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Old 02-06-2013, 09:59 AM
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cobalt327 cobalt327 is offline
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Originally Posted by AutoGear View Post
Only thing I'll add is if you get a pump and wonder if it has the billet or Powdered Metal (PM) gears; put a mark on it with a felt-tip pen. If the mark fades away, its Powdered Metal. Nothing wrong with PM in the correct application, however if you put any trash through the pump, it can break the gears, where a billet gear will probably chip a tooth and pass it through.

I haven't seen a PM one in awhile but, it sure is nice of companies being forced to upsell you if you question their old stock having the PM gears or not. I understand that there are rising costs of manufacture; but I also know that investing in the powdered metal dies is NOT cheap at all and takes tens of thousands of pieces to amortize the cost in a reasonable timeframe
That's good to know, thanks.

Also FWIW, I had occasion to tear down a '97 Vortec engine w/a thrown rod. It wasn't pretty- the rod was in about 8 pieces (no exaggeration)- and it looked to have shattered (reminded me of a failed hypereutetic piston) instead of bending/breaking like a normal forged steel rod tends to do.

I still have the pieces if anyone's interested in seeing them all, here's one of the bigger ones:

I don't know the exact mode of failure, the crank's rod journal was badly worn, so it might have been driven in desperation long after it started knocking. That could have overheated it, although there's no discernible bluing of the metal. The rod bolts were still nutted and were holding onto pieces of the cap and rod (in two separate pieces) and hadn't broken although they may have stretched.

Until seeing this I believed the PM rods were at least as good if not better than the forged steel rods before them. The finish is much better on the PM rods, that much is known. But this does raise a little doubt, although one case does not mean that much either way.

Last edited by cobalt327; 02-06-2013 at 10:04 AM.
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