Distributor gear roll pin. Need some expert guidance.

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Just checked a few more items.

The refurbished autolite from Rock Auto had a cast gear, has the vertical play I mentioned, and has an oblong area to the cross hole from where the pin failed on it.

The O-Reilly Dizzy, which was a brand new unit, has a steel gear and no vertical shaft play. So considering I onl have a couple hundred miles on that one, should I just put in and run that setup, or replace the gear with a new steel gear?
 
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Hi kcmash, the shims come into play if you are at or approaching approximately 4.000-4.005 maximum compressed distributor gear length (Ford commonly uses the longer "expanded" measurement). Using a shim will eliminate the extra hassle to redrill.
As you stated, if one is lucky enough to be dead center(or close) to length spec on a gear change all the better.
 

Spike Morelli

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I have been down this road, some 22 years ago. I overhauled my 351c myself, as I am in that business. I installed a new high volume oil pump. I also left out the dual diaphram advance/retard distributor, and purchased a rebuilt ( non-California ) single advance distributor correct for my '71 with that distributor. Maybe a month or so after driving on the new engine, it happened. Driving along, the motor just stopped, and the culprit was a sheared dist gear roll pin. I pulled the dist, replaced the roll pin, and drove for another few weeks, then it happened again. When it happened a third time, I yanked the dist . At that point, I started to read that this is a common issue with high volume pumps in these engines putting heavier loads on the pin that holds the dist gear. Further, I was using a re-built auto parts store distributor, which, had the gear replaced, and as most of you know by now, the hole in the shaft and gear only line up once.....when it is assembled at the factory. So yes, my dist had an oblong hole in the gear where the pin goes, and didn't help things.
Also, after shearing the roll pin 3 times, and spinning the gear on the shaft, the gear now didn't quite have the press fit it might have originally had. I wasn't going to let this gremlin haunt me another God [email protected]*#& time!
My fix, which has run everyday for the last 20 years.............read that again, the last 20 years.....and still going strong, is this. OK, in the interests of being thorough, I jacked the engine, pulled the pan and pump, cleaned out the broken roll pins from the pan, and cleaned and inspected the pump and pan, and re-installed the pan with the HV pump ( no metal ingestion was observed, thankfully ). I had been using a heavy duty moly drive anyway, so everything was back to go downstairs.
Here's what I did to keep the Dist happy. After having the gear spin on the shaft, I neded to address that first. I took a sharp center punch to the dist shaft where the gear presses on and put a series of punch "pips" all around the area where the gear goes, effectively expanding the metal's OD for a tight press fit. I then put red locktight, the stud and bearing mount stuff, around the gear location area and pressed the gear back on to the proper location, being cogniscent of the roll pin location lining up. It pressed on very well and tight. So far, so good. We're not done. Remember the rebuilder pin hole that wasn't qite the same after they installed the gear? Well, I re-drilled it, but this time, I didn't use a 1/8th inch roll pin, I drilled the hole to 3/16th which eliminated the mis-matched pin hole in the gear and provided a high percentage of added strength to the holding power of the assembly. Still determined to show this assembly who's boss, and knowing that many rebuilders will drill a new hole 90 degrees to the old pin hole, I added a SECOND roll pin, 1/8th this time, above and 90 degrees to the original pin location. I'm talking freakin' overkill to put this Bi-otch to rest once and for all.
Like I said, it has been happy for 20 years. I don't run a heavy oil anyway, just 30 Racing, and last I looked, maybe 5 years ago when I had the dist out for a manifold change, the dist gear showed no signs of abnormal wear. This fix has worked very well. However, in all honesty, when the next engine goes in, and I AM planning to do a fresh engine, I'll likely address the engine's oiling upgrades using bushed tappet bores, possibly some redirection/restriction where it would help, and probably use a standard pump, oil pressure will tell me whether to shim it or not, instead of altering the dist gear mounting . That's Hot-Rodding, Huh? Funny, coming from a guy who keeps his car "stock".
 
