Distributor Drive Gear for a Vortec Roller Cam

[Bobs85PU]

My 85 Pickup has a later model, Roller Cam Vortec Engine (the engine number crosses to a ZZ4 engine)...I've read there may be an issue with the Distributor Drive gear.

I've heard two stories....

Story one: A Vortec Roller cam requires a special (bronze/brass) Distributor Drive Gear.

Story two: There's no need to have any kind of special Distributor Drive Gear.

Which is correct???

When I recently had a Dual Point, Mechanical Advance Distributor rebuilt by Mallory, I left it up to them...They installed a special (bronze/brass) Distributor Drive Gear, based on my info that the Distributor will be install in a Vortec Engine.

The Distributor now installed, an HEI, has a steel drive gear. I have noticed that the timing had changed dramatically, when I checked it after re-jetting my Edelbrock Carb. Might I be witnessing the Cam and Distributor Drive Gears "eating" each other...requiring a new cam and the proper Distributor Drive Gear installed on my new distributor???

[Fairlane514]

I would pull the distributor and check the gear teeth, If they are worn down the material may have caused some damage to bearings etc.

The bronze gears aren't the best remedy, they make a composite gear.............I believe Comp Cams makes one.

[bd]

I would pull the distributor and check the gear teeth, If they are worn down the material may have caused some damage to bearings etc.

The bronze gears aren't the best remedy, they make a composite gear.............I believe Comp Cams makes one.

X2 - But before yanking the distributor, check the rotational play in the shaft.  Shouldn't be more than ~2-3 distributor degrees.

Link to Comp composite gear...
http://www.compperformancegroupstores.com/store/merchant.mvc?Screen=PROD&Store_Code=CC&Product_Code=12200&Category_Code=&AID=3236

Link to YouTube - Comp Tech Video, "Selecting the Correct Distributor Gear"...
http://www.youtube.com/watch?v=31JHSUkhJLY

[9511234]

The gear on your 85 will not work on a newer vortec roller cam.  I will take some pics later, but I have a vortec cam pulled and I can get to one in another 85 engine I have in a while.

There is also another problem.  I bought a BWD gear, that appears to be steel, that lines up perfectly with the splines on the cam.  The problem is that the shaft of the 85 distributor must be larger than that of the vortec one, because it most definitely does not fit.

I was actually working on this last night and there is another oddity - there is a spacer with 3 tangs pointing into bottom of shaft housing on the 85, while the one that came with the vortec has 4 and is not a triangular shape.  I'll post some pics when I get a chance.

[9511234]

[9511234]

I would pull the distributor and check the gear teeth, If they are worn down the material may have caused some damage to bearings etc.

The bronze gears aren't the best remedy, they make a composite gear.............I believe Comp Cams makes one.

X2 - But before yanking the distributor, check the rotational play in the shaft.  Shouldn't be more than ~2-3 distributor degrees.

Link to Comp composite gear...
http://www.compperformancegroupstores.com/store/merchant.mvc?Screen=PROD&Store_Code=CC&Product_Code=12200&Category_Code=&AID=3236

Link to YouTube - Comp Tech Video, "Selecting the Correct Distributor Gear"...
http://www.youtube.com/watch?v=31JHSUkhJLY

There are two different size in shaft sizes -referring to your link-- .491 and .500- not having a micrometer I can't double verify that both are for chevy's.

[84c20]

I have a stock vortec gear next to me right now and its steel.

[9511234]

Ok.  Here is what I have learned thus far about the dizzy gears-

From the naked eye- the two look the same.  Both gears I took pics of are steel.

OEM uses steel for longevity of parts.  Brass and composite are more used in race applications where they are supposed to self sacrifice if something doesn't sync up right.  You destroy gear, but you din't have to sink money into a cam.  Probably have to take your pan out and clean out the lower part of your engine, but you don't destroy your cam.

I called my engine shop, total engine service, and they recommend melonized steel.

I think you have to take comp cams advice with some skepticism, because they are also trying to up sell you on parts.  If you have a pretty street rod, with stock Vortec heads and a mild cam ( I'm using one used in ht383 and ramjet 350) I melonized steel will do fine.  It is all OEM.  Once you start modding your heads for more lift and get a camshaft to match it that is a little more aggressive and all the other parts that can put more stress on that gear- like a high volume oil pump- it will want to jump off that cam more and more.  If you've ever looked down from the top of engine with cam in and oil pump and dizzy out you will realize how little of the cam that gear has to bite into.

I would check what size shaft you have, because there are two out there, before you decide to order one, though.