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Why does my LT1 camshaft keep eating distributor gears?

82355

82355

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I had an LT4 Hot Cam in my 1988 V10 Suburban. I figured a stock LT1 (from a 1995 Z28 I believe) would be a better camshaft. So I swapped in the smaller cam. It chewed up the distributor gear on the stock distributor from the 1988 LO5 350 TBI. It was originally a flat tappet cam distributor. I then tried a distributor from a 1992 Camaro LO3 305 TBI that had a factory roller cam.

It chewed up that distributor gear.

I then tried an MSD distributor. Seen here.

j

It has begun to chew it up already.



What is my problem?

Martin
 
Last edited:
Stock distributor out of a 454 Vortec.





Just the nature of the beast?

Martin
 
roller cams REQUIRE the use of a hardened distributer gear. :waytogo:

simple fix.
 
The term I've head before is a "mellonized" distributor gear...?

I believe it's a harder material that's used for certain applications, and I'm pretty sure MSD can supply them as a separate part if you need one for your application.

Pretty sure my 502BBC requires one, but I don't know all the other applications out there where it is required.

-G
 
You know, some trucks engines around 89 or so were set up as roller blocks but came with flat tappet cams. I have my ex's 89 block in the garage, the tappet bosses are milled down and the valley has bosses for the tappet guide "spider" to screw to.


I was surprised when I saw this, I was sure it had a roller cam.
 
Greg72 said:
The term I've head before is a "mellonized" distributor gear...?

I believe it's a harder material that's used for certain applications, and I'm pretty sure MSD can supply them as a separate part if you need one for your application.
Click to expand...

That is what I thought, but I talked to someone at MSD, and they told me what I had was right. He also might not have known what he was talking about.

Martin
 
Big Ray said:
You know, some trucks engines around 89 or so were set up as roller blocks but came with flat tappet cams. I have my ex's 89 block in the garage, the tappet bosses are milled down and the valley has bosses for the tappet guide "spider" to screw to.


I was surprised when I saw this, I was sure it had a roller cam.
Click to expand...

Most 1987+ blocks are roller blocks. The truck engines however still got flat tappet camshafts until the "Vortec" engines in 1996.

Martin
 
82355 said:
Straight out of an LT1.

Martin
Click to expand...

Im inexperienced with LT1 stuff and putting the cams into SBCs but is there any chance the dizzy gear isnt cut properly due to the LT1 not having a dizzy? I know there must be something there that drives the oil pump, but just a thought.
 
Stomis said:
Im inexperienced with LT1 stuff and putting the cams into SBCs but is there any chance the dizzy gear isnt cut properly due to the LT1 not having a dizzy? I know there must be something there that drives the oil pump, but just a thought.
Click to expand...

The oil pump drive is no different than the bottom half of as distributor.

It is a pretty common upgrade.

Martin
 
when i pet a carb on the lt1 Put in my k20 I used the gear that was on the original dummy drive.
 
Well, when it comes to GM stuff, you guys are the experts. I can hang in there pretty good with Fords, but my primary field is electronics, electromechanical, and general troubleshooting of obscure problems.

So, without going into specifics of hardened gears, cams, and what goes where, I'll throw in my opinion for what it might be worth.

If you brought me those dizzys, and asked me what was wrong, without knowing any of the detail about what they were, I would have three ideas.
1: The wear pattern looks like the gears might not be meshing fully.
2: I would check lubrication.
3: And probably most important, if you keep replacing half of a gear set, because that half keeps wearing out, then the problem is most likely with the half you did not replace.
Are the gears an odd number of teeth? If so, then then any one tooth will eventually touch all the other teeth.
So, one small burr would eat up all the other teeth.
 
Google "LT1 distributor gear wear" and you'll find Martin has lots of company ..

I guess "something" causes the gears to get wiped out,but none of the threads I read on the subject seem to have pinned down a cause...some blame a high volume or pressure oil pump,the oil pump drive shaft or coupling,or claim a specially treated "melonized" gear or one made of hardened billet ,bronze,or unobtanium is needed..others say an aftermarket intake may allow the distributor to drop down too far and it will need shimming to get correct gear alignment..

:screwy:
 
82355 said:
The oil pump drive is no different than the bottom half of as distributor.

It is a pretty common upgrade.

Martin
Click to expand...

I know its a common upgrade was just curious if that substituted piece perhaps had a gear made from a different material.
 
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