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Duncan Mach72

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George Pence has previously advised that a second roll pin be installed on any performance build where higher oil pressure is generated eg by shimming the relief valve (for 90psi) and/or using a hv pump. I use a hv pump because I run 5w-30 synthetic & the lifter bores are worn. I'm happy on one pin as my pressure never exceeds 60 psi with the thin oil.
 
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KC, I got curious exactly what the spec is for a 351C dist, shaft end play allowance. The Ford manual shows .024 - .035", and gear location as 4.031 - 4.038". So you're right, there is quite o lot of free play allowed, meaning the gear will tend to find its own position. None the less, I wouldn't want to be outside of those tolerances.
+1 with Stanglover. Here are the instructions he was referencing. If the new msd gear came with a spec sheet you will see spec numbers are difference. The difference is with the msd the instructions they tell you to push the shaft in while the Ford instructions tell you to pull the shaft out. Either one of the two instructions will work.

MSD Distributor Gear.png
 

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So I read in other guidance to put a steel pin in the old hole before drilling your new hole. Looks like everyone thinks I should go get a steel gear. I think if I do that I would rather use the Autolite distributor than the other one since I understand the endplay thing now.

I did get the oil system primed today. So that was cool.

Kcmash
 
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kcmash, as you now see everyone has their opinion on these things. I'm happy you got your situation sorted out. As my parting opinion on the gear thing: pull the distributor after a five minute test run and inspect that steel gear. Then pull it a couple more times thereafter for follow-up inspections, until you are comfortable with the wear pattern. Be sure to coat the gear well with break-in lube, consider using a toothbrush (I use an old one, not the one I brush my teeth with...😛) and "scrub" the lube into the gear teeth and surface structure. The break-in is critical with steel gears!
 
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+1 with Stanglover. Here are the instructions he was referencing. If the new msd gear came with a spec sheet you will see spec numbers are difference. The difference is with the msd the instructions they tell you to push the shaft in while the Ford instructions tell you to pull the shaft out. Either one of the two instructions will work.

View attachment 59998
Thank you Kilgon. The pfd is really informative, I printed it off!
On my Autolite distributor, it was a reman I bought from a parts store probably 12 years ago, it is still running the gear that was supplied with it (as far as I know) unless the engine builder changed it without telling me back in 2012. In other words, I really have no idea what material it is, but, like a Cardone Select new Chinese made one I have, it appears to be cast. I've had no issues with it, not even when the HV oil pump that got installed, took out the cam and subsequently, the main bearings. If it ain't broke, don't fix it is in order for me.
 
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Just to add a notation; With regards to the description given on the sheet. They make it sound easy to cross drill through a round shaft. Doing this in practice, is not that easy. As a (former) machinist, I would want to set that process up in a mill, using an edge finder to calculate the exact center of the shaft, center drill and then cross drill the hole. While it is not that important to be exactly on center, it is important the the hole be straight and square to the shaft. i.e. not off at an angle. It would be nearly impossible to do this with a hand drill. Even with a good drill press, not that easy without care taken.
 
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So I call the machine shop today to see about having them put a steel gear on my Autolite Dizzy, and I get a bunch of questions I can't answer. I tell them I want a steel gear and they say "What is your cam made from? " I told them I thought it was billet steel and the tag said use steel or bronze gear only. They say, well is that Steel Billet or Cast Steel Billet? I appreciate them looking out for me, but geeze I just want to drive the friggin car!

So when I got the custom ground cam from Cam Research, I assume that is a steel billet core? I am waiting for Cam Research to call me back, but I want the quickest answer I can get.

kcmash
 
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I understand your frustration with your gear situation. But hang in there until Cam Research verifies what your core material is. Many but not all cam companies state Melonized steel gears work on all cores. Don't know why your machine shop doubts CR gear recommendation tag though. I know you're inclined towards steel (as I generally am) but with my steel billet cams I usually end up with Bronze.
But again, do it right and TALK (no emails) to Cam Research about it.
 
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Well, I started her up today. Leaking radiator cap and drain cock, leaking PS fluid, Curing paint, poor timing.

I need a driveway buddy.

