Guys quick question. Is the gsl se oil pump larger than the 12a one? is it a direct fit to a 12a?

 

The gsl-se has the best oil pump that'll work in a pre-86 engine. I do believe the 83-85 12a's had it to. Oil Pump Rotor width is 17.5mm wide. Other 1st gens were 12.5mm.

It is a direct fit. Plug and play.

 

If you only read Racing Beat, you're lead to believe only the GSL-SE had the 17.5mm oil pump and that thay're kinda rare, highly desired sought after pumps for all 12As... But this oil pump was found on several engine models.

These engines came stock with the 17.5mm oil pump:

83-85 beehive 12A
nitrided J-spec 12A
nitrided J-spec 13B
GSL-SE 13B
RE-SI 13B

Wouldn't it suck if you bought one for your beehive 12A only to discover upon teardown that you already had one? I bet it's happened before.

By the way 74-75 engines had a medium 15mm oil pump. The ouside housing looks the same as the small 12.5 pumps so you gotta pop the gear out to measure it. Only the 17.5mm pumps have a larger outside aluminum casting making them visually easy to tell.

 

Never heard of the old school 15 mm pumps.

Seems like I'm always learning something here,

Thanks Jeff!

 

One thing I forgot to mention above is the nitrided J-spec 12A and 13B are known as the R5 engines I refer to quite often. That's one of the reasons I like these engines, and they're different from the US-spec 79-80 which also used R5 plates but a small oil pump.

I would estimate these R5 engines probably came out before the 83 model year (they test things like this a year or two ahead of when we get them) and were probably Mazda's first use of the 17.5mm oil pumps. Seems Mazda was so confident they used full flow oil jets in the e-shaft which results in low oil pressure at idle. I'd been scratching my head for a while why it was only these famed R5 engines which suffered low oil pressure down low. But it was just the jets the whole time. And it can be kind of a good thing to have really cool rotors in a boosted application. PercentSevenC's R5 blow through DCOE takes plenty a licking and keeps on ticking.

 

Thank you very much everyone and yeah racing beat leads you to believe that 13b's are the only one that have the larger pumps. Thanks for the clear up.