[Sun Tuned]

Everyone should know by now the proper orientation of their rotor tip and that little divot at the bottom of their distributor gear. Or maybe by now they should.

Well, what happens if you buy a new gear bronze or phenolic and it doesn't have that mark at the bottom?

Simply take your original and look closely at it. Pay attention to the side with the divot. Look at the roll pin hole... see where the hole lines up with the teeth above. On some gears the holes on both sides of the gear line directly up with a tooth. On others like Chevy there is one hole that lines up with a tooth directly on one side and on the other side the hole is between two teeth.

Pay attention to this. Simply install the new gear as close as possible as the old one was originally.

Now some gears are the same on both sides. In that case it really doesn't mattter as you can install it either way and that's all you can do. But look at this in your original, and match up the new replacement in the same manner.

[mrennie]

Thanks...I new it meant something but didn't know exactly what, and also saw gears with no marking and wondered what I was missing.

Much appreciated!!

[64speed]

My polymer gear was just a straight drilled hole and the distributor shaft had just a straight drilled hole in it so I guess I am alright. My worse fear did come true though. On the last tap of the hammer driving the pin in I slipped and hit one of the teeth on my composite gear. It only made a superficial mark but it still makes my mad. I don’t have dial calipers here but I am sure I am within the .005-.012 spec range for shaft play but it’s still dis heartening to go from no slop to a little wiggle. On a related note. My engine will be stored for about three years with all the openings plugged to keep unwanted stuff out. Before I start the engine I will prime it of course but since this is a composite gear should I slather it in grease before first start up to insure proper lubrication in those critical first moments?

[Sun Tuned]

On most Pontiac factory gears if I remember this correctly, the pin hole "looks" as if it is right in line with a tooth on each side. It in actuality, if you look closely is just off about 1/4 of the hole on one tooth and about the same opposite distance on the other side. So inspect closely. You'll see it if you look at it.

[Sun Tuned]

Well I don't really know what to say...
Has nothing to do with how straight through the hole is drilled. That's not the point. It's where in relation to the teeth the hole is.

Somebody should've put a drilled plug to positively oil the distributor gear in the engine. If not, that's a missed opportunity that should have been utilized.

Break in lube if you're the nervous type, and not 5 lbs of it either. The stuff can plug an oil filter.

Aluminum housing distributor? If so ,and it were mine, I would not want it that tight. I know, the gear people say... follow the directions they give you if all else fails. I'm thinking they offer warranty...
That may come in handy one day.

Didn't someone tell you that no clearance is bad , already in another thread? Damn good advice if you ask me. Who built a new distributor with no clearance at all? Who does that?

How bout a lowly set of feeler gauges? They work wonders.

[Sun Tuned]

If you don't have the calipers and or at least the feeler gauges... how the hell did you measure the play you have?
Don't guess at it. That sounds like what the company that built it when you bought it did.

Find out these numbers! Don't assume. Know.

It will be short lived if you don't.

[69 Limelight]

64speed do you absorb any of the information people give you on this forum after you ask a question? You are supposed to have play/clearance between your distributor gear and housing. .005-.012 is probably fine although I believe Sun Tuned, the distributor guru, likes more like .020. If your new distributor came with no clearance/play it probably would have eaten the housing and failed. By the way you don't check clearance with dial caliper you use a feeler gauge.

[dataway]

Someone might want to check my work ... but based on the coefficient of thermal expansion of aluminum ... it looks to me like a 10" long aluminum distributor housing would expand .019" going from 50 to 200 degree F.

Subtract from that the expansion of the steel shaft ... maybe .010" ... leaves you with potentially .009" the gap between the bottom of the housing and the gear could close up.

I'm guessing other factors are involved ... but if you got down to .005" cold clearance .... you'd be really pushing it when the housing got to 200 degrees.

(I was just guesstimating the coefficient of the steel shaft at about 1/2 that of aluminum)

[64speed]

When I say play I mean out of the box the gear and shaft would not move up and down in the housing at all. Now that the polymer gear is on it will wiggle up and down just a little. I listen to every damn word I am told but I am not always given consistent information. You don’t get the benefit of reading my private messages like being told not to use a punch but to use a vise. Slather was a bad word but it seems like the gear is just made out of plastic and that having some grease on it before startup would be better than starting it dry.

