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Cam gear dilemma

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Trader View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Jun/18/2019 at 9:08pm
So I did a little test to see if there is a difference between 1969 and late 1978 distributor and cam gears.
Just a small facing on the lathe;

The distributor gears from these to eras are definitely cast iron. Likely ductile and good quality by the finish. Both, from my perspective, very close to being exactly the same.

The camshaft gear from 1969 is slightly softer then 1978, but both are either a face hardened steel or tempered steel. Press with bullet firing pin to dimple, showed same size dimple at 2000 PSI. Hardness is close but cutting finish was slightly different. 1969 was definitely softer "skin".

So 74 you are correct on the camshaft gear hardness changed as far as I can tell.

But they are definitely different materials.

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304-dude View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: Jun/19/2019 at 4:19am
Originally posted by Trader Trader wrote:

So I did a little test to see if there is a difference between 1969 and late 1978 distributor and cam gears.
Just a small facing on the lathe;

The distributor gears from these to eras are definitely cast iron. Likely ductile and good quality by the finish. Both, from my perspective, very close to being exactly the same.

The camshaft gear from 1969 is slightly softer then 1978, but both are either a face hardened steel or tempered steel. Press with bullet firing pin to dimple, showed same size dimple at 2000 PSI. Hardness is close but cutting finish was slightly different. 1969 was definitely softer "skin".

So 74 you are correct on the camshaft gear hardness changed as far as I can tell.

But they are definitely different materials.



From past experience with bad wear on oem gears, it always ended up with distributor gears being replaced. The cam gear was worn but within good limits. These were post 72 engines.

Ever since starting on the internet, the root cause for cam gear failure was either bad oiling flow from cam sprocket, cam end play from loose chain, or the use of hardened distributor gears. As for distributor gear issues with oem gears, is mostly due to distributor alignment (either out of spec from wear, or bad installation of timing cover)

I have stated in the past, when bulltear stopped making sets, to use a bronze distributor gear, or MSD.

I admit i am no engineer, but to me, with the type of gear mesh used, having both gears of near equal hardness or same material will allow a wear fit before failure.

Again, this may be wrong in my reasoning, but this discussion has been inlightening, even though very strong stances have been made on both sides.

Edited by 304-dude - Jun/19/2019 at 5:29am
71 Javelin SST body
390 69 crank, 70 block & heads
NASCAR SB2 rods & pistons
78 Jeep TH400 w/ 2.76 Low
50/50 Ford-AMC Suspension
79 F150 rear & 8.8 axles
Ford Racing 3.25 gears & 9" /w Detroit locker
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74Bubblefender View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 74Bubblefender Quote  Post ReplyReply Direct Link To This Post Posted: Jun/19/2019 at 1:46pm
Originally posted by Trader Trader wrote:

So I did a little test to see if there is a difference between 1969 and late 1978 distributor and cam gears.
Just a small facing on the lathe;

The distributor gears from these to eras are definitely cast iron. Likely ductile and good quality by the finish. Both, from my perspective, very close to being exactly the same.

The camshaft gear from 1969 is slightly softer then 1978, but both are either a face hardened steel or tempered steel. Press with bullet firing pin to dimple, showed same size dimple at 2000 PSI. Hardness is close but cutting finish was slightly different. 1969 was definitely softer "skin".

So 74 you are correct on the camshaft gear hardness changed as far as I can tell.

But they are definitely different materials.



Yes I know I was right (pat, pat) but like I said there is a lot of speculation that will get you into trouble when your building an AMC or maintaining one.
We are just about to forge new AMC V8 crankshafts.. please check here
http://www.bulltear.com/forums/showthread.php?19564
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