[carbking]

Originally Posted by Tom Vaught

I would disagree with you will on this one. Everything an Engineer does is for a reason. Maybe the first year of production he gets to make it the way he wants but then each successive year the bean counters and management are after him to REDUCE the cost, increase the line speed to install the part, open up the operating specs to allow more parts to be accepted (vs rejected) from the vendors, etc.

Tom V.

I loved this post. As some of you know, I am the caretaker of many of the existing Stromberg Carburetor records. Some of the most interesting reading is the "try to get around the patent" file. Carter had many patents which Stromberg had to pay royalties for using. Often as high as 8 cents per carburetor! For every one of these, there was an engineering team assembled to attempt to acquire the same result by modifying the carburetor, thus avoiding the royalty payment. I don't remember any instances where a modification was made. But the bean counters demanded the attempt, and obviously paid for it in salary!

Jon.

[dataway]

I got my washers from other distributors and Summit sells them from somebody, forget who.

My big question is still ... does the distributor gear try to climb the cam gear because of the force require to drive the oil pump? And if it does, what does it bear against vertically? I assume the shims/dist body.

[ponyakr]

Originally Posted by Kenth

There is no distributor gear walk on the cam gear as long as the engine is running at any rpm.
As long as the engine runs the distributor gear is pushed up against the wear shim, thus no timing variation.

So, are you saying that the shim is rubbing the housing, even at a 700rpm idle ?

If so, I suppose that means that even more pressure is being applied to the housing, by the shim, as the rpm increases.

If this is so, I reckin I don't understand how those old dist could go 100,000 + miles without chewing off the bottom of the housing.


I don't recall throwing away a bunch of old factory shims, because they were worn too thin. And never remember finding one that was completely wiped out. And most of the engines I bought had a 100k or more miles on 'em. Plenty of miles to wear out a shim/housing, if shim rubbing the housing would do it.


I also got my shims from other dist & Mr. Gasket. I never used the thinnest Mr. G shims, and always used a factory shim on the dist housing side. I assumed they were made from a harder material.

[dataway]

Kind of answers my question. The gears must be cut to not generate much climbing force, or the power required to drive the oil pump would destroy those shims in no time. So the gears must be cut to generate forces horizontally .. pushing the cam forward ...but then that seems like it would be awful tough on the lower dist. bushing.

Just usually ... when gears are trying to turn something like an oil pump .... it's going to push back pretty hard somewhere, in some direction.

Obviously more going on there that it looks like, and it's making my head hurt.

[tom s]

This is one of those post that pretty much tells us NOTHING!You get people that set them tight,other that set them loose.Since 1962 I have NEVER had a dist shim issue.In the last 20 or so years I have professional people like Suntuned set them up and have never asked or payed attention to how they were done.When I have changed over to a bronze or poly gear I just put the same shims back in.Nice to have blind luck for 55 years.I have 3 Xra dizzys in my drawer right now and will go out and get the numbers on them.Tom

[tom s]

OK,these are fresh dizzys.Iron points dist with iron gear .064,iron 421 SD pertronix with iron gear .017,alu pertronix with poly gear .036.FWIW,Tom

[dataway]

Hey ... I'm learning

I'm learning how much I don't know. And I'm learning what matters and what doesn't. And what I don't know does matter, and what I do know doesn't matter .... if that makes sense then we are making progress ... progress towards an unknown end, of unknown rewards.

It's an ADVENTURE in learning !!

[Tom Vaught]

Originally Posted by carbking

I loved this post. As some of you know, I am the caretaker of many of the existing Stromberg Carburetor records. Some of the most interesting reading is the "try to get around the patent" file. Carter had many patents which Stromberg had to pay royalties for using. Often as high as 8 cents per carburetor! For every one of these, there was an engineering team assembled to attempt to acquire the same result by modifying the carburetor, thus avoiding the royalty payment. I don't remember any instances where a modification was made. But the bean counters demanded the attempt, and obviously paid for it in salary! Jon.

Jon, people here think I make this chit up with my stories. Engineers do stuff for a reason, whether it is because they are ordered to do it, by Management, "Bean Counters", Patent Attorneys, OR BECAUSE IT WAS A GOOD IDEA, there ALWAYS is a reason.

Tom V.

