Distributor Gear Roll Pin Broke

[Coubra]

Took our '69 Shelby to Road America for the Optima event this weekend.  The car (and I) have a lot of sorting out to do, but the big problem was a broken distributor gear roll pin.  Using a Precision Oil Pumps blueprinted HV oil pump/billet driveshaft and Edelbrock (think MSD) Pro Flo 4 distributor with their gear/roll pin. Not running lots of oil pressure with a Canton remote filter and Mishimoto cooler (thinking about installing the high pressure spring kit).  Going to put the MSD 85813 gear on the distributor (Comp roller hydraulic cam with Morel 8591 lifters)

Question 1: Is the distributor gear supposed to make contact with the block? 
Question 2: Is there a procedure to make sure the bottom of the gear is a specific distance from the point where the distributor housing makes contact with the block to the bottom of the gear?
Question 3: Should the new gear/distributor shaft be drilled out for a larger roll pin?
Anything else?

For what it's worth, the engine pulled very nicely (thanks for the great job on the heads Barry) and I look forward to getting it on the track again.  Yeah, we were the only FE there...

[jmlay]

1 and 2 have been covered in a couple of previous discussions.:

http://fepower.net/simplemachinesforum/index.php?action=search2

[blykins]

Roll pins generally just don't break without something causing interference in the oil pump/distributor relationship. 

I would pull the pan and check out the pickup and the oil pump, take it apart, etc.  My guess is that there's a piece of metal in the pump that locked the pump up, which would shear the pin.

To answer your other questions, there is a specific dimension on the distributor/gear install that has to be held.  With all the end play removed, you should have 3.045-3.050 from the bottom of the distributor flange to the bottom of the distributor gear. 

You do not need a larger roll pin.

[jayb]

+1 on Brent's comment, I would give it a 98% probability that some trash has gotten into the oil pump and seized it, causing the roll pin to shear.  Time to pull the pan.

Your car looks great, by the way, is it an original?  I have a 69 Shelby clone set up for drag racing, I think it's the same color as yours:

[Coubra]

Forgot to mention that we turned over the oil pump with a speed handle and got 50 psi quickly - turned over smoothly too.  Will get to draining the oil today and checking the oil filter. 

Thoughts on the high-pressure spring kit?  Only pushing around 50 psi max and twisting it to 6K+  The remote filter/cooler setup drops 20 psi.  Would like to run a heavier oil but the Morel lifters restrict it to 40 weight (using 10W-40 Lucas synthetic racing)  Idles at 20 psi.

Lots of additions here - full track temps were high.  220 range.  Going to swap 195 thermostat out for 180 but not confident that will make a difference.  It can idle and run around town all day long without a problem.  For some strange reason I tried using Evans waterless coolant, but I'm going to drain that and use water/antifreeze.  Also noticed coolant coming down from the front of the Edelbrock water pump (Billet Specialties accessory drive)

Pulling the pan is a total pain in the ass because I've got an AJE strut suspension and the K-member has to be dropped.  The big shame is that the alignment is perfect and I loved how the car turned in at the track.

Thanks.  Yes, it's a real one - #237.  It was my Dad's daily driver and was an AO Smith demo car at the home plant in Milwaukee where he was a safety engineer - he bought it in 1970.  Acapulco blue - the original color.

[jayb]

I hope you are right, and it's just a pin failure.  But that would be very, very unusual.  I've run 150+ psi cold with a high volume, high pressure pump, and never sheared a pin.  I suppose it could happen, but its a good idea to drain the oil, cut the filter open and check everything very carefully for foreign material...

[My427stang]

I'll go a little against the grain here.  The only ones I have ever seen break were installed too deep. As you tighten the hold down, instead of tightening the housing against the block support, it loads the gear upward and therefore the pin.  It doesn't take much to eventually make that pin let go as the gear is trying to push upwards and the ends of the pin are the only thing holding it back

Of course if the pump locks solid, it'd probably break a pin, but you'd see some sort of twisted shaft I'd suspect, even if it was just the ends of a heavy shaft

In the end, the fix is set the gear depth right, regardless though, you absolutely have to make sure there aren't pieces in the pump, either from the pin or before. Set depth as Brent said

[Coubra]

Thank you for your responses.