Kcmash
 
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I have been down this road, some 22 years ago. I overhauled my 351c myself, as I am in that business. I installed a new high volume oil pump. I also left out the dual diaphram advance/retard distributor, and purchased a rebuilt ( non-California ) single advance distributor correct for my '71 with that distributor. Maybe a month or so after driving on the new engine, it happened. Driving along, the motor just stopped, and the culprit was a sheared dist gear roll pin. I pulled the dist, replaced the roll pin, and drove for another few weeks, then it happened again. When it happened a third time, I yanked the dist . At that point, I started to read that this is a common issue with high volume pumps in these engines putting heavier loads on the pin that holds the dist gear. Further, I was using a re-built auto parts store distributor, which, had the gear replaced, and as most of you know by now, the hole in the shaft and gear only line up once.....when it is assembled at the factory. So yes, my dist had an oblong hole in the gear where the pin goes, and didn't help things.
Also, after shearing the roll pin 3 times, and spinning the gear on the shaft, the gear now didn't quite have the press fit it might have originally had. I wasn't going to let this gremlin haunt me another God [email protected]*#& time!
My fix, which has run everyday for the last 20 years.............read that again, the last 20 years.....and still going strong, is this. OK, in the interests of being thorough, I jacked the engine, pulled the pan and pump, cleaned out the broken roll pins from the pan, and cleaned and inspected the pump and pan, and re-installed the pan with the HV pump ( no metal ingestion was observed, thankfully ). I had been using a heavy duty moly drive anyway, so everything was back to go downstairs.
Here's what I did to keep the Dist happy. After having the gear spin on the shaft, I neded to address that first. I took a sharp center punch to the dist shaft where the gear presses on and put a series of punch "pips" all around the area where the gear goes, effectively expanding the metal's OD for a tight press fit. I then put red locktight, the stud and bearing mount stuff, around the gear location area and pressed the gear back on to the proper location, being cogniscent of the roll pin location lining up. It pressed on very well and tight. So far, so good. We're not done. Remember the rebuilder pin hole that wasn't qite the same after they installed the gear? Well, I re-drilled it, but this time, I didn't use a 1/8th inch roll pin, I drilled the hole to 3/16th which eliminated the mis-matched pin hole in the gear and provided a high percentage of added strength to the holding power of the assembly. Still determined to show this assembly who's boss, and knowing that many rebuilders will drill a new hole 90 degrees to the old pin hole, I added a SECOND roll pin, 1/8th this time, above and 90 degrees to the original pin location. I'm talking freakin' overkill to put this Bi-otch to rest once and for all.
Like I said, it has been happy for 20 years. I don't run a heavy oil anyway, just 30 Racing, and last I looked, maybe 5 years ago when I had the dist out for a manifold change, the dist gear showed no signs of abnormal wear. This fix has worked very well. However, in all honesty, when the next engine goes in, and I AM planning to do a fresh engine, I'll likely address the engine's oiling upgrades using bushed tappet bores, possibly some redirection/restriction where it would help, and probably use a standard pump, oil pressure will tell me whether to shim it or not, instead of altering the dist gear mounting . That's Hot-Rodding, Huh? Funny, coming from a guy who keeps his car "stock".
Wow! I LOVED the response, the details of not just the mechanically related aspect of the story, but also the way it is being told from the perspective of your thinking processes at the time.

Magnificently done. Many thanks for sharing this perfect example of what many see as an extreme point of view for a car lover. But, no, it is more a look at the very beginning stages of the mental processes of a Mustang Loving Extremist! Well done. Just, wow... Thank you, thank you, thank you...

For anyone who may not know me well, please do not be frightened just because I understand what others may think of me when they find out what an extremist I seem to be with respect to loving First Generation Mustangs and Shelbys... No need to contact any law enforcement agencies, whether they be Local, State, or Federal operations. They no doubt would already understand we often choose to be non-hostile in nearly all situations. Can you guess the one exception is to the various kinds of situations that might make me flip my lid? Asking for a friend.
 
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Well, I started her up today. Leaking radiator cap and drain cock, leaking PS fluid, Curing paint, poor timing.

I need a driveway buddy.

Kcmash
Hang in there. At least it's running again. Take care of the problems addressing the most critical ones first. We all have those times with our cars. I'm going through one right now with mine.
 
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