[Formulajones]

Originally Posted by Tom Vaught

Jon, people here think I make this chit up with my stories. Engineers do stuff for a reason, whether it is because they are ordered to do it, by Management, "Bean Counters", Patent Attorneys, OR BECAUSE IT WAS A GOOD IDEA, there ALWAYS is a reason.

Tom V.

And from that list you provided that tells me the reasons weren't always the best ideas, lol.

[Tom Vaught]

Originally Posted by Formulajones

And from that list you provided that tells me the reasons weren't always the best ideas, lol.

GM came out with some real POS deals over the years, same for Ford and Chrysler.

You really want to blame the hardworking Engineer for some of these deals vs Management/Bean Counters/ Advertising Guys/ Regulatory Guys, etc???????????

Tom V.

PS GM FIRED Herb Adams, Tom Nell, and several other Engineers for Racing a car on their own time and money.
That knowledge helped Herb later build Fire Ams, etc. Real Chitty deal to lose your job that way.

[Formulajones]

Not blaming anyone, just pointing out that what ever the end result winds up being, it probably isn't always the best it can be, for the various reasons you posted.

[Blued and Painted]

Originally Posted by Sun Tuned

The real question I got is... if everyone is shimming these things.
Where do they source the washers?
I got lots to say about that.

Sourced mine from a couple of old Chevy distributors.

[72projectbird]

Originally Posted by Tom Vaught

Well now you have me in an agreement mood.

I was thinking about the Front-end Accessory Drive Engineer (FEAD Guy) who worked for Pontiac.
That sucker changed the Pontiac FEAD System ever year for about 10 years.
For No Reason that I could see (BUT) He had a REASON, he was paid to make changes to parts to get his Merit Increase from the company each year.

I say that because I saw personally at Ford when a Commercial Truck Guy (Wheel and Wheel Cover Guy) never got promoted or put in for a merit because he never needed to change anything on the Commercial Wheels.

So out of spite, he came up with a 6 LUG WHEEL for the E-150 vehicles and a 8 lug wheel with a different bolt pattern so that it would not work with the 8 lug wheels that had been used forever. It went into production. Then the Commercial Truck and Van customers who bought Fleets of Vehicles found out that all of their spare wheels and tires on the shelf would not bolt up to the new Truck/Van.

The days of having a truck get a flat tire and throwing on a different tire and wheel and back on the road were gone. My company lost $,$$$,$$$ on that deal.

They tried to fire him but it was not possible because he was doing what management wanted for him to do to get a Merit Increase.
So that BS Deal stopped asap and there was no more pressure on doing the same job year after year any longer and not getting a good Performance Review.

Tom V.

Your Bumper Guy/Girl was probably right out of college and on His/her first Design Position.

That's interesting. I always wondered why Ford decided to change their 8 lug pattern when they went to the Super Duty trucks.

And I agree with the 70-73 nose comment. These noses are a royal pain to mount and line up!

[Sun Tuned]

So...
Been sick for a few days with a nasty sinus infection. Im not ready to die just yet, but a couple days ago I wasnt sure it was gonna be my choice one way or another the way I was feeling. Headed in right direction now though but not quite 100% yet.

Wasn't trying to leave everyone hanging. Hope everyone had a good Thanksgiving.

Lets talk about this distributor endplay thing a bit more,

Why did the engineers who designed these things set the endplay so wide?
Honestly, I have no idea. The guy I trusted to answer that, I have no way of getting in touch with anymore. Someone had told me he had passed a few years back or so they thought. When GM started scaling back subcontractors his company got the proverbial ax, and I mean but good. Virtually none of the people I had contact with at Delco could be found anywhere. I say Delco, but thats technically not correct, it was actually Delphi Energy Engine Management Systems. I guess they got "absorbed" by GM or something, maybe broken up in pieces, im not sure, but my main guy was set to retire in about another year anyhow so who knows. Ill ask Tom V if he knows of or crossed paths at some point and see maybe hes actually ok and just enjoying being retired. I hope thats what happened anyhow.

Seriously I never thought to ask that question, however there were a couple more I wish Id asked also when I had the chance. So clearly one might say they did it because of stack up tolerances on other parts and to cover possible issues there, maybe, maybe not. Lot of oil splashing around in that area anyhow already. Even with the factory clearance they had, I've noticed on All the GM distributors Ive taken apart the wear pattern is almost always nearly in the same location plus or minus some .020 up or down on the distributor gear. That can not possibly be by accident. Certainly not on that many distributors. Being that on most GM distributors the gear runs up into the housing and not down in the block as on an olds I know that they held their clearances pretty damn close .

