Double pinning distributor gear?

If anything gets caught in the oil pump it will shear the pin (note: this is not theoretical, this has happened on numerous occaisions). Basically anything that can cause an increase in force necessary to drive the pump can cause it. No downside to double pinning. Its also recommended you get a high strength drive for the pump (goes between dist and pump).

I have personally suffered a sheared pin, which caused a WHOLE lot of pain and suffering (missed a friend's wedding and the boat that was to send the Pantera to me in France).

I'll never forget that, and have mine double-pinned.

My post is to comment that I've suffered first-hand this problem, and have read numerous times that the pin is just too weak, and there is no downside to double-pinning it.

1717 has a Unilite, and I had a shear pin failure, was just driving down the street and had a POP, then nothing. Mallory encourages driling out and using a 5/16" pin. I did this and havent had any other problems.
Jeff

The stronger pin allows somewhat larger debris to pass before the pin breaks
or the distributor driveshaft wraps up like a barber pole. One common form
of debris is from the OEM umbrella seals which disintegrate after 35+ years.
The 351C pick up has a bypass hole in the pick up screen which allows relatively
large debris to pass. The pickup from a 351M/400 truck engine does not have a
bypass hole so is more effective at blocking debris and will bolt on in place
of the 351C pick up. See:

http://www.bacomatic.org/galle...Onews17of38.jpg.html

Dan Jones

OSOFAST
Are you sure it was 5/16" and not 5/32"?

The oem oil pump drive shaft twists & absorbs shocks, but the heavy duty oil pump drive shafts don't twist so the pins shear off.

The twisting of the oem shaft causes "spark scatter", the heavy duty shaft was desinged to prevent spark scatter.

If you can put up with spark scatter, use the oem shaft and it becomes a non-issue.

Better yet, install a distributorless ignition, use the oem drive shaft, and you have neither spark scatter or sheared distrubtor gear pins.

-G

To my knowledge my oil pump drive shaft has never been modified or replaced. Does this mean I am relatively safe, or is this something I should be worried about?

quote:

Originally posted by SoonerBJJ:
To my knowledge my oil pump drive shaft has never been modified or replaced. Does this mean I am relatively safe, or is this something I should be worried about?

You're safe. Unmodified Clevelands don't have a problem in this area (the valves and rod nuts are another issue however)

I don't believe the R code/Q code oil screen has a hole in it, only the earlier - flatter oil screen. Melling #M84-AS1 oil screen (aka an oil pick-up or an oil pump suction line) is a duplicate of the R code/Q code high volume oil screen. There's a pic of this oil screen in my 351C photo album.

Or am I showing signs of senility again?

-G

I respectfully disagree on the pump driveshaft issue. Wrecking yards have lots of Ford engines (not just Clevelands) in which the stock soft steel driveshafts are twisted or broken. It's easy to spot; the driveshafts are hexagonal and the edges are often twisted in a graceful spiral. Additionally, the hex-edges that actually drive the pump are worn almost round in some engines. A round shaft will not power an oil pump for long. A characteristic of Ford V-8s is, a broken oil pump shaft does not shut the engine down.... for a few minutes. Then it seizes and you get to spend a couple of thousand $$ to overhaul it. Performance driving, high rpms, bolt-on power adders, high-pressure or high-volume oil pumps or even shimming the pump relief valve- all can overstess the pump driveshaft and drive-gear spring pin. A 4130-steel pump driveshaft from Ford Motorsports, Moroso or Milodon will cost less than $20 and IMHO is cheap insurance. They install exactly like stock.
FWIW, the coil-of-thin-steel spring-pin failure mode in distributor drive gears is, impacts from micro-debris going thru the pump progressively cracks the thin layers until the pin breaks in two. On some engines during the progressive failure period, the distributor retards perhaps 20 degrees, causing lots of heat, detonation, pinging and loss of power.
If you have trouble finding real roll pins to double up in your distributor gear, a short piece of drill rod, staked on each end also works. Again, real roll pins or a chunk of drill rod literally only costs a few pennies and is very cheap insurance. Buying a high-buck ignition distributor is no guarantee, either. They all use the same cheap spring pins and they all can fail the same as stock. Both of these breakdowns have happened so often, it ought to be a mandatory upgrade for all pushrod Fords. Tell your mechanic to just do the mods; a free tow-truck ride is not fun at any time.

