[STEELCITYFIREBIRD]

[QUOTE=Kenth;5806708]Same answer as in "the other" distributor post:

There IS no endplay with engine running due to the helical drive/driven gears and the force from oil-pump drive shaft.

Totally waste of time and effort shimming to .010" with the risk of getting glitter in oil from oil-pump bottom plate and excessive wear on distributor/cam gears located too far down.

I have several NOS Pontiac distributors having ,40"-.60" "endplay".

And as for lubricating the lower bearing "endplay" is NO issue since there is a space between wear shim and distributor housing on alu housings and a hole in distributor body just above bearing on cast iron housings.[/QUOTE


0,040"-0.060" ?

[Half-Inch Stud]

Originally Posted by Scarebird

not so sure of that, Tom, as anybody that has fitted up a 70-73 Firebird front bumper would love to query the assembly engineer WTF he was thinking/smoking...

and 69 bIrds front bumper Tom S beat me to it

[Half-Inch Stud]

Such a small dizzy gear combo. seems ya got to get and keep the gear centerlines bang -on, otherwise


the gear teeth don't have full mesh and......either grind the teeth or/and eventually jump the time.

[Tom Vaught]

Originally Posted by Kenth

Same answer as in "the other" distributor post:

There IS no endplay with engine running due to the helical drive/driven gears and the force from oil-pump drive shaft.

Totally waste of time and effort shimming to .010" with the risk of getting glitter in oil from oil-pump bottom plate and excessive wear on distributor/cam gears located too far down.

I have several NOS Pontiac distributors having ,40"-.60" "endplay".

And as for lubricating the lower bearing "endplay" is NO issue since there is a space between wear shim and distributor housing on alu housings and a hole in distributor body just above bearing on cast iron housings.

X2

Tom V.

[Tom Vaught]

Originally Posted by Scarebird

not so sure of that, Tom, as anybody that has fitted up a 70-73 Firebird front bumper would love to query the assembly engineer WTF he was thinking/smoking...

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.

[chevymad]

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.

You have me wondering if this is why Ford uses so many different types of quick connect fuel fittings. Seriously, you can find 3 or 4 different kinds on one fuel tank/filter assembly.

[Sun Tuned]

Anyone got any ideas on whether they believe that shimming within reason will cause a marked decrease in the timing mark jumping around when viewing with a timing light??

[dataway]

I always thought that it would help ... certainly doesn't mean it's true though Combined with a little timing chain slapping around ... might help shimming? Seems like bushing condition might have more of an effect on spark scatter. Just guessing.

Now the oil pump takes quite a pit of power to turn at RPM .... is all the force of the dist. gear, trying to climb the cam gear, placed on the bottom of the dist. housing? Or are the gears designed not to cause much climbing force?

[Tom Vaught]

Most likely, Suntuned, my friend, it is like the 20 carbs we inspected at Holley from all of the modifiers of Holley carbs at the time that ran businesses and changed stuff on our carbs.

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.

Same deal for some of these Trick Mods on engine components. At the end of the day
what did the mod really do for performance, durability, F.E, Emissions, etc.

So I am betting not much, or they made it worse..

Tom V.

[Kenth]

[QUOTE=STEELCITYFIREBIRD;5806713]

Originally Posted by Kenth

Same answer as in "the other" distributor post:

There IS no endplay with engine running due to the helical drive/driven gears and the force from oil-pump drive shaft.

Totally waste of time and effort shimming to .010" with the risk of getting glitter in oil from oil-pump bottom plate and excessive wear on distributor/cam gears located too far down.

I have several NOS Pontiac distributors having ,40"-.60" "endplay".

And as for lubricating the lower bearing "endplay" is NO issue since there is a space between wear shim and distributor housing on alu housings and a hole in distributor body just above bearing on cast iron housings.[/QUOTE


0,040"-0.060" ?

I stand corrected! Thank you for noticing.

[Blued and Painted]

A wide .040 sounds like a good number. My factory hei was in the .120 range. IIRC I was able to get it down to .050 ..

[Squidward]

I see .040+ on mine.

Funny: making change = more money! The U.S. Mint figured that out years ago!

But yes. All too common where change is implemented for the sake of change, and not necessarily change for the better. I see it in my biz, too.

How much timing variation are we talking about, and is it actually significant? It seems to me like distributor slop where the distributor gear walks the cam gear would only take place at acceleration and deceleration. I don't personally care about a degree or two of ignition timing slop, especially when driving on the street where I have close to 30 degrees of variable timing between mechanical and vacuum advance. During WOT I would think that the gear would walk up to close the gap, and then achieve a static equilibrium state. It all becomes relative where it becomes accounted for in the tune.

And the walk of a distributor gear back down would be dampened by the feedback force of the oil pump working against the cam. At least that's the way it plays out in my mind.

[STEELCITYFIREBIRD]

Originally Posted by Sun Tuned

Anyone got any ideas on whether they believe that shimming within reason will cause a marked decrease in the timing mark jumping around when viewing with a timing light??

I know it doesn't.

[Sun Tuned]

The real question I got is... if everyone is shimming these things.

What are they shimming them with? Where do they source the washers? And what how are the washers finished?

I got lots to say about that.

[Kenth]

Originally Posted by Squidward

I see .040+ on mine.

Funny: making change = more money! The U.S. Mint figured that out years ago!

But yes. All too common where change is implemented for the sake of change, and not necessarily change for the better. I see it in my biz, too.

How much timing variation are we talking about, and is it actually significant? It seems to me like distributor slop where the distributor gear walks the cam gear would only take place at acceleration and deceleration. I don't personally care about a degree or two of ignition timing slop, especially when driving on the street where I have close to 30 degrees of variable timing between mechanical and vacuum advance. During WOT I would think that the gear would walk up to close the gap, and then achieve a static equilibrium state. It all becomes relative where it becomes accounted for in the tune.

And the walk of a distributor gear back down would be dampened by the feedback force of the oil pump working against the cam. At least that's the way it plays out in my mind.

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.

[Squidward]

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.

That's what played in my mind, that there would always be resistance from the oil pump, and it would create enough "backpressure" to keep the distributor gear in a stable state. But I am not an advanced player in the hobby, and have not ventured very far beyond stock performance levels. I still have to rely on really smart well payed people who do this for a living.

[ponchjoe]

Probably a stupid question but is a certain amount of tolerance required to align the rotor and distributor cap terminals for the best possible spark?

[STEELCITYFIREBIRD]

Originally Posted by Sun Tuned

The real question I got is... if everyone is shimming these things.

What are they shimming them with? Where do they source the washers? And what how are the washers finished?

I got lots to say about that.

When someone in the know and the biz is talking, I'm listening.

Sooo, tell the facts, I'm interested..and listening.

[johnta1]

What are they shimming them with? Where do they source the washers? And what how are the washers finished?

I used shims from other distributors.

[STEELCITYFIREBIRD]

I got mine from MR GASKET kits.....a long time ago. HO use to sell them in their "accuracy" kits as I recall. Nowdays, no idea, I have a decent stash....if I even need them.

Do tell SUN TUNED!