Re: V8 Pistons

Posted by Jack Vines On 2009/2/20 12:36:04

We've been over this many times. Let's try to explain it one more time. Diesel pistons, rods and crankshafts have to be built hell-for-stout to withstand the 20-1 compression:

1. The International Harvester truck diesels are the closest in the book, offered in a 4.00" and 4.110" bore sizes. These pistons w/pins are TWICEas heavy as a Packard piston w/pin. This doubling of the reciprocating weight would make it practically impossible to balance the crankshaft. If it could be balanced by milling out the counterweights and filling them with Mallory metal, the combined reciprocating/rotating weight would then overstress the crankpins and break the light Packard crankshaft.
2. The IH piston pins are 1.1101" in diameter. This is .1297" larger than the Packard pin. The machine work cost to bore and hone eight rods to size is considerable. The rod small end could possibly be bored out to that oversize, but strength would be unknown.
3. Diesels don't turn fast, so the inertia of heavy pistons isn't a problem at 2250 RPMS. Inertia goes up by the square of the RPM, so the doubled weight of the diesel piston would literally pull the spindly Packard rod apart at anything above 3,500 RPMs.

Bottom line, a diesel would be the worst possible place to look for a piston interchange.

thnx, jack vines