65 L84 Oil Pump

[John M.]

What is the correct GM part number or replacement part number for a 65 Fuel Injected SHP Oil Pump and pickup.
The Melling that I put in the engine has failed after a few minutes. Can't wait to see what went wrong. I was suspicious when I put it in; it made a clicking noise. But hey, it was brand new....
Thanks very much.
John McRae 30025

[John D.]

Re: 65 L84 Oil Pump

JB. Now that is something I have not read here before. Melling is one of the biggest producer of oil pumps in the world.
I think the part number is M55. I will be back to confirm that although the guru's will know it off by heart.

JB, That's the correct number. 58 and up to ? = M55.
Do NOT use: M55HV and M55S. Those pumps are the pits for FI cars, etc.
The key to an oil pump from other suppliers is not to have a suffix after the part number.

You didn't ask but here is some more info on Melling Pumps.
55-57 use M46
58 and up use M55 (repeat info)

Where did you buy the pump? Complain and maybe you can get a new one for nothing. Course the labor to put one in and all the damage to your pretty paint job. I feel for you.

[John M.]

Re: 65 L84 Oil Pump

Thanks John,
I should have taken the pump apart when I got it and heard that clicking, but it's too late now, no oil pressure at all.
I tack welded the pickup on there to so I might as well get another of those too. I got it from Summit after a Google search. I think you or Don gave me the number. I'll let you know what I find. Yes, a bummer about the paint.
JB

[Michael H.]

Re: 65 L84 Oil Pump

JB. Now that is something I have not read here before. Melling is one of the biggest producer of oil pumps in the world.
I think the part number is M55. I will be back to confirm that although the guru's will know it off by heart.

JB, That's the correct number. 58 and up to ? = M55.
Do NOT use: M55HV and M55S. Those pumps are the pits for FI cars, etc.
The key to an oil pump from other suppliers is not to have a suffix after the part number.

You didn't ask but here is some more info on Melling Pumps.
55-57 use M46
58 and up use M55 (repeat info)

Where did you buy the pump? Complain and maybe you can get a new one for nothing. Course the labor to put one in and all the damage to your pretty paint job. I feel for you.

Jd.... how can the M55 pump be the correct one for a 65 FI engine if it's the same one for a 58 and later. Late 63 through 65 mech lifter engines had a higher pressure pump?

[Joe L.]

Re: 65 L84 Oil Pump

Jd.... how can the M55 pump be the correct one for a 65 FI engine if it's the same one for a 58 and later. Late 63 through 65 mech lifter engines had a higher pressure pump?

Michael------

I believe the M-55 is now supplied with 2 springs, one for standard pressure and the other for high pressure. The springs were the only difference between the standard and high pressure pumps.

[Joe L.]

Re: 65 L84 Oil Pump

What is the correct GM part number or replacement part number for a 65 Fuel Injected SHP Oil Pump and pickup.
The Melling that I put in the engine has failed after a few minutes. Can't wait to see what went wrong. I was suspicious when I put it in; it made a clicking noise. But hey, it was brand new....
Thanks very much.
John McRae 30025

John-----


The original part number was GM #3848907. The current part number is GM #12555884. However, I believe the latter pump is manufactured by Melling. That does not mean it's the same as the M-55, though. It's not.

You could also use a Melling #10553. This pump is WAY higher quality than an M-55. As you'd expect, it's 4 times the price, too.

The oil pump pick-up screen you need was GM #3830080 but it's discontinued. A Melling 55-S3 is the same as the 3830080 and easily available.

[Duke W.]

Re: 65 L84 Oil Pump

The only difference between the late '63 to '65 SHP/FI "high pressure" oil pump, and the 300 HP pump is the relief spring. It is the same housing and gear set as the pump used in other 327s, so it's "standard volume", not "high volume." It just has a 55-60 psi relief spring rather than 40-45 psi spring.

John - why didn't you disassemble and inspect the original pump? It's probably perfectly serviceable.

Duke

[Michael H.]

Re: 65 L84 Oil Pump

Michael------

I believe the M-55 is now supplied with 2 springs, one for standard pressure and the other for high pressure. The springs were the only difference between the standard and high pressure pumps.

Ok, thanks. I now vaguely remember reading that here a while back.

[John M.]

Re: 65 L84 Oil Pump

Duke,
Two things about the original. The part number was not the right one for the engine, but I don't remember now what it was.
And, on inspection the gear to plate clearance varied from one side to the other and the plate was worn. It was .002-003" different. However, if I had reused the pump I'd probably be driving the car in this beautiful NE weather instead of looking at this new job. Slightly discouraged..

[Timothy B.]

Re: 65 L84 Oil Pump

John,

If the gears don't show noticable wear all that's needed is to plain the cover flat then plain the highest gear to match the other gear. After that sand the pump housing to bring the gear/cover end play into the .002 spec. A flat table and some 220 wet paper works good, sand in figure eight.

The relief spring is another issue and be careful with the Melling because the M-55 standard pressure spring relieves at the PSI of the GM high pressure pump spring. I was told by Melling it's 55-60 so no need for anything else. My 67 300hp car has a standard M-55 pump and spring and pressure gage will move to 60lbs so I know it's true. Check archives for discussion.

I want to say other than that higher relief pressure the Melling is a very nice oil pump with pin oiling etc.

[Joe L.]

Re: 65 L84 Oil Pump

Duke,
Two things about the original. The part number was not the right one for the engine, but I don't remember now what it was.
And, on inspection the gear to plate clearance varied from one side to the other and the plate was worn. It was .002-003" different. However, if I had reused the pump I'd probably be driving the car in this beautiful NE weather instead of looking at this new job. Slightly discouraged..

John------


If you're referring to numbers cast on the pump housing or cover, those are not the part number for the pump assembly. However, they may be useful in identifying the pump.

[Bill W.]

Re: 65 L84 Oil Pump

John,
For several years the GM high pressure spring was available separately, it's idientified by a white paint stripe. If you want to rebuild your original GM oil pump to the high pressure standard I will give you one of these springs. Back to the garage! Bill

[Joe L.]

Re: 65 L84 Oil Pump

John,
For several years the GM high pressure spring was available separately, it's idientified by a white paint stripe. If you want to rebuild your original GM oil pump to the high pressure standard I will give you one of these springs. Back to the garage! Bill

Bill------


It's still available. GM #3848911. About 4 bucks, GM list.

[John D.]

Re: 65 L84 Oil Pump

Hi Tim, Good info but what might make it even better is if one used a granite surface plate to resurface the parts.
Today you can pick up a surface place for peanuts.

No shortage of M55 oil pumps on ebay. Prices all over the board.
JB, Go to Car Quest or NAPA and order nice new pump.

[Joe L.]

Re: 65 L84 Oil Pump

Hi Tim, Good info but what might make it even better is if one used a granite surface plate to resurface the parts.
Today you can pick up a surface place for peanuts.

No shortage of M55 oil pumps on ebay. Prices all over the board.
JB, Go to Car Quest or NAPA and order nice new pump.

John------


Keep in mind that the M55 is, basically, an aftermarket quality pump. Is it adequate? Yes, usually it is but John's experience indicates the contrary.

For an OEM quality pump, one has to use the GM pump I mentioned or something like the Melling 10553.