I've got a used Comp XFI 280 HR retro-fit cam I'll be using. What the recommended distributor gear (besides the pricey composite) stock or melonized (hardened steel)?

 

For roller cams, use the melonized gear.

 

I'd go melonized but a call to comp wouldn't hurt.

Ive had the composite gear on my solid roller for over 10 yrs and it still looks new

 

COMP's hydraulic roller cams are cast iron or austempered cast iron. Do you have the full Comp part number including the -2 or -8 suffix? -8 I believe is austempered iron and has greater durability than the -2 to -5 versions.
Either or, they're compatible with the stock distributor gear (according to Comp). A melonized gear doesn't hurt although not all melonized gears are the same. There are iron and steel versions. Typically the iron gears are readily available while the steel version I've found to be a little harder to come by.

I've a billet steel roller cam and my cam designer (Jones) specified and supplied a melonized steel gear.

FWIW: I've run several Comp hydraulic rollers with different distributors. All used the gear the distributor came with whether they were GM originals or aftermarket. All survived without issue.

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Pulled from Comp Cams

Distributor Gear Materials:
1. Cast Iron

2. Composite (offers great life, conforms well to the mating cam gear, and is compatible with ANY camshaft gear material)

3. Melonized or hardened steel
(material that OEMs use with factory roller cams; many aftermarket
distributor manufacturers use these as the default gears for their
distributors)

4. Bronze (conforms well to the mating
camshaft gear and will not damage the camshaft gear, but it is a self
sacrificing gear intended to be used in race applications only and
should be replaced about once a year)
If you have a cast iron hydraulic or solid flat tappet cam, your distributor gear options are:
1. Cast iron distributor gear

2. Composite distributor gear
If you have an austempered ductile iron hydraulic or solid roller cam, your two options are:
1. Melonized or hardened steel distributor gear

2. Composite distributor gear
If you have a billet steel hydraulic or solid roller cam, your two options are:
1. Bronze distributor gear

2. Composite distributor gear



COMP
Cams recommends the composite gear because it is compatible with all
camshaft gears – flat tappet, austempered cast iron cores, and billet
cores. If the steel gear is not hardened, it is not compatible with
either of the roller cam types.

 

Also pulled from Comp Cams:

Cast-Iron Cam Cores

As the name implies, a cast-iron core is just that. It appears to be an unfinished cam, cast in the rough shape of the camshaft. “[Cast-iron camshsafts] start off as an unground lobe camshaft blank. The blank is very rough on the lobes. The lobes are cast to a certain range of lift and duration, but the camshaft is unfinished. However the journals [on a cast cam blank] are pretty much finished,” Campbell explains.

“These are usually the blanks we’ll use for a flat-tappet camshaft, either solid- or hydraulic-style lifters. The distributor gear is hobbed on, but can sometimes be pressed on. They all use a cast iron distributor-drive gear, and you can pretty much use any gear that comes on your stock or aftermarket distributor.”

Camshafts from COMP ground from a cast iron core typically have a part number ending in “-2” through “-5”.

Austempered Iron Cores

Austempered iron camshafts, also known as Austempered Ductile Iron (ADI), are similar to cast-iron, in that they are iron, and they are cast, but that’s where the similarities end. “Austempered iron is not the same as the cast-iron used on a flat-tappet cam,” says Campbell “ These are typically used in hydraulic-roller or mild solid-roller street-style camshafts. Austempered iron camshafts are compatible with traditional distributor gears, but we do recommend an upgrade to a melonized style of gear, but it’s not absolutely necessary.”

COMP’s Austempered iron cam cores have a part number ending in “-8”.

As I've experienced several times (maybe a half dozen plus) is that Comps hydraulic roller cam will work well with any distributor gear you'll get on an out of the box distributor.
And again, all melonized gears are not created equally. I can get a direct quote on that from Mike Jones at Jones Cams. That said, if the cam core isn't steel, then the iron melonized gear will cause no harm but not necessarily needed

 

FTR: The XFI 280 HR has Comps 08-467-8 part number. So, if I have my facts straight, this is austempered iron as indicated by the -8.
So, any gear can be used although a melonized iron gear wouldn't hurt.

My question now is, will a melonized steel gear kill the cam gear? That would melonized steel on austempered iron.

 

The cam gears are extremely hard. I have a Crower cam that uses a cast core, but the gear section is hardened.

I had an incident where (long story) I accidentally installed a distributor that had the lower bushing missing. This allowed the distributor shaft to flop around and have marginal engagement between the distributor gear and the cam gear.

Ultimately the melonized distributor gear just got absolutely annihilated. But, there literally wasn't a scratch on the cam gear.

 

Here's a quote from Mike Jones over at Speed Talk.

https://www.speed-talk.com/forum/vie...64167&start=15

I'm presently inquiring there about using the melonized gear on an austempered iron cam which, I wouldn't think would have a hardened gear on it. Just good old cast iron (austempered as it might be).

 

Yup 467-8 Austempered cast iron. Thanks for the intel.

 

I've run whatever came out of the box distributor gears on a -8 cam and I can't say I've ever had any issues. And that's for tens of thousands of miles in one form or another. This isn't to say that there isn't an issue but none that I could detect.
That said, the use of a melonized gear of the iron variety I'd think would be harmless at the least. A benefit at best. I'm still waiting for some input on a melonized steel gear on a -8 cam. I've been told there is a difference.