Distributor Hold Down Issues!

[Don Payne]

So in efforts to be a cheap a$$, I pulled an OEM Ford hold down clamp from the junk yard to put on my $$$$ motor. Well, I think it came back to bite me. This will just be an extension of the whole "My camshaft is getting eaten" thread.

So I found that by using the OEM clamp to hold down my distributor that it was causing my distributor shaft to be pinched against the housing of the block pad down in the block. I initially thought that the gear was located too low and the clamp was seizing the gear, but after further review this was not the case. It was the shaft being seized against the block pad housing causing the gear to be difficult to turn.

See video:


So, after looking into this more I found that the Ford OEM clamp is only pressing down on the edge of the distributor instead of applying even pressure in the middle of the distributor like on many GM clamps.

Ford clamp


GM clamp


Interesting eh? Looks like I need to find out how to make a GM clamp work on a Ford.

[Mark Reid]

Uh, no. Millions of engines run with the Ford clamp and work just fine. It moves when you clamp it down because your cam is not installed. Your problem is that the distributor gear is too low on the shaft.

[Don Payne]

I found that technically my gear is not seizing on the block pad, but rather the shaft is pushed against the housing, not allowing it to spin freely. There is still upward travel for the gear so I can now say with certainty that the gear it not installed so low as to be pinned against the block pad.

Go Fish.

[Erik W. Treves]

maybe there is something wrong with the block and hole the distributor sits in is somehow too big or not square or not round....I am with Mark.. those hold down clamps (OEM) are on a TON of fords..dare I say millions!...if you have a stock oem distributor laying around, do the same test.... The distributor should be in there flush, so simply adding the hold-down should not load the distributor like that in my opinon.... If you move the gear up some it may help the issue, but now the gear will be too tight against the cam I would think...which is probably why it's getting chewed up...

[Big Blocker]

Don,

In all my years of building and running Fords engines, I have never used anything but a factory Ford distributor hold down, both big and little block . . . never had an issue . . . never.

You need to look at your dizzy gear install position carefully. Leave the front cover off, as well as the timing chain (I'n assuming you're running a chain and not gear drive).
Drop in your dizzy and clamp it down. You're clamping the housing so the gear shaft should be able to move up-n-down with ease
You should be able to see if the dizzy gear is "crushing" the block pad. If it is, your gear is installed too far down on the shaft. If it's not, your problem lies elsewhere.

Since the dizzy housing rests on the block and is clamped to the block, the distance is factory set . . . the only variable is the gear mounting position. If you were to have a one in 100 million block castings that was machined wrong, I'd have to see it to believe it. Ford has been making these blocks beginning in the early 1960's (221, 260, 289, 302 & 351, 400), and you could count on one hand, how many have casting shift or poor machining. Fords are NOT known for that.

From your other thread: "I guess I could either place the gear on the shaft right next time, or shim it up at the block boss where the distributor goes down into the block".

Moving the gear up will not make it press harder on the cam, these are helical gears and mesh evenly from top-to-bottom, albeit, it's nice to see them "centered" on each other. Like anything in a race bred engine, blueprinting is required to make sure everything is working in harmony, well balanced and as friction free as mechanically possible.

Happy blueprinting . . .

Doc

[Dana]

It's suppose it's possible due to machining errors, but not likely, that the distributor shaft is binding on the machined hole in the block.

With the distributor clamped down in the block, you should be able to lift the gear off the machined pad at least .005". I would look for more like .010"-.015". Use a dial indicator to see what the end play really is.

[Big-Foot]

Originally Posted by Mark Reid

Uh, no. Millions of engines run with the Ford clamp and work just fine. It moves when you clamp it down because your cam is not installed. Your problem is that the distributor gear is too low on the shaft.

The last sentence here summarizes the bottom line on the problem.

This is not an unheard of problem....

Edit --

When the distributor is clamped down tight, the body of the distributor will be tight to the block. No gasket like a GM, that's the job of the O-ring to seal it all..

[Erik W. Treves]

Doc,
when I mean that it will move the gear closer to the cam...when you look at the vid, the cam is already moving toward the cam but is stopping either because housing of the dissy has bottomed on the top of the block OR the dissy gear is contact with the block. Without understanding why the shaft is moving inboard by moving the gear up "MAY" allow the shaft to move even more inboard effectively mashing the two gears together in a bind. This is what I meant by closer....

Might take the gear off completely and then repeat the test. See if the dizzy shaft still move inboard....

-E

[Don Payne]

Originally Posted by Dana

It's suppose it's possible due to machining errors, but not likely, that the distributor shaft is binding on the machined hole in the block.

