I posted this in my lifter thread but I guess should have here...
Not sure what gear Im seeing with scope. Cam gear? Looks like it's broken on the edge..Getting ready to go look closer and try to figure out what I'm seeing...
turning the crank it looks like maybe an optical illusion.. The scope is kinda weird.... will try to get a video in a bit...getting pretty chewed up looking though?/but the scope is hard to judge...the resolution is too much and too little at the same time imo...
Hello scott2093,
Your distributor driven gear looks good. For comparison purposes, check out what this
new distributor gear looks like:
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And to familiarize yourself with what a very worn gear looks like when worn to a 'knife edge',
this is what you should be on the lookout for:
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(credit: corvetteforum.com)
Although anything is possible,
normally the driven distributor gear shows nearly all of the wear, while the drive gear
on the camshaft is still OK. And given the 100+K miles you have estimated to be on your crate motor, I would expect at
least some wear?
Note: In order to understand why there's wear in this area, <1% of the wear is due to power required to spin
the moving bits inside the distributor, whereas 99+% of the load is caused by the fact that the oil pump is driven from
the bottom end of the distributor shaft. (Easily seen/comprehended once you remove the distributor.)
Back in the pre-roller lifter days, normally there was little/no trouble in this area - everything just worked. But once
the cam core metallurgy was changed to meet the needs of the roller lifter, now came the requirement for a 'melonized'
distributor driven gear. (By the way, the first internet pic I posted above is of a brass distributor gear, which should
be considered a sacrificial gear that must be changed out on a regular basis. (!)
So, in order of desirability, the replacement distributor gear looks like this:
* Melonized gear (spendy but longest lasting)
* Brass gear (Much cheaper but can last as little as a single driving season)
* Old dizzy gear originally designed to work with a flat-tappet cam (
not recommended!)
When you remove your distributor you should be able to get a clear shot of the
camshaft's distributor (oil pump) drive gear. I seem to remember that you had a
lot of glitter in the last oil change photo you posted, so if this is still occurring we
need to locate where this metallic debris is being generated/shed.
Again, the photos of your dizzy gear look good, especially given the accumulated mileage.
And I agree w/Shurkey, the cam gear photos are too low-res to make a determination.
But once you pull the distributor and take a well-lit shot of the cam gear viewed from
the opening you should get a sharp photo we can look at.
Best of luck in your repair journey --
