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Eating distributor gears

16K views 104 replies 30 participants last post by  69GT350H 
#1 · (Edited)
I assembled the engine 2 years ago, and finally got it running, and drove it this past year. I trailered it up to Tn and drove it around the PITS show for 4 days, trailered it back home, and drove it a little down here.

After replacing my over ported head, but before starting it, I noticed that the distributor center shaft moved too much. I pulled the distributor and noticed that the teeth on the gear are worn, the edges of the teeth are worn sharp.

I replace the gear, oil, filter, and within 30 minutes of the engine running, driving the car, it has destroyed the gear on the distributor. One section of teeth are so worn down that the distributor is no longer turning.

I replace the oil pump, pickup, replace the gear, oil, filter, and within 1 min, I see it marring the new gear, complete contact on one side of the tooth edge.

I replace the distributor with a fairly well used Mallory, and after about 15 min of trying to get the engine to run (it's a dual point and not adjusted well) I stop and pull the distributor and see that it is starting to scratch the same edge of the distributor gear.

This is a Comp Cam Hydraulic lifter cam. Comp Cam recommends either they steel or composite gear. This is the steel gear that I have been replacing with. The oil is 10w-30. Before installing the distributor I lube the gear, and when I pull it out most of the lube is washed off and the gear has engine oil on it.

The first oil pump was a Melling standard, the 2nd is a TRW HV. The pump shaft has play, it is not binding.

The only other thing I can think of is somehow the gear on the cam has gone bad and is eating into the distributor gears. Any though on what I might be missing?
 
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#3 ·
From left to right 1st gear is the original, but over the past 6 months has worn the teeth sharp. 2nd is the one that lasted all of 30 minutes before wiping an entire section of teeth off. 3rd is the one where the engine ran for only about a minute. 4th and right most is the Mallory where the engine fired but did not run.


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#5 ·
I assembled the engine and yes, put the thrust plate on. Is it loose and the cam is walking? When I had the intake off I pulled and inspected the lifters and they are all perfect. Unfortunately, now there is no way to see the plate until I take the timing cover off.

Metal in the engine, that is one reason I replaced the pump and pickup. Any of the debris should be stuck in the old oil filter.
 
#8 ·
When I put my GT40P in I spent some time trying to understand what I needed to do. So, here’s what I learned and believe is pretty accurate. First off is understanding what the cam is made out of. Ford factory cams are billet 5150 steel. They are fully machined even between the lobes. Ford used a steel distributor gear. Most aftermarket hydraulic roller cams are not billet 5150 steel. They are “SADI” or Selectively Austempered Ductile Iron. They are cast ductile iron that only the lobes are hardened. These cams you can use a regular cast iron distributor gear, the same as a flat tappet cam. I got this info from Howard’s Cams. Howard also told me all cam companies are buying their blank cores from the same suppliers.

This causes problems with distributor companies. I read a article by MSD said they as most aftermarket distributor companies use a Melonized gear. This is a hardened ductile iron gear. It’s the default material as it will work on flat tappet, SADI or billet Ford 5150 cams. I’m using a $29 MSD Melonized gear I bought at Autozone. I called MSD and verified it would work on a 5150 cam.

The other part of the equation is the gear must be properly located on the shaft. These MSD Melonized gears have only 1 roll pin hole drilled. You must drill a new hole through the distributor shaft 90* from the factory hole after you properly measured and located the new gear. MSD has a pdf on their web site how to do this.
 
#13 ·
I know, just saying that’s what it looks like. That second gear, where did it come from? Maybe there’s a bad batch, or some Chinese knockoffs running around. I’d still give comp a call, then maybe MSD and see what they recommend for a gear. How does the cam look if, you can shine a light down there and see that hopefully the damage is limited to the distributor gear.
 
#14 ·
Time to buy that expensive magnet thing summit sells to snap on the oil filter....maybe not so expensive in the scheme of things! That sux...You buy good parts, put things together carefully,....and crap like this happens..I hope you get it figured out and no permanent damage to the motor.
 
#17 ·
Couple of things occur to me,


1) The first gear damaged the cam gear and now the cam gear is damaging all the rest of the gears
2) The dizzy is either dragging dramatically or somebody modified it in such a way that the gear doesn/t mate correctly, shaft size is too small for the bearing surfaces, bearing surfaces including in the block could be toast... In any case, trying a different dizzy would be on my list.



Next time the pan is off, pull a rod cap just to see...


Good luck, these are teh worst kinds of problems where a new engine gets debris...
 