With the distributor clamped down in the block, you should be able to lift the gear off the machined pad at least .005". I would look for more like .010"-.015". Use a dial indicator to see what the end play really is.

Good call, I'll verify that and post.

I know is sounds as if I am spitting hairs here. This issue already cost me $800 + on the engine that I have already spent well north of $12K on so I am just a little frustrated right now. Please forgive me.

I will also check the gear meshing when I get the block cleaned out and ready to rebuild.

Thanks for the comments guys, keep em coming. I am still a novice with engine building and am still learning.

[Erik W. Treves]

I can feel your PAIN...believe me...I am in "head gasket" hell right now pulling apart a brand new zero time freshly installed motor.....

[Don Payne]

No pain, no gain!

[Don Payne]

Originally Posted by Erik W. Treves

Doc,
Might take the gear off completely and then repeat the test. See if the dizzy shaft still move inboard....

I did verify that the shaft is stopped by the block housing. I took video from a view from below and you can clearly see that the shaft has like .025" tolerance for movement inside the block housing. When clamped, it just moved the shaft all the way to one side and pins it there.

Also, I had used POR-15 to coat my block. The top of the block that the distributor housing rests on had a layer of POR-15 on it originally when I shot the video. I scraped that stuff off so that the distributor could rest directly on the block surface. This helped eliminate a majority of the binding, but the clamping still moved the shaft over to one side. I am still worried that this can cause a gear meshing issue. This is why I wanted to explore using a GM style clamp that applies pressure evenly on the distributor. Maybe my block is just the one in a million, who knows.

I am not willing to ignore these observations just to tear it down again next week and spend ANOTHER $800 bucks on it.

[Big-Foot]

When you are checking your end play in the distributor once it is installed, how are you moving (or attempting to) the distributor shaft up and down?

Does this distributor have a mechanical advance in it?

Make and part number of the distributor is?

[Erik W. Treves]

do you have an OEM dissy you can stick in there and see if isn't something screwy with the dizzy housing?

[Big Blocker]

Erik (and Don),

Normally, and I say normally because what I'm seeing here is NOT "normal", the dizzy shaft should not move in or out when the housing is clamped down. It would appear to me that the top of the block surface where he dizzy clamps down is warped, causing your issue.
In this case, moving the gear up may cause a "tighter" mesh. Is this a factory Distributor? Seems to me that the hole in the distributor housing was bored off perpendicular center-line and the shaft isn't 90° true to the housing. This condition would create a side load on the housing and the cam gear.

Doc

[Don Payne]

It is a Mallory MaxFire 1255404. I'll see if I can find an OEM dizzy.

[Erik W. Treves]

Originally Posted by Big Blocker

Erik (and Don),

Normally, and I say normally because what I'm seeing here is NOT "normal", the dizzy shaft should not move in or out when the housing is clamped down. It would appear to me that the top of the block surface where he dizzy clamps down is warped, causing your issue.
In this case, moving the gear up may cause a "tighter" mesh. Is this a factory Distributor? Seems to me that the hole in the distributor housing was bored off perpendicular center-line and the shaft isn't 90° true to the housing. This condition would create a side load on the housing and the cam gear.

Doc

Doc, EXACTLY what I was trying to say ... just did a bad job of it.

[Darren]

Seems like it would be a long shot that the Mallory distributor would have any problems in the shaft/collar area. It is a machined piece of billet aluminum... not saying it is impossible, just improbable. Too bad you didn't catch this when my block was still out, I'd check for that on mine.

Anyone local have a 351w block sitting naked that I could clamp my dizzy in?

[BigLeo69]

Ford hold downs no issues, Ford had some bad castings in the 80's
i am thinking it was 1985-86 when they went to EFI

[Someday I Suppose]

Don, as the others have said, I don't think its an issue with the clamp, but man I don't like the way that gear moves inward as you clamp it down. I would take a real close look at how the dizzy is seating on top and see if there isn't something there keeping it from sitting down all the way and causing the rock when it gets clamped.

-Scott

[Don Payne]

Yeah, I looked at the seat that the distributor sits on up on top. It is a just cast that way, not a bad casting from the looks of it, but it is definitely not machined. I'll try to take a close look at it to see if I can find any high spots that allow it to rock back and forth.

As for end play of the shaft I measured with the hold down clamp off it is .020", with the hold down clamped it is .013". That said, the distributor gear does rest directly on the block pad. Maybe tonight I'll poke the old cam in and see how the gear meshes with it. Maybe I'll even use some paint on the teeth to see the marking.

