[SusieQ]

I have a 1967 GTO with the engine out of it.

Back many moons ago when I started this project, the advice I got at that time was that for my stock 400, an 80psi oil pump would be a smart upgrade. So, many years ago, I purchased a Melling 10541:

https://butlerperformance.com/i-3164...h.html?q=10541

Now I'm not entirely convinced that the 80psi is the best choice.

I've read a lot of forums and it seems that the general consensus is that 80psi is unnecessary, and can even be harmful to a degree. Some people are of the opinion that it can put unneeded stress on the gaskets, can wear the cam/distributor gear prematurely as well as other parts, and will rob horsepower.

Just as I was coming to the point of considering buying a 60psi pump, I spoke to Dale from Melling tech who disagreed with all of this and said that the 80psi "shouldn't" cause any problems and the upgrade would be fine.

What do you guys think?

While I'm at it, let me ask a couple of other questions.

What is the best way to tack the pickup tube so it doesn't fall out or shift out of place? There seems to be a WIDE range of opinions on this.

Should I buy a hardened oil pump drive shaft? I think it could be cheap insurance. I'm looking at this one:

https://butlerperformance.com/i-2445...-opds-std.html

Any other advice?

Thanks for your help everyone!

SusieQ

[racegto65]

Oil pump choice depends on a lot of factors, bearing clearances,rod side clearance, crank end play and intended max rpm. If this is a stock build with close to factory clearances the 60 psi pump should be fine. Also the hardened drive is good insurance for either pump.

[Joe's Garage]

If your engine is fairly stock, with 'normal' bearing clearances, 60PSI is plenty.

But you don't need to purchase a different pump to get to 60psi. Just change out the relief spring assembly to a 60psi setup.

And, YES, get the hardened driveshaft. One less thing to have an issue with.

[Dragncar]

Few things. You must use a hardened shaft with a 80lb pump. But, do not use that shaft in the link. I do not see the little 'dimples" or a clip to prevent the shaft from being pulled up too far when your distributor is removed. Its made by AP. And their shortened shaft that comes with the IA2 block does not have those either so I will not use their shaft.
That shaft gets pulled up and falls off the pump it will more than ruin your day. Nightmare makes the proper shaft for IA2 blocks so I am sure they make the correct one for stock blocks too.
And there is no reason to run a 80lb pump in any Pontiac that is not some loose big power beast. And even then most do not use them.
Your pump, I have a Dyna Gear 80lb pump and it comes with a kit to turn it into a 60lb pump. Also came with the right hardened shaft with C clip. I bet Melling has the parts needed to turn it into a 60lb pump. Might want to ask. Folks did use to cut either .75 turn or 1.5 turns out of the spring to drop the pressure. But I would not do that, hit or miss.
BTW, I have a 455 with 60lb pump forever. Crosses the line at 60lbs, no need for a 80lb pump.

[SusieQ]

Sounds great Tom thank you. I'll message you privately.

Melling doesn't have the spring either as it turns out.

[78w72]

keep in mind the unofficial rule is 10psi per 1000 rpm. unless you plan on running 8000rpm, or over 6000 rpm frequently, the 80lb pump is overkill & not needed. especially if you live in colder climates &/or run thicker oil.

[SusieQ]

Cliff...I think I'll make a bracket thanks for the info. I was already leaning in that direction but wanted some advice.

I'm also inclined to get that hardened drive shaft. Probably not necessary, but just a little bit of added insurance.

[Tom Vaught]

1) You can take a spring and cap from any normal Pontiac Oil Pump and swap the parts with the 80 psi spring cup and spring. I used to buy the 80 psi spring cup and spring from Melling for about $4.00 and convert the stock 60 psi pumps to 80 psi pumps.
So going the other way, if you have your old pump laying around should work unless the pump had 150,000 miles on it.

2) Pure street vehicle I would run the 60 psi pump parts too.

3) The hardened Driveshaft is a good idea if you run the 80 psi pump but I have never seen a stock 60 psi driveshaft fail in normal usage. Not Racing stuff with thick oil.
Maybe if you got a chunk of material inside the gears of the pump from a crappy oil pick-up design.

4) I would run the later oil pan with the baffle welded in the pan. Helps on right hand turns off freeway ramps.

Tom V.

[Steve C.]

Concerning the parasitic loss from a 80 lb pump. This from Jim Butler on the subject....

"We've never seen a noticeable performance loss from the added load," says Butler. "Racers will sometimes run a 60-psi pump to reduce parasitic drag and free up a few horsepower. While that's acceptable in a dedicated race engine that's frequently torn down, it's certainly not something we recommend for all engines."

