I put up some posts on the C4 Tech/Performance board about my TPIS ZZ9 eating my distributor gears.

Take a look and give me any feedback you can.

Thanks,

Jake

 

Do you have a cam button installed?If not then you need one unless you have a roller cam block,if you do then is the cam plate installed?

 

Yep, yep. That's why I referred everyone to the other board because that's where I posted all the correct mods, including roller thrust bumber, 3 piece Torrington bearing set, end play shimmed to .002, new timing gear set bolt locking plate, etc., etc. I just didn't want to have to re-type it all here.

Thanks,

Jake

 

Jake,
Are you running a Melonized distributor gear? The part number is GM #10456413 and currently GM lists for $35.19. If you are using a bronze gear, it will continue to get chewed up.

 

I don't know what, exactly, is meant by, "chewed up" distributor gears. But if that process has anything to do with the removal of material from your distributor gear by your cam gear I believe I'd be worried about where that metal is going. (Into the crankcase where it's picked up and pumped through your block and between your crank, cam and the bearings.) I hate to be the voice of doom here but you may just have other things to worry about.

 

Jake, I have the ZZ9 in my 90, I pulled the top end off it today, the dist gear looks just fine.
I out about 17-20K miles on it already

 

Thanks, Bill. I sure wish I knew for certain what was causing my woes.

Maybe I'm running too much oil pressure even though Melling says that High Volume and High Pressure oil pumps causing this is a myth. Crane disagrees, so I don't know who to believe.

Jake

 

file a .020 deep V shaped groove from the oil passage groove in the distributor housing so that oil is sprayed onto the gears. this will help if you have no other problems such as the gear placement. also if you have the factory roller cam you need the melonized factory gear part #10456413 :chevy

 

I cut the groove in the distributor housing many months ago, following Crane'e recommendation.

The cam is a TPIS ZZ9 not a GM hydraulic roller but I intend to try the melonized gear if my current one continues to show wear.

Even though Meling says high pressure pumps DON'T cause accelerated gear wear, I plan to drop the pan and replace the pump with a standard pressure variety if all else fails. Crane is emphatic that HP pumps cause early gear failure.

Anyway, just another problem to solve; like so many others in the past.

Thanks,

Jake

 

I bought a Melling High Volume pump from Jegs and it was defective. The shaft stuck up out the top of the pump a little too high putting a bind on the gear whenever the distributor was tightened. I had the same problem with gears being eaten off. You could replace the pump or cut the tip of the distributor shaft down about an 1/8th of a inch.

 

Thanks for the post.

I'd considered that as a possible cause and did a lot of looking around to find a way to make an accurate measurement. Best I could come up with was "CompCams is working on a tool" that can be used for that purpose.

I dropped the oil pan last week to take a look and there was not a hint of the aluminum/brass distributor gear in the pan. So I cut open the oil filter and it was clean too.

Now I'm thinking it a metallurgical mis-match problem; the metal of the cam gear didn't agree with the metal of the distributor gear.

Ain't these cars fun!?

Jake

 

set the dist in the engine without the gasket to see if it seats on the manifold. if it does there will be even more clearance with the gasket under the distributor. i have had to cut .030 of off the bottom of the dist gear because it hit on the block. :chevy

 

JAKE,
Man does your woes sound familiar. Today was the first chance in a while I've had to go poking around the forum... I'm running very close to your setup minus the bigger stroke...

I was the 'other' person a few others refered to.

Bad news is I've never arrived at a 100% good answer. I have three daily cars which gives me breathing room on the vette. Here's what I do know...

My first set of stock gears wore COMPLETELY through on one side and by then were working the other sides edges pretty good. Followed some others and tried brass gears...

I only kept them in for a 100 miles and inspected them and saw visible wear.

I now am having someone tear apart the block and check all the bearings since all theat metal isn't good for anything but destruction. I did get the melonized gears but have not tried to see if that fixed the issue.

I tried the spacer problems andit appeared that I have plenty of play so I don't believe that was ever the issue.

I also had the mellings hv pump. I can say that does put more load on the distributor. Perhaps enough to slow it just enough to always fight the alignment of the gears. I am think of yanking it and going another route with it too. If you tried the melanized and it is showing no wear I would love to hear that so I can put my mind to rest.

In about a week or so I should have a hard answer as my machinist (who happens to be my cousin) will do a very good inspection to tell me what he thinks was the issue. Including tearing out that ZZ9 and giving it a good look over.

Please let me know what you have found out to this point. :nopity

 

Well, I think I've found the answer.

I ordered a new cam from CompCams and have been spending the last couple of days installing it.

The ZZ9 gear looks find and the aluminum/bronze gear I put on it a few weeks ago still looks like new. So that wasn't the problem.

What I think it was is - despite what Melling says - is that I was running too much oil pressure and in so doing placed too great a load on the distributor gear.

Not only was I running a HV/HP oil pump, but I had shimmed the pressure by-pass spring to increase the pressure even more. I did this because I'd installed an Derale oil cooler which called for about 12 to 15 feet of hose and I thought that the additional oil flow path would reduce the oil pressure. So I shimmed the spring to account for it.

I was also running an oil that I now think was too heavy - 20W50.

Bad move.

I've since dropped the pan and removed the shims and my pressure is more reasonable now, and as a result, the distributor gear lives. I've dropped my oil weight to 10W40 too.

BTW, I also learned that the distributor gear is only hardened to a very shallow depth, I mean only a really thin hardened layer , so once that hardening is worn through/off, wear increases dramatically.

You live and learn.

Jake


[Modified by JAKE, 3:05 PM 3/29/2002]