand full of +25 mile just about WOT romps during local poker runs. Hey, maybe I've just been lucky. But the ZZ has held up well. Still runs as well as the day it was dropped in the boat. Maybe the 20 hr. oil changes helped

Great thread, and information. I'm about to deliver my engine to a machinist/assembler for some upgrades. And because of the anticipated increase in hp, I was wondering about piston/wall clearance. I plan to have that checked. Like I said, maybe I've just been lucky.

I think lucky also.

Would the tolerance change with coated pistons (ceramic dome and Teflon skirts ),piston sprayers,closed dry sump with 10# suction ?

Pistons would run cooler and smaller. This would count for some of the need for larger clearances.

The rest of it is two fold.
One: what block/coolant temp you planning to run?
Cold blocks = smaller bores (with a touch of taper)

mcollinstn,the first set is finished.Sheet metal intake is the second set.

The blocks are new cnc bowtie gen IV.The first set is: bore 4.535,6.635 rods and 4.75 crank.Pulled 1,000 hp @ 6,000,non inter cooled,6.2 # boost,10#suction,+40*intake manifold air temp,110* water temp, 32 *timing,.065 clearance w/coated pistons w/dlc pins and sprayers.

The next short blocks will be 4.375 crank w/a little heavier flywheel,same rods and pins below the support rails.The heavier flywheel is first, for idle torque.

Would ceramic coated piston tops add or subtract from the clearance? My builder said run 006 and another said run 0065. JE max is 0075. Out of 2 meltdowns none were from skuffing of the pistons to the cylinder. Both were detonation. This time I ceramic coated the pistons, chambers and Exhaust ports. I wonder if that was a mistake. Keeping the heat in the chamber might increase the detonation possibility. No teflon on the skirts though.

I don't think you've been lucky Kidnova. You always had a good tune, good cooling and good maintenance. That is why you never needed the insurance of extra clearances.

BT

HPjunkie,4.56 bore will unshruod the valves.However,cylinder wall is that much thinner and effected by boost pressure,crank diameter,RPM and crank to rod ratio.

Your ceramic coating should be fine and not trap heat subject to a good set of adequate tube size headers and propped so the motor is not lugging.