Spec changes to original oil pump gears?
 

I purchased the billet oil pump gears on the very first group buy in 2008. I'm finally ready to use them and would like to know if there are concerns or spec changes when installing these gears. They are going to be installed in a '99 pump.

Thanks!

We upgraded the mechanical design (geometry) to be stronger, they are now much tighter tolerance because of better machining. All in all though, you shouldn't have any issues with it. OUt of everything we've sold (thousands?) I've only seen about 3 failures, and all of those looked like they ran double ought shot through the pump. I guess they are bullet proof upto a certain size bullet anyway. ;)

I plan on significantly raising the rev limit and power goals are >400whp. As long as you don't see any issues I'll run them as is and at stock tolerences in a '99 pump.

Thanks!

There is an issue - give me a moment to type it up

All of the miata's OE oil pumps were - as far as I know - manufactured to identical specifications from 1989-2000. In 2001, mazda increased the flow volume of the oil pumps by increasing the thickness of the oil pump gears and the housing in which they reside - it is primarily believed that this was for the extra oil needed to power the VVT of 01+ cars. To the naked eye the difference is impossible to see, the difference in thickness is somewhere in the range of 15-20 thousandths of an inch.

Here's why this is a potential problem for you:
In 2001, when mazda changed the specification of the oil pump, they SUPERCEDED the 99-00 OE part number with the higher volume 2001 pump. 1989-1997 pumps all retain the original geometry, but 99-00 pumps are problematic at best. The best case scenario is that you screw it up by putting thicker gears designed for the newer housing into the thinner older style housing, in which case you won't be able to close the housing up. The worst case scenario (and FAR more likely) is that you end up putting the older style gears into a new OE replacement housing expecting it all to fit. It will all go together flawlessly and appear to work - unfortunately the thinner gears in the thicker housing leaves a clearance of somewhere around 20-25 thousanths of an inch - which doesn't sound like much - but that 20-25 thousanths of an inch, when trying to pull vacuum on the oil in the pan - will fail to prime reliably as air rushes across the face of the gears between the gears and the housing from the high pressure side of the pump to the low pressure side of the pump. Once primed, the viscosity of the oil prevents this from continuing to occur, but chances are: it will simply not prime at all - providing no oil to your engine.

So: chances are - if you're installing gears from the original group buy into a pump housing which was ORIGINALLY INSTALLED AT THE FACTORY - you're good to go - but if you're installing those gears into a "brand new '99 factory specification" pump, you're going to run into problems.

At some point in time, Travis started selling thicker gears "by request" - but eventually BE stopped selling gears for probably this specific reason and started selling fully built pumps only, which is a complete solution to the potential problems associated with mazda's pump changes.

Thank you fooger!

I have a couple of '99 housings that I think are of old vintage. Either way, as long as I measure endplay and it is in the OEM spec of .0012" - .0043" then all is good?

Props for taking the time to share important (and hard to find) information.

As long as your thickness is of OEM spec (the BE pumps tend to run at the high end of OEM clearance specs - somewhere in the 5 thousandths realm IIRC, which is perfectly safe) then you are ok. If you see something closer to 20 thousandths, then you've got a no-go situation. One option is to set the pump gears in the housing, put a machinists flat edge across the gear/housing, and run a feeler gauge between the flat-edge and the gear face to find clearance. Second option is to compare the old/new gears against each other with a caliper. Before you start taking old gears out, mark the new gears with a sharpie or something so you don't mix things up when you've got 3 different sets of gears all pulled out on your workbench.

Thanks!

I will do the straight edge method.