All replacement vortec distributers have .427" shafts!

[Jackaru]

So I'm looking for the guy who really knows his stuff on the Vortec distributer gear issue.

I made what I am finding was a fatal mistake of putting a Comp cams K01-417-8 computer controlled cam kit in my '96 L29 454. I thought this was a strait forward upgrade, but had to take my heads back after having them rebuilt because my springs needed shimmed for proper tension and also the rods were the wrong length. I had to juggle oddball rod lengths, rod end size, rod shaft size and ended up modifying (relieving) the rod guideplates to accept the 3/8 shaft rods because guideplates from summit just didn't fit right. It turned into a major goat-rope.

I have certainly gotten a schooling. Comp Cams recommends always changing the distributor gear with a new cam, but not a word about gear compatability. So like many others, seeing gear prices, it seemed to make sense to just replace the whole distributer for one with an aluminum housing, so I did that.

Due to firewall and intake plenum restrictions with the crab-style cap, I couldn't get it to time. I pulled out the distributor to rotate the gear 180 degrees and found almost immediate adverse wear on the gear after only a couple hours operation.

So...... researching the issue tells me I have an Austempered ductile iron cam. one video from Comp Cams on their "cores" states the gear (for the -8 cams) is pressed on and compatable with normal iron distributer gears. Yet most of my research, and a more detailed video from Comp Cams says you need a Melonized steal or composite ditributer gear, or you will eat it up. I have read many post of people eating standard iron gears. I look at my old votec cam and no doubt it is a steel cam, meaning the distributor would have had to have a melonized steel or composite gear. Like an idiot, I disposed of the old distributer. I kick myself every day. My pathetic memory tells me it had a composite gear.

So obviously just get a damn melonized gear, right? Now comes the real problem; You know the Summit Vortec distributer? (by the way, NOT billet, cast aluminum) Absolutely no different from the United Motor Products distributor from RockAuto. The gear also is EXACTLY the same gear. even though they say its a melonized gear. It is not! Both of these distributors have a oddball Chinese .427" shaft, so you can NOT even buy a true melonized or composite gear for either of them.

Enter MSD. My machine shop guy says they really know there stuff...... NOT. FIVE phone calls that left me with more questions than answers, once talking to some errogant punk kid that acted like he knew it all and all their distributers drop into any chevy with no problems. The only distributer they have for the Vortec is their Surefire (which is just another chinese import). I called a sixth time when I did not get a call back with the shaft size two days later (they had to go to the engineers to find the shaft size). Finally a callback saying it was .488" to .489". I figured that to be the .491", so I ordered that, a Comp Cams Melonized .491" gear and new roll pin from Summit.

Guess what?........... I'm surprized I have hair left! Lying sacks of ****! All of them! from Summit, to Comp Cams, to MSD. Even their engineers! Was it too hard to drive the pin out and put a set of calipers on the shaft so they know what they're selling? Shaft size is .427". The gear looks slightly darker than the others but does not have the dimpled coating, characteristic of a Melonized gear, and it weighs exactly the same as the (chewed up) first gear (on the right in photo).

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Left to right; MSD Surefire gear, Comp Cams melonized gear, United Motor Products (worn) gear (Summit distributor exactly the same)

I simply can not find a computer controlled Vortec distributor with a .491 or .500 shaft, so I can put a composite or what I am convinced is a melonized steel gear on it. I can only find this import **** with undersized shafts. There is not enough data published that I have found to verify the shaft size of even Delco Remy remans. So here my truck sits....still. I am thinking I'm just going to machine a bushing to adapt the Melonized gear I have to the first UMP distributor.

Any other thoughts?

 

[someotherguy]

I am thinking I'm just going to machine a bushing to adapt the Melonized gear I have to the first UMP distributor.

Exactly what I was thinking before I got to the bottom of your post. If they don't make what you need, you make what you need. :/

Richard

 

[L31MaxExpress]

The stock GM small block gear is melonized. I have never not seen a distributor gear with similar looking wear during break-in. Also those distributor shafts need to be shimmed much tighter and then the whole housing will probably need to be shimmed up.

The stock GM shaft is the same size. The reason you cannot find a distributor with a shaft that dimension is because they were never made with a mainshaft that dimension that I am aware of anyway.

 

[L31MaxExpress]

Also FWIW the small cap HEIs use the same size shaft. A TPI Camaro or Vette or TBI Caprice uses the correct gear as well. I just looked and most sources show the GM Melonized gear for the 0.427" shaft as discontinued. GM will show it as a 0.428" gear.

 

[L31MaxExpress]

Distributor shaft end play fail!

I noticed my distributor making some weird noises. The rotor tip was contacting the cap electrodes, causing a clicking/tapping sound. I pulled it out and discovered I had 0.055" end play and cracked distributor cap mounting bolt holes despite the thing being aluminum. The gear had some wear...

www.gmt400.com

The distributor gears are softer than the cam gear and the wear on my gear is about how they will all look after 20-30 minutes of run time. With the shaft and housing properly shimmed the wear pattern is a bit narrower, but still looks much the same.

