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Distributor Gear

dwdwMember
I know this topic comes up quite often, but today I ran across something that I haven't heard before. The shop that built my engine didn't follow my instructions and decided to use an MSD ready to run distributor instead of the smaller MSD 8577 I had requested. They had replaced the iron gear with a bronze gear.

Since I am making the shop take back the RTR and get me the distributor I asked for, I thought I would call Comp Cams to find out what gear they recommend. My cam is a solid roller lifter. Using my serial number, I guess to determine the core material of my cam, the Comp Cams guy said I have two options. 1)a bronze gear or 2)get a stock iron gear and send it to them to have it nitrided - Cost $45. He said the nitrided iron gear will last twice as long as the bronze gear.

Since the MSD distributor comes with an iron gear, I'm planning on sending that gear to Comp Cams to have it nitrided. Cost will be comparable to buying another gear. Is anyone else using a nitrided iron gear, and with what success?

Thanks, Dennis
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George PGeorge PAdmin.
quote:
Originally posted by DW:
... He said the nitrided iron gear will last twice as long as the bronze gear ...



that's not saying much, is it?

I am under the impression that all solid roller camshafts are machined using steel cores, the same cores as Crane's hydraulic roller camshafts. If that's the case then the Crane steel gear should be the best choice. Of course, Comp Cams is not going to recommend a Crane gear for their camshaft.

My 2 cents.

-G
bosswrenchbosswrenchMember
If you've ever seen a worn distributor gear pulled out of a 351-C, the gear teeth are razor-thin and makes one wonder just where all that metal went....
Along with George's comments, I'll add that when a bronze gear wears, the particles torn off don't seem to cause much engine damage, but when a nitride-treated iron gear wears, the hard particles could cause quite a bit of damage to cylinder walls, bearings and the oil pump body.
Rule of Thumb on bronze gears is- change them when the ignition advance retards more than 3 degrees, or in any case after 3000 miles of use. Frequent inspections of the gear teeth might extend this duration a bit on street cars.
garth66garth66"When speed is the only thing that counts"
quote:
Rule of Thumb on bronze gears is- change them when the ignition advance retards more than 3 degrees, or in any case after 3000 miles of use. Frequent inspections of the gear teeth might extend this duration a bit on street cars.

Change a bronze gear with every oil change, assuming you actually drive the car and don't just admire it as art in the garage.

Check out this info posted from Dan Jones regarding the Mallory Steel Distributor gear:
quote:
Mallory steel distributor gear (Ford 351C Part Numbers 29420 and 29420PD

http://pantera.infopop.cc/eve/...=651102286#651102286

quote:
We are using the Mallory steel alloy distributor gear on this engine since the Accel distributor supplied has a 0.490" shaft and the Crane gear is only available in 0.500" and 0.531". In any event, the Mallory gear looked good and showed no signs of wear.

http://pantera.infopop.cc/eve/...=302105095#302105095

Here's my own communication with Mallory about their steel distributor gear for the 351C:
Q) Will your Alloy Steel Distributor Gear work with my hydraulic roller cam?
A) Our alloy steel distributor gears will work with all core material except 8620-9310 steel where our bronze gear will be used. The 8620 steel with iron gear option will work with our alloy steel gears.
http://www.malloryperformance.com/Faqs.aspx

Q) Is your distributor gear #29420PD compatible with a steel roller cam? Is it actually steel, or a treated ductile iron? Thanks!
A) The 29420PD is harden steel, sometimes the 29420 is a better choice because it's not drilled all the way through. This way you line up the hole in the gear with the hole on the shaft and finish drilling through, it always lines up that way.
dwdwMember
I contacted Comp Cams again to ask them if I could use the Crane steel gear and they told me that my cam core is 5160 steel. Is that really steel, or is that the material Dan mentioned? They said I would have to contact Crane to verify that their gear is compatible with the 5160 steel cam. The steel gear definately sounds like a better choice than the bronze if it will work. Thanks for all of the info.
Dennis
dwdwMember
The cost of the Crane steel gear is almost twice the cost of the Mallory gear at Summit Racing. I wonder what could justify such a difference in price?

I also cleared up the cam core mystery. Dan Jones is correct that the Comp Cams street rollers use an austempered ductile iron core. However, when they went to grind my cam, they had none of those cores in stock so instead they used a billet steel core that they use for their race rollers.
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