Melonized Distributor Gear
 

How do you guys feel about a Melonized distributor gear vs. a Bronze gear on a roller cam motor??

Thanks in advance,

Chris

Man, I've heard of iron,steel,bronze and nylon. But never a melonized gear. Guess it's time to learn something new.. I use a bronze gear though.
Tim

I hadn't heard of it either. Here's an interesting link about it which also talks about Tuftriding.
http://www.trutecind.com/heat/melon.htm
Late Hemi cranks were Tuftrided. I have not found anyone who knew the difference between Tuftriding and Nitriding.

Tuftride, Melonite and Tenifer are the same thing essentially, Salt bath nitrocarburization.

All three names are trademarks of Durferrit; in Europe they call the process Tenifer, in the USA it is sold as Melonite, and in other countires they call it Tuftride.

Similar proceses include Kolene Nu-tride, and anything else with "QPQ" in the name.

It is a heat treat that infuses nitrogen into the steel lattice near the surface, that increases surface hardness and rust resistance, along with reduced scuffing. They also black oxide it, polish that off, then blacken it again.

The local place around here that does it is Burlington engineering.
http://www.burlingtoneng.net/melonite/default.asp

Fixit,
OK here is a tufftride question for you: The factory maintenance manual for my 1967 GTX states that if the crankshaft in the Hemi is worn beyond limits, it is junk. I.E. it cannot be cut. I have asked many shops if the crank can be cut, then nitrided. They said they THINK SO. Some had doubts due to the tuftrinding penetrating to various depths on the journals. This, they said could cause an uneven cut due to various levels of harness at the same depth.
Do you know if people successfully cut then re-treat original Hemi cranks? and if so can you give me the name of someone who does this?
Steve

I don't know, I have never ground cranks. I think it can be done.

I have a Tufftrided 396 Chevy crank sitting behind me, thankfully it is still uncut and the right size.

Fixit,
What year engine is that 396 crank out of? I did not know Chevy tufftrided their cranks. If so, that helps.
Steve

late 60's, I don't know the exact year.

Re: Melonized Distributor Gear
 

A bronze gear, since it is softer, is going to wear faster, without wearing the gear on the cam. With a steel gear , it will last longer, but you are at risk of wearing/destroying the gear on the cam, therfore ruining the cam. I have used a bronze gear in the past, and after 1000 miles, there was noticible wear, but not nearly to the point of gear failure. So I switched to a steel distributor gear, by Crane cams, and after another 1000 miles, there is no noticible wera at all, on either the distributor or cam gears. I have not yet buffed the leading edges on that cam gear yet.

One thing that is not talked about much, but I have noticed myself, is that the gear on my comp cams roller cam ( a different engine) had sharp leading edges on the teeth, so it was recommended by somebody on this forum, and I did, to use a dremel to buff the edges smooth to the touch. I have not yet ran this motor to see how durable it is. I plan on running a steel distributor gear with it as well. I think I remember in that person's post, that they said they do this on all engines they build with roller cams, and have not seen any wear problems. I wonder how much wear I would have had with the bronze distributor gear in the above engine if I had done this to the cam gear. I think it also depends upon the engine design itself, as some engines may get less oil to the teeth when running, and have a predisposition to gear wear/failure, such as the sbf.

GM uses melonized distributor gears on their roller-camed engines. As mentioned, it's a surface-hardening procedure; I was able to drill one to fit a larger distributor shaft without any problems.

Thank you all for your responses. I've done some more research on the subjectand found exactly what carnut427 cas confirmed, that both GM and Ford use Melonized gears on their Roller motors. I suppose if it is good enough for two of the Big 3, it should be good enough for me.
Thanks again for your help.

Chris

Yeah, but do GM and Ford use these gears with factory billet steel roller cams or cast-iron roller cams (or are the gears on their cams billet or cast iron)? Most aftermarket roller cams are billet, so there may be a compatability problem. I'd call your cam manufacturer to see if the distributor gear is compatable.

Anthony,
Very good point. I'll make the call tomorrow.

To my knowledge, all roller cams are steel. If the cams were cast iron, there wouldn't be a problem using a standard distributor gear. The gears on the cams are steel. GM went through the motions of installing cast iron gears on the cams but settled on leaving the cam gears steel and using the melonized distributor gear.

If the distributor gear was at the back of the cam you wouldn't have any problems. :p (Sorry, GM guy having a dig at you Ford guys).

One thing I think people often don't take enough care to do is checking the engagement of the ditributor gear. We just stick a new gear on the end of the dizzy and drop it in. When we get a new set of diff gears the guy installing them goes to great effort to make sure the tooth contact is in the right spot. We should take the same care for the distributor gear.

You don't have the same range of adjustment as a differential but you can adjust the height of the gear in relation to the cam. Have a look at the wear patern on your existing gear and see if it's biased towards one end of the tooth or the other. By adding shims between the distributor and the block can raise the distributor or machining it's base of you can lower it. Getting the contact patch even across the gear will mean the center and strongest part of the tooth has the most engagement.

That tiny little gear gets a lot of punishment especially when you use a high volume or high pressure oil pump in your engine. The manufacturers have engineered this failure out of the newer engines. A lot of your more modern engines don't have a distributor any more (My LS1 doesn't have one). Plus the oil pump is often driven directly off the crank.

Cheers

You make an excellent point on adjusting the wear pattern on the dizzy gear, Aussie Mike. Through no help from me, my original bronze gear has 6600 miles on it and it's still looks like new. Obviously, luck has been on my side. I wish I could remember where I bought it so I could buy the same brand when the time comes...then again, perhaps I'll use a melonized one. I don't suppose anyone makes one for an FE???