Jack,

How does one identify a "real" roll pin, especially if purchasing online? Do you have a source and part number?

John

I got mine from McMaster-Carr. I can send extras if you want them. (they were a bulk item I think I got 25 or so)

quote:

I got mine from McMaster-Carr. I can send extras if you want them. (they were a bulk item I think I got 25 or so)

Thanks, but how do we identify a "real" roll pin?

John

quote:

I got mine from McMaster-Carr. I can send extras if you want them. (they were a bulk item I think I got 25 or so)

Hey Husker,

I could use one if you can spare an extra. How much would you want?

Jack,

For people who missed your article in POCA, that dealt with double pinning distributor gears, perhaps you could put the specifics in this thread, so people know exactly what to use.

I have wanted to do this mod for a number of years to my OEM dual point. However I have been warned against pulling the distributor because of potentially having the distributor gear drop in to the oil pan. Not really sure how this could happen unless the pin is already damaged.

The individual who guided you in that manner is an alarmist. The gear is pressed on and in most applicatons requires reasonable force to even rotate it on the shaft w/o a pin. I'd take that bet for big money.

A more reasonable concern is the oil pump shaft. I have heard of incidents where rebuilders have neglected application or positioning of the Timmerman Collar that prevents the shaft from separataing from the oil pump and dropping into the pan upon removal of the pump. Also, a low probability event.

Go ahead pull it.

Oops, for better accuracy, "dropping into the pan upon removal of the pump" should read "dropping into the oil pan upon the shaft's disengagement from the oil pump"

Maybe thats clearer

Garth66: I PM'd you.

I've read enough posts where owners have sheered the pin to make it worth it. Its an easy mod to prevent a failure, even if a low probability, which would leave you high and dry.
BTW when I replaced my gear it was not pressed on.

Hi Dennis,

I would be concerned if your engine builder does not realize what many know here as common knowledge. Double pin it.

What else has he not done correctly......

Mark

I've also been through this a few times ...

The first time is chronicled HERE. Pictures included ...

It also happened twice last summer because I couldn't source the proper roll pin (the ones I was finding were too weak). I have since sourced some higher grade roll pins and I will be double-pinning the gear in an 'X' across the gear. There is no way to get a smaller roll pin inside the 3/16 roll pin that fits inside the gear. My gear was drilled for the second pin; however, I have to get the dist drive shaft drilled to match. I'll post pix once I undertake the work ...

Ciao,
EA
#3528

Mark, I hope the engine builder hasn't done anything else incorrectly. He has been building engines since the seventies and came highly recommended. He's built a number of clevelands over the years, but I think that a lot of his customers are drag racers.

As far as the roll pin, he contends that if it breaks, it broke for a reason. He feels that a broken pin is better than the potential of more serious damage if it isn't allowed to break.

I've now heard many stories of cars being disabled by a broken roll pin, but none about engine damage caused due to double pinning.

Looks like I'll be double pinning!
Dennis

Here,s a coil pin.

Ford's oil pump drive shaft is designed to twist and absorb problems that try to stall the pump. The lower shaft is not the picture of an under-engineered or defective shaft, its the picture of a shaft that faithfully performed the job it was designed to do until the very end!

Notice how severely twisted the shaft is, that's how much twisting it takes to make a drive shaft snap in two. The normal shaft removed from a high mileage Ford may have one to two full twists in it. The shaft removed from a motor that is clean inside, maintained well by the owner, may not be twisted at all.

Passing debris is not what caused the severity of the twisting you see in this picture. The aftermarket pump in this motor had a burr inside the casing that made the pump hard to turn, and over twenty to thirty years of use the shaft slowly twisted into the shape you see.

The lesson here is not to replace the shaft with one that doesn't twist, the shafts twisting is a beneficial thing and an intentional design feature. Rather, the lesson here is to disassemble a new pump, inspect it, deburr it, and hand fit the rotors and housing for 0.0025" clearance. Thoroughly clean it, make sure its free of debris. Twist it by hand and make sure it turns freely BEFORE you install it in your motor.

