Best source for '85 Duraspark distributor?
- Thread starter 92LX5spd
- Start date
-
Sponsors (?)
I would agree about measuring to the flat pad area on the gear, but the pictures you attached made me question it??
Had to pull it back out to prime it anyways...., I like to do that right before first start...
When I reinstall it I will check it for the wiggle room..
I did measure to the flat pad ( with it pulled out) and got 4.041 using the ford method.....Again that was by myself using 3 hands...
I have my original too... I had it apart to clean it and some small plastic parts ( its been awhile but I think they were on the Mechanical advance) crumbled into dust and I could not find the parts.... STill would have to install a steel, bronze or composite gear for use with the roller cam..
Here's a bit a guy did about positioning the gear (albeit on a 351 in this case).
Like I mentioned earlier, a quick check would be to hold down on the distributor body when its fully seated in the block (technically you could even bolt in down with the hold down clamp) and try pulling up on the distributor shaft. If it has a little upward travel its (the gear) probably not being pressed hard into the block surface down inside.
A really nit pick way to do it would be to pull the cam. With cam out, you can see where the gear meets the thrust surface down inside the block, but that's little excessive for my taste unless I was building the motor from the ground up.
Last edited:
Well, I thought I'd update this for any future readers. I bought the same distributor from LMR. It was a new Cardone unit with an LMR sticker slapped on. Of course the same unit is available at Rock Auto for only $68 so some money was wasted there. D'oh! At least I got free shipping.
Shaft free play was only 0.015" which is about 0.010" to 0.020" shy of what it should be. There appears to be a shim washer between the distributor body and the shaft collar that could be possibly removed to gain more free play.
With the shaft pushed in, tested against the MSD measuring method, things look bad, MSD is looking for 3.995" to 4.005" and the LMR piece measures at 4.035"
With the shaft pulled out, tested against the Ford measuring method, things aren't great either. Ford calls for 4.031" to 4.038" and the LMR piece measures at 4.050"
I measured my block depth as best as possible from where the distributor clamps down to the thrust pad for the gear down in the block and got 4.038" to 4.040". In theory with the LMR piece running from 4.035" to 4.050" this should just make it within that range with just 0.003" to spare. If I pull out the shim washer, it should be even better. The extended length is still too long but that's less critical than having too much compressed length which could wreck the block, distributor and possibly the engine.
Shaft free play was only 0.015" which is about 0.010" to 0.020" shy of what it should be. There appears to be a shim washer between the distributor body and the shaft collar that could be possibly removed to gain more free play.
With the shaft pushed in, tested against the MSD measuring method, things look bad, MSD is looking for 3.995" to 4.005" and the LMR piece measures at 4.035"
With the shaft pulled out, tested against the Ford measuring method, things aren't great either. Ford calls for 4.031" to 4.038" and the LMR piece measures at 4.050"
I measured my block depth as best as possible from where the distributor clamps down to the thrust pad for the gear down in the block and got 4.038" to 4.040". In theory with the LMR piece running from 4.035" to 4.050" this should just make it within that range with just 0.003" to spare. If I pull out the shim washer, it should be even better. The extended length is still too long but that's less critical than having too much compressed length which could wreck the block, distributor and possibly the engine.
So I would not pull the shim I would move the collar down. Drive the roll pin out, rotate the collar 90 deg, position to the correct depth, drill a new 0.125" hole and drive the roll pin in. Did this on a Cardone unit for another car (friend of a friend) and it worked great. Up to you but I like having the washer between the body of the distributor and the collar as I really do not want the steel collar contacting the aluminum body.
gear install
It could be depending on the engine. In my case, if I did nothing, it should work out ok.
This link shows you how to measure for the exact engine you have. Using your calipers, measure from where the distributor body sits on the block down to the thrust surface pad where the bottom of the gear rides. In my case, this was about 4.040". My LMR dizzy runs from 4.035" to 4.050" in length, shaft pushed in to shaft pulled out. In theory this will work in my case because 4.040" falls in between 4.035" and 4.050". If the compressed length (shortest measurement with all the freeplay removed) was greater than 4,040" in my case, there would be damage because bolting the dizzy down would drive the gear into the thrust surface rather than letting in just rest on it.
While it technically works, it bugs me that all the measurements don't really match up with either the Ford nor MSD measuring method and the freeplay isn't great enough. In the end to make it "perfect", we can pull the gear and collar off, turn them 90 degrees, reposition them properly and drill new holes.
For the record, I've measured old Ford dizzys with 0.100" freeplay (from 4.000" to 4.100") which ran fine despite having too much freeplay. The rotation of the engine will pull the gear down properly against the thrust surface.
It could be depending on the engine. In my case, if I did nothing, it should work out ok.
This link shows you how to measure for the exact engine you have. Using your calipers, measure from where the distributor body sits on the block down to the thrust surface pad where the bottom of the gear rides. In my case, this was about 4.040". My LMR dizzy runs from 4.035" to 4.050" in length, shaft pushed in to shaft pulled out. In theory this will work in my case because 4.040" falls in between 4.035" and 4.050". If the compressed length (shortest measurement with all the freeplay removed) was greater than 4,040" in my case, there would be damage because bolting the dizzy down would drive the gear into the thrust surface rather than letting in just rest on it.
While it technically works, it bugs me that all the measurements don't really match up with either the Ford nor MSD measuring method and the freeplay isn't great enough. In the end to make it "perfect", we can pull the gear and collar off, turn them 90 degrees, reposition them properly and drill new holes.
For the record, I've measured old Ford dizzys with 0.100" freeplay (from 4.000" to 4.100") which ran fine despite having too much freeplay. The rotation of the engine will pull the gear down properly against the thrust surface.
So the gear is hovering about 0.011" above the thrust surface in the block. That's far better than the opposite scenario of being too tight. Ford says it should be 4.031" to 4.038" pulled out and your only 0.002" over that which might be negligible considering what we're both trying to measure with.
My endplay was about the same. That little washer they added above the collar is 0.020" thick BTW. I don't know why its there. I have 2 TFI dizzys from EFI cars and a points dizzy from a '69 here and none of them have that washer above the collar.
My endplay was about the same. That little washer they added above the collar is 0.020" thick BTW. I don't know why its there. I have 2 TFI dizzys from EFI cars and a points dizzy from a '69 here and none of them have that washer above the collar.
I am going to remeasure later today a couple more times...... The block depth measure for sure....
If it comes out the same I am probably gonna run it.....
I almost ordered a DUI yesterday....... LOL.... STill might and swap it out when it comes in.....
I ended up ordering a DUI duraspark distributor.... Ship date is 9/18/23.....
I might try doing Aerocoupes idea of drilling a new hole for the collar with my LMR dist so I can use it...... Lack of free play in the shaft is my biggest concern...
I need to find a new buddy with a nice drill press... When I made my big move from Oregon to Florida, I lost all of my life long car friends and my 1500' garage... Hard to replace those.
I might try doing Aerocoupes idea of drilling a new hole for the collar with my LMR dist so I can use it...... Lack of free play in the shaft is my biggest concern...
I need to find a new buddy with a nice drill press... When I made my big move from Oregon to Florida, I lost all of my life long car friends and my 1500' garage... Hard to replace those.
