Distributor Gear / Cam Gear Reality Check

[007]

So we've all read and heard about distributor gear / cam gear horror stories etc. There's so much information it's overload.

That said, I have my Prestolite distributor "somewhere, I think", but in 2014 when I did my TeamRush upgrade, I put in a Motorcraft. I went to NAPA and asked for a distributor for a 79 CJ7 with a AMC 304 , and put that one in. During my upgrades this spring I removed it to lock it out for timing control, the gear was in excellent condition, but that said it probably has 500 or so hrs on it.

Anyway, as a part of this Sniper EFI install, you really need to phase in your distributor to make it idle right and to make the timing control accurate/efficient and phasing in a Motorcraft distributor like this seems to be a bit of a joke. I've not found an adjustable rotor that will pop on a Motorcraft distributor. SO, I got an MSD Pro Billet that will accept the MSD adjustable rotor. To lock this unit out, you simply remove the weights and springs, remove the gear, rotate shaft 180deg, drop the bolt and tighten it down, then reinstall the gear.

This leads to my question...is the MSD gear fine/made correctly/not too hard to run with my stock cam gear OR should I move the one from the Motorcraft that looks good with little use OR should I dig through the storage unit and find my Prestolite...assuming I still have it?

Any advice? Anyone using this distributor?

Thanks in advance...

 

[Posi]

I would lean towards using the MC gear if it fits correctly. However, I would talk to msd tech and get their thoughts concerning msd gear match up to your setup. Also their thoughts on swapping the MC gear onto their distributor.

 

[007]

Well I called MSD and they say that broken in correctly there is no known issue with their gear on the stock cam gear. They would not advise either way about putting the Motorcraft gear on their distributor.

My first impulse is to believe them especially considering the fact that I have no idea if there are any issues with my existing distributor gear because I really haven't had it on there and long enough for there to be a problem.

Then on the other hand there's that general feeling of dancing with the one that brung ya so-to-speak and just moving the gear over.

I'll give it some thought, but I'm inclined to think that provided they are the exact same dimensions I will use the Motorcraft gear on the blissfully oblivious assumption that it isn't as hard as the MSD one.

I guess I could do a quick and dirty test using a center pin punch that is spring loaded and see if the indentions are markedly different.


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[mtnwhlr]

Having just replaced both gears on my '79 AMC 304 because the one on the cam got eaten by a new dissy I wouldn't take a chance and put the gear from your MC on it.

 

[007]

Having just replaced both gears on my '79 AMC 304 because the one on the cam got eaten by a new dissy I wouldn't take a chance and put the gear from your MC on it.

So to be clear...you're saying don't take the chance on the MSD - use the Motorcraft gear...?

 

[mtnwhlr]

So to be clear...you're saying don't take the chance on the MSD - use the Motorcraft gear...?

Yes

 

[JR74CJ5]

My DUI gear ate mine before. And it wasn't supposed to according to manufacturer...

It took a while too. Happened while on side trail to the rubicon...

JYG has a few tests to see too - can do a drill test on it if I remember from one of his "friends / fans" that was on here years ago.

The only sure way though is to buy a matching set, or change your old to the new on distributor, but since you're not sure about the one you were running it's hard to tell...

Remember, it's not the distributor gear that will get the damage when inspecting - you have to see the cam shaft gear to know if it's happening or not. I know you probably know this but couldn't tell which gear you were saying you inspected in first post...

 

[007]

Thank you. It seems any aftermarket distributor not made or remanned by Dorman has a potential issue. I'll swap gears. It's the best odds.


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[1986cj7]

I'm also would like to know I have replaced my camshaft with a pro cam and replaced the dizzy with an hei has anyone had trouble with these gears getting chewed up. I haven't even started this engine because I am in the process of restoring the whole thing. This is on a 1986 AMC 258 i6 / 4.2l . Thank you and don't mean to high jack thread.

 

[JR74CJ5]

ensure the gears are of the same "hardness" of metal. Or, to be sure, spend the money on a new matched set that will fit your new components. I used a matched set from Summit - MSD models.

 

[Belizean]

ensure the gears are of the same "hardness" of metal. Or, to be sure, spend the money on a new matched set that will fit your new components. I used a matched set from Summit - MSD models.

I'm installing a competition cam and have been reading some comments of this for some time in the forum. How do you know / find out they are a matched set? Or equal hardness. I was thinking of getting a new distributor, replacing the original since I have no history on it, or condition. I purchased the engine to do a complete rebuild and replacement of my existing engine.

 

[JR74CJ5]

I believe you could drill them slightly or use a punch to check hardness... i ended up buying the MSD set. Im not sure the exact details on drilling or punch testing for hardness... the guy who was trying to tell me how to do it when i had the issue was a bit hard to deal with...

I'm also not sure if your cam has a larger id for the gear than a srock one...

Most of the cheaper HEI distributors had a hardened gear. As to wheather or not your cam or distributor gears are one or the other or both hardened... not sure...

 

[Belizean]

When you say an MSD set, do you mean distributor and gear ? I was thinking of going with the MSD since I already have a 6AL & Blaster SS . Thanks for the response,,,,

 

[JR74CJ5]

No MSD sells a cam and distributor gear set - i got them from summit racing. If you got a new MSD distributor, it would come with a new gear too but you would need to talk to support and tell them you want to get a matching cam gear too to be sure.

That make sense? Im not on my computer (cell phone) so hard to post links of what im talking about.

 

[007]

I'm installing a competition cam and have been reading some comments of this for some time in the forum. How do you know / find out they are a matched set? Or equal hardness. I was thinking of getting a new distributor, replacing the original since I have no history on it, or condition. I purchased the engine to do a complete rebuild and replacement of my existing engine.

You "could" do similarly as I did. You could use your existing cam gear if it's good and your existing distributor gear if it too is good. It's the safest thing next to getting both new. If you've not already done the cam swap AND you're definitely doing it, then get the set and be done with it.


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[Belizean]

I'm doing a complete rebuild of a AMC 258 i6 / 4.2l and already have the cam. Just trying to figure out where to go from there........

 

[007]

I'm doing a complete rebuild of a AMC 258 i6 / 4.2l and already have the cam. Just trying to figure out where to go from there........

Gotcha. Get the kit with both.


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[tarry99]

Lots of new distributors are shipped with shims for the gears and gaskets for the top end while others are not...........

My experience around the so-called problem with dissimilar hardness's is doubtful....with the new QC process's as they are now vs years back when parts were heat treated in small batches in a more antiquated method.... Although getting a bad part in any batch is possible.......

Most of the problems with distributor gears eating a cam gear is because the new distributor does not fully mesh correctly with the old cam gear...........just like gears in the axle there is proper depth to match , not to high or low.......when people change manifolds , distributors, mill heads or deck the block all the dimensions are subject to change even if it's only .010-.020 which then may require a slight adjustment to get back to the correct mesh.

Measure your old setup, if it is running correctly then duplicate that distance. If your old gear is showing uneven wear then change both gears and make an adjustment in depth with your new setup. Some distributors are end loaded that sets in a cavity or drive an oil pump , while others are hung from above resting on the block or manifold........get your calipers out and measure.

 

[hagar]

I'm doing a complete rebuild of a AMC 258 i6 / 4.2l and already have the cam. Just trying to figure out where to go from there........

I've never heard of any issues with AMC 258 i6 / 4.2l only V8s.
Maybe I have cotton in my ears too....

 

[mtnwhlr]

I've never heard of any issues with AMC 258 i6 / 4.2l only V8s.
Maybe I have cotton in my ears too....

Me too