[Sun Tuned]

Here we go.
You feel you must do something with the factory endplay, I mean you'll just lose sleep over it if you dont. Ok we can actually do a little something to make it better, but endplay is not a cure all, and I seriously doubt youll notice one hair of a difference good or bad or at all.

Sit down because when I tell you what measurement tools to bring,you wont believe me anyway, and I dont want you to hit your head when you pass out.
We wont need any!
Yep! Thats right I just said that.
Seriously leave all the feeler gauges, slide rules, protractors, Coordinate measuring stuff, lasers, and all that junk where it is in your box ... for now.
Before you start this if your using all GM parts, lets get some factory shims...

DELCO # 1965864

Is now once again, for however long this go around, still as of 2 weeks ago a good number. I know this cause I just bought 1000 more. They come 5 to a package, not 10 like they used to. And they are a hell of alot more at 1.10 each than they used to be too. They have changed them up a skosh from the originals. They are a 3 tang thrust as was before, although they did reduce by a small tick the surface area, nothing to fret about at all. acquire some from your local Delco dealer or friendly GM dealer. The GM number is same as DELCO number. Raise a little fuss at the counter if you can get by with it if you have to, to get em to really look it up but i promise you they are still available for now.

From there lets get started.

Pull bottom gear off and the original flat shim on your factory GM Pontiac HEI and install three tang thrust and reinstall the gear and roll pin.

It is at this point you will have noticed you closed the gap considerably on your endplay.

Now put it in the vise with a rag wrapped around housing so you dont mar the aluminum. Dont get rag in between the drive gear and shim.

Next pull up on the whole shaft assy, specifically the part that the rotor screws to, better yet leave the rotor attached to avoid any confusion.. In other words take all the endplay clearance out of the shaft just as it would be running in the car.

Now lets look real close at the 8 tooth rotating pole piece (reluctor) the part that spins. Then look at the stationary pole piece (the pickup coil itself) Now if we were to turn the teeth on the reluctor to where they line up with the pickup coil teeth, lets look real close at the relationship there. What you want to see is that if you were to take a very small straight edge and place it on the pick up coil teeth... you want to get the reluctor teeth to rise up to that straight edge and just touch it but not go above it. In other words you want the topmost edge of the reluctor teeth to not rise above the topmost edge of the pickup coil teeth. It is at this point Im told by GM/ DELCO engineers that you will not lose nor will you gain any more or less signal strength to the pickuo coil. Thats as good as you are going to get or make that interface. Now at that point you just let the endplay be what it is. Tightening it further is only aesthetic.

If you put the 3 tang washer in and you still have clearance at the bottom thats good and if the teeth are level with each other that even better! But what happens if the reluctor teeth still rise above the PU coil teeth?
Heres a few more things for the folks that think they got this figured out.
So while were getting rid of some hysteresis issues...
Well here we can do a couple things . And this is a little back and forth but it works out fine. This is what to do if you got a shall we say bumped around distributor.

First thing is when you checked the clearance at what was left at bottom, if its wide enough and you have room at bottom and the reluctor is still rising above the PU teeth... simply try your original flat factory .030 washer you originally took off. Usually I find some will need the thick three tang and a factory flat washer and then theyre fine. Still check to see that you have ample clearance left at bottom no matter what you end up doing.

In the event you cant get it to work out and fit a factory .030 shim in there we can cheat a little. Pull shaft assy and go back up top and inspect the PU coil/top bushing/ retainer clip...
1. the clip should be there on the bushing holding the PU coil.
2.Pull up on the pickup coil and feel there is probably a good bit of slack or "endplay" in those two parts.
3. You can gently drive the top bushing farther into the housing to close up the clearance and get rid of some of the excess slack of the pickup coil travelling up and down on that top bushing a little bit.

BE ABSOLUTELY SURE TO LEAVE A LITTLE PERCEPTIBLE UP AND DOWN FEEL TO THIS INTERFACE SOMETHING LIKE .010 AND NOT LESS
We want that pickup to be able to freely rotate as the vac adv does its deal there and too tight there is not good.

You will now find when you mock up the shaft assy you will have gained likely needed clearance where you can install a factory .030 flat washer and still have needed room to spare. Recheck reluctor teeth and you will likely find life is now good there.

YOU MUST CHECK TO SEE THAT THERE IS STILL MORE THAN A MINIMUM OF .030 CLEARANCE at bottom drive gear. WE WANT ENDPLAY HERE FOLKS !!

If you wish to go get the feeler gauges and get a number go ahead. When you see what you got, and seriously on most all stock factory GM HEI Pontiac distributors 90% of the time that one 1965864 washer will nail it right on the nose, if you have sufficient (Im saying minimum .030) endplay let it be.