Curious, anyone have testing data with the difference in power/torque loss on a engine between the two pumps ?

https://www.hotrod.com/articles/hppp...-observations/


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[SusieQ]

Good stuff guys.

I like the idea of switching the spring to convert it to a 60psi. That's a big help if I decide to go the 60psi route. I was thinking I had to buy an entire new pump.

I'll look into the cost of the spring and then make a decision on what I'm going to do.

The collective wisdom is that the 80psi isn't necessary, and would "probably" be fine, or "shouldn't" cause any problems. I'm not a big fan of doing things that have disclaimers such as "probably and "shouldn't," especially when there's no clear advantage, so I'm leaning towards changing that spring.

An added advantage going with the 60psi is I don't really need to spend money on a hardened driveshaft.

Thanks again guys!

[Jay S]

The first time I ever tried an 80 psi pump the new engine started and ran then quit. Pulled the distributer cap off and the rotor wasn’t turning. Pulled it out found nothing wrong. Pulled a valve cover off and the valves were not moving. Found that the key on the cam sheared. Replaced the key and it start up an ran, when we rev’d it up the cam key sheared again. Grrrrr...20 some years later I can smile about it. We weren’t back then. We pulled the engine and put in a 60 psi spring and never had any trouble after that. Not saying it will happen to you. But Pontiac didn’t exactly overbuild the cam gear or the cam drive.

[Mister Pontiac]

One last idea I haven't seen mentioned yet is simply wrapping safety wire around the pickup tube, and tying it off tight to the body of the pump. In my old aircraft mechanic days, we used safety wire on everything. I saw the opportunity with the Pontiac oil pump pickup years ago, and have done it a few times since with no issues.

Wrap the wire tight around the outlet tube right next to where it presses into the pump body, pull it taught around the body of the pump a couple turns, and then twist the safety wire tight. Even though the wire may have a little 'give' over time, it won't give enough to allow the pickup to come out of the pump. Haven't seen this method fail yet, and requires minimal effort and zero cost for the piece of mind. Probably the simplest 'fix' I've seen too.

In lieu of welding or drilling/tapping/screw install, just another idea that has been successful for me.

Hope that helps.

[coonhunter70]

60 psi

[Steve C.]

Every so often, someone comes along and proposes reducing oil pressure to free up horsepower..............


https://www.eng-tips.com/viewthread.cfm?qid=350063

Interesting read, not for any endorsement but offered for general interest.


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[SusieQ]

Sweet ride Singleton! I had a red '66 hardtop before buying my '67.

[formula kid]

Built a 73 block to SD specifications Nunzi did all the machine work. He asked me what rpm the max was for the engine. I said max 6K to 6.2 K. He asked about the oil pump, since it was a block I got from the junk yard I told him it was new. I gave him a NOS SD pump, he switched the spring to 60 psi and did work to the pump gears. He said no reason to run a 80 psi pump.

[Steve C.]

So for a 6000-6200 rpm street engine... who is correct Butler or Nunzi. NOT to insinuate either is 'wrong'.



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[SusieQ]

Cliff R....I'm actually quite shocked that a bracket isn't readily available. Some exist for other applications, but not for an older Pontiac 400. Surprising.

[BGus16]

I think Steve asked about Hp/Tq delta testing between the 60 lb and the 80 lb spring.
May not be apples to apples but I have done lots of development testing on gear pumps for aviation turbine engines and have measured torque at various back pressures on our pumps which are integrated into fuel control units for the engine. Some years ago it was a GE38 engine that is being used on the new CH53 King Stallion 3 engine helicopter heavy lift. its a beast, anyway engine is rated at like 7500 shp and metered flow around 10 GPM ( we actually use PPH for fuel controls) up to about 950 psi discharge pressure.
So JetA and not oil and temperature will make a difference on load. We run from -40 up to about 250 F inlet. Cant remember the torque delta though.

Hint, we measured torque required in inch/lbs. not foot/lbs.

It was about 80 in/lbs, I would guess there is very little difference in load between the two spring pressures you are referencing..

Don't even get me started on the whole "hardend washer" thing to shim the spring up to increase pressure. You would be very surprised in the material we use to shim our springs, think beer cans. We actually shim the spring as a calibration for our high pressure relief settings.

[Dragncar]

The hardened shaft is needed for a 60lb pump. Thats what Dan Whittmore sent me with my pump. I asked him about it and was told you can still twist a shaft with a 60lb pump on a cold morning. Just do it, peace of mind is worth the 30 or so bucks.