[64speed]

Originally Posted by Sun Tuned

Everyone should know by now the proper orientation of their rotor tip and that little divot at the bottom of their distributor gear. Or maybe by now they should.

Well, what happens if you buy a new gear bronze or phenolic and it doesn't have that mark at the bottom?

Simply take your original and look closely at it. Pay attention to the side with the divot. Look at the roll pin hole... see where the hole lines up with the teeth above. On some gears the holes on both sides of the gear line directly up with a tooth. On others like Chevy there is one hole that lines up with a tooth directly on one side and on the other side the hole is between two teeth.

Pay attention to this. Simply install the new gear as close as possible as the old one was originally.

Now some gears are the same on both sides. In that case it really doesn't mattter as you can install it either way and that's all you can do. But look at this in your original, and match up the new replacement in the same manner.

I don’t get this. My gear steel or polymer has no divot. It has a hole for the roll pin in the gear and in the shaft. I punched the old roll pin out, slid the old gear off, slid the new gear on, lined the holes up and drove the new pin in. Now you are telling me I am supposed to be looking for teeth alignment when I believe in my other thread said I was making it too difficult and it was THAT easy.

[grivera]

You’ll be fine as rotor phasing shouldn’t be difficult with the Holley dizzy. I’ve done the same swap on my small body HEI and prior to on an MSD did zy. Never knew to look for dimple and ignition wise everything has been fine.

[Sun Tuned]

As is usually the case with a field repair, you can get by with a modicum of very basic, rudimentary, if you will tools in a pinch. A vise is very helpful, not needed though, but we sometimes have to use what he have available not what we would prefer if we were in a place that had everything you could think of.

A member on this board that I had never met until that day watched me disassemble his new whiz bang 90.00 chicom HEI to prove it had no grease in the grease well, on his backyard sun porch with nothing more than a brick and a 20 penny nail that we cut the point off of with a pair of rusty Klein pliers. That's no joke. I put it back together and took it home to be fixed. No vise, held it on my chest and the gear in my hand. Today he's one of my best friends.

So yes, it can be done with very little very quickly.

The aftermarket gears sometimes lack the divot, some have it, most don't. I'm not explaining what it was for in this thread but yes I can tell you all about it if need be. There actually is a right and wrong way to position that gear in that shaft. Will it work either way? Sure it will.

Sometimes though one can get caught by doing that. It pertains to the rotor phasing as was mentioned somewhere above. On the 135 mm large cap HEI onecan get by with it easier than on the small 85 mm point size caps as the terminal spacing is much closer than the hei, which was another reason they went to the larger caps. Not the ONLY reason but more of a side advantage they found out. Yet another post for that story.

On the chevies they almost in every case will have the gear where it's lined up on one side with a tooth directly under the roll pin and in between on the opposite side. Get that deal switched and your off some 22.5 degrees on the rotor phasing. Depending on your timing settings you may get in a pickle or you may not. The Pontiacs are a tad different but the concept is the same.

Trust me that was an additional machining operation to put that mark in that gear which cost more $$$. If they could save it they would have.

Dataway, I'm not an engineer. Sounds like you did some math. I'd guess expansion rates would be dictated by the number grade of the aluminum (say 1001 vs 3003 Vs 6000 series etc) , the wall thickness of it and the length. But you have the idea of it all right. It certainly will grow.

I don't see any need to shim these aluminum housings tighter than .025. And then just cause the aftermarket wants to build a polymer gear and decides they want a certain endplay clearance. The question I have is endplay for who's distributor housing? Based on your expansion rate exercise, you can bet your hiney the old original will expand lengthwise at a different rate than this new aftermarket whatever will. It's likely different aluminum number series, different wall thickness etc. That will dictate different numbers.

So who's housing are they talking about? They sure as hell don't specify that in the instructions. So in all this aftermarket stuff who's shixting who here? In the end you pay your money for this stuff but you are the quality control that they don't have the time for anymore, or at least you need to be.

["QUICK-SILVER"]

Factory gear install doesn't change "rotor phasing". Trigger, rotor, cap orientation isn't effected by the gear.

The "FACTORY" gear divot on "FACTORY" distributors, insures you can set timing without the vacuum advance hitting/touching/bumping in to the intake or firewall.

