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Discussion Starter · #21 ·
Just got off work. Gonna check dizzy. Should Ihook a magnet to it in case it wants to fall apart while removing?

Also, a sudden change from running normal to explosive backfire out of carb can only be a limited amount of suspects right? Distributor off, timing chain, sticking intake valve, and possibly carb or bad ignition coil?
 

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Discussion Starter · #22 ·
I wouldn't think the carb because there's definitely an intake val ve open during the wrong part of the cycle forcing air and gas back out through the carb
 

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I wouldn't think the carb because there's definitely an intake val ve open during the wrong part of the cycle forcing air and gas back out through the carb
Not necessarily intake valve....if an exhaust valve is not opening, it will puke back through the open intake valve during overlap.
Could be bent pushrod, broken rocker stud or rocker nut, broken rocker arm, bent valve....or maybe a couple of those combined.
Pull the valvecovers and start checking through the valvetrain.
 

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Discussion Starter · #24 ·
Ive finally got the time to look at what caused the fire and sudden timing problem/spewing of air and gas through the carb.

First I lined up the harmonic balancer at tdc. The rotor looks a couple degrees to the right of where it use to sit, but nothing major, and I could be wrong I didn't make a mark on the intake or anything when I first put it together, it does look off though..

I pulled the distributor. There are witness marks on the top sides of every gear tooth, no marring or deep gouges, but the witness marks are definitely on the upper part of the gear teeth.

Then I looked at the roll pin, and I cannot see through it, in fact I see shiny steel at the base of each roll pin and I cannot get a needle to go through the roll pin. It looks like my roll pin has sheared, and the gear has twisted on the shaft, but I could be wrong this is my first time looking at this. I should be able to look straight through one side of the roll pin and out the other right? Unless this is some sort of dual roll pin setup?

It's hard to see in the pics but you can definitely see shiny steel at the base of the roll pin on each side you look at. I'm trying to pry the roll pin out but its not coming out.



 

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Discussion Starter · #25 ·
The roll pin ends were wobbling around in their holes but wouldnt come out. I stood the distributor on the ground, put tool on top of the dizzy gear, then gave it a couple firm taps with hammer and the gear slid off. I really hope I actually didn't just shear off a good roll pin mistakenly... But it couldn't be that easy to break a roll pin with a hammer tap right?

Well when I look at the markings on the inside of the distributor gear and the shaft, it definitely looks like it's consistent with the way the gear would've spun when it broke. Looks like it spun about 1 to 3 mm then wedged itself up good.



 

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Discussion Starter · #27 · (Edited)
Im gathering what I need to replace pin.

A Ford guy drilled out the holes with a #22 bit, then put a 5/32 roll pin in and then another 3/32 pin inside that one, I like that idea. Another guy replaced the roll pin then drilled a 2nd roll pin hole through gear and shaft 90 degrees and offset from the first.

After I get these back together I also need to check oil filter and see if there's any crud in it, and spin the oil pump to see if it's binding. From the marks on my dizzy teeth, I think the problem has to do with the gear not sitting where it's supposed to, something about thrust clearance not being correct on aftermarket distributors as I read on a Ford site
 

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Discussion Starter · #28 ·
When I drill out the shaft and the gear, at least for the original pinhole, should I have the gear pressed onto the shaft first or should I drill them out individually then put the gear on the shaft?
 

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Yeah, it sheared in operation, not from your hammer taps.

Yeah, Fords have to have correct thrust clearance set, and aftermarket distributors can be a real problem for guys who don't know about it.

The smaller shaft size of Ford distributors(compared to GM) makes it shear a little easier, especially with high volume or high pressure pumps.....which is a double edge sword, since the oiling system needs higher pressure to prevent starvation elsewhere.
I've only had experience with 351W doing it, but to fix it we went with the slightly larger drill and larger pin, with a second pin inside that.....got to check that vertical clearance first though
 

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Discussion Starter · #31 ·
How do I check the vertical clearance? Do you know what the measurements should be? Where do I measure from/to?

Also, if I'm installing 3/16 pin, what size hole should I drill?
 

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Been a long time....but the only way I remember being able to set the distributor thrust clearance was with everything off the front of the engine including the timing chain set, so you can get in there and measure it with feeler gauges...???

Maybe a search around the Ford sites like the Cleveland specific forums and maybe there is a better answer or how-to.

For the roll pin, typically the holes size is the nominal size of the pin, so .125" for an 1/8" and the un-installed pin will measure about .132-.134" giving about .008" press into the hole.
Makes sure you have a 1/8" pin....a 7/64" pin (.1094")at free diameter of .115" often gets confused with 1/8"
 

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Discussion Starter · #33 ·
Ive ordered some heavy duty 3/16 spring pins from McMaster Carr and also regular spring pins in assorted sizes. I'll have to judge if a regular spring inside spring is better than the single h.d. spring. The regular pins are rated around 1000 to 2000lbs of shear Force, while the h.d. springs are 4500lbs.

