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Less Zinc in Oil contribute to dist gear wear??

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Post Options Post Options   Thanks (0) Thanks(0)   Quote 12Gauge Quote  Post ReplyReply Direct Link To This Post Posted: Sep/17/2007 at 3:57am
You originally asked an interesting question regarding the zinc content and the distributor gear wear and (failure).  If I recall, the distributor gear failure was pretty well documented early on in the day regarding the 290 -390~ class AMC V8 engines as well as some failures in the Ford FE V8 and to a lesser extent Buick V8 family as well. 
 
There seemed to be "batches" of dizz gears that were somehow manufactured not up to spec during the past 39 years for both engines.  Perhaps other engines (Cheby, Pontiac, Olds and MoPar) also had this but because I do not own those engines I am not as aware (or as tuned in) of the problem or lack thereof with them.
 
From what I have read, the reduced zinc and other additives in modern sunburst logo'ed oils could contribute to premature failure in "impact" areas of the engine such as valve lifters and their associated cam lobes.  I have not heard or read of spiral gear mating failures associated with the presence or reduced quantity of the zinc anti-wear additive package.
 
It seems to me that exessive runout or play in the diz gear shaft could contribute to a failure.  Also using an old diz gear (previously mated with a old cam) with a new cam may have some cause for concern. 
 
 
 
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Sep/17/2007 at 4:11am
Until the last few years (meaning roughly 10-15 years or so) I'd never seen an original AMC gear fail that wasn't caused by other issues - too high oil pressure, too low pressure, gunk, wear, "mechanic error" etc.
I worked in a former "Rambler/AMC" shop and later a shop along I80 and never once saw a failed AMC distributor gear. (I've seen them towed for a lot of other reasons, however! Some downright funny)
Not stating it didn't happen, but I suspect the reports of "failures" are a bit overblown until people started resurrecting older AMCs, rebuilding them, etc. in the last couple decades.
In an original engine that was never overhauled or rebuilt, never saw a failure.
And in recent years, I suspect the vast majority of failed gears are on "touched" engines, not original engines that haven't been worked on in some fashion.
In other words, I am in effect challanging the "documentation" that says AMC had a gear issue from the factory and there were mass failures on un-touched engines that could not be contributed to other factors.
I suspect most "documentation" comes from the last say, 15 years or so....... and what's happened in those years? I'll be blunt - many failures are due to aftermarket parts and mistakes.
I'll add, I've never seen a "PREMATURE" gear failure on any brand engine that could not be contributed to other factors - oil, wear, care (lack of), etc.
I worked on hundreds of vehicles from tune-up to overhaul to restoration and never saw a bad gear. If there was wear or failure, there were contributing factors unrelated to gear quality in each case - however, human pride being what it is, a lot of failures are blamed on other factors.
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