Oil Pump

[BARRY MISHLER]

It`s leaking real bad after engine gets warm. Engine is a complete rebuild with about 100 miles. New H.D. melling pump. DO I have to drop the engine to pull the pump?Anyone ever done it with out pulling the engine?

[Jason Porter]

You may not have to pull the engine to pull the pump, but I don't know how you're going to fit in there with the engine in. You've gotta pull the fan and shroud just to get to it, as I'm sure you know. I've never done it without pulling out the engine, just because I'd rather have some space to work comfortably. Be cause I know at some point, the "teener" is going to piss me off. The good news is that it only takes a couple of hours tops to pull the engine.

Good luck!

[F4i]

I have heard that the HD pump req. some material to be removed from the drive tab. Do you know if this was done on the rebuild?

[BARRY MISHLER]

Well its going up on the jack stands again. Hope it gets warm this week-end! I can`t remember if I took anything off the tang when I installed it?As I recall it fit real good, didn`t bind up.Guess I`ll get the camera out take pictures so I don`t forget how it goes back together,as I`m not a tech just a parts(good)replacer. I`ll keep you posted . thanks.

[Jake Raby]

Its a Melling, and it leaks- Thats normal.. Those pumps are NOT round!

[BARRY MISHLER]

OK this is not just a drip but a river,about 1/2 qt. in less than 2 min.

[HarveyH]

On the Melling pump drive tang, From what I've heard, you have to grind 0.010" to 0.020" off the end to get them to seat correctly. If not, they can end load the cam and not seat on the case correctly. I've also heard of problems with burrs, and having to stone the end surfaces of the pump body and end plate to clean them up. (the old abrasive paper on the glass plate trick).

Harvey

[Bleyseng]

Some mill a grove on the back of the pump to accept a rubber O ring so it won't leak.

Geoff

[BARRY MISHLER]

Well if the weather cooperates,got a friends motorcycle jack, looks like this will work great to lower the engine & trans. I hope I can change out the oil pump this weekend. I`m going to check out the H.D. pump to see what went wrong. I may just put the stock pump back in.I was getting about 40 lbs. anyone know what the stock one should put out?

[Jake Raby]

40 lbs when???? at hot, cold?? what weight oil were you running...

the only fix for a Melling is to remove it and throw it as far as you can and hope that no one ever finds it again! The tolerances in those pumps are so far out that its impossible to blueprint one.

[mike95125]

Layperson question: What do you do, and how do you blueprint an oil pump?

[Dave at Pelican Parts]

Rule of thumb for oil pressure--when warm, you should see at least 10 PSI per 1000 RPM. Up until the pressure relief valve opens.

Blueprinting an oil pump is a lot like blueprinting an engine. You measure everything (but everything!), set the clearances up just right, and possibly even match up the inlet and outlet ports to the passages in the crankcase. Yes, this means machining stuff.

--DD