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

[4zpeed]

Could core shift be a possibility?


Frank

[Sun Tuned]

Ill try and cover the rest of the questions I posed in the rest of this post, kinda like a sitdown sorta affair where I just start talking, and hopefully cover the junk you wanna know about.

We know the factory clearance on this stuff works just fine as is. How do we know this? No one has ever shown me a service bulletin from anywhere that outlined repair procedures on shimming a distributor. Ive taken apart and had MY hands on close to 2800 distributors to date. Most of which already had 100,000 miles on each to start with but you get the idea. I dont know the individual persons name who developed the idea to begin shimming this stuff but I do know it was started by racers back as early as 1957-1960 or somewhere in that time period. The reason they originally started doing this was not for the endplay clearance itself but as a tail wagging the dog type of deal to cure another problem... Point float.

It seems they were finding that the points were floating not because of the quality of the point sets but because of the so called excess clearance in the shaft. (This is apparently a racer type of thing) And by shimming the excess clearance in the shaft they found they cut down considerably on the point float deal. Well.... sorta. Not really ,but, yeah,.. ok. So then a guy tells another racer he did this and then as Tom V said in his Holley post every racer worth his salt magically then believes he "needs" to do this. Then to sell a few magazines in the mix, an article or two pops up, then hell, were off to the races selling all sorts of parts that werent available before.

See the deal was in actuality, the points were floating, but in reality endplay had ZERO to do with it. Reluctor bore clearance to the shaft had all to do with it. When the cam lobe which is the one piece part of the reluctor bore flops around it will set up an oscillation and whip around and do all sorts of tricks which in turn makes the points do goofy stuff. Now keep in mind this stuff was still relatively new back then and certainly not the 100 and 200,00 mile stuff I get to look at regularly. The way to fix it would have been to either find a reluctor or cam lobe assy that fit better or to bush the bore and ream to size to fit the shaft much more snugly so that you didnt have all this loose sloppy stuff rattling around. That was too much trouble, so they did what was easiest and shimmed the excess clearance out of the shaft down to like .005 or so and effectively cured most of the issue. I wont say that it didnt help cure it because it did, quickly, but there was a better more finessed way to do it. I guess at the end of the day it really didnt make a damn how you got it fixed, just that you got it fixed. As they took clearance from the shaft endplay it would also slightly rest the inside reluctor bore seat face on the top bushing of the distributor, which helped curtail the wobbling all over of the parts causing the problem. Without all the factory clearance the wobbling was far less. Thats why they did this early on.

However, no one bothered to mention in later years, why this was originally done, and so, people being creatures of habit kept doing it not really understanding why. That whole concept reminds me of my father inlaw who was from about as far north in the U.S. as I can think of without being in Canada, Straussburg , ND. used to say about farmers down south. Now he grew up on a farm in ND and when he moved to the south with the US Navy he stayed, got tired of 5 feet of snow all the time. He said all these guys down here just wont rotate the crops like they really should, like they did back in ND. I asked him what he meant, and he said take that field right there, since I met your mother in law back in 1965 that field has had cotton planted in it, every year, without fail, and its 1988, why? hed say because the guy who plants it now had a great grandfather that planted that same field with cotton in 1855 and by god thats what hes planting there now. I laugh everyday I drive to work, because my father in law died in 2003, and that same field he talked about still has cotton in it, just like it used to ,although it doesnt look to be a very high yield deal. Probably cause the soil is used up. My point is for years people have been doing the same monkey motion thats been done for years without giving much thought as to why or what theyre really accomplishing.

We move out of the points era and into the electronic age of distributors and we find the same stuff being replicated... shimming the hell out of shaft assemblies, and for what? Theres no points to be bouncing around, so what are we doing it for now??

Whos got a good answer for this one? Hold that thought cause anytime now Hot Car magazine will have an article on why we need to do this and im sure itll free up a bunch of extra power.

[Cliff R]

I've done enough of these distributors at this point to know that they will be fine if you avoid a couple of things. NEVER use thin shims in them, especially aftermarket varieties as they can/will break and end up in the assembly. I much prefer factory shims, and do whatever I can to only end up with one of them in place. If you choose to use factory shims they need to be closely inspected as some will be worn some and have a "lip" on them where they were against the housing. The gear side doesn't seem to be as hard on them.