I read up on sizing roll pins and drill bits and that the the spring pins are made to be condensed a bit too fit inside the holes and expand. I was just coming back to comment on that and I see you've replied on it already thanks.

I also went to a Ford site and read that They actually measure from where the distributor sits on the block to the bottom of the gear with all of the play taken out of it, and if that measurement falls into the specified tolerance then it is okay. I'll read more about it and get this distributor ready to put back in.

All in all I am happy that this problem seems to be caused solely by the distributor rather than valve train damage
 

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Discussion Starter · #35 ·
I will. Just waiting for pins in mail, should be here tomorrow night.

I plan on heating up the gear with gas torch (propane or map) then sliding it on shaft and lining up holes with a 1/8" hole punch. after it shrinks Im going to drill it out to 3/16 and add h.d. spring pin, then I will drill another hole 90 degrees and higher up the gear and installing a second pin
 

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If in fact this sheared in operation it is often a sign that the oil pump is or has hung up. Roll pin failure is highly unusual without an underlying cause. A pin that is loose fitting in either the gear or the shaft needs to be corrected to where both the gear and the shaft holes make a tight fit with the pin. Hammering a pin inside of a pin is no solution. Drilling holes in either the gear or the shaft needs to be done on a drill press at the minimum or on a mill. The degree of alignment precision exceeds anything you’ll achieve with a hand held drill motor. The shaft is probably at least surface hardened which will be are really hard start for a standard high speed bit. Working this at home getting started drilling the shaft can be facilitated with a smaller than finish hole size carbide masonry bit to get through any hardening or a small dia diamond faced grinding bit then drill to size. There is no reason to use multiple retention pins. Hole size can be a problem when mixing after market and factory parts, you have to keep an eye on these things aways, even today with all factory parts as these are sourced all over the world and one mans millimeters are not exactly the same millimeter one country to another let alone to our concept of an inch and part inspection is expensive so not often done, the OEM mostly takes the subcontractors word that they meet the spec. In the mangled words of Rawhide ‘Pack-’em up and ship-‘em out’.

Ford uses a hex shaft to connect the oil pump to the distributor gear, if the the oil pump hung up even for a moment it is likely this shaft has some twist. It is retained by a spring washer and should not come out with the distributor.

Bogie
 

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Discussion Starter · #37 ·
From what I've read on the Ford sites (there are tons of threads about pin breaking, it happens on Aftermarket Ford distributers alot) it's not typically the oil pump, that only seems to happen when something clogs up the oil pump screen and or gets into the pump, like a piece of a nylon gear. They say it is typically due to vertical alignment of the distributor gear. Many of them have either added a washer, or milled the bottom of the distributor that touches the block. They have measurements on how far your distributor gear should be from the bottom of the pad on your distributor that sits on the block, I will double check these when I get distributor back together.

We have drill presses at work I may use those
 

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What I’m suggesting is that there is wear or damage in the pump not necessarily that something got past the inlet screen. The pump is an aluminum housing against which a steel rotater which is circular on its OD that has something of a female tooth and cavity pattern on its ID. This is rotated in the aluminum housing by male patterned tooth and cavity rotator that is driven by the hex jack shaft that plugs into the distributor shaft.

My concern is anything steel rotating against aluminum as its bearing will allways wear the bearing surface which can tear off material from the aluminum to where the driving shaft gets bound.You will note that Chevrolet uses gear rotors in a cast iron case and pins the distributor gear to the shaft yet pin failure outside of pump failure is very rare. Now while I much prefer the gerontocracy design over the meshed gear design, I really am not a fan of something like gerotor running steel against aluminum. While it’s done it is most successful where varying oil pressure is not likely to cause intimate parts to chatter which happens with wear.

The hex shaft should provide enough slop, I sorry an engineer would say clearance, that miss alignments between the distributor and the oil pump shouldn’t have an effect on the pin loading to a point where it shears. To that end a loose fit of gear to pin or shaft to pin will but what I would expect to see is a mark from that in the circumferential direction of the shaft, but the only mark I see is vertical from hammering the gear off. The slip you spoke of being 2mm is like 1/12 of an inch which could be addressed by resetting the distributor timing. Though finding the pin sheared and being unable to be driven out is itself disturbing. But you need to get to the root cause or it will happen again.

Bogie
 

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Discussion Starter · #39 ·
I got the gear back on and pinned with an h.d pin. Ford says the base of the dizzy pad that sits on block to base of dizzy gear should be 4.031"-4.038" with all play removed. Mine is at 4.060". Is that enough to warrant a shim? That's 3/128", or .64mm roughly to get my gear up into the sweet spot.
 
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