Distributer gear pin sheared off

[chas427fe]

I have about 350 miles on my rebuild and my engine died. After checking I found that the pin that holds the gear on the distributor shaft has sheared off. The engine is 428 FE with a MSD Unilite distributor with a steel gear, the cam is a Comp roller cam, the oil pump is Melling HV 57 and 10w40 oil. Any help trying to solve why this happened so that I can fix the problem and get going again. Thanks, Chas

[LMH]

It's a somewhat common problem with small blocks and the fix as I've been told is to replace the pin with one made for a Chevy. It's both larger and stronger. It tends to occur on small blocks that are using a HV oil pump.
That said, I don't know if FE's are subject to the same situation but it might be a fix for you anyway.
Larry

[JBCOBRA]

Don't feel bad. It happens.
Mine crapped out on me right in front of a police station and the car wasn't legal yet. They didn't care anyway, but liked the car.
The fix is easy. Have it drilled and put a 3/16 press pin in (dare I say chevy pin)
in there. LOL
JB

[chas427fe]

Thanks for the quick response. I will have it drilled out and a new pin put in like you both suggested. Chas

[PROFESSOR FATE]

This is not a common problem on FE motors. If the pin sheared, it was probably caused by something other than the pin. Those gears are supposed to be a press fit on the distributor shaft. If not, there is an excessive load placed on the pin. If the gear spun on the shaft, the proper press fit is definitely history. If there is still some interference, you might be able to get away with using Loctite when you reassemble, but you're taking a chance even with an oversize pin. Also, I would think twice about going to a 3/16 pin. The bigger you make that pin, the more you reduce the cross sectional area of the shaft, and the weaker it gets. If the gear is properly installed on the shaft, redrilling and replacing the stock 1/8 roll pin with a 5/32 roll pin should provide a substancial increase is shear strength without overly weakening the shaft.

[Carnut427]

While Professor Fate makes a good arguement, and the (light) press fit is indeed important, loctite will solve that problem as long as you can't wiggle the gear on the shaft. That being said, Chevies have the same size shaft and use a 3/16" pin, as I did some time ago. The shaft has plenty of "meat" for it. An alternative is to reinstall another 1/8" roll pin and another 180* off about 3/16" - 1/4" away from the original. This will make installing a new gear difficult in the future, however, unlike merely installing a 3/16" pin. BTW, this is a common problem when running a hv pump.
Another thing I noticed...most roller cams require a bronze cam gear, as the steel in a roller cam is so hard it wears out a standard gear. If the gear on your cam is removeable, it's probably a standard gear; otherwise, I suggest buying a bronze gear and installing a 3/16" pin as suggested above.

Dan

[Jamo]

As Fate would have it...

Yup...common with HV pumps, as the threads here indicate over the past several years. Use a Chevy pin and don't worry about it again.

[Anthony]

Originally Posted by chas427fe

The engine is 428 FE with a MSD Unilite distributor

Do you mean mallory unilite, as the MSD FE distributors have a larger shaft diameter than stock , I think .531" or something like that. I think the mallory distributors may have the original spec distributor shaft diameter, something like .467" or something. I would think the MSD shaft would have a much less of a chance of snapping after enlarging the gear pin hole in the distributor shaft.

[RICK LAKE]

Chas If your oil pump picked up something and locked up the oil pump the pin should give first. You should pull the pan down and check that oil pump. Pins don't break just because. I run a HV-HP oil pump with 100 psi spring in the pump. On startup I pin the gauge to 120psi. 7 years of racing and have not broken a pin. I am not lucky. I have a MSD distributor and FFP oil pump drive
shaft. Check the oil pan plug ( hope it is magnetic) and see if there is any metal chips on it. If so, pull the pan. Pulled the pan is better that wasting a 15G motor with a quick fix. Rick Lake

[ERA Chas]

Anthony is correct about the different shaft diameters. An MSD may not do that in your combination - unless: the distributor hole in the manifold is cut too deep or off center to the oil pump shaft. Ricks advice is excellent also.
Please check so you may sleep well at night.

[John Owen]

My primary experience with this problem is with the Accel version of the Mallory - a slip fit with 1/8 pin and it will shear with a HV pump, as I have demonstrated several times. Think they use slip fit to change bronze gears quickly in a race environment. Put in a 3/16 pin and roughed up the shaft a little to provide more stability - no problems on any of them. The MSD is a press fit and may not need the 3/16, but I plan to use it anyway. No shaft failure problems.

[chas427fe]

Thanks for all the other post. Before I read all the other post I had already drill it out and put the 3/16 pin in. Yeehaa. I am up and running again til the next hurdle. Some other points made were the the steel gear which was installed by Keith Craft based on the cam he installed. The oikl pressure is back to 60 PSI at start up. I will take it out tomorrow for a test ride. Chas

[Jamo]

Good advice (as usual), Rick...but I had a couple of them snap without any problems with the pump.

Here's the best part...that was when I was running the damn bronze gears with roller cam, and the gears held (sharp, but no broken teeth)!

Switched over to the solid lifter, steel gear, and bigger pin...now, no problems (which means it will scatter to pieces tomorrow since I said that).

[Lowell W]

Just an observation...

I carry an extra MSD distributor, along with a bunch of other "extra" stuff. When I pressed off the original iron gear and pressed on the new steel gear, it took a lot of pressure to move the gears on the distributor shaft. I mean A LOT. I don't know how much torque it takes to turn the oil pump at 6K+ RPM but it appears to me that most of the torque to the gear is intended to be applied by the friction fit of the gear on the shaft; not by the pin. Is it possible that those of you who've sheared roll pins may not have a tight enough gear to shaft fit?

Also, I agree with the observation regarding not drilling any more holes than necessary in the distributor shaft. I used the original gear as a fixture to set up the new gear in the Bridgeport, although a drill press could work as well (located the old gear with the hole oriented to the spindle, locked down the table, then clamped the new gear in place), then drilled the hole in the new gear in the same place as the hole in the old gear.

Yeah, so now I'll probably twist off a gear on start-up tomorrow...but at least I have an extra distributor timed and ready to drop in.

Lowell

[Bill Wells]

same here...my pin failure was the slip fit ACCEL. I called their tech line and they said "ya must have a high vol oil pump and a 1/8 inch pin , drill it out and go to a 3/16th inch" ...duh...So , instead, I switched to a MSD distributor with a press fit . Fixed the Accel and carry that as a spare in case the MSD fails - so far with about 3,000 mi on MSD all is ok. It was obvious the Accel folks were having some failures with the smaller pin, and in fact, he inferred the thicker 3/16 inch pin is now on their Distributors, but not sure about that.

On my older 392 Ford Racing Crate, the Accel was the standard distrib. A coupe of years ago they switched to MSD as their standard 392 crate distributor . A message there methinks.

Bottom line, both brands report failures, so what ya gonna do ? carry a spare as insurance I guess, like I do for my fuel pump - went thru 3 Holley Blues so now a Carter pump . Breakdowns many times happen near a mechanic shop if ya need em, but never seem to happen near a parts store that carries what ya need . Wonder what part I will need next as a spare candidate . Bill

[chas427fe]

My distributor has the .47 diameter shaft. The gear is a slip fit and just slid right on the shaft. My distributer is part number 4755301. Is there another model that I should consider for the long run?