Heavy duty oil pump shafts were not designed to improve the lubrication system, they were designed to benefit the ignition, they are designed to eliminate spark scatter. For the average Joe like myself, the issue of spark scatter is a moot point, I never noticed a problem caused by spark scatter; therefore the heavy duty oil pump shaft is a solution to a problem I didn't know I had.

If you don't install a heavy duty oil pump shaft in your motor you won't have a problem with shearing roll pins. The oem shaft will twist as it was designed to do.

-G

George Fascinating perspective and visual. I was unaware that the shaft's were designed to twist to that magnitude with out failure.

Frankly, I assumed they could flex; however, any flex that resulted in a permanent twist, I thought, would soon result in a broken shaft not far down the road. We've dismantled quite a few 351C engines among Space City members and I've never even seen a bent shaft.

OK, so my question is this. What is your source of knowledge around this design feature. In house Ford produced documents on the Clevelands design, A trusted engine builder, design papers of another engine that uses an oil pump shaft?

Seeing is believeing and I do not doubt the shaft's design can serve that purpose. However, you state with emphatic confidence that this was an intended design element by Ford engineers. I'd really like to know whether this is reasonable conjecture based on visual observation of the twisted shaft or does this design element exist stated in a document produced by Ford or it's engeeneers responsible for the engine's design?

I'm trying to cut through fact and Panteraspeak before I relate this insight to others in the future. Thanks

George,

Are both of those shafts from the same displacement engines? The twisted shaft appears to be longer and of a greater cross section than the untwisted shaft (camera angle?).

The twisted shaft brings up another interesting point. As the (drive) shaft twists, it becomes shorter, which reduces the depth of engagement in one or both of the mating shafts (dist and pump)

John

quote:

Originally posted by Cowboy from Hell: The normal shaft removed from a high mileage Ford may have one to two full twists in it.

Several twists are normal? Maybe on junk yard engines. To me it's just a sign of a poorly maintained engine that has survived a couple of near oil pump failures and/or correspondingly one that has had a lot of debris through its lubrication system. They'll usually also have a matching set of bearings and journals that are badly damaged too. Even when considering rebuilding, it raises questions as to whether you can get all the crud out of the oil passages that caused the damage. That's partly why you see all those oil pumps and braided steel lines from the NASCAR teams on ebay. They'll never trust them after they’ve seen a blown up engine and they just pitch'em.

quote:

......and over twenty to thirty years of use the shaft slowly twisted into the shape you see.

Looks like every shaft that comes out of an engine with a seized oil pump to me. How do you know those twists developed over 20-30 years and not just as a result of a catastrophic failure caused by debris too large from the pump to tolerate?

quote:

…the shafts twisting is a beneficial thing and an intentional design feature.

If shafts really do routinely twist multiple revolutions in use, one could argue that is truly a means of making the engine more tolerant of gear rotor oil pumps intolerance to debris and it would wreck fewer engines and strand fewer people by not failing catastrophically.

One could also argue that the weak link should be the roll pin so an engine that may have just lost it's oil pump is shut down by losing its timing mechanism too.

G, you’re a faithful disciple of the Ford engineers of the day but for me, the design lesson here is gear rotor oil pumps may be simple/reliable but do not tolerate large debris. Faithfully: debur your rebuilds, keep your engine internals spotless during assembly, and change your oil frequently.

Take care,
Kelly

After being respectfully disagreed with I initially just walked away from this thread. I was willing to let you guys believe whatever you want, but Chris' honest question brought me back. Here's a guy that innocently asks, "is this something I need to be concerned about?" And outside of the Pantera hobby the answer is an emphatic no! If you don't install that heavy duty shaft, the roll pin isn't gonna snap! That's the way Ford built it. Ford wouldn't stay in business very long if its cars were leaving owners stranded regularly.

quote:

Originally posted by JTpantera:

... What is your source of knowledge around this design feature ... However, you state with emphatic confidence that this was an intended design element by Ford engineers ... I'd really like to know whether this is reasonable conjecture based on visual observation of the twisted shaft or does this design element exist stated in a document produced by Ford or it's engeeneers responsible for the engine's design ... I'm trying to cut through fact and Panteraspeak ...

