Oil pump questions

[Dennis O.]

As some of you know, I have been having problems with the freshly rebuilt L79 in my '67. A couple of symptoms are a puff of blue smoke at startup, excessive oil consumption, oil fouled plugs, and super-high oil pressure. (The only time the gauge is not "pegged" is at a full hot idle, when it still shows 50 lbs.) The car seems to run great except for this, so I have decided to remove the oil pump and replace it with a Mellings 10553 standard pump I just received. I plan on removing the bottom plate and pack the gears with grease (if not already done so), and tack welding the pickup to the pump. The pump came with an extra spring and the following note :

" This oil pump comes assembled with a high pressure relief spring. The enclosed yellow spring will drop the oil pressure 10 to 15 psi. Changing the spring will not affect the engine oil pressure at low speeds (idle)."

So my question is, which spring should I use? I am more into driving the car over showing it or racing it. (I would probaly have a much greater tendenacy to show it than race it.) One of the things I have found out in getting this car to run and drive as well as it currently does is that the original GM engineers had just about everything right when they designed these cars, and factory settings are usually the optimum.

Also, this is the last time I will ever have a basically stock enging rebuilt by a shop specializing in race engines, not matter how highly recommended they are. They do you "favors" you don't need.

[Scott M.]

Re: Oil pump questions

Assuming your bearing clearances are "normal" and not opened up, you want to use a standard volume, standard pressure pump for a street car (58# yellow spring). The old rule of thumb is 10psi/thousand RPMs. I haven't followed your posts, but high oil consumption and fouled plugs can be a sign of the intake manifold not sealing to the heads correctly or even the rings installed incorrectly. Often shops will mill the heads and the geometry gets thrown off, then you need to mill the intake to match. Did you install the intake?

[Timothy B.]

Re: Oil pump questions

Dennis,

My suggestion is to use a stock 45psi oil pump, I think Scott is correct in that the Melling standard spring is 58lbs which I think is too much pressure.

I seem to remember your original post and you mentioned the M55 oil pump. Why not call Melling and try to find out what's in there because I believe they make a 49psi spring but I would make darn sure you get it right before going through all that work.

[Dennis O.]

Re: Oil pump questions

To be clear; the pump comes with the high pressure spring installed and the standard pressure (yellow) spring in a plastic envelope in the box. I was leaning towards using the standard spring, and you folks seem to confirm that.
It looks like changing the oil pump is not too bad, especially with the new Fel-Pro one piece pan gasket.

[Duke W.]

Re: Oil pump questions

I plan on removing the bottom plate and pack the gears with grease (if not already done so),

HEY, Scott, Tim, waddaya think? My honest response would probaby get me banned.

Duke

[Scott M.]

Re: Oil pump questions

OK Duke, I'll say it, what the hell is grease doing in the oil pump?

[Duke W.]

Re: Oil pump questions

Okay, I have nothing more to say.

Duke

[Dennis O.]

Re: Oil pump questions

Duke,

Thank you.

Scott,

It is a technique used by more than a few respected engine rebuilders to ensure that the oil pump primes as quickly as possible.

Also, from the semi-seriousness of your reply, I suspect you too may have missed whatever obtuse point Duke was trying to make.

I'm done.

[Jim L.]

Re: Oil pump questions

It is a technique used by more than a few respected engine rebuilders to ensure that the oil pump primes as quickly as possible.

I'd never heard of this but a friend who has a 390 AMX tells me that this is the procedure recommended by AMC.

Jim

[Bob I.]

Re: Oil pump questions

Dennis
I myself, search the Archives, prior too asking a question. There are many discussion's on oil pumps.
Bob

[Dennis O.]

Re: Oil pump questions

Bob,

I have searched the archives, but could not find the answer to this specific question.

Dennis

[Timothy B.]

Re: Oil pump questions

Dennis,

That's not necessary to grease the pump, those gears mesh so close together that the pump will prime with a few turns. Make sure to use a new pick up because the tube is a press fit to the pump inlet and there is a tool used to install it tight (even if you spot weld) and don't get it to close to the pan or it will drum on the bottom. After it's reassembled to the engine remove the distributor and prime the complete system. Using grease would make me feel like the oil and filter needs to be changed again which is not needed.

What's important is to get the correct pump relief pressure and I would be careful with the Melling pump but IMO it's a nice pump. Can you remember what pump is installed now, if the new pump standard spring makes 58lbs the gauge will still be very high. In the archives from a few years ago there is a post from me about this same subject with my 67 327/300hp engine and the M-55 pump. I don't like the extra pressure and GM certainly did not think it was necessary.

It's good to see Duke post, we have a good discussion board so everybody "happy happy, happy" :-)

[Paul D.]

Re: Oil pump questions

Use the stock pump if possible....If using the melling there are 3 different springs for the pump. You can call Melling Tech Dept for the PSI rating and number.If you are going for PV,you want about 35# hot idle +- and about 45# about 2000 rpm with 10w 30 weight oil.No grease is needed as the pump will start to pick up oil very quickly. The fel pro gasket is good,just make sure you get the right one for the 327 as timing cover sizes changed in later years...P..

[John H.]

Re: Oil pump questions

As I recall, the GM standard spring was #3814903.

[Joe L.]

Re: Oil pump questions

As I recall, the GM standard spring was #3814903.

John------


Yes, that's the part number for the standard pressure small block spring and it remains available from GM. What I don't know, though, is whether that spring installed in a Melling pump will produce the same pressure as that spring installed in a GM pump. It's very possible, even almost certain, that the current GM pump is manufactured by Melling. However, it's possible the OEM pump Melling manufactures for GM is manufactured to a GM specification and differs in some ways from the aftermarket Melling pump.