RB25 oil pump identification

[daemonyk]

So I'm kinda at a loss. I've searched everywhere in every way I can think of, but I got nuthin.
I have a S2 RB25DET that I'm pulling apart and noticed that some of the parts weren't standard, like it had an N1 water pump. So I was investigating the oil pump and I noticed a few disparities. It's stamped NISSAN on the front left like any other nissan pump, and looks like a standard OEM pump. But the bottom is a little different. Every picture I can find of the oem, n1 and / or nismo oil pumps all have a smooth bottom with an oval shaped hole in the middle, like these

oem standard

n-1


However, mine has a slightly raised rectangle with a plug. Looks like its part of the case, not added after the fact.


Also the bolt hanging off the bottom on the standard pump seems to be mounted flush while the n-1 has it projected, but mine has the projected bolt, but has the backplate screw placement of the standard pump. So I'm really not sure what pump this is. Is it an old version, or a differernt version, or a common variation, or what? Thx for any insight

[SullivanRacing06]

the hole thats on the bottom of the oil pump is the relief hole, when your oil pump pressure relief spring opens, oil bypasses the oiling system and shots down into the pan

[daemonyk]

What's got me is that mine does not have that hole. It has a raised area with a plug threaded into it. It looks like it was made that way from the factory (originally cast that way, rather than a separate piece attached after the fact), and even if it wasn't, what would be the reason for doing that? I'm going to be replacing the pump anyways as part of the rebuild, but I'm more than a little curious as to why this one doesn't have that hole that all the others seem to have.

[Carl H]

might not be a factory pump...might be something sweet like a nismo pump. real proof is in the backing plate of the pump.

[daemonyk]

I should be so lucky... Thx for the input guys, I'll post up once I pull it off and know more myself.