I do indeed have Ford documents that describe the purpose for the heavy duty shaft as "to eliminate spark scatter".

Can anyone with a contrary opinion provide Ford documents prescribing any other use for a heavy duty oil pump drive shaft?

I don't have Ford docs old enough to describe the design of the hex shaft, the docs I have just mention it in passing as a "heavy duty 5/16" hex shaft".

Please stand back and look the oil pump drive system over. Look how many twists that shaft took without shearing a roll pin! The pump had a serious problem, but the car kept running, it left nobody stranded. Doesn't that seem like an engineered system?

Install a heavy duty shaft and the roll pin shears very quickly. That is not an engineered system any longer, is it? So next you have to beef up the roll pin. Let me ask you this, where's the give in the system after you beef up the roll pin? What will twist or shear next when the pump tries to stall? The hexes on the shafts end? The distributor shaft where its drilled for the roll pin? The teeth on the distributor drive gear? The gear teeth ground into the camshaft? Where's the engineering now?

quote:

Originally posted by jb1490:

... Are both of those shafts from the same displacement engines ...

Hi John. Its not my picture, but no, those shafts aren't for the same vehicle. One is much shorter than the other.

quote:

Originally posted by Panterror:

... Several twists are normal? Maybe on junk yard engines. To me it's just a sign of a poorly maintained engine that has survived a couple of near oil pump failures and/or correspondingly one that has had a lot of debris through its lubrication system ...

Precisely. I did write that the shaft from a well maintained motor may not have any twists.

quote:

Originally posted by Panterror:

... Looks like every shaft that comes out of an engine with a seized oil pump to me. How do you know those twists developed over 20-30 years and not just as a result of a catastrophic failure caused by debris too large from the pump to tolerate ...

I'm trusting the evaluation of the mechanic who emailed the picture to me. He had never seen a shaft with so many twists and thought I'd enjoy seeing it too. I did. I laughed, but at the same time, it answers the question, just how many twists can these shafts take.

quote:

Originally posted by Panterror:

... If shafts really do routinely twist multiple revolutions in use, one could argue that is truly a means of making the engine more tolerant of gear rotor oil pumps intolerance to debris and it would wreck fewer engines and strand fewer people by not failing catastrophically ...

One could indeed take that position

quote:

Originally posted by Panterror:

One could also argue that the weak link should be the roll pin so an engine that may have just lost it's oil pump is shut down by losing its timing mechanism too.

Ford obviously took the former position.

quote:

Originally posted by Panterror:

... you’re a faithful disciple of the Ford engineers ...

I have no problem calling a terd a terd. Engineers are humans, they make mistakes. I bump heads with inept engineers every day. Most engineers would tell you its the managers and accountants that screw things up. But often hobbyist call good engineering "bad engineering" because they don't understand it, or they don't understand the criteria, or they don't understand the process involved in designing things for something like a large automotive corporation. Automotive engineers don't engineer haphazardly like some hobbyists believe. Things are designed, reviewed, tested, reviewed, evaluated, reviewed. Several designs for the same part are often compared before a decision is made regarding which design to put into production.

In general, I believe Ford put a lot more engineering into the original parts than the aftermarket and hobbyists put into the replacements. That was especially true in the 1960s which is when my involvement with cars began.

_______________________________________________________

I have a story for you.

I had built a stout little 302 to replace the tired 289 in a fellas Mustang. One evening I get a phone call, the guy says the motor I built "just stopped" and left him stranded. It was his work car and he needed it fixed asap. I spent the evening at his home, troubleshooting the motor. After a lot of head scratching and butt scratching I accidentally noticed the distributor rotor wasn't turning when my customer cranked the motor. I pulled the dizzy and found the sheared pin.

The next day I skipped school and took the dizzy to the race shop I hung out at (with a case of Bud) and asked one of the guys "whats up with this". He looked me in the eye and asked me straight out "why did you install a heavy duty oil pump shaft in that motor?" Uh Oh ... I hadn't mentioned the heavy duty pump shaft to anyone yet. I knew I was in for a "lesson".

