So on the new motor the front cover is apparently from a 12A or something, so my 13B OMP doesn't fit. The upper bolt hole is in the wrong place, and the oil opening is on the bottom instead of side. Hole is no big deal, that can be drilled, but the oil opening is a bit of an issue, because it extends past the oval seal on the OMP, and it doesn't overlap with the pump's opening.

Dammit. I don't want to swap the old cover onto the new motor just for the OMP.

Are there any adapters I can buy that would make this work? I don't want to use a 12A OMP, because it only has two lines. Does the 12A cover even have enough oil passage to provide sufficient oil amounts for 13B?

Premixing might be the most viable option left, but I was really looking forward to using my freshly cleaned and rebuilt OMP.

 

just pre-mix it. its proven to be far better in every way...

why do people complain that rotarys burn to much oil? cause were injecting like its gas!!! stop burning oil, run cleaner, and with better protection.

I use Pro-tek R from Pettit racing. Been using it for years. Love it...

 

The oil volume is the same. Just cap off the other two oil injectors and run the 12A OMP.

Or premix.

 

Just tee the lines to feed all 4 oilers.

 

Or get a 13B OMP?

 

What? Another one?

 

Doesn't the 4-bung OMP supply oil to the extra lines at a different time?

 

never checked, but i really doubt it

 

He's got one, but he has a 12A front cover so it won't fit.

Oil discharge from FSM is 1.8-2.2cc after 6 minutes for a 12A, and 4.2-5.6cc after 5 minutes for a Series 4 13B.

I think premixing is your safest bet. Or buying a front cover from a 84-85 13B (GSL-SE trim), a 2nd gen OMP will fit on that too.

 

I see. I guess I'll premix. Thnx.

Or maybe if I feel like going through the trouble of putting on my old front cover I'll do that...

 

Really? Are they tested at different engine RPM or throttle positions? I know for a fact that 4-port 13B and 12A OMPs are identical (same part number), so using the 12A pump should be just fine either way, and I've seen it done many times without issue.

 

They can't be identical/same part number because they don't even fit the same cover. Their internal design is slightly different, too.

 

The OMPs are tested differently. You will see that the FSM shows somes tests with the rod down (min. OMP flow) and others are rated with the rod pulled up. Expect the total flow to be about the same between the 12A and 13B OMP.

- use the 12A OMP + Ts
- premix
- or use 13B cover + 13B OMP

 

6-port 13B OMPs are a slightly different design with 4 outlets. Old-school 4-port 13B OMPs are the exact same part as 12A OMPs.

 

different part number...

n249-14-600 is the 12a pump, there are/were other numbers for the older stuff, but they are basically the same

n246-14-600 is the gsl-se/s4 13b pump. notice the SIMILAR part number.

in mazda's (and mercedes, porsche, etc) part numbering system, 14-600 tells you its a metering pump, the first four numbers tell you WHAT metering pump.

 

Read what I typed. The 4-port 13B, as in '74-78 13B, OMP is the same part number as 12A (N249-14-600). Obviously the '84-88 13B OMP has a different part number, because it is a different part! It has 4 outlets instead of 2, and a different bolt pattern, as the OP has discovered. Sounds like there might be internal differences, too. However, old-school 13B OMPs, like 12A OMPs, have 2 outlets and flow the same and have the same bolt pattern, because they are the same part with the same number.

 

'74-'78 meetering pumps had short nipples. Same bolt pattern as 12A '79-'85 but long nipples. There are probably minor volume differences such as I beleive the short nipple pumps flow more.