More to come...

[canuck1]

Originally Posted by Don Payne

No pain, no gain!

I know I've fought battles like this as well that just shouldn't be... but your piece of mind is worth chasing down the solution until you are satisfied. I would do exactly the same thing.

Have you tried inserting the distributor with the o-ring removed (just to see how true the distributor sits in the hole?) That might make it a little easier to identify a high spot or any kind of distortion in the block/distributor interface. What is the condition of the o-ring itself?

Sean

[Don Payne]

Originally Posted by canuck1

I know I've fought battles like this as well that just shouldn't be... but your piece of mind is worth chasing down the solution until you are satisfied. I would do exactly the same thing.

Have you tried inserting the distributor with the o-ring removed (just to see how true the distributor sits in the hole?) That might make it a little easier to identify a high spot or any kind of distortion in the block/distributor interface. What is the condition of the o-ring itself?

Sean

Good ideas...

Along this line I was thinking of marking the seat on the block with a sharpie and pressing the distributor housing down and twisting it a little to see where any high spots may be on the seat. As for the O-ring, it is perfectly new and does not seem to affect the seat.

[Don Payne]

Originally Posted by Darren

Seems like it would be a long shot that the Mallory distributor would have any problems in the shaft/collar area. It is a machined piece of billet aluminum... not saying it is impossible, just improbable. Too bad you didn't catch this when my block was still out, I'd check for that on mine.

Anyone local have a 351w block sitting naked that I could clamp my dizzy in?

Darren,

If you put a reference object somewhere next to the top of your distributor you will be able to clearly see it move or not when you clamp it down. Hanging a simple wire out next to the distributor housing would suffice as a reference point.

[Darren]

Originally Posted by Don Payne

Darren,

If you put a reference object somewhere next to the top of your distributor you will be able to clearly see it move or not when you clamp it down. Hanging a simple wire out next to the distributor housing would suffice as a reference point.

Roger that, will perform a test tonight if I have a moment. I'm thinking mine doesn't move at all but will confirm. Can you visually see the upper portion of the dizzy move or is it imperceptible without a reference? Seems it would be visible compared to the distance the gear moves.

[Don Payne]

It is visible without the reference point, but it is a heck of a lot easier (and definitive) to see with a reference point.

[MikeKelly]

Originally Posted by canuck1

Have you tried inserting the distributor with the o-ring removed (just to see how true the distributor sits in the hole?)

I think this is on the right track - I think the hole in your block is too big or the distributor housing is too small.

You might consider bushing or sleeving the distributor housing where it engages the block.

The distributor shouldn't have room to move around like that (even if the top of the block isn't perfect).

Consider how much it must be flexing other direction(s) under load when it's turning the oil pump.

JMHO,

Mike

[Don Payne]

Originally Posted by MikeKelly

I think this is on the right track - I think the hole in your block is too big or the distributor housing is too small.

You might consider bushing or sleeving the distributor housing where it engages the block.

The distributor shouldn't have room to move around like that (even if the top of the block isn't perfect).

Consider how much it must be flexing other direction(s) under load when it's turning the oil pump.

JMHO,

Mike

Hmm, I wasn't thinking about it correctly the first time I read it, but now I get what you guys are trying to say. I'll measure it and let you know what I find.

[Darren]

Don, I just checked my dizzy. Clamped and unclamped it several times and couldn't detect any movement at all.

[Big Blocker]

Don,

Any chance that Mallory sent you a dizzy for a 302? 351's use a larger shaft (I'm looking for the spec now) and should fit pretty snug into the lower boss of the distributor bore. IF Mallory was to send you the wrong distributor, I would understand why you are getting the side movement . . . the dizzy housing isn't correct for the block it's being installed in (read: lots of clearance in all directions). With that much "wobble" it wouldn't take long to have the dizzy shaft "egg" the dizzy bore, causing even more play and finally total destruction.

Following this train of thought, you would have a 302 style pump with a 302 style drive shaft plugged into a 302 style distributor. The dizzy would fit but not correctly but the cam gear would still mesh pretty close . . . cams are interchangeable between small blocks.

I'm not really going along with this line of thinking strongly because the pump would have to be wrong to make that scenario work (302 pump and drive shaft) but, I've seen worse things happen by both pro and inexperienced builders..

FWIW, I've seen many big blocks (non-427 side oilers) be destroyed by putting the 427 side oiler pump in them.

Any chance there is a "burr" on the under side of the dizzy housing where it rests on the block, causing a "high-spot"?

Doc