Well I didn't want sparks to scatter! lol

He asks "when has spark scatter been a problem in the past"

Uh .... never

"So the heavy duty shaft was a solution to a problem you didn't know you had?"

Uh ... yeah

"Learned your lesson?"

Yeah ....


the good ol' days

I'd give my eye teeth if I could walk back in that shop today with a case of beer

put up with their teasing, see their old weary faces, hear their gruff voices

-G

George,
If I am reading your posts correctly, double pinning the distributor gear is only necessary if someone has gone to a heavy duty oil pump shaft? And would not be recommended or necessary for use with an OEM oil pump shaft?
Jeff

quote:

Originally posted by Pantera 4134:

... double pinning the distributor gear is only necessary if someone has gone to a heavy duty oil pump shaft ... And would not be recommended or necessary for use with an OEM oil pump shaft ...

-G

My bad...3/16ths.

can someone please explain what "spark scatter" is, or is it a joke?

"the twisting of the oem shaft causes spark scatter"-how can anything that happens to the oil pump drive have any effect on the rotor in the dizzy?the dizzy is gear driven off the camshaft,the oil pump is driven by the dizzy not vice versa

I read somewhere that spark scatter and distributor timing issues are more of an issue for SBC and BBC than for Fords... Given that the distributor is driven by a timing chain thru a camshaft that is moving lifters and deflecting along the camshaft's length, it makes some sense.

i agree about twisting the shaft remember the syteel shaft is under constant pressure and a nice warm temp. look at wrought iron bars and how easy it is to twist them also be careful of where you drill the holes for you double pinning don't weaken the shaft. by removing metal from critical areas ofthe shaft.

So whats your thoughts on a slightly tapered solid pin thru the gear an shaft ? To hell with these roll pins. The hole has to be machined for the proper placement of the gear anyway and your trying to line it up with the existing HOLE ? Why not take this a step further ?

Also whats your thoughts on the new Polymer gear from Ford ?

I agree a after market solid pump drive shaft is the way to go .. because my pin sheared on my stock motor because of a small ring of permatex which must have been used on the threads of the pickup ?

Also there are some who believe the heavy viscosity oils 20W-50 play a role in the strain on the pin and gear ... today cars are running 5w-30 ... I have always had success in light weight oil high volume / high pressure pumps.

Ron

quote:

Originally posted by Cowboy from Hell:

quote:

Originally posted by SoonerBJJ:
To my knowledge my oil pump drive shaft has never been modified or replaced. Does this mean I am relatively safe, or is this something I should be worried about?

You're safe. Unmodified Clevelands don't have a problem in this area (the valves and rod nuts are another issue however)

I don't believe the R code/Q code oil screen has a hole in it, only the earlier - flatter oil screen. Melling #M84-AS1 oil screen (aka an oil pick-up or an oil pump suction line) is a duplicate of the R code/Q code high volume oil screen. There's a pic of this oil screen in my 351C photo album.

Or am I showing signs of senility again?

-G

Maybe signs of the Buttery Nipples?

On the subject of distributor gear pins; I recently had a discussion with an engineer at Spirol, who make slotted roll pins. As per conventional 351C engine building wisdom, he confirmed that double pinning a 1/8" carbon or chrome stainless steel roll pin (with a 3/32" roll pin), increases its double shear strength from 1,875 lbs to 3,025 lbs. Some have mentioned increasing the size of the hole and going up to a 5/32" roll pin; however, that's not quite as strong (double shear strength of 2,750 lbs). It is possible to double pin a 5/32" roll pin (also with a 3/32" roll pin), which gives a double shear strength of 3,900 lbs, but you need to drill a smaller hole than you would if you were using a 5/32" pin on its own. You only benefit from the inner pin if it fits tightly into the ID of the outer pin.

As an aside; Chevy's use a 3/16" roll pin, which has a double shear strength of 4,150 lbs. Unfortunately, it's not a good idea to drill a 3/16" hole in your 351C oil pump drive shaft because the diameter of the shaft isn't sufficient.

Great post David. This is an issue long discussed with no actual data. Thanks for filling in the blanks