All replacement vortec distributers have .427" shafts!

[Hipster]

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?

Dude, welcome to the world of custom engines.

 

[Schurkey]

This is what I put on my newly rebuilt L29.
https://www.summitracing.com/parts/ado-10457708#overview

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

That is NOT a SBC gear. It's specified for Vortec big-blocks. Those distributors are different from the small-block Vortec, and pre-Vortec distributors as the L29 comes with a "Thermal Washer" above the gear.

My unproven suspicion is that the L29 gear is shorter to make room for the "Thermal Washer".

 

[Caman96]

That is NOT a SBC gear. It's specified for Vortec big-blocks. Those distributors are different from the small-block Vortec, and pre-Vortec distributors as the L29 comes with a "Thermal Washer" above the gear.

My unproven suspicion is that the L29 gear is shorter to make room for the "Thermal Washer".

https://www.amazon.com/gp/aw/d/B000C9BXDC/ref=ox_sc_act_image_1?smid=ATVPDKIKX0DER&psc=1

 

[BeXtreme]

That is NOT a SBC gear. It's specified for Vortec big-blocks. Those distributors are different from the small-block Vortec, and pre-Vortec distributors as the L29 comes with a "Thermal Washer" above the gear.

My unproven suspicion is that the L29 gear is shorter to make room for the "Thermal Washer".

Hmmm. I don't think that is true. It was my impression that all vortec V8 distributors are the same. The description on the one Caman posted above says it is for a 4.3 Vortec V6, but there are comments saying they successfully used it on a 98 Tahoe 5.7. I bet all of the gears are close enough to work, but I couldn't say just what the differences are and what other problems you might have from them. The one I posted comes up on every resource I can find as being applicable to an L31 and an L29.. so I don't know what to tell you.

 

[Schurkey]

All Vortec V8 distributors are NOT the same.

The OEM big-block Vortec distributor uses a "Thermal Washer" that the small-block and V-6 distributors don't use. The V6 and SBC gears are likely identical, but different from the L29 gears.

The big-block distributor is a different part number than the small-block; the gears are also different part numbers, and you can see in the links posted previously that the BBC gear comes with extra pieces that the SBC gear doesn't include.

SBC:

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BBC:

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[BeXtreme]

All Vortec V8 distributors are NOT the same.

The OEM big-block Vortec distributor uses a "Thermal Washer" that the small-block and V-6 distributors don't use. The V6 and SBC gears are likely identical, but different from the L29 gears.

The big-block distributor is a different part number than the small-block; the gears are also different part numbers, and you can see in the links posted previously that the BBC gear comes with extra pieces that the SBC gear doesn't include.

SBC:

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BBC:

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OK, well the second picture on your Amazon link also shows an extra washer. I know I've used them interchangeably before, but I don't have an L31 so I can't say for sure.

What I DO know, is that the one I posted is the correct one for the OP in THIS thread. For anyone else looking for something similar for an L31 in the future... do your own due diligence.

 

[Scooterwrench]

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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.

That looks like it was assembled dry!

 

[Caman96]

Hmmm. I don't think that is true. It was my impression that all vortec V8 distributors are the same. The description on the one Caman posted above says it is for a 4.3 Vortec V6

The gear I posted IS the correct part for a 5.7…

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…or go to Acdelco.com, enter part number 10457356 to verify fitment on a 5.7 Vortec.

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