As for shimming them up, one needs to look closely at the wear pattern on the old gear. Few will be well centered but all will be well on the gear so it tells me that there is a "range" the gear will run in and be fine and it doesn't have to be exactly centered.

The gear also needs to be closely inspected. They typically lead a pretty good life and give few if any troubles, but I've seen later Chevy distributors with the gears chewed up pretty hard when then spent their life being driving by a factory roller camshaft. This will be from about 1987-on, until they went to other methods of firing these engines.

When you are replacing the gear with a non-factory part shimming is going to be required, and I've even had to trim a few gears in the lathe to be able to use a decent thickness shim with them, as thin shims are avoided here.

I've never tried to obtain very tight clearances with these things, but if and when we install new gears and shim I like to see around .020" or so end play. This isn't always possible due to the combinations of parts you may have available, but for sure I would never run them tighter than .012" or so and I see no need to be past about .060" for any reason.

The "loose" tolerance probably doesn't matter for the reasons mentioned, but having a .100" of more of room to "slop" up and down for any reason simply makes to sense to me......FWIW.......Cliff

[Cliff R]

"At the end of the day, 17 out of the 20 modified carbs really did nothing and were Smoke and Mirrors. No better vs the carb calibration right from Holley. But they got your money."

Reminds me of WAY back when I started drag racing my 1970 Roadrunner and obtained two Holley carburetors to try on it. I had an early 780cfm vacuum secondary carb first. Tried every possible combination of jets in it, and every secondary diaphragm spring from the "kit" they sell. It ran the very best with the factory jetting, and any attempts to make the secondaries come in sooner slowed it down considerably.

Went to an 850 DP next, and despite having the bowls off of it enough times we had to install heli-coils in the housing, throwing fuel at it never resulted in any measureable improvements in ET or MPH. When the smoke cleared and dust settled it ended up 2 numbers richer on both metering blocks than the factory calibration and I quit messing with it.

Same thing with intake manifolds and Edelbrock AFB clone carburetors. For as far back as I can remember the factory parts were quickly removed from a high percentage of these engines only to install parts that often required "cobbling" to get them in place, and most if not all of them made LESS power than the parts being replaced.

I went to our local/annual car show and cruise last summer and walked thru the event. Several hundred cars in attendance with the hoods up. At least 80 percent were equipped with an Edelbrock Performer intake and matching carburetor. I was only able to find two engines in the entire place that still sported their factory intakes and carburetors.

Goes to show how folks then and now still buy into all the BS about how well that stuff works and is superior to the factory stuff. I'll bet not a single one of those folks actually did any dyno or track testing before or after the swap. They are just happy that their engines roar to life and they are able to make it to a local cruise or car show right to start with.......Cliff

[Sun Tuned]

All right back on topic or I'm gonna be quiet again and do like alot of the guys did, take that info along and sit on it and not share it even till its too late. Eventually everyone figures it out sooner or later, but then again we are still spending way too much time rehashing stuff thats still incorrect. Everyone wants to know what is the deal here with the shimming and so lets get to it, from a practical level, that when we get there , youll find we arent too far off from where the engineers were going.

First let me say this, Cliff I love ya , what youve done for not just the Pontiac hobby , but the car deal in general as far as QJet carbs are considered is simply outstanding. The parts you sell me are always appreciated, they make it much easier to get an excellent finished result. You got me out of 1972 thinking when it comes to Qjets...
Now let me return the favor and get you and some others that may choose to spend the time reading this out of 1972 thinking when it comes to distributors.

On the iron case distributors which Pontiac used up until best I can see till early August of 1966, the housings were extremely stable. Nothing at all like the aluminum housings whatsoever. As such the oiling was better to the bottom bushing, the housings were stable and as a result of that the top bushing absolutely did not move around. It stayed put very well. So much so it pretty much takes a very specialized puller or a press and a little heat on the housing to gently get it to move. They put em there and they bygod expected them to stay put... they got that worked out.

