MM89

Hi all,

Have not come across any specification in the FSM or alternative researching, regarding the clearance between the flats of the crankshaft and oil pump gear.
Could I please request to be pointed in the right direction to obtain this information?

It appeared to me that the clearance, prior to being removed, may have been larger than the allowable limit to cause localised wear as per the images.

The crankshaft and oil pump flats measured to be 37.42mm (1.473") and 37.60mm (1.480") respectively.

Mudflap

I've got a boundary engineering pump showing the exact same wear and the exact same crank pattern. Is that an OEM pump you've got there? I'm also worried about the same thing.

Mud

MM89

Yes, it is an oem bp4w pump.

Such wear does seem common amongst other used b6/bp crankshafts (google images).

I speculate that the BE gears being of greater hardness than oem could exacerbate the issue?

I have not run an indicator over the surface of the crank, but there is tangible difference under the nailmometer test...

Mudflap

I've got a second motor sitting in my garage with an OEM pump attached. I plan to get it off the motor (this weekend?) and check it. I'll provide details.

MM89

Obviously not applying to any miata, but I found some clearances that you could expect to see for the same type of oil pump drive design.

Nissan Skyline GTR Oil Pump Failure Problems

Mudflap

Very good find. The Boundary Engineering owner is very responsive. I'm going to send him a note and link to this page - see if he has any opinions.

Thanks

TravisR

iTrader: (9)

The clearance we provide on our pumps is made that way so that the gear can move around under heavy crank walk conditions. As far as I know we've never lost a pump due to actual structural failure up to 900 whp and over 10000 RPM in the BP engines. So as far as structural failure you are safe, and these wear patterns look typical for what we would see in a BP motor. Our gears are a fair bit harder then OEM, and will tend to wear the crank surface in general compared to the stock units which read below Rockwell C.

Mudflap

Awesome - thanks Travis!!

MM89

So what would be the minimum crank collar width one could work with before having to add material / find an alternative crankshaft?

Gee Emm

Can the crank be rebuilt to eradicate the excessive wear on the collar? Similar to the way journals are built up to increase the crank throw?

MM89

Yeah, that's what I had in mind with regards to adding material. Would probably be a case of welding sufficient material on the collar flat to mill to the right width. Though I would hope that the current width doesn't necessitate this..