 

[Schurkey]

researching the issue tells me I have an Austempered ductile iron cam. one video from Comp Cams on their "cores" states the gear (for the -8 cams) is pressed on and compatable with normal iron distributer gears.

I don't know why an iron-core cam needs to have an iron gear pressed-on.

I bought a steel-core roller cam for my boat with a pressed-on iron gear and rear journal. Lunati called it "Everwear", I think.

I look at my old votec cam and no doubt it is a steel cam, meaning the distributor would have had to have a melonized steel or composite gear. Like an idiot, I disposed of the old distributer. I kick myself every day. My pathetic memory tells me it had a composite gear.

No "composite" (Plastic) gears from GM. If it had a plastic gear, someone added it later.

Vortec distributors are known for excessive gear wear. TBI distributors are not, at least I've never seen problems with them.

But someone on this forum was saying that Vortec distributor shafts were not the same diameter as TBI distributor shafts, although both were in the 0.430-ish range.

Anyway, the Treasure Yards are full of Vortec and TBI distributor cores to scavenge a usable gear from.

You know the Summit Vortec distributer? (by the way, NOT billet, cast aluminum)

Yup. Machined casting not a "billet".

The gear also is EXACTLY the same gear. even though they say its a melonized gear. It is not!

When GM actually made stuff instead of buying-in everything from outside suppliers, their Melonized gears didn't look all that different from non-melonized.

The visual change came when Delco quit making distributors and the GM Parts Department was selling (Korean?) replacements. ProForm, I think.

Both of these distributors have a oddball Chinese .427" shaft, so you can NOT even buy a true melonized or composite gear for either of them.

Yup. TBI and Vortec mainshafts are skinny.

Best I can figure, GM used to buy .500 steel rods or steel "wire", which when straightened and polished, became .491 because they lost .0045 all the way around in the polishing process.

I don't know how the aftermarket came up with .500 shafts, but it might have been a matter of not being able to source oddball .492-ID bushings.

Enter MSD. My machine shop guy says they really know there stuff...... NOT. FIVE phone calls that left me with more questions than answers, once talking to some errogant punk kid that acted like he knew it all and all their distributers drop into any chevy with no problems.

MSD has been passed around from company to company like the town pump. The folks who own Holley own MSD, and that's not a good situation.

The only distributer they have for the Vortec is their Surefire (which is just another chinese import).

Surefire? I'd have guessed "Streetfire", their bottom-feeder discount line which has always relied on imported components and the MSD parent-company name to jack-up the prices above what Chinese crap should command.

Now that the majority of MSD products sold are imported junk, I don't know why they continue with the Streetfire line.

The gear looks slightly darker than the others but does not have the dimpled coating

I wouldn't rely on visual differences. It's not the "coating" that's dimpled, it's the rough-cast iron underneath. When GM made the gears, they were nicely-machined all over, and then they got the Melonizing surface treatment. Once the Koreans made the GM gears, they didn't finish the gears before coating, so they were coating the machined teeth, and the rough-cast remainder of the gear.

Melonizing itself isn't thick enough to form "dimples". Melonizing is about one thousandth of an inch thick, more-or-less, often less.

https://www.northeastcoating.com/salt-bath/engineering

I simply can not find a computer controlled Vortec distributor with a .491 or .500 shaft

Not surprising.

I can only find this import **** with undersized shafts. There is not enough data published that I have found to verify the shaft size of even Delco Remy remans.

As said...TBI and Vortec distributors came from GM with ~.430 shafts. .427 is what I hear most-often, but there's folks claiming minor differences. Maybe that's a Cheap-Junk import difference, maybe they have crappy measuring tools.

Go to a Treasure Yard, look through their pile of distributors, find a TBI or Vortec gear that looks acceptably good.

I'm told that the NEW gear at the back of the camshaft, and the NEW gear on the bottom of the distributor need to be "dressed" with a file or stone to remove burrs/sharp edges.

I have also heard that a QUALITY (Ampco 45, properly machined) bronze gear, properly-dressed, can be a long-term solution; but bottom-feeder Chinese bronze gears can be wiped in a thousand miles.

 

[Jackaru]

Distributor shaft end play fail!

I noticed my distributor making some weird noises. The rotor tip was contacting the cap electrodes, causing a clicking/tapping sound. I pulled it out and discovered I had 0.055" end play and cracked distributor cap mounting bolt holes despite the thing being aluminum. The gear had some wear...

www.gmt400.com

The distributor gears are softer than the cam gear and the wear on my gear is about how they will all look after 20-30 minutes of run time. With the shaft and housing properly shimmed the wear pattern is a bit narrower, but still looks much the same.

You must be registered for see images attach

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I thought some closer photos might help. When I pulled the distributor out, there was a flake of metal still hung on. You can see in the photos ridges at the base of the gears you can hang you thumbnail on. I'm an Aviation sheet metal mechanic, have a trained eye for .***" measurements and estimate depth to be around .020" at least. Also clearly visible is the spauling has eaten completely through the champfer on the teeth. Again .020" to .030". I just don't see this as normal break-in.