Then they went to aluminum for a few reasons, cost of mold maintenence being the principal reason followed by cost of material ,and a couple others . These things were not as stable as the earlier iron units and youll find at the bottom of all the 1967 and 1968 Pontiac housings ,they were hedging their bet on this bottom bushing deal, as these housings are noticeably thicker and slightly more robust at the bottom of the housing where the thrust washer sits. The thickness of the housing that sits in the block register is also slightly thicker by about some .015 of an inch over later 69 and up units. The reason I mention this is that these aluminum housings from 1967-1981 will naturally "move" around much more than the earlier iron counterparts. That has bearing on this whole thrust washer topic , so keep that in mind for later.

As I said earlier, they would shim the iron stuff much tighter than you can concievably get by with on an aluminum housing. Im not sure about the math on the expansion rates and engineering info needed to compute that nearly as much as say Tom V would be and Im not gonna try and figure it out. Principally because Id think youd have to know the iron mix of stuff they were using in order to properly figure it anyhow. Id venture to guess same as the block and heads but who knows. Now as that housing did expand some number, this is where it gets down to the important stuff.

This is a kind of general description with a few notations for the 3 different distributors. Lets use the old iron deal. say we cut the endplay to .005. put it in the engine and go happily motoring away. Stuff builds heat and as stuff gets heat soaked junk starts to expand and at different rates and at different times. We got cast iron housing ,Bronze alloy bushings and a steel shaft, and a iron gear and steel shims, or in the case of the iron dist one real thick steel shim, unless weve added some which we did to get the .005 so now we got a whole lot of stuff whizzing around. And it will all heat soak and get to a normalized temp. You can bet that the .005 you had cold in a vise is something different than what it is now when all hot and normal temp. The trick then and now would have been to close that gap to just the bare minumum without all that crap getting tight and binding up, and folks at .005 ya aint got much room to be goofing around. In the case of the early stuff the parts did just that and when done right I was told that bottom face of the inside of that reluctor bore( the inside face of the point cam lobe where the shaft comes out) would just slightly kiss the top bushing. Not smash it, and not really need to touch it but just barely float over the top. At that point they figured they removed all the wobble stuff out of the equation and stuff just worked better without movement all over with 48oz points and such.

Pretty much after a few people started "sharing" ideas and such ,then everyone was in on the "tricks" and then everyone was doing it. Come out of the point distributor era and then what was all the fuss about doing it for now? Well hell, noone really knew or maybe even thought about it but they used to do it and it must have made a difference so everybody kept on keeping on. Only problem was on these aluminum housings you cant shim em that tight. But people were still doing it and then sooner or later somebody stopped and said "Hmmm... Well we cant do this this tight anymore.?" Why? "Cause were binding up stuff." Ok fine but they still only backed off a bit but they got that figured out.

What happens on a iron housing is when you get it too tight... you end up "machining" down the top bushing. You get it real tight it will bind up and lock the top weight assy on the shaft.

You do this on any aluminum housing factory GM distributor: point or HEI.... it will take up the slack and "clearance itself" somewhat, by pulling by force the top bushing into the housing which, on all aluminum factory distributors , is a tapered bore top and bottom. Then it will press the hell out of the top point plate on a point dist or the pickup coil on an HEI and wedge the retainer clip to where its a pain in the ass to get off. At the same time for those of you who are running an operable vac adv, it now dont want to work smoothly because its all bound up and cant contract or release properly. These also will, if too tight , bind up the mech adv as there just isnt anymore room to be found clearance wise except there, and if need be it will find it , use it up , and bind that as well.

Soooo... where the hell am I going with all this? My point is for years on these boards Ive heard people get all spastic about this endplay thing. Ive even sent distributors out that folks paid me for and they didnt "think" i did a good job on that part and "had " to fix it, likely because they read one or several magazines while i had it that said it should be done this way. Total lack of understanding on what is going on with the parts guys.

Heres a tidbit of info for all these guys doing magazine articles so that they can look so neat and cool and actually havent got the first damn idea what the hell theyre doing at all. All they know is they got a cool toolbox full of measuring stuff and some idea how they should use it.

Since most everyone on this board uses an HEI by say some 60% of you lets use that for this example. Im only gonna expalain this trick once so pay close attention.

[Skip Fix]

He said all these guys down here just wont rotate the crops like they really should, like they did back in ND. I asked him what he meant, and he said take that field right there, since I met your mother in law back in 1965 that field has had cotton planted in it, every year, without fail, and its 1988, why? hed say because the guy who plants it now had a great grandfather that planted that same field with cotton in 1855 and by god thats what hes planting there now.

Here they usually rotate sorghum/milo/maize. Great for dove hunting