Dreaded distributor Pin

You are going to get all sorts of opinions on why they break.

I'm not claiming to be the authority on this issue. Just sharing my experiences.

I have never broken a pin in any distributor that I have run. That's 40 years now.

I do not run stock oil pumps. I run high volume pumps. I do not run stock oil pump drive shafts.

I run chrome molly ones.

I have never run a rebuilt distributor. Always new ones.

I have broken an Accell. Trash canned a Mallory Unilite. Found a home with the Ford Duraspark distributors.

My personal feeling is that the pin failure is associated with a rebuilt distributor. One where the drive gear is removed. You need to remove the pins to do that.

Either the roll pins are not intended to be reused in reassembling the distributor OR other roll pins are installed that do not have the same shear strength as the stock Ford roll pins.

That seems to be the most likely scenario?

There has been a lot of discussion here about this before.

I run other Ford engines as well. 302/347. 427. 428. I have never even heard of an issue with distributors in the other engines. Only the 351c.

I mention all of this because according to some, I should have broken a pin by now. The additional load placed on the gear by the HV oil pump, the lack of flexing in the chrome molly drive shaft are both major players in the pin failure according to others.

For the last 7 years have run the Ford Motorsport (now Ford Racing) version of the Ford Duraspark II distributor, in my Pantera. It better not break.

As of yet, none broken. My opinion as a result, those are not the determining factors in the pin failure. There is something else causing it.

Smucks re-assembling them maybe? I think highly likely?

Was your distributor re-built lately?

I forgot to mention I have a high volume pump fitted as well and it looks like the dizzy hasn't been rebuilt as all the screws look like they have never been touched and with minimal wear on the shaft and the cam drive and virtually no wear at the bottom of the shaft and even the rotor arm looks virtually new but I suppose at least the fix is pretty simple and very cheap it just stays at the back of your mind that this really should not happen and makes me very reluctant to take the car on any trips to Europe.

Yes. It is very disconcerting.

quote:

Originally posted by stelios101:
I forgot to mention I have a high volume pump fitted as well and it looks like the dizzy hasn't been rebuilt as all the screws look like they have never been touched and with minimal wear on the shaft and the cam drive and virtually no wear at the bottom of the shaft and even the rotor arm looks virtually new but I suppose at least the fix is pretty simple and very cheap it just stays at the back of your mind that this really should not happen and makes me very reluctant to take the car on any trips to Europe.

i'm ready to help with a new pin if you manage just across the sea

Is the engine fitted with a heavy duty oil pump drive shaft (aka intermediate shaft)?

Hi George,
Yes a high volume oil pump is fitted.

many times rebuilt dizzies don't have any press left to the fit of the gear on the shaft, add to that an HV oil pump & heavy grade oil and you have a recipe for breaking pins

turns out the standard volume 351C pump is already comparable to HV pumps in other engines, now increase upon that & you're comparably running a DV (double volume) pump

when you went for your ride was the engine thoroughly warmed? it takes longer to properly warm the oil than it does the coolant

You mis-read my question. I did not inquire about a high volume oil pump. I inquired about the shaft that turns the pump.

The reason that I ask is because the heavy duty oil pump shaft has no "give" in it like the OEM hex-shaped shaft. When the oil pump passes debris and tries to stop turning the distributor gear pin will shear because the heavy duty shaft doesn't twist and absorb shock as it is supposed to.

Pantera Doug is right, buy a hardened distributor shaft ( Morroso from Summit)I also would when installing the roll pin, install a second roll pin inside the stock pin, this added pin is a standard fix in the racing world. )

quote:

Originally posted by stelios101:
Hi Guy's.
I decided to go for a drive with my son in the few minutes of dry weather we've had in the UK in the last 3 months and low and behold the dreaded pin in the dizzy broke, my son initially thought something severe had happened to the engine as after a back fire a loud metallic noise was heard by both of us but fortunately just the pin.
I am a little confused as to why the pin actually broke because I think the back fire came AFTER the pin broke and not before.
My first thoughts were something caught in the oil pump but unless a small piece on metal is stuck in the engine, I can't find anything in the oil, I think the timing may have been out, now set to 18 degrees and the car seems to pull a little better.
Can anyone shed any light as to why this may have happened could it be that time has simply made the pin brittle (it was double pinned) and I have also double pinned the new one. The dizzy is a Petronix II and although the engine was built around 1999 very few miles few added in the years since.

I've never seen the OPDS (oil pump drive shaft) fail?

seen one wind up like a pretzel, must've had 20 twists in it but it didn't break. if the stock OPDS has the capability to do that, why do we need a stronger one?

the pin is the weak link, and the OP says his was doubled

unfortunately, aftermarket dizzies are being produced with the gear set too low on the shaft. there's no shaft free play clearance when the hold down is snugged down, causing excessive drag at the bottom of the dizzy gear and the block ledge

more unfortunately, this situation destroys the drive gear on the camshaft. you may need a dental mirror & a light to see the damage on the underside of the teeth down in the dizzy hole

found it, almost 1/2 way down here,
http://twiddler.typepad.com/cobra_lads/page/6/

that was an MSD, mine was a Mallory, & this is not the first Pertronics post I've seen. i'll put $2 on this as the cause of the OP's pin breakage

Well it seems to me that there needs to be a "fuseable link" in the system?

