distributor shaft length

[Teal68]

I hated to keep crudding up another thread with unrelated info and questions so I thought I'd start one that may be helpful in the future. Does the distributor shaft length really matter between 289/302 roller and pre-roller motors?

The oil pump shafts are the same length in all 289/302's so I don't see how the extra half inch matters. To add to that, I primed my roller motor with a stripped down pre-roller distributor no problem. This could be very relevant for people that want to run original distributors, with the gear swapped to steel, on a newer roller motor.

Thanks,
Tyler

 

[Ourobos]

Who said there was a difference?? You have two basic lengths that should matter to us, the 8.2 deck and the 9.5 deck lengths.. 302/289 and 351w. No matter if the engine was a roller or flat tappet, the oil pump distance to the boss in the block where the distributor engages the pump shaft is the same.

 

[jckkys]

To the best of my knowledge the only difference between 351w and 289-302 distributors is the size of the hex hole on the bottom. The 351 has a 5/16" oil pump shaft, and 302s are 1/4".

 

[DirtDonk]

Well, I hate to say I totally forgot, but I totally forgot. We ran into this issue when installing a TFI distributor into a 5.0 engine. What I can't remember is just what was different. The location/height of the gear? The overall length of the shaft? Size of the hex hole?
I do remember we had to fiddle with it for quite awhile before we could get it to seat. I just don't remember the details.
And I've definitely heard of others having the issue here, so there's something going on there.

Someone will clear it all up.

Paul

 

[Teal68]

Paul,
Good point. I don't think you can fit the later, longer shaft into the non-rollers because it won't seat all the way.

 

[broncnaz]

The 5.0 dizzy shaft was supoosedly about 1/2" longer and the oil pump driveshaft is supposedly the same lenght between the 2 engines. But sometimes people have issues trying to install a 5.0 dizzy into a 302 block when they also use a 302 pumpshaft. Usually you can just shorten the pump shaft 1/4" or so and all will fit usaully right again.

Sometimes The clip that is usually on the stock oil pumpshaft may prevent the pump shaft from fully seating in the oil pump and also prevents the 5.0 dizzy from fully seating until you get the clip to move enough.
Some of the aftermarket pumpshafts with the thicher center sections may also have a similar issue because the hex portion is not long enough to allow the pump shaft to bottom in the oil pump.

 

[DirtDonk]

The one we had trouble with had a Ford Racing (Motorsport) drive shaft.

Paul

 

[Teal68]

To sum all this up it seems an older style distributor should be no problem in a roller block, but you may run into issues putting a later model distributor into a older non-roller.

I notice on summit they use the same dizzy for all the 302's. Or at least 68 and 97 since I checked both of those years.

Note: It's actually a bit scary how little the older motors allow the dizzy to engage the shaft! That said, I have never heard of anybody stripping one.

 

[Fairlane514]

I have been researching this topic for a little while.

Yes the 87-95 original distributors are longer from just under the gear to the end of the shaft by a 1/2 inch. I can't confirm it, but I believe the original pump shafts in those engines were shorter. The extra 1/2 inch of course made up for that. What was the reasoning behind this……who knows.

I have been measuring my block (1987 E7TE) and can conclude that the distance from the distributor "seat" and the distributor gear pad down in the block is the same from old to new.

Also if you look at new pump shafts they all seem to be the same length. My question is how much engagement of the pump shaft and distributor shaft is enough? I'm going to use my oil priming shaft to measure how much engagement it gets and then measure my distributor shaft length. If they match and I get 1/4 to 3/8ths I will assume it as much as Ford got originally.

I base this loosely on the position of the retaining clip on the pump shaft that keeps it from being pulled out. I know it can be moved down and they aren't "set" to any specs, but it will give me an idea.

Also, there were two part number from ford for pump shafts….6605-B302 and 6605-A302……the A302 is no longer available………I don't know the difference.

 

[Teal68]

Fairlane,
From what I observed, but did not measure, you are about right at 1/4" to 3/8".

I think FE blocks use the same size shaft but too long for a windsor 302. It could be cut down if someone felt they need more depth.

 

[Fairlane514]

Heres what I found.

Using my harbor freight calipers, I measured from the seat area of the block where the distributor base would sit, to the block "pad" where the dist gear would ride. I got 4.020 (some may be 4.030)

Measuring from the very tip of the oil pump shaft to the gear "pad," the shaft is .625 below that surface. So adding the 4.020 and .625 gives me 4.645, add another .250 for shaft engagement and I get 4.895.

So, theoretically if you measure your distributor shaft from the "seat" area that contacts the block seat to the end of the shaft under the gear, and you get at least 4.895 you will have a 1/4 inch engagement.

Anybody see a flaw in my measurements?

I forgot to add, I'm using the ARP pump shaft

 

[Teal68]

I think I follow your math. As long as 1/4" is enough.

To figure how much from the factory I was thinking measure from the base of dizzy to tip of shaft, measure distance from block to tip of drive shaft, and subract the two. That should equal the engagement as it came from the factory. Make sense?

 

[Ourobos]

To my dismay, there is a difference. I have here a Duraspark (pre-1985) distributor with a cast iron gear and an 87-93 HO TFI distributor. They are IDENTICAL other than the new TFI distributor has the shaft extended exactly .500" inches longer per my calipers. The depth up in the holes are the same, I could only image the retaining clip being the only item that could possibly prevent a TFI distributor from being installed on an older 302. A stock 302 oil pump shaft is the same item, from the 60s to the 2000s. Make note that the Motorsport pump shaft and ARP pump shafts do have some dimensional differences, and one is not a direct fit all the time, but I can't remember which at the moment.

 

[Fairlane514]

It makes you wonder the purpose of the extension…..it seems it would engage more of the pump shaft, like 3/4 of an inch instead of 1/4 inch with the shorter distributor shaft. This of course being the pump shafts are the same length.

I wonder if anyone has an original pump shaft from a 87-95 HO engine.

 

[Teal68]

It makes you wonder if they identified a problem with pump shafts stripping???? I have never heard of that problem though.

 

[Ourobos]

I have seen several pump shafts (albeit on Mustangs with the longer distributor shaft) twist and stop pumping oil...

 

[Teal68]

I have seen several pump shafts (albeit on Mustangs with the longer distributor shaft) twist and stop pumping oil...

Exactly. Twisting is common, but never heard of one stripping out. You?

 

[Ourobos]

Nope, never, not in 20 years.

 

[DirtDonk]

I've seen both. Some just twist, some twist to snapping.
Probably was a bigger deal with racers and those running high-volume oil pumps, and don't know how often they went to the breaking point, but it's happened.

I wonder if the change came about simply because they found that shortening the shaft X-amount was enough to reduce the dynamic twist flexing of the shafts enough to overcome a host of ills?
Or maybe as a cost thing, if, with the longer late-model 5.0 version, they were then using the same distributor shaft in both the 5.0 and 5.8 engines and decided that changing the length of the 5.0 pump shaft was the lesser of two evils.

Wish we had someone here in Bronco-land that was in every meeting, on every design committee, and for every running assembly line change for the the full run on EB's, and then on through the end of the 5.0 in the Explorer. %)
Kind of a pipe-dream, but man, what an asset in the reference material department!

Paul

 

[Ourobos]

The 5.0 HO distributor shaft and the 351w distributor shaft are not the same length, nor are the actual distributor lengths, never have been, I don't see your point?