Need New Oil Pump - Recommendations?

[Jeff G 78]

Nice. I vaguely remember that, but it has been a while since I dropped a pump from an installed engine.

[Captain Obvious]

Well I'm still waiting for the new pump to arrive, so I'm not time critical yet. Unless there's a Saturday delivery, which is doubtful, I've still got a few days to gather thoughts on this.

Maybe I'll start a specific thread to priming the pump and see if that attracts any more input.

[siteunseen]

That new thread would be great. I thought about it so I'll watch yours. Thanks Captain!

[Captain Obvious]

Just started a priming specific thread....

http://www.classiczcars.com/forums/showthread.php?45440-Priming-New-Oil-Pump-How-to&p=392008#post392008

Let's hope that all the priming wizards catch wind.

[Captain Obvious]

So my oil pump arrived. Step one... Install it? Heck no!!! Take it apart :

I chose the Melling M152 and here's my reasons:

a) It's a cast iron pump body instead of the more typical aluminum body. My thinking here is that the whole thing will expand and contract at the same rate and might do a better job of maintaining pressure once hot. I haven't seen anything about this in print, but after seeing how the pump works, and the fact that the OEM pumps are a steel rotor inside an aluminum body, I could be convinced that the mismatch of materials would result in increased gaps when hot which would cause internal losses of pressure. The Melling should be immune to this.

There are three options listed for Melling. The direct replacement is an M90, the ZX turbo manual trans calls for the M152, and the ZX turbo auto trans calls for a M111. On paper, the only difference between the M152 and the M111 is the pressure at which they operate. I don't need the extra pressure required for the auto trans oil cooler, so I picked the M152. Interestingly enough, the body casting for M152 has "M111" cast into it. Lends credence to the theory that the only difference is the pressure which is adjusted with a different pressure regulating spring. Everything else is the same except for the "M152" stamping on the spring retainer plug:

c) The M152 is a higher volume pump than the stock pump. Here's a pic of the internals and you can see the length difference between the two. I measured them, and the M152 is about 14% longer than stock, which means it pumps, ummm... let's see, this would be volume not just length, so ummm.... it pumps "more".

I put the pump in, sans drive shaft, primed the system with my 88 Magnum:

Took the pump back out again, installed the drive shaft and pump for the (hopefully) final time. Next on the agenda is to put everything else back together and see if all is good!

[Jeff G 78]

Very cool. Thanks for the write-up and photos. Good luck with your motor.

[siteunseen]

Yes, very cool. That's what I wanted to see and you nailed it! Thanks.

[Captain Obvious]

Something else I did a little different was my pump installation procedure.

After I was done with the priming process, I pulled the pump out, dumped most of the oil out of it, and while it was mostly empty, put the drive shaft into the pump, aligned the shaft punch mark with the oil hole, stuffed the shaft and pump up into the engine, used one bolt to hold it loosely in place, and verified that the distributor drive tab was where it belonged. So far, other than putting the pump in mostly empty, everything is by the book:

And then here's where I veered a little from tradition. I clipped a small pair of vice-grips onto the distributor end of the drive shaft and used some masking tape to hold them temporarily into place. This allowed me to pull the pump back out without the drive shaft coming with it:

Why? Two reasons. 1) Because the pump alone without the shaft is smaller and easier to handle. Less risk of dumping out my priming oil, and 2) Because now I could put a little gasket sealer on the pump gaskets and not have to mess with getting the distributor shaft in the right orientation. I didn't want to smoosh the gasket sealer, only to find that I had to pull the pump out again because the dist drive wasn't in the right spot.

So I pulled the pump again after the vice-grips, gooped it, primed it, stuffed it back up for the final time, in and tightened all the bolts. Only other detail to keep in mind is that you cannot rotate the pump internals during this process or the tab on the driveshaft won't line up with the pump slot. Just pour oil into both sides of the pump, but don't rotate the internal gear and rotor.

One last thing I forgot to explain why the first thing I did was take the pump apart, and it goes like this... I did a little searching for Melling pump topics on the Z forums, and there are threads on both zcar.com and hybridz that indicated it would be a good idea to check the pump end clearances before installation. Members jeffp, Pyro, WangsMan seem to be the ones most involved, and here are some of the threads I found:

http://www.zcar.com/70-83_tech_discussion_forum/cast_iron_oil_pump_689487.msg1279920.html

http://forums.hybridz.org/index.php/topic/88729-truth-on-l6-oil-pumps

http://forums.hybridz.org/index.php/topic/61680-kameari-high-performance-oil-pump-worth-it

So anyway, I took the pump apart, deburred all the razor sharp machined corners (pet peeve), lapped the mating surfaces to check for high spots, and checked the end clearance. Lapping the mating surfaces highlighted that there was some metal upset when Melling pressed in the two locator pins, and once that was ground flat, the rest of surfaces were good.

And for the end play, I measured .002 cold, so I think I should be OK. Also for posterity, the thickness of the Melling gasket, and came up with .006 thickness. Then I measured the Datsun gasket from my old worn out pump, and it is .004 thick.