Clay

[Sun Tuned]

And I forgot to mention...

If somebody built a housing with no endplay, which is what 64speed said came out of the box, I gotta believe him. Hell im not there to see it. So I take him at his word. But then he says the polymer gear "wiggles" now. Ok, and he feels sure he's ok within spec of .005-.012. Not sure how he measured this but we will accept this also. Again we aren't there.

So here's the deal...
Last time I explain this, so better save it...
Originally these distributors were setup with clearances. Wide on the stock stuff. Let's say an HEI.

Ok, take it off the GM parts counter, or hell just disassemble it on the Pontiac parts counter. This time we got a hammer, screwdriver, and a 3/16 drift,, and that should do it.

Pull cap , shaft gear and shaft. Reach down and pull up on the pickup coil. Notice it pulls up and down on top bushing a smidge. There's clearance there. Remember this.

Reassemble it , thank the parts man, clean up his counter and ask him for 3 more endplay shims. Pay him and go home. Get home and shim this turkey to where there is only .005 endplay. Put it in car and drive to work for a couple weeks. Pull distributor out and disassemble it. Wonder why the hell or rather where the hell the endplay in that pickup coil went to??? As now it's tight and won't move. Reckon the fuel mileage went south because of this???

Here's what happened...
Shimming it too tight caused the thing to drive(pull) the top bushing farther down into the housing seeking to make needed clearance that you took away when you put the 3 shims in the bottom. When that happened it squashed the retaining ring onto the pickup coil and that bound up the pickup coil from rotating and blocked the vac adv from doing its job. It's not a bulldozer, it's just a vacuum diaphragm.

That's an extreme example but exactly what happens when this stuff gets shimmed too tight.

[Sun Tuned]

It sure does clay! Guaranteed.

[Sun Tuned]

At least not on the distributor by itself. But when you talk about the exact spot on the cam gear it most certainly does.

Changing the initial timing setting to correct is not what we're talking about here.

Go look at a factory gear and you'll see it. Rotate it 180 and it will be obvious.

["QUICK-SILVER"]

Originally Posted by Sun Tuned

Go look at a factory gear and you'll see it. Rotate it 180 and it will be obvious.

Got one in hand.

Turning the gear 180° would change where the rotor button points in relation to the gear. Thus having to turn the distributor housing to compensate.

No change in phasing...Just clocking position of the distributor to set timing right. And that's where the vac advance bumping (intake or firewall) comes into play.

Clay

[ponyakr]

"...Everyone should know by now the proper orientation of their rotor tip and that little divot at the bottom of their distributor gear. Or maybe by now they should..."


Maybe everyone should, but I'm one of the old dummies that never heard anything about the divot, except on this forum.

I've swapped out a few gears & never even knew there was a right & wrong way to install the gear. Never had any ignition problems with any of those dist. Was I just lucky ? Or does the position of the gear not make any difference in ignition performance ?

I tried to look up some other threads & posts that mention this divot, every way I could think of to word the search. This is the only thread I found that mentioned it. So, would somebody who has the time please post links to some of the threads/posts that deal with this divot alignment.

I even Goggled it. Only thing I saw that said it really made much difference was on certain Corvette models. It seemed to indicate that if it was 180° out, the vac advance would be in a position that would not allow correct positioning of the dist housing.

[adynes]

Clay ("QUICK-SILVER") is right. Gear to shaft orientation doesn't effect rotor phasing, only "firewall phasing". But it doesn't matter anyway. By my count, the gear has 14 teeth, and being an even number, phasing will be the same no matter which way you install it.

If I had to guess, I'd say the dimple was possibly for parts identification/differentiation, or maybe locating during manufacturing.

[JSchmitz]

Originally Posted by adynes

Clay ("QUICK-SILVER") is right. Gear to shaft orientation doesn't effect rotor phasing, only "firewall phasing". But it doesn't matter anyway. By my count, the gear has 14 teeth, and being an even number, phasing will be the same no matter which way you install it.

If I had to guess, I'd say the dimple was possibly for parts identification/differentiation, or maybe locating during manufacturing.

I agree. Dimple was for indexing during manufacturing. Rotor phasing is between the reluctor ring and the rotor. Correct?