When did GM Start to use the Melonized Dist Gear ?

[axisg]

The current distributor in my car is giving me trouble ( advancing way too fast and occasionally sticking advanced ) and I have 2 good spare distributors in my tool box that I can use.
One I pullled from my early 90's engine rebuild ( it was a 70's block flat tappet ) and another which is from a mid 2000's crate engine ( 383 roller block ). They both look identical to me. Is there any way to tell which is which ?? I dont see any markings on the gear itself.
I believe the one from the 383 roller block is the one I need to mesh to my new roller camshaft as I know it has the melonized gear. Or are they both fine ?? So much information on-line about steel vs cast vs bronze vs melonized....

When did GM start using the Melonized gear ? I would assume late 80's or early 90's when they introduced the "roller" block. Worst case I know the distributor in there now is a melonized gear and I could swap it out but there must be an easier way.

 

[crotchss]

Don't know for sure on what year. What roller cam are you running? I know most of GM's cams were cut on billet cores. For all the roller cam builds I do for customers and myself, I have started to get the cams made with a pressed on cast gear to get rid of any problems of running a bronze gear. It usually costs me around $30 depending on the cam manufacturer, but it beats buying an expensive distributor gear and wearing it out.

 

[axisg]

I am using Comp xr270hr camshaft with retro roller lifters and nylon cam button.

I pulled the distributor this morning and after maybe 400 - 500 kms ( 2 full tanks of fuel since the cam swap ) I am seeing wear on the supposed "melonized" distributor gear. This distributor was pulled from a freinds GMPP crate engine with factory roller valvetrain so we all assumed it would be hardened and it looked new when we put it in. So I called the local speed shop. Its going to be appx $50 to get a hardened gear. I called Comp as well and their suggestion was to use their composite gear.

The car is getting a little frustrating this year spending more time wrenching than driving.

 

[rustyroger]

What is a "melonized" gear?.

Some kind of anti wear treatment perhaps?. Maybe it's an American term for something we use over here, it wouldn't be the first time I've come across different terminology for everyday stuff.

Your "fenders" are our "wings", we load luggage in the "boot" rather than the "trunk", we lift the "bonnet" to look at our engine, you open the "hood"... the list goes on.

"Two nations divided by a common language" as Winston Churchill once remarked. 🙂

Roger.

 

[Fox80]

I believe the "melanized" gear or soft gear was used by GM since the onset of the roller cam, say mid 80's, the composite gear Comp recommended would be a good choice, but nothing beats a bronze gear. The idea is to not have the gear wear the cam gear out, the key with any "soft" gear is to get the mesh correct, or basically the depth, look it up online, I have always used the depth probe on a caliper to check from the pad to the top of the pump shaft, most aftermarket intakes take a shim to get it right, and some even need the collar turned down on the dist. body. Get it set right it will last forever, we could get three seasons out of one on a 8,000 rpm motor with straight 50wt oil in it

 

[axisg]

I went to the speed shop last night and picked up a Composite Gear as Comp recommended. That put me another $100 over on this years car budget. Hopefully the "wonder" gear will fix the problem that I didnt know I had. 🙂
If the stars align Friday night I will get some time to put it all back together, set my all-in timing and see where I am at performance wise. There were so many variables to sort out after the cam swap but I think I am dialing it in.

 

[axisg]

What is a "melonized" gear?.

Some kind of anti wear treatment perhaps?. Maybe it's an American term for something we use over here, it wouldn't be the first time I've come across different terminology for everyday stuff.

Your "fenders" are our "wings", we load luggage in the "boot" rather than the "trunk", we lift the "bonnet" to look at our engine, you open the "hood"... the list goes on.

"Two nations divided by a common language" as Winston Churchill once remarked. 🙂

Roger.

my understanding is that GM started to heat treat the distributor gears when they switched to the 'roller" setup. Its kind of a "candy coating" on the outer surface of the metal.

 

[rustyroger]

Thanks, Fox80 and axisg. I learned a little more today.

Roger.