 

[Jackaru]

I don't know why an iron-core cam needs to have an iron gear pressed-on.

Comp Cams calls it "Austempered" ductile iron that creates a harder surface than standard cast iron. There are some CC videos available on you tube. My bad, I heard in my head it was pressed on. They say its compatable but still recommend a melonized gear.

youtube comp cam cores - Google Search

I bought a steel-core roller cam for my boat with a pressed-on iron gear and rear journal. Lunati called it "Everwear", I think.


No "composite" (Plastic) gears from GM. If it had a plastic gear, someone added it later.

Copy that.

Vortec distributors are known for excessive gear wear. TBI distributors are not, at least I've never seen problems with them.

But someone on this forum was saying that Vortec distributor shafts were not the same diameter as TBI distributor shafts, although both were in the 0.430-ish range.

Anyway, the Treasure Yards are full of Vortec and TBI distributor cores to scavenge a usable gear from.


Yup. Machined casting not a "billet".


When GM actually made stuff instead of buying-in everything from outside suppliers, their Melonized gears didn't look all that different from non-melonized.

The visual change came when Delco quit making distributors and the GM Parts Department was selling (Korean?) replacements. ProForm, I think.

This day in age you simply can't rely on anything. One article read that you know a melonized gear by it's dimpled appearance. Comp Cams Melonized gear has a very distinct dimpled apearance. This is the problem, what or whom do I believe. There is no reliable data. Representatives of all these companies don't know. I took a spring center punch to all three gears and a metallic tap test and none seamed harder than the next.

Yup. TBI and Vortec mainshafts are skinny.

Best I can figure, GM used to buy .500 steel rods or steel "wire", which when straightened and polished, became .491 because they lost .0045 all the way around in the polishing process.

I don't know how the aftermarket came up with .500 shafts, but it might have been a matter of not being able to source oddball .492-ID bushings.


MSD has been passed around from company to company like the town pump. The folks who own Holley own MSD, and that's not a good situation.


Surefire? I'd have guessed "Streetfire", their bottom-feeder discount line which has always relied on imported components and the MSD parent-company name to jack-up the prices above what Chinese crap should command.

Correct, "Streetfire"

Now that the majority of MSD products sold are imported junk, I don't know why they continue with the Streetfire line.


I wouldn't rely on visual differences. It's not the "coating" that's dimpled, it's the rough-cast iron underneath. When GM made the gears, they were nicely-machined all over, and then they got the Melonizing surface treatment. Once the Koreans made the GM gears, they didn't finish the gears before coating, so they were coating the machined teeth, and the rough-cast remainder of the gear.

Melonizing itself isn't thick enough to form "dimples". Melonizing is about one thousandth of an inch thick, more-or-less, often less.

https://www.northeastcoating.com/salt-bath/engineering

Not surprising.


As said...TBI and Vortec distributors came from GM with ~.430 shafts. .427 is what I hear most-often, but there's folks claiming minor differences. Maybe that's a Cheap-Junk import difference, maybe they have crappy measuring tools.

Go to a Treasure Yard, look through their pile of distributors, find a TBI or Vortec gear that looks acceptably good.

I'm told that the NEW gear at the back of the camshaft, and the NEW gear on the bottom of the distributor need to be "dressed" with a file or stone to remove burrs/sharp edges.

I have also heard that a QUALITY (Ampco 45, properly machined) bronze gear, properly-dressed, can be a long-term solution; but bottom-feeder Chinese bronze gears can be wiped in a thousand miles.

Just got a lead on a domestic, family owned supplier, highly recommended by a knowledgeable 65 year old engine builder. will see what they say and pass it on.

 

[Vic327]

I may be a bit late to the game on this one but you could find a brass tube with the right wall thickness and drill a hole for the pin to make a shim or get some shim stock of the right thickness to roll a shim. Have a look at shim stock on mcmaster.

 

[BeXtreme]

Comp Cams calls it "Austempered" ductile iron that creates a harder surface than standard cast iron. There are some CC videos available on you tube. My bad, I heard in my head it was pressed on. They say its compatable but still recommend a melonized gear.

youtube comp cam cores - Google Search

Copy that.

This day in age you simply can't rely on anything. One article read that you know a melonized gear by it's dimpled appearance. Comp Cams Melonized gear has a very distinct dimpled apearance. This is the problem, what or whom do I believe. There is no reliable data. Representatives of all these companies don't know. I took a spring center punch to all three gears and a metallic tap test and none seamed harder than the next.

Correct, "Streetfire"

Just got a lead on a domestic, family owned supplier, highly recommended by a knowledgeable 65 year old engine builder. will see what they say and pass it on.

This is what I put on my newly rebuilt L29. Summit doesn't have them, but the ACDelco store on Amazon does.

https://www.summitracing.com/parts/ado-10457708#overview

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Its a factory roller SBC/BBC replacement melonized steel gear.