Distributor Gear

[ffdemoss]

I've read the horror stories on aftermarket distributor gears stripping out and I think I have that problem. Previous mechanic installed junk Dormann distributor and about 1000 miles later the gear stripped. The engine has 25,000 since rebuild so I'm not convinced it was an oiling issue, more of a bad aftermarket part. I installed a Crown Distributor gear and Jeep ran great for about 100 miles. I told the owner this was most likely a temp fix and it was. Before tearing the front of the engine apart, anything else to try? Thanks.

[440sixpack]

The problem usually comes with running a new gear ( junk most of the time ) against a worn original gear. this can give you problems on anything that has gears.


Obviously the best remedy is a new MSD gear on the cam and the distributor. but it's obviously the hardest to do as well.


If you're not up to that you might try a new MSD distributor gear and hope for the best. also it's not impossible you have a timing gear set without the oil passage cut correctly that happens. but if it made it 25k it's not likely.

[FSJunkie]

The distributor drive gears fail because the new camshaft sprockets for the timing chain don't have the oil groove on the back side of the sprocket machined in the proper place to allow oil to flow through to the cam gear. Always check the alignment of that oil groove when building an AMC V8 and buzz it out with a grinder if you need to.

[ffdemoss]

Thanks for the replies. I wasn't the one that rebuilt the engine, so I wouldn't know the if the oil hole was lined up or not, but I would guess it wasn't based on the stories I've read. Since I'm in there, I'm assuming I may as well rebuild the oil pump and put a new timing set on (ensuring the oil groove is right or fixed). Is it possible to pull the timing cover and water pump as a unit so I can try my best not to snap any bolts? Or any pointers on getting it all apart without snapping bolts?

[440sixpack]

Yes the pump can stay on.

If your engine made it 25k without issues I'd doubt oiling is your problem. more likely a crap gear. do you know if your chain cover is OEM or Chinese ? that can be an issue.


If it were me I'd replace the distributor gear and run it a while and see what happens. pull it in 500 miles and see what it looks like. if it's good then good. if it's showing wear then you know what you have to do.


If you do pull it down be sure to use only MSD gears on both the cam and distributor. if it was apart 25k ago your bolts shouldn't be a major problem.

[Heavy_Metal_Thunder_81]

Or shine a small flashlight down the distributor hole to see if your cam gear is chewed up. If your distributor gear is chewed up, more than likely the cam gear is as well. I'd replace them both as a set and not risk it.

[440sixpack]

I agree that would be best . any noticible damage to the cam gear is too much.

But I had a chinese distributor gear take a crap in my 390 and I assumed the cam gear had to be bad too . so I tore it down and found it was fine. if you're not running OEM or MSD gears you're probably in for trouble.

[joe]

The issue is not that it's an aftermarket gear used with the orig cam gear, though Crown isn't famous for quality. It's a mismatched issue. Ya need to use the orig worn-in dizzy gear with the old worn-in together cam gear or go with a new dizzy/cam gear set. Don't know the engineering/voodoo on why this is but seems just to be an AMC 360/401 thing? Never had that old/new mismatch issue on other brands GM/Ford or even Euro. Never even had the old/new mismatch issue on an AMC 258 swapping in a Chev dizzy.

[ffdemoss]

To update everyone, just finished installing new MSD cam gear and distributor gear. Also rebuilt oil pump, double checked cam gear oiling with a scope, New water pump, New fuel pump and rebuilt carb. Crossing my fingers that it lasts this time. Thanks for all the advice/replies.