Excessive distributor gear wear from billet cam
07-20-2012, 11:02 AM
#21
Intake is still on motor, so hard to see any pattern on cam. I dropped a boroscope down the distributor hole this morning to look at the cam gear, and it did not look excessively worn to me. Pattern seemed to be down the middle. I tried to take a picture of the monitor of the scope, but it did not come out very clear.
07-20-2012, 11:35 AM
#24
GM recommends the use of the melonized gear with their billet core cams. I still don't know of any way to verify that my gear is in fact the melonized one. I bought what I thought was one and installed it. Now I'm starting to wonder what I really bought.
Yes, some (especially racers) run the bronze gears with billet cams. They are designed for sacrificial wear, so they must be replaced regularly. But come on - Merc has been running the billet cams in all of their mag motors for years without gears wearing out. That is exactly what I have - a Merc mag roller cam that was reground - dist gear on the cam was not touched. Therefore, the correct melonized gear should have held up, unless A), I DON'T have a melonized gear, or B), there is some other problem like gear pattern or oil pump issues. I guess that's the $500 question.
Now I have to decide where to go - try another melonized gear, or run something else, like bronze or composite.
Yes, some (especially racers) run the bronze gears with billet cams. They are designed for sacrificial wear, so they must be replaced regularly. But come on - Merc has been running the billet cams in all of their mag motors for years without gears wearing out. That is exactly what I have - a Merc mag roller cam that was reground - dist gear on the cam was not touched. Therefore, the correct melonized gear should have held up, unless A), I DON'T have a melonized gear, or B), there is some other problem like gear pattern or oil pump issues. I guess that's the $500 question.
Now I have to decide where to go - try another melonized gear, or run something else, like bronze or composite.
07-20-2012, 12:39 PM
#25
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OK, Its the original cam. Did you install a new dist. gear, also did you inspect the old gear or see it? DO NOT RUN A BRONZE GEAR! You need not to machine for more oil. Either the gear has gone bad or it was never changed and the new pattern has prematurely worn the gear. Even if the contact pattern is off, it will not effect gear wear in a short period of time.
Go back and think about the details of what it looked like at tear down, not saying you did not inspect it, but tear-down inspection is very important, so you do not duplicate issues that were already there. I have seen worn Merc Distributor gears at tear down, with no other mechanical issues.
Hope this helps, Mark
You could use a bronze gear, if it was a dry sump or wet sump with external oil pump, the bronze will just wear out driving a oil pump.
Go back and think about the details of what it looked like at tear down, not saying you did not inspect it, but tear-down inspection is very important, so you do not duplicate issues that were already there. I have seen worn Merc Distributor gears at tear down, with no other mechanical issues.
Hope this helps, Mark
You could use a bronze gear, if it was a dry sump or wet sump with external oil pump, the bronze will just wear out driving a oil pump.
07-20-2012, 01:59 PM
#26
MER, it was a low hour Mag cam that a friend was running in his 502 Mag. I had it reground for more lift. Should not have affected the gear at all.
I did change the gear on my distributor to what was supposed to be the correct GM melonized gear (PN 10456413). At this point I am starting to think they may have sent the wrong gear. That is about the only explanation that makes sense at this point, but I guess there is no way to prove it without a metalurgist involved.
I took my oil filter from the 10-hour break-in to the shop and had it cut open. Could be game over at this point - we spotted some copper flakes in there. Pictures at 11. At this point I need several cold beers.
I did change the gear on my distributor to what was supposed to be the correct GM melonized gear (PN 10456413). At this point I am starting to think they may have sent the wrong gear. That is about the only explanation that makes sense at this point, but I guess there is no way to prove it without a metalurgist involved.
I took my oil filter from the 10-hour break-in to the shop and had it cut open. Could be game over at this point - we spotted some copper flakes in there. Pictures at 11. At this point I need several cold beers.
07-20-2012, 02:15 PM
#27
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+1 on the Comp Cam gear. We used to use the bronze gear but today we are getting little to no wear with the Comp cam dist gear.
Engine builder is suggesting that I go with Comp Cams' composite distributor gear. He says he has had good luck with those for all types of cams. Can anyone tell me whether Merc is using the .491 diameter shaft or the .500 shaft in their distributors? Anyone had any experience with these gears?
07-20-2012, 03:55 PM
#28
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MER, it was a low hour Mag cam that a friend was running in his 502 Mag. I had it reground for more lift. Should not have affected the gear at all.
I did change the gear on my distributor to what was supposed to be the correct GM melonized gear (PN 10456413). At this point I am starting to think they may have sent the wrong gear. That is about the only explanation that makes sense at this point, but I guess there is no way to prove it without a metalurgist involved.
I took my oil filter from the 10-hour break-in to the shop and had it cut open. Could be game over at this point - we spotted some copper flakes in there. Pictures at 11. At this point I need several cold beers.
I did change the gear on my distributor to what was supposed to be the correct GM melonized gear (PN 10456413). At this point I am starting to think they may have sent the wrong gear. That is about the only explanation that makes sense at this point, but I guess there is no way to prove it without a metalurgist involved.
I took my oil filter from the 10-hour break-in to the shop and had it cut open. Could be game over at this point - we spotted some copper flakes in there. Pictures at 11. At this point I need several cold beers.
Sorry about the news, not good for a Friday. Better you find it now and not parts in the bilge. Now you have my interest in whats going on, the cam gear shouldn't have put bearing material in the filter, for the amount of wear I see.
Turn the A/C on and get it apart. Mark
Iam not even going to ask why you reground the cam for more lift.
07-20-2012, 04:16 PM
#29
I had the cam reground because I wanted more than .480 lift, which is what the stock Merc cam is running. In retrospect, I should have just found one off-the-shelf, like the stock HP500 cam. Live and learn - but still to-be-determined if that is my problem here.
07-20-2012, 04:17 PM
#30
Oh yeah - I promised pictures of the oil filter. I put them on another thread of their own => http://www.offshoreonly.com/forums/g...ml#post3735248
