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  1. #1
    LIB MR SHEEP dmeis's Avatar
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    I found this quote today regarding the AMC engines chewing up distributor gears and thought it was worth sharing...


    "Re: Mallory Distributors/No Gear

    Date: Friday, December 1, 2000 03:15 PM
    From: Jock J Jocewicz <namdra@juno.com>

    Saw the post on a Mallory distributor that came with no gears so I contacted Robb McMackin, Design Engineer at Mallory. Below is his answer and one that makes real good sense! The ten part series he is talking about is the series he wrote for NAMDRA's newsletter

    On Fri, 1 Dec 2000 09:49:31 -0800
    Rob.McMackin@dana.com writes:
    Jock,
    I explained why Mallory doesn't include the gear on AMC V8 disributors a few years ago in my ten part series on ignition, however, it is worth repeating. Mallory stopped including the gear about ten years ago on V8 distributors. (6 cylinder distributors are still supplied with a gear).
    As most long time AMC fans know, AMC V8 engines are famous for chewing up the distributor and cam gear. There are even oil line kits sold to supply additional oil to the distributor. Back when Mallory was supplying the gear on V8 distributors, nearly one third of our customers experienced gear failure within a few hours of running time. When the gear fails, it also destroys the gear on the cam which means the front timing cover has to be removed. This problem is not exclusive to Mallory. When I was at the Mopar Nats a gentleman came by our trailer looking for a new distributor gear as the gear on his new MSD distributor had failed after only about 30 minutes of running time.

    AMC V8 distributor gears (and the mating gears on the cam) act like cam lobes and lifters. Once they are broken in together they are "mated". If you then install a different gear on the distributor, there is a good chance that both gears will fail. (just like installing different lifters on a used cam will often lead to a failed cam lobe). There are only two ways to make sure that the gears do not fail (and even these methods are not 100% successful). The first method is to install two new gears; one on the distributor and one on the cam. If both gears are new, the failure rate is low. The other method is to use two gears which have already been successfully used together (ie. "mated" . When installing a new Mallory or Accel distributor, we recommend that the gear from your old distributor be reused on the new distributor since (in theory) the old gear is already mated to the gear on the cam. The shaft on a Mallory/Accel distributor is not predrilled for the roll pin which holds the gear onto the shaft. We tried this for awhile but it didn't work very well because the hole in the shaft rarely lined up properly with the hole in the gear. The only way to make sure the holes line up is to use the hole in the gear as a guide while drilling the hole in the shaft. I am sure that it is disappointing to purchase a new distributor and not get the gear. But having a gear fail can really ruin your whole day.
    Robb"

    [img]smilies/old_glory.gif[/img]
    The American Indians found out what happens when you don't control immigration...

  2. #2
    Trail Boss Eric's Avatar
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    Interesting, I've never had a gear problem like that. I took the distributor out of my 304 and put it in the 401, and it looked fine when I recently pulled it. When I had the 401 torn down a long time ago, I had a local speed shop go thru the block for me and they installed new cam bearings (among other things). They were aware of the distributor gear problem and the recommended solution was/is to file a small groove in the front cam bearing allowing oil to reach the distributor gear (I forget if the groove is on top or on the bottom though). That said, my HEI came with a gear already on it so hopefully I have the same luck that I did with the 304 distributor. I'll let you know whenever I finish this thing [img]smilies/rolleyes.gif[/img]

    In case you're curious why the heck I used my 304's distributor on the 401, it's because the 401 came with points and the 304 was electronic. I'm no fan of points, so that went in the round file cabinet [img]smilies/thefinger.gif[/img]

  3. #3
    LIB MR SHEEP dmeis's Avatar
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    I have installed a half dozen or so new/used distributors and didnt have problems either...

    I filed the passage in the timing gear to allow more oil flow to the gear. I have noticed on 4 sets of timing gears that this passage is always a different size.

    As for the points distributor, I hacked off the gear and the top of the housing to make a "preluber" for my 1/2 inch drill [img]smilies/biggrin.gif[/img]

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