The cost of a roll pin is by far the cheapest fuse to have?



Seems to be a matter of choice? A twisted stock drive shaft would be an indication of a very serious oil pump issue and I'd rather shear the pin.

What's the point of having a drive shaft that turns itself into a pretzel? It still needs to be replaced.


The issue here really is the pin shearing under "normal" use or was there additional issues with the pump drive system?

That's a debate that can go on forever with no resolution.



Reinforce the pin. Double pin with Loctite on it is a "reasonable" solution. Even if the alloy of the steel in the pin is incorrect, a double pin should take care of that.


As far as running the pressure down to 10 psi, I don't feel comfortable with that. I'd rather over oil than under oil.

My oil idiot light is set at 10ish as well. A high volume pump that shows 80 psi isn't a ridiculous strain on the system. It drops to 35psi hot at idle. That's still within the safe limits.


There is absolutely no control with the aftermarket as to the sourcing of components. The drive gear seems to be a "person of interest" in the case.

Aftermarket companies I suspect are buying them in bulk from "off shore" companies and I suspect is the largest single factor with the issue.

The backfire was the result of your distributor not turning "in time" with the engine. The reason your pin sheered off is probably due to foreign material being drawn into the oil pump, momentarily stopping it's rotation.When you drop the pan remove the pump and check for scarring on the gears and metal in the pan.

quote:

Originally posted by stelios101:
Hi Guy's.
I decided to go for a drive with my son in the few minutes of dry weather we've had in the UK in the last 3 months and low and behold the dreaded pin in the dizzy broke, my son initially thought something severe had happened to the engine as after a back fire a loud metallic noise was heard by both of us but fortunately just the pin.
I am a little confused as to why the pin actually broke because I think the back fire came AFTER the pin broke and not before.
My first thoughts were something caught in the oil pump but unless a small piece on metal is stuck in the engine, I can't find anything in the oil, I think the timing may have been out, now set to 18 degrees and the car seems to pull a little better.
Can anyone shed any light as to why this may have happened could it be that time has simply made the pin brittle (it was double pinned) and I have also double pinned the new one. The dizzy is a Petronix II and although the engine was built around 1999 very few miles few added in the years since.

I don't know if the shaft is uprated and it looks like it was double pinned, the dizzy did have a small amount of play in the shaft(up and down) which it should have, 75-80psi oil pressure cold and around 35 hot at idle seems very normal for a HV pump and the oil was up to temp when this occurred but I would rather the pin broke and the motor stop running because no damage seems to have occurred, I would like to think because of the amount of variables in the pin breaking I will not find out exactly what the cause was (without stripping the engine down) so I will start with the obvious, change pin to a double, even though the engine has very few miles it still is a 14 year old rebuild and that dizzy pin must have been heated and cooled many many times, ordinary castrol oil as I don't know what type the motor was filled with (I do know it was golden and very clean), no debris in the sump, no visual damage to the oil pump pick, I will also fit a magnatised oil sump plug in the hope if anything metal ends up in the sump it will stick to it.
But the truth of the matter is I adore driving my Pantera and no matter what what the reason I will continue driving it.

Ford recommends you check the installed height of the gear, whenever installing a new distributor (or a new gear on an old distributor). Also, a distributor gear should be a press fit onto the shaft. If the gear's loose on the shaft, there's too much load on the pin and it will fail in short order.

These are both common problems. A friend of mine bought a brand new Mallory distributor. When he checked the installed height of the gear, he discovered it was indeed too low on the shaft. When he removed the pin to rectify the situation, the gear literally fell off the shaft.

quote:

Originally posted by stelios101: ... the dizzy did have a small amount of play in the shaft(up and down) which it should have...

yes, it should have a small amount of play, When The Distributor Is Installed !

it doesn't matter how much play it has when it's out of the engine, it can be ridiculously sloppy, it doesn't matter until you snug the clamp bolt

the less play it has outside the engine, the more I would worry. when you snug that clamp bolt, it can only have the same free travel or likely less, possibly none or negative

what I did was set the new gear intentionally low on the shaft, with the pin holes in alignment and snug the dizzy down with the clamp bolt. now remove the dizzy & inspect the pin hole. I found that snugging the dizzy down set the pin hole in the gear ABOVE the pin hole in the shaft. the clamp bolt was jamming the gear down onto the block ledge with no oil clearance, causing drag. measure where the snug down set the gear & raise it the amount of oil clearance you want higher on the shaft. a new hole will need to be drilled in either; only the new gear to use the original hole in the shaft, or drill through the new gear and the shaft, 90* from the original. I drilled only the new gear to use the original pin hole in the shaft

don't get me started on rotor phase...

I have had only one broken pin in my life time of FORD Engines and it was in my Stock 351C ...the cause was a piece of Permatex Sealant must have been used on the oil pic up and jammed the oil pump ....twisted the drive like a pretzel.

They make double roll pins ... from mcmaster carr and HD oil pump drive should cure your problems.