Steel/Iron Dist. gear/Cam gear/Small Body HEI questions [Archive] - Team Camaro Tech

: Steel/Iron Dist. gear/Cam gear/Small Body HEI questions

Mar 29th, 09, 10:49 AM
I'm trying to get a good understanding of the different cam gear/distributor gear options out there and what distributor gear material works well with each. I'm about to order a new cam and want to be fully informed. (See my other post ( on solid vs. hyd DCR)

Here is a list of my understanding of cam gear/distributor gear combination options (which could be far from correct):

• Iron gear of iron, non-roller cam - Use with stock early distributor gears.
• Steel billet gear of aftermarket steel billet roller cams - Not for use with early stock distributor gears, use with softer bronze gears, or composite gears.
• Gear of GM stock hyd roller cams (Is this steel billet or something slightly different?) - Use with special GM melanized gear.
• Iron gear pressed onto steel billet roller cam - Use with stock early distributor gears.
• Non-billet gear on special non-billet hyd roller cam core from Comp Cams (not sure what material this is exactly) - compatible with GM melanized gear.

(I'm not sure I really understand the GM melanized gear correctly. I thought it was softer than previous stock gears so as not to wear out the cam gear on stock steel roller cams. But I read on a crate engine website: "…distributor incorporates a hardened (melanized) drive gear that is compatible with a cast iron cam gear. Use of a non-hardened distributor gear will result in excessive wear…" This seems to contradict my understanding.)

I'm currently using a GM small body HEI with external coil. This distributor has a smaller shaft size than any other GM distributor and there isn't as much aftermarket support for replacement gears.

I think the melanized gear is all that GM makes for the .427" shaft size of the small body HEI, is that correct? And the only aftermarket gears for this shaft appear to be bronze or the new Everwear from Lunati. These are both designed for billet cam gears. Lunati states the Everwear is for any steel cam gear. I called an was told it also will work on an iron gear, but that isn't in writing in the catalog, so not sure that is true. (The only other option is to have a bushing made to allow the .427 shaft to accept a larger distributor gear and then the options expand.)

Also, what exactly is a GM factory roller cam made from, billet, or some other steel similar to the non-billet one from Comp Cams?

So, what happens if you combine a GM melanized gear with a iron cam gear (on an iron cam or pressed on an aftermarket billet roller cam)? Would the distributor gear wear faster because of the harder iron gear? I ask because I ran this combination and the distributor gear did wear faster than I would have expected. Or did my small body HEI not have a melanized gear? (I thought they all did.) Or as stated above, am I misunderstanding the melanized gear?

Unless I'm completely wrong in my above thoughts, does this mean that with the small body HEI, that it's best not to go with any type of iron cam gear? What about the non-billet Comp Cams hyd roller core/gear?

Thanks for any insight,


Mar 29th, 09, 01:53 PM
I used the GM melonized gear on my MSD dist with a billet roller from Ud Harold that incorporated his press on cast iron Everwear gear. I have run some 10K long distance cruise miles. Last two tear down inspections revealed no wear issues.

I did have to ream out the GM gear shaft id to fit the .500 MSD shaft.

Mar 29th, 09, 06:05 PM
Instead of trying to make generalizations, just go with whatever your camshaft manufacturer recommends. That is the safest way to do it.

Mar 29th, 09, 06:59 PM
Hi Bill,

Thanks for the suggestion.

Sorry if you read my previous reply that I just edited and deleted. I was totally confused. I thought your answer above was to my other question that I posted just before this one on DCR. No wonder your answer didn't make sense to me at first. I'm sure glad I went back and reread this so I could correct it.

Boy do I feel stupid. I should have read the title closer.


Mar 30th, 09, 02:11 PM
To answer one of your questions - the factory roller cam in my FB385 and the LT4 hot cam I replaced it with were steel billet cams - gear and all. The FB385 came with an HEI and a melonized gear, and worked fine w/o issues. I replaced the hot cam with a Comp full billet HR, and ran the melonized gear for a short while. I pulled the dist one day to check the gear and noticed some tiny pitting on the melonized gear. I replaced it with a Comp composite gear.

Mar 30th, 09, 02:24 PM
From all my research a pressed on cast cam gear and a melonized distributor gear is the cats meow. Instead of the worry of all the different combos, you need to figure out what camshaft you need.