Hi Jon -
After a defective oil pump fouled my engine, there was a long 'Metal In The Oil' thread. Several posters helped identify the subpar aftermarket pumps that are prone to failure, and I've summarized the info. I think it's worth adding to the FAQs. Thank you!
David OD
Laguna CA
There have been some durability issues with marginal aftermarket oil pumps. In particular, pump drive gears made from softer metal have failed, fouling the oil system with metal particles. It’s possible some of these marginal pumps are still for sale from vendors who must rely on manufacturer’s QC, several steps up the supply chain.
Some characteristics of marginal pumps are:
Drive gear is shiny brass instead of darker factory phosphor-bronze (Pic 1).
Marginal gear tooth root diameter is visibly less than the factory root diameter (Pics 2 & 3).
The reduced diameter portion of the gear is fully machined, while that part of most factory gears is not completely machined. A raw cast surface is proof the gear is not made from bar stock (Pic 4).
The holes in the screen on the pickup are larger - 2.0 mm vs 1.25 mm
Star lockwashers under the four nuts.
The cotter pin hole is double-drilled (Pic 4).
Black threaded hex socket plug on the bypass port.
The three pump base holes are larger 10.5 mm diameter, vs the 9.9 mm original factory holes (Pic 5).
Not all traits occur in every pump that has failed, but these are pretty consistent and should help identify faulty pumps before they're installed. Look twice before installing any new aftermarket pump, so you can leave that AAA Roadside Service card in your wallet.
Finally, with all oil pumps, correct installation is critical. See the attached factory bulletin to avoid shaft misalignment (Pic 6). And be sure the distributor drive offset pins align with the offset slot in the pump shaft.