[64-3Deuces]

Oil pump by-pass spring question for all of you oil pump/oil system gurus.

OEM Pontiac pump purchased in the late 80s, maybe early 90s. Pump was disassembled to tack the pick-up and never reassembled. It has two springs. My MPC shows some engines had a 50 lb. pump and others a 60 lb. pump. That would account for the two springs as the installer could use the appropriate spring. However, I don’t remember which spring is which.

Both springs have the same specs EXCEPT for the length.


I did some research and never got a clear answer on the length other than increasing the spring pressure would raise the by-pass pressure.

Based on the above I’m thinking the LONGER spring would be the 60 lb. spring. My reasoning for this is that the longer spring would stick out farther from the pump and compress more when the spring cap is installed.

Correct, incorrect, or way off base?????

[25stevem]

If both springs are the same wire diameter, then yes the longer spring is the 60 psi one.

[Tom Vaught]

Originally Posted by 64-3Deuces

Both springs have the same specs EXCEPT for the length.


Based on the above I’m thinking the LONGER spring would be the 60 lb. spring. My reasoning for this is that the longer spring would stick out farther from the pump and compress more when the spring cap is installed.

Correct, incorrect, or way off base?????

Correct on all counts. A 80 psi pump (455SD) for example would require an even longer spring and a special longer length "Cover" to contain that spring.

Tom V.

[TxSportCoupe]

Originally Posted by 25stevem

If both springs are the same wire diameter, then yes the longer spring is the 60 psi one.

Agreed.


Sent from my iPhone using Tapatalk

[Cliff R]

Yes the longer spring is the high pressure spring and I would NEVER tac weld the pick-up to the pump. I've seen enough of those break loose to avoid that deal all together. Since I've open up a number of "built" Pontiac engines and found the weld had failed on the pick-up floating around in the bottom of the pan it makes me wonder how many are still out their in service with this problem and the only reason the owner doesn't know about it is that the windage tray is keeping it from getting sucked into the spinning crankshaft.

There are several much better methods to retain the pick-up without welding it to the pump. Here I like to drill and tap a hole for a small hardened machine screw, 8-32 is adequate. There is a nice flat spot on the pump you can drill and tap to install a screw, It's not fussy and only takes a few minutes. You can also weld a piece of steel flat bar to the pick-up and retain it under one of the pump top plate bolts. A little more work but very effective..........

[Mr Anonymous]

I also do the "Cliff" mod on all my engines.

[Mr Twister]

So while you all are talking pumps, is an M-54-F (80 lb) pump the same as a M-54-D (60 lb), except for the spring and its cover?

[Tom Vaught]

yes, exactly!!!!!!!!!!!!!!!!!

I used to buy the "Longer Spring" (455 SD pump) and "Lengthened Cover" from a Michigan Oil Pump supplier for about $6.00 total and could convert the 60 PSI M-54-D pump to the 80 PSI M-54-F pumps and make a nice profit at the Pontiac Swap meets back in the early 80s.

Tom V.

The two parts were designed to work properly when a 80 psi pump was desired. Course Straight Shot Oiling from the aftermarket
(Moldex Crankshaft and others) was a better oiling solution so the 80 psi pump requirement went away with the better crank oiling design.

[25stevem]

The basic pump body is , yes.
The difference is the 80 lb spring and the extension cap it sits in .

[64-3Deuces]

Hey guys, thanks for the info on the by-pass spring length, much appreciated.

[QUOTE=Cliff R;6366623]
...Here I like to drill and tap a hole for a small hardened machine screw, 8-32 is adequate. There is a nice flat spot on the pump you can drill and tap to install a screw, It's not fussy and only takes a few minutes... .QUOTE] Hmmm, quote didn't seem to show properly

Do you have picture of the location you referenced in regard to the screw type securing method? Just saw a screw location in the later post from grivera....is that the spot you use?

[grivera]

I believe it's this one: https://forums.maxperformanceinc.com...63&postcount=9

[Dragncar]

Welding cast iron to steel is usually a bad idea for a novice and really not a very good idea even if you know what you are doing. There are better/safer ways to accomplish holding the pickup to the pump.
Nightmare Performance sells a flat 1/4' thick steel bottom plate that makes it easy to make a strap and weld one end to the pickup tube and bolt the other to the bottom of the pickup.
If you use one of the cast iron plates they have countersunk holes and you have to deal with them.

[Cliff R]

I don' t have a picture of securing the pick-up with a machine screw but it's pretty obvious when you look at the pump and pick-up where it has to go.

You will need to take the pump apart after the drilling/tapping operation to clean out any chips that dropped in there.

As far as bottom plates and Melling pumps, the stock Melling pump is adequate for any power level. I use them on aftermarket 505 builds to 750hp and fine for decades.

The reason we MUST secure the pick-up tube to the pump is that the material they make them from is pretty "soft" and doesn't have the "memory" required to keep it in place once you drive it in. It's been like that for at least 30 years now.

It's alarming the number of engines I've pulled down to be freshened up or rebuilt where the pick-up had been "tack" welded to the pump and broke a chunk off the pump, fell out and was laying in the bottom of the oil pan. EXACT same deal with welding the snap ring for the intermediate sprag on a TH400 direct drum. BAD idea and it will kick the ring off the drum and DISASTER at that point.

It only takes a few minutes to do the job right and if nothing else you'll sleep a little better at night..........