SBC distributor gears

[enjenjo]

This was touched on a couple days ago, but I can't seem to find a definitive answer.

I am doing a car right now with a TPI injection. For clearance reasons, I could not use a coil in cap HEI, I had to use an 89 Model separate coil setup. It dawned on me that this was originally set up with a roller cam. I am now using it with a flat tappet cam.

The info I can find says GM roller cams were made from cast steel, and need an iron gear on the distributor, rather than the steel gear GM used with flat tappet cams. I know that you can't use a steel gear, on a steel cam, but what about the other way? Using an iron gear on an iron cam?

[tomslik]

This was touched on a couple days ago, but I can't seem to find a definitive answer.

I am doing a car right now with a TPI injection. For clearance reasons, I could not use a coil in cap HEI, I had to use an 89 Model separate coil setup. It dawned on me that this was originally set up with a roller cam. I am now using it with a flat tappet cam.

The info I can find says GM roller cams were made from cast steel, and need an iron gear on the distributor, rather than the steel gear GM used with flat tappet cams. I know that you can't use a steel gear, on a steel cam, but what about the other way? Using an iron gear on an iron cam?

i know some of the vortecs have been eating dist. gears for some reason but i'd think a steel gear on a cast cam might be the ticket (or maybe a bronze one)

[Crosley.In.AZ]

i know some of the vortecs have been eating dist. gears for some reason but i'd think a steel gear on a cast crank might be the ticket (or maybe a bronze one)

What about a cast camshaft?

The metals must dis-similar so they do not eat each other.

it is better for the dizzy gear to be softer since it is easier to change than the camshaft.

I called MSD tech guy when I was about to use a MSD dizzy in my ZZ4 motor with roller cam. They said all was good, neither the cam or dizzy gear  ever wore out.

[Bruce Dorsi]

I know that you can't use a steel gear, on a steel cam, but what about the other way? Using an iron gear on an iron cam?

Of course you can! ....But do you want to?

I don't know the answer to your question, but I do have a follow-up question.  ....As Tony mentioned, similar materials rubbing together will not control where the wear takes place.  Similar metals are also more prone to galling when rubbed against each other.  .....However, steel gears are frequently meshed against each other in transmissions, differentials, and other types of gear boxes.  ....Is there another reason why a steel distributor gear should not be run against a steel cam?  

According to the 1998 GM Performance Parts catalog:

" #1958599 HEI Distributor gear - This distributor gear is used with all V8 engines without steel roller camshafts."

" #10456413 -Gear, Distributor - This new melonized gear is used on all Chevrolet small- and big-block engines, including steel roller camshaft applications."

There is no mention of the composition of either gear.  ....If you have a newer edition of the catalog, there may be more information.

[enjenjo]

Well, Bruce, You have answered my question, the distributor I have has the Melonized iron gear, so it should be ok. I can't answer yours, I have seen torn up gears, and they do it in a relatively short time.

What complicates this even more, some of the new steel cams have a cast iron gear shrunk onto a cast or billet steel shaft.

[Bruce Dorsi]

I have the Melonized iron gear, so it should be ok.

I once had a girlfriend who was MELON-ized, so I could pick her out in a crowd.  ....But, how do you recognize a melonized distributor gear?  I'm not familiar with them.

I have seen torn up gears, and they do it in a relatively short time.

My hunch is that most steel-on-steel gears use a viscous lubricant, which actually clings and cushions the contact.  ....I'm guessing that there is not enough engine oil bathing the dist/cam gears to be effective.

[Crosley.In.AZ]

kool

ol Bruce has come through again.

makes the ol RRT a good place for needed info.

manual tranny gears are all the same material. I belive the difference is the material hardness as compared to the camshaft and dizzy gear

[enjenjo]

Well Bruce, the way I recognized the gear was read the instructions.    It said it was a melonized gear. I am using a reman distributor.