If you toast an impeller, you might end up wishing you'd have gone a touch bigger on the gap..

mcoll, why is that?

Crazyhorse,
JMHO but .022 top gap seems "snug" for a forced induction marine engine. Thats .0048" gap per inch cylinder bore. These numbers are from JE installation guidelines.
High-Perf. Street-Strip Bore x .0045"
Street Moderate Turbo/Nitrous Bore x .0050"
Late Model Stock Bore x .0050"
Circle Track / Drag Race Bore x .0055"
Nitrous Race Only Bore x .0070"
Blown Race Only Bore x .0060"

Bob

end gap on my 598" project??
 

So in my case with a 4.600 bore JE pistons naturally aspirated would it be smart to use their recommendation for Street Moderate Turbo / Nitrous and set the top ring at bore X .005" (.023) and the second ring at bore X .0055" (.025")? Is that still slightly to tight on top? It sure would be nice if JE would list some marine applications on their end gap table. I guess us boaters are still only a small percentage of the racer industry. Thanka for the opinions in advance!!
Craig

Ive never heard of the second ring needing a larger gap. Whats up with that?

Puder,

Ring heat closes the end gap.
Cylinder sleeve heat opens the bores which opens end gap.

Problem is, the ring heat is transferred to the cylinder liner and it is then absorbed into the cooling water.

While lack of coolant will indeed allow the liners to get hot and grow, the rings heat more quickly than the liners, and the gap closes. If the gap completely closes, the rings try to lock up in the bore. At a minimum, this scores the cylinder walls. At worst, the rings try to seize up and while there is plenty of piston meat to push the rings UP the bore, when the piston tries to some DOWN, it rips the top of the piston off (usually partially, not completely which allows the ring to peel out and lose tension). New parts will be required...

F-31, the new school of thought on a larger 2nd-ring gap concerns the ability of air passage through that gap. If the second ring has a tighter gap than the top ring it causes a restriction in the airflow between the top and second ring, reducing the sealing effect of the top ring. Pressure differential is what causes ring sealing. The greater the pressure differential, the greater the sealing effect.

This is the answer Back4More gave in another tread about the difference between automotive crate engines and marine, I thought it was pretty good and clear.
The thread;
http://www.offshoreonly.com/forums/s...threadid=61488