Next time lets talk about these thrust washers and what happens to them.

["QUICK-SILVER"]

Obviously shims are to prevent ware, keep the distributor gear close to centered on the cam and keep top distributor components in the right spot.

End play is for longevity in a street application. Top bushing grease gets smeared up and down when you start and stop the engine. The more you limit up/down movement the faster the top bushing wears out. Good example would be to look at how often "race" (tight shimmed) distributors have to be rebuilt or replaced.

Same reason most electric motors have somekind of spring on one end of shaft through the armature. Magnetic force pulls the armature one direction when the motor is running. Cut it off and the spring pushes the armature back the other way to distribute lube.

IMO
Clay

[4zpeed]

"Sun Tuned" Why did they set the clearances where they did? I dont know, but Im open for a reasonable answer.

Originally Posted by "QUICK-SILVER"

Obviously shims are to prevent ware, keep the distributor gear close to centered on the cam and keep top distributor components in the right spot.

End play is for longevity in a street application. Top bushing grease gets smeared up and down when you start and stop the engine. The more you limit up/down movement the faster the top bushing wears out. Good example would be to look at how often "race" (tight shimmed) distributors have to be rebuilt or replaced.

Same reason most electric motors have somekind of spring on one end of shaft through the armature. Magnetic force pulls the armature one direction when the motor is running. Cut it off and the spring pushes the armature back the other way to distribute lube.

IMO
Clay

"QUICK-SILVER" "(Keeping the distributor components in the right spot)(End play is for longevity in a street application)" I agree, in addition, the (unknown factor) of core shift could possibly lead engineers to allow variances and excessive end play.


IMO
Frank

[Sun Tuned]

Yes thats true, the shims are there for two reasons, one to control endplay specs on a production level, and also as a "shield" of sorts for the housing ends. Especially on the aluminum housings the top side of the as finished iron gear would make very short work out of the aluminum and bronze bushing at the bottom of the housing without a shim or thrust washer as the case may be.

No, not really on the top bushing grease thing, at least not in an automotive distributor application.

That debate has raged among the big three engineers back and forth for 60 years on Ball bearings vs. Bushings, and they worked it out years ago. Bout like asking Ford vs. Chevy. But apparently MSD didnt get a copy of that SAE paper...
Ball bearings seem to be the better option at face value, but ,when you begin to add the pros vs cons and especially in an OEM automotive application one sees fairly quickly why they all ended up doing what they did. Its all about radial vs axial apps , and embedability and being self flushing, and cost, and being self lubricating, etc. etc... and what not and I'm not about to erupt that can o worms.

In the original app GM top bushings were as it pertains to the aluminum housings, quite simply a bronze bushing that had a chrome plated outer shell to retain lubrication ,that had 2 1/16" holes drilled in sides in line with the middle fill line of the grease well. As stone age as it sounds it worked like 50 million bucks. First it worked and damn well, not sure what engineering service life was quantified as, as far as service life in miles ... but suffice it to say ive pulled 1956 model distibutors apart that had minumum of 100,000 plus miles on em and never been touched that looked day one new at top of shaft. The key is in how the design worked.

That design also saved them gobs of money doing it that way, as they could use non hardened shafts, the bushings were dirt cheap compared to bearings and they were sort of self flushing unlike a sealed ball bearing which when it goes to hell basically hand grenades itself like a cam lobe going flat... it just gets worse as it goes. I doubt anyone has seen a ball bearing distributor with no maintenece at all since 1956 not need replacement. I sure havent.

As the shaft gets warm in the top bushing, the deal is designed to gently wick some base oil from the grease through the 2 holes in the bushing, and that is all thats needed to properly lube that shaft and bushing for the life of the distributor, or in this case Id wager 150,000-200,00 miles. That deal proved to work just splendidly and the up and down motion of the shaft or the limited lack of moving up and down of the shaft doesnt really have any adverse affect on it any measureable amount anyways. The grease well is not designed to do anything more that dispense liquid base oil and not grease in any way. If it did that youd have a service interval for the grease in the well. At least the moving up and down is not on the same wear scale as rotating in a circle at an average of 3000 rpm for 150,000 miles... math anyone? Which generally was farther than most old cars went on first engine. As a side note the old chevy 985 tach drive ball bearing racing iron distributor had ball brgs in top and Ive yet to see but 1 that didnt need a top bearing, and Id guess it spent a good time on the shelf.

Now our fine pals across the way in Dearborn took almost the same approach but with an added twist on the money deal, they decided theyd spend a tad more of Henrys stash. They also used bushings, some in the top and bottom of the housing, usually HIPERF stuff, and most everything else used only one long top bushing.
But get this!!

They didnt have a means to keep it greased in later years say after 1967 or so, before that like GM they had a oil wick and capillary tube. They ran that new after 67 deal greaseless.... How?

