[roy381]

Hi folks please school me on distributors and gears. I decided to go with a roller cam on my 461 build. Butler recommends a .500 polymer gear for a roller. I have to get a distributor and MSD offers one for their ready to run distributor to the tune of $650 total.

I was looking to run DUI RTR distributor to save some $$$. I need a small body as I am going with a 66 tri power setup. Is it as simple as swapping the .491 gear with .500 on the dui?

Thanks in advance

[Formulas]

The .491 and .500 refers to distributor shaft diameter if you change any gear on any distributor you have match new gear up to shaft diameter

[Skip Fix]

Most DUI distributors are HEI sized. HEI and MSDs have different shaft diameters.

[roy381]

So the MSD has a .500 shaft? and the DUI has a .491?

Any other .500 shaft options ?

[Steve C.]

Related:
https://forums.maxperformanceinc.com...ght=MSD+bronze


.

[firechicken]

I'm going to throw this out there as it seems not to many are aware of this distributor and there isn't much for long term reliability reviews but I've been using one for a couple weeks now and really pleased so far especially when comparing cost to an MSD RTR. Not tons more than a Davis either but the tuning eaae is worth every penny.

https://progressionignition.com/

[firechicken]

To add it has a melonized gear which is supposed to work with roller cams but there seems to be some debate on this.

[roy381]

Thanks Steve, great read!

Firechicken is it a .491 shaft?

Also what is the reasoning Butler recommend a .500 over the .491

Thanks again

[wbnapier]

Originally Posted by firechicken

I'm going to throw this out there as it seems not to many are aware of this distributor and there isn't much for long term reliability reviews but I've been using one for a couple weeks now and really pleased so far especially when comparing cost to an MSD RTR. Not tons more than a Davis either but the tuning eaae is worth every penny.

https://progressionignition.com/

I just learned about these and wish I had known. If it works as advertised, they are a true step up.

[firechicken]

Originally Posted by roy381

Thanks Steve, great read!

Firechicken is it a .491 shaft?

Also what is the reasoning Butler recommend a .500 over the .491

Thanks again

Not sure on the shaft size and didn't check because I installed it as it came but I assume it's a .491. As Formulas pointed out already, the shaft size is not important, only that if you are changing the gear, the new gear needs to be the correct size to fit your shaft.

[Skip Fix]

They make that polymer gear in either sized diameter, just needs to match the distributor.

[76TA462]

I always used the BOP polymer gear with my OEM distributer and roller cams on 462. A couple years back I changed to an MSD Pro Billet which comes with a steel gear and is a different diameter, so I couldn't use the polymer I have. I ended up swapping to a bronze gear instead of polymer for no particular reason. A friend has been using bronze gears for years with no problem. I have had absolutely no problem either, but it isn't a daily (??). Should it wear prematurely I will go to polymer but so far, no wear.

[Cliff R]

Here is a pic of the bronze gear on my distributor. It's been in service over 10 years on an Old Faithful HR cam and barely has any witness marks on it and no measurable wear.......

[tempest1964]

Cliff, didn’t you do some prep work. Seems like I remember reading this some time back. Jewelers file and glass beading?

[steve25]

The real key to long gear life of any type is having the .030” oil squirt hole in the end of the oil galley plug situated right in front of that gear!

[Cliff R]

I learned the hard way to take every single one of these custom ground roller cams and take a jewelers file and smooth stone to the edges of the gear teeth plus a trip to the bead blaster and hit them with ultra-fine industrial glass beads to remove sharp edges and smooth out tooling marks, etc.

Failure to do this can and will cause them to "eat" a plastic gear in several hundred miles and they'll chew up a good bronze gear pretty good till things get smoothed out.

If you prep the cam gear nicely a bronze distributor gear will last just about forever, at least that's what I'm seeing here........Cliff

[lust4speed]

roy381, Just to clarify what was said above the Butler tech probably reacted to your mentioning going with the ready to run MSD unit, and all MSD distributors require the .500 gear - so he recommended the .500" shaft diameter polymer gear. If you had mentioned a stock distributor or one of the aftermarket ones that used the original .491" shaft, the tech would have recommended a .491" polymer gear.

All brass gears wear and are the sacrificial component since it is much easier to replace a distributor gear than a cam when things wear out. Some brass gears wear very slow and some wear really fast, but they will all wear. Paying the big bucks for a polymer gear pretty much eliminates wear.

From what I've seen, some distributor companies advertise a Melodized gear but somewhere in the fine print you will read the gear is only available for Chevy and Ford with no one taking the initiative to produce that gear for Pontiac.

[roy381]

Thanks much appreciated. I didn't know if there was a advantage to having the .500 gear. But I realize that its just a difference of manufacture shaft sizes.

Thanks again guys