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Cam gear for distributor
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jblue1555 View Drop Down
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Points: 280 		Post Options Post Options   Thanks (0) Thanks(0)   Quote jblue1555 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/15/2020 at 8:55pm
You mean like making a dung load of cams that go flat, or water based paint that comes if in 2 years, or take a solid auto trans and screw it up so it needs warranty in a year, and those are factory mistakes not aftermarket.
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Originally posted by 74Bubblefender 74Bubblefender wrote:

AMC oem gears were soft. You cannot trust ANY aftermarket distributor gear. These companies are sourcing them from the cheapest mfgs which means ...well one is hard and one is soft. If there is a difference of 10 on the Rockwell C scale one becomes a cutting tool. That appears to be the case with your distributor gear. Back in the late 90s early 2000s we tested hardness of every possible gear being made. Today there are so many factories that have been making distributor gears I am not sure of the feasibility or keeping up with the changes from month to month. To make it even more difficult AMC parts are often made in smaller batch sizes. Meaning in the world of manufacturing standards can be lost from batch to batch. Obviously the distributor gear you got was part of a batch of gears designed for long term use with a hardened camshaft gear. A lot of this tech comes from the roller camshaft cam gear discovery era of the Chevy small block where changes in material for long lasting lobes meant changes in distributor gear metallurgy and hardness. It does not translate well into the AMC engine as you have noticed. The manufacturer of your distributor should be help accountable for the engine damage. That is what product liability is designed to cover.



What is "soft" on the RC scale? Typically, hardened gears are RC 50-60; standard is 55-60. Anything above 50 would not be called "soft".

We all know these gears were not an issue before 1990, and much later than that, but I can't remember when the problems started happening. Anyway, the AMC gears are fine, because they were machined correctly- not a simple process.   It's amazing that this is still an issue. I guess the best solution is a used set from an original engine- obviously harder to find each day.   
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Originally posted by Heavy 488 Heavy 488 wrote:

And yet people are apalled when a NON AMC engine is swapped in when crap like this happens. 


The sad part of your statement is that it implies this problem (cam to distributor gear) only occurs with aftermarket parts for AMC engines. This is a universal problem with all aftermarket parts, not just the ones for AMC.
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74Bubblefender View Drop Down
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Originally posted by Steve_P Steve_P wrote:

Originally posted by 74Bubblefender 74Bubblefender wrote:

AMC oem gears were soft. You cannot trust ANY aftermarket distributor gear. These companies are sourcing them from the cheapest mfgs which means ...well one is hard and one is soft. If there is a difference of 10 on the Rockwell C scale one becomes a cutting tool. That appears to be the case with your distributor gear. Back in the late 90s early 2000s we tested hardness of every possible gear being made. Today there are so many factories that have been making distributor gears I am not sure of the feasibility or keeping up with the changes from month to month. To make it even more difficult AMC parts are often made in smaller batch sizes. Meaning in the world of manufacturing standards can be lost from batch to batch. Obviously the distributor gear you got was part of a batch of gears designed for long term use with a hardened camshaft gear. A lot of this tech comes from the roller camshaft cam gear discovery era of the Chevy small block where changes in material for long lasting lobes meant changes in distributor gear metallurgy and hardness. It does not translate well into the AMC engine as you have noticed. The manufacturer of your distributor should be help accountable for the engine damage. That is what product liability is designed to cover.



What is "soft" on the RC scale? Typically, hardened gears are RC 50-60; standard is 55-60. Anything above 50 would not be called "soft".

We all know these gears were not an issue before 1990, and much later than that, but I can't remember when the problems started happening. Anyway, the AMC gears are fine, because they were machined correctly- not a simple process.   It's amazing that this is still an issue. I guess the best solution is a used set from an original engine- obviously harder to find each day.   

Rockwell C scale soft is 1. AMC always had some form of a distributor cam gear issue since the early 70s. It was nowhere near what it is the last 20 years but it any type of production motor will have a percentage of failure rate. In a simple example of a 30 degree profile gear riding on a 60 degree profile gear like in an AMC V8 distributor transferring power 90 degrees from the camshaft the profile of the gear is a very rudimentary design. It is the depth of the profile that you would assume would be the issue if common practices are adhered to. However it is the base material that is the culprit and how that base material of one gear reacts to another with a hardness variation. AMC gears were never 55-60Rc. Cast iron gears are very soft and if mixed with one cut from solid bar stock the bar stock should be within 10 points of hardness. Matching hardness within 0-4 points is preferred for the true 13 tooth gear to find a long service life wear pattern. Some of these so called sets have a cam gear at 8RC-c and the distributor gear at 48RC-c. Quite a bit of these mfg are just buying chinese gears and assemblies.

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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Trader View Drop Down
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I picked this up on a Jeep Forum. Talk about quality control issues with distributor gears:)
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Originally posted by Trader Trader wrote:

I picked this up on a Jeep Forum. Talk about quality control issues with distributor gears:)

That distributor is for an AMC in Japan with RHD.  



Received the new MDS gear set and had the distributor gear machined larger (OEM distributor gear is .491) for the .500 shaft of the PerTronix distributor.

I also received another matched set from an AMC Site Vendor.  Don't know if it is Crown or OMIX - ADA or some other brand.  I can tell you that the MSD set looks to be a more precision piece in appearance and finish -  but both appear to be the same weight (I didn't weigh them), match dimensionally, and gears mesh the same.

I'm sure the hardness is a factor with either of these gear sets.  

MSD indicates that their set is:
  • Increased outer hardened layer thickness (RC 55-60)
  • Micro polished surface for smooth contact
  • Proprietary formulated ductile iron
  • Melonite QPQ coated reduces friction and initial wear
  • Interstitial carbide concentration improves wear resistance and running properties

The machinist thought the MSD distributor gear (#8005) was a "hardened part".  MSD has a lot of verbiage depicting various metallurgies of their parts.   The matching MSD 8007 Cam gear has the same denotations.

The parts coming is a sealed box with part numbers (MSD) gives me some peace of mind as the "other set" was just in a plastic baggy.  I hope this isn't the only reason the parts were 3-4 times the cost.

My research to date shows that others have been happy with MSD and is the way to go.

 I will let you know how it goes for me.
    
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Points: 6875 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Sep/17/2020 at 10:31pm
Japan had 2nd or 3rd generation AMC V8 boat motors?
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74Bubblefender View Drop Down
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MSD has a hardened layer to help the gears break in that is all. It has been known for quite some time that break in is ultra important.
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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Nor Cal CJ5 View Drop Down
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Originally posted by Trader Trader wrote:

Japan had 2nd or 3rd generation AMC V8 boat motors?


Just being funny, sorry for the confusion.  Japan - as in driving on the right side instead of the left - or backwards, as that distributor gear is messed up too!
1972 CJ5 304 2 barrel 3 speed
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Nor Cal CJ5 View Drop Down
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Points: 126 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Nor Cal CJ5 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/18/2020 at 5:01pm
Originally posted by 74Bubblefender 74Bubblefender wrote:

MSD has a hardened layer to help the gears break in that is all. It has been known for quite some time that break in is ultra important.

I tell you the gears looked absolutely fine and that the newer distributor and original cam gear have been together for 4 plus years.
 

It was probably too much of a change with these old gears when changing out everything else.  I'm sure it doesn't take much to have the gears try to "break in" again and fail.
 
1972 CJ5 304 2 barrel 3 speed
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