My cousin just pulled the distributor on his Malibu. He has an HEI in his smallblock 350. He looked at the gear and it is worn bad to almost a sharp edge. He just rebuilt the engine last year, he went roller cam and everything went smooth. He did everything to the book, plenty of cam lube on the gear. What could have gone wrong. The gear was also new and not brass. Anyone have any thought or experience to the problem. He is tearing the engine down this weekend to check out the cam.

His roller cam is not compatable with a standard distributor gear, it sounds like. I bet the gear on the cam is just as bad as the one on the distributor.

I hate to say it, but pull the motor and go through it. Clean it throroughly, and might as well replace the oil pump while you're at it. All those metal particles circulating in the oil won't do any good.

I ate a distributor gear last year and ALL my bearings were shot as a result. Gouging on each and every one of them, down to copper in several places. Do not just toss another gear in and keep going. You will most likely need a new cam as well.

If the cam is billet you need a bronze or polymer distributor gear, unless the cam has a pressed on iron-gear, in which case you can run a melonized iron distributor gear, which will be the longest lasting option.

Another thing to keep in mind is even the right gear for the application will get torn up in a big hurry if the installed height of the distributor is wrong. A decked block, aftermarket intake, etc can all contribute to improper distributor height. This is what killed my gear; I changed intakes and neglected to check the height. The distributor sat too high, and wouldn't you know, it ate the gear clean through in 2500 miles.

Troy

He used the wrong gear, probably used a plain cast iron grea on a billet roller cam. This is a well-known no-no. AFAIK, the Melonized gear is what is used on GM factory roller cams. You don't want to use a bronze or cast iron gear on those, "premature wear" is the polite term. I have a Crane biller roller with the pressed on iron gear and rear journal in my Chevelle, it uses a plain cast gear to match. Crane didn't recommend the Melonized gear on that cam. One piece billet rollers use a bronze gear, and they wear out regularly. It sort of sacrifices itself to protect the billet roller.

Avoiding HV/HP oil pumps helps with all this.

Tom

and Gokou is right, he's looking at a teardown. A little cast iron dust is one thing, a whole bunch of iron filings is another and hardened steel filings are another ballpark altogether when it comes to collateral damage. That hard stuff will damage the cylinder walls and pistons in addition to the oil pump and bearings. Wonder what he was thinking??

Tom

He now has the engine out, He is going to go through it all again, He found a lot of very fine dust like and some larger stuff, The bearings all looked fine. He is having the lifters rebuilt and a new cam all new bearings a complete rebuild. I will tell him about the gears you guys mentioned and have him contact a the manufacture to find out which one he should use, Thanks for all the help guys.

Absolutely the best thing to do, contact the cam grinder and ask them what to use. Saves a lot of hassle.

Tom

Have him magnaflux the pistons. Iron particles embedded in the skirts will very readily stand out. Embedded iron in the skirts will wreck the bores in a BIG hurry.

I got off sort of easy on my motor when I ate the gear; I was expecting everything to be toast. The bearings were the only real casuality. I polished the crank and lightly honed the bores. I will be installing new rings, oil pump, all bearings, and obviously the cam. The lifters and pistons checked out OK.

And remember-- CHECK THE INSTALLED HEIGHT OF THE DISTRIBUTOR! Take measurements and get it close, cut the intake or get a slip collar if it needs changing. Get it close with measurements, then paint the gear with dykem and run it for a few minutes. Remove the distributor and inspect the wear pattern, adjust the distributor up or down as needed to center the wear pattern, then put more dykem on it, run it again, and pull to verify. Cheap insurance!

Troy

I know someone who is running a GM Billet cam and the melonited gear from GM got eaten up in a few hundred miles. Sounds like alignment to me. He thinks he needs a bronze gear now but If the melonited gear was eaten up pretty quick, wouldn't the Bronze gear be eaten up even quicker if nothing else changes.

yes.

If he had a production Chevy roller and not some aftermarket cam sold thru a Chevy dealer it's probably an alignment issue if it ate a Melonized gear. Chevy sold millions of these things with warraty. Ask him what the cold oil pressure is. Peg the gauge?

Tom

Thanks Tom

The cam is a Mercruiser Billet Hydraulic Roller.

If you see the word billet it means bronze gear unless it has a pressed-on iron rear section like the Crane I got.

Tom