#27 · (Edited)
Going to drill the .030 hole in the lifter galley end plug to squirt extra oil on the gears. Normally this will produce a slight drop in oil pressure, but a HV pump will make up for it.

edit: I started off with a standard oil pump and look where I am. :surprise:
 
#37 ·
camshaft

69, you're eating dizzy gears because th gear on the cam blank was cut incorrectly when Comp made the cam. A few years ago, Comp had a large batch of blanks with bad gears on them. I know small block Fords were affected, don't know if there were others. You have to replace the cam. Comp ought to give you a new one, but, after two years,.....I don't know if they be helpful or not. AND, to the poster who thought that an HV oilpump can hurt your cam & dizzy gears, forget it, just a senior married woman story. While it IS true that the load is increased, think back to Arnold S in his Mr Universe days,....if he picks up 4 lbs or 5 lbs, it doesn't really matter. He is so strong he won't even feel the difference. Your cam and dizzy gears are just like that. Stronger than your oil pump will ever even know. That pin in the shaft that some dizzies have is for lacation, not to hold the drive. It is a locator, not a shear pin. There is a difference. LSG

**just a note, we have been using the plugs with a tiny hole drilled in them. I don't know if the dizzy notices or cares, but the lifters are happier if the air in the system has an easy place to piss out. Use the on BOTH of the lifter gallery ends. **
 
#45 ·
Just for the record, I did have a serious problem with a HV oil pump. It twisted the rod between the dizzy and pump, giving only intermittent oil pressure. The previous owner also disconnected the oil pressure warning lamp, so I didn't know that there was anything going on until my motor started running hot.

When I stopped to find out why, there was a lot of blow-by coming out my breathers, so I checked my oil. It looked fine at first glance! Level was good on the stick. But when I looked at the rag I'd used to wipe it, it looked like silver paint.

I towed it home, tore down the engine, and despite the fact that it started easy, ran smooth, and seemed fine (except for the blow-by), my main bearings were riding on top of each other.

So my advice? If you're going to use an 'improved' pump, make sure the engine's been built with that in mind, and use a hardened ARP pump shaft. Also, idiot lights suck. Especially when they don't work.
 
#48 ·
Just for the record, I did have a serious problem with a HV oil pump. It twisted the rod between the dizzy and pump, giving only intermittent oil pressure. The previous owner also disconnected the oil pressure warning lamp, so I didn't know that there was anything going on until my motor started running hot.



When I stopped to find out why, there was a lot of blow-by coming out my breathers, so I checked my oil. It looked fine at first glance! Level was good on the stick. But when I looked at the rag I'd used to wipe it, it looked like silver paint.



I towed it home, tore down the engine, and despite the fact that it started easy, ran smooth, and seemed fine (except for the blow-by), my main bearings were riding on top of each other.



So my advice? If you're going to use an 'improved' pump, make sure the engine's been built with that in mind, and use a hardened ARP pump shaft. Also, idiot lights suck. Especially when they don't work.
I know how to, and have built this and several other motors. To eleavate the non existant issue of a HV pump, I will be drilling a 1/32 hole in the lifter galley plug. This will give all that extra oil a place to go and the engine will not suffer from too much or too little oil.

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#49 ·
So it seems the photos do not do a good job of representing the items. Thrust plate was on tight and has normal wear. The lifters were pulled and only a couple show light Mark's of rotation on the bottom surface, the majority look brand new. The cam was pulled and all the bearings show none to slight indications of the cam being installed. The lobes are all normal looking, appear to have no markings or scratching indicating a wearing issue. The gear teeth on the cam does show excessive wear on the one side of each tooth. Casual inspection shows no Nick's or chips in the teeth. The cam bearings are smooth and correctly clocked for the oiling. All oil passages are clean and clear as they should be. All 4 gears of the gear drive look as if they are brand new.

This block was used back in the 80's and 90's with no issue so i will rule out the block. As I have used 2 distributors and 4 gears I am going to rule out a distributor problem. As i have replaced the oil pump i am going to rule that out as well. I checked the oil pump shaft and found no binding. Once all the lifters were removed the cam rotated easily and also was removed easily from the block.

The last item is the cam itsself. The new CompCam and lifter set has arrived and will be I stalled. Lifters will be primed first, conventional oil with break in additive will be used for the cam break in. I will interrupt the 30 min break in at to be decided intervals so that I may pull the distributor to inspect the gear.


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#50 ·
I haven't read the whole thread, but you are correct to replace the camshaft.

I went through the same thing on a high hp 351W decades ago.
Whether it was bad steel on the camshaft
Whether the camshaft gear teeth were dented from a bad install at the mechanic
Whether the cam was walking around.

It didn't matter, whatever dizzy went in, the gear was destroyed or whatever.

When the engine was taken apart, there were multiple issues, but the camshaft was changed at the same time.
No more busted gears
 
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