At this point I feel like an idiot.  After a catastrophic failure two years ago where the original block was ruined, all moving parts were replaced except for the push rods, rocker assemblies, and, you guessed it, the distributor.  I cleaned it, looked at it for any damage, but did not replace the roll pin or even take it out to check it. 

The oil pan and pump will be removed, cleaned, and inspected.

[My427stang]

You may want to consider slipping a drill bit or other locator through the hole and get a measurement of where you were.  It would give you a potential cause.  Not inferring you shouldn't pull it down, you should, but it would be nice t know where you were

I know Brent sells gears and has put gears on for customers, could use him or any of us for that service if you are concerned. 

FYI - We have seen MANY in the wrong place from rebuilders, even aftermarket new parts.  Always measure on any distributor

[blykins]

I think if the distributor was mashed down hard enough against the block to shear a roll pin that there would be other symptoms and here's why I think that....

I had an engine builder send me a distributor to use on a Windsor once.  Trusted him to put a gear on, I didn't check it.  Primed the pump, put the distributor in, fired it up on the dyno, and the distributor starting spinning as it was starting to wad up all the plug wires.  I grabbed the distributor with both hands to hold it while I was screaming at my dyno guy to "SHUT IT DOWN!".

The engine builder had put the gear on and didn't get it on at the right dimension.  It had taken all the end play out of the distributor and it was enough that it was starting to spin the whole shooting match. 

[Drew Pojedinec]

Brent,
You shoot 4,000 hours of you tube videos and yet neglected to get a video of that?

[blykins]

This was a long time ago, well before my YouTube days.

Brand new MSD distributor with a gear change.  Fired it up, couldn't figure out why all the plug wires were getting shorter.

[My427stang]

I think if the distributor was mashed down hard enough against the block to shear a roll pin that there would be other symptoms and here's why I think that....

I had an engine builder send me a distributor to use on a Windsor once.  Trusted him to put a gear on, I didn't check it.  Primed the pump, put the distributor in, fired it up on the dyno, and the distributor starting spinning as it was starting to wad up all the plug wires.  I grabbed the distributor with both hands to hold it while I was screaming at my dyno guy to "SHUT IT DOWN!".

The engine builder had put the gear on and didn't get it on at the right dimension.  It had taken all the end play out of the distributor and it was enough that it was starting to spin the whole shooting match.

We are talking different situations.  A gross difference in height, enough to shear a pin immediately, or bind the distributor, would likely do exactly as you saw, not sure how it couldn't, and it would blow my mind if I saw that on the dyno LOL

Consider just less than zero clearance between the gear and block, in fact, it could be that you even have a little cushion with the distributor seal, which of course isn't supposed to locate the distributor.   As that engine runs, it's slightly lifting off and on the block locator, or trying to, putting pressure on the pin and more so as the gear heats up.  It's like working a piece of wire until it breaks.

Gross binding versus incorrect clearance....I can't say that WAS the issue with this one, but the fix is all the same anyway.  Get the gear right, or check it is, and see if any carnage in the pan

In the end, not the same parts, but we ran into this with rebuilt distributors as long as we had the old shop in MA.  Cardone was the worst, random gear height installation, especially FE and Windsors.  Much smaller diameter pin in a stocker, but the initial failures, before we started checking every one, were usually days or weeks down the road.  When we finally figured it out, every one we checked was deep.  We told Cardone, not sure they cared LOL  but it does happen

[rockhouse66]

The only sheared pin I have experienced was caused by the pin not being snug in the hole.  It would tend to walk out, and once it got out far enough that only one end of the pin was engaged, it would twist the pin.  I ran a piece of safety wire through the pin to prevent its movement in the hole and never had another problem with it.

[machoneman]

Sheared pins on old (Ford) engines were often caused by chunks of old, dried-up, cracked off valve seals or a shredded OEM nylon cam gear. Came to find out that when inspecting a SBF pickup, that 1/2 round sheetmetal moon as I'll call it hid the fact that under it, there was no screen! Small stuff could easily get into the pump and jam it up.

Why Ford did this is still a mystery as having the screen cover 100% of the bottom of the pickup then adding the moon (or leaving it off) would have made more sense.

In our Boss 302 dragster, the previous owner wrapped the pickup with fine SS mesh and tied it around with safety wired SS wire. Worked fine to trap bits and pieces from all the engines we blew up (3 in fact!) before we sold it.