Old Crankshaft Pulley, New Crankshaft Pulley - The "Washer Plate"
 

Greetings, all. I recently acquired an NB1 Miata with a BRP MP62 supercharger. It has a wobbling crank pulley, with a 110mm 6-rib pulley for the supercharger attached (looks like the ones on the FFS website).

The crank pulley on the car is the "older version," with a built-in "washer/plate" through which the four 10mm bolts pass. I have a new "newer version" crankshaft pulley in hand, which of course does not have that built-in washer in it. What is the conventional wisdom as to how to address this?

I have an angle grinder, and could go to town on the old crankshaft pulley to obtain the washer, but I suspect someone has come up with a more elegant way to address this. Thanks.

I think I may have found what I am looking for. PLATE,C-SHAFT (B3C7-11-408) - $5.30 - B3C711408
Hoping that the wobble is related to a worn crankshaft pulley assembly and not something more sinister.

That washer is not "built in", it should just fall off. It's probably just caked on with some dirt to your old pulley. I'd keep it for any and every install, those 4 bolts are not something you want to fuck with.

Greatly appreciated. Thank you. I have gotten that impression regarding the four bolts from a number of threads. Thanks again!

Some NB1 engines had the No4 crank bearing issue. Mine did and the first replacement engine under warranty from Mazda had a bent crankshaft nose. There was enough wobble that the crank position sensor occasionally missed a trigger causing misfire. Mazda replaced the replacement under warranty. Hoping you don't have that issue.

My supercharged NA8 had pulley wobble caused by a worn pulley boss as well. Is it coincidence or do superchargers wear out pulley assemblies?

OK, Today I got the old wobbling pulley off the car and there are two different styles of pulley for my car. The first has a cast center, which has a built-in inseparable thicker portion where the four bolts pass through that is close to 1/2 an inch thick (this was the "washer/plate" to which I was referring). The second type has a stamped steel center, which is closer to 1/8 inch thick. The one I just bought from Rosenthal is of this type.

My other NB1 Miata has the thicker center type, so I took it off that car and put it on my "new" Miata, and the pulley wobble is pretty much gone. I do wonder if the pulley boss center might be worn, because the pulley assembly on the new Miata pretty much fell into my hands with the removal of the four bolts, and I had to fight the pulley off my old car.

I am getting my first good drives in the new Miata, and at 7 lbs it's pretty fun, but I can already see the need for a bit more.