They hard chrome plated the shaft, more $$ but at that point what gets in the bushing for debris gets either flushed out or embedded into the bushing. After the years went by I guess thay kinda had that deal figured out and dare I say possibly a tad better than GM? You see Ford distributor shafts scored, but they are few and far between.

I always wished GM had done it on all of their shafts, as we had a distributor shaft chromed here on a friends truck just for the hell of it and opened the bushings up a tad to match. Over 3 engine rebuilds he put 627,000 miles on a ton work truck, and went diesel, and I still got the distributor in my 89 dually after putting another 30,000 on it. Shaft looks like it just came from the chrome shop. In reality you can remove it, and scuff the discoloration off it with some worn out 600 shop roll and it looks like new. But then GM wasnt trying to make stuff last 1,000,000 miles either.

[Sun Tuned]

Thats true also.

GM original specs, as I went into in a post somewhere else on this forum, were relayed to me as and I quote the man who was in charge of Plant 20...

" Nothing tighter than a dime, nothing wider than a nickle"

Hadnt gone and measured that deal in like 25 years, and aint gonna now, plus money looks like monopoly boardgame stuff nowdays anyhow, so who knows but you get the idea.

It was most certianly a specific range, most certainly for a specific reason, and at one time or another before I settled down from my youth and started thinking logically and quit trying to reinvent the wheel ... its a spec you and certainly I and likely everyone else has hit all around those numbers on both ends....
small and large.

[KEN CROCIE]

Re: dist . shims. We made ours from "blue clock spring" steel, at the exact Pontiac size, in lots of 1000. We made them in .005" and .035" thickness. lately I have been using the Moroso dist. shim kits. I think we can blame Bill Jenkins for popularizing dist. end play reduction to "reduce spark scatter" in his great SBC book.

[KEN CROCIE]

Hey, Tom V-Tell 'em about the 7 lug wheel guy earning his keep !

[Tom Vaught]

Originally Posted by KEN CROCIE

Hey, Tom V-Tell 'em about the 7 lug wheel guy earning his keep !

Have told that story several times Ken.
I knew the guy personally. Released the same excellent parts year after year with no warranty issues (but eventually the "No changes no merit Increase" finally got to him.
So he did the 7 Lug Rotor and Wheel and the 8 lug Rotor and Wheel with the .080" larger hub (required unique wheels for that deal available only from the Ford Dealer and Ford). And he got his merit increase. But it cost Ford millions in Commercial Sales after that mess.

So That is my story about the "Wheel Guy" again. The Guy I would like to "go after" was the FEAD Guy at Pontiac who changed brackets, water pumps, alternator mounting, A/C hardware every year on the basic Pontiac Engine FOR NO REASON!

Tom V.

[Squidward]

Originally Posted by Tom Vaught

So That is my story about the "Wheel Guy" again. The Guy I would like to "go after" was the FEAD Guy at Pontiac who changed brackets, water pumps, alternator mounting, A/C hardware every year on the basic Pontiac Engine FOR NO REASON!

Tom V.

Almost ALL of my classic car experience has been with Pontiacs, which gives me a narrow data sample. I always thought Pontiac stuff was pretty good about the FEAD stuff.

How do the other brands stack up for consistency year-to-year, or with big block/small block setups? It seemed like Chevy and Ford were all over the map on their different accessory setups, at least from my limited wrenching experience on those brands.

[dataway]

Since I'm only a 68 guy, I was amazed that the different pulley part numbers for all the different configurations. Surely there was an easier way. Really, you have to change the design of a basic V-belt pulley?
I had no idea people actually got paid to make changes whether they were necessary or not. But I guess it's a way to motivate innovation.

[Tom Vaught]

Originally Posted by Squidward

Almost ALL of my classic car experience has been with Pontiacs, which gives me a narrow data sample. I always thought Pontiac stuff was pretty good about the FEAD stuff.

How do the other brands stack up for consistency year-to-year, or with big block/small block setups? It seemed like Chevy and Ford were all over the map on their different accessory setups, at least from my limited wrenching experience on those brands.

FEAD for the different years "Looked the Same" from a quick glance into the Pontiac engine compartment.

When you actually get into the Interchange stuff maybe the parts will bolt up to the engine the same BUT THE PULLEY ALIGNMENTS AND INTERFACE WITH THE OTHER PARTS IS ALL MESSED UP. That is why you see Pontiac pictures with the alternator pulley 1/2" rearward of the waterpump pulley.

Tom V.

[Ben M.]

Originally Posted by Tom Vaught

FEAD for the different years "Looked the Same" from a quick glance into the Pontiac engine compartment.

The '71-79 v8 era was pretty consistent with minor changes, but the '60s were a mess!