Oil Pump Rant:

[TerryD]

Ok, I've been on another forum and read a post about a "high volume" oil pump.

I dont know how many of you build motors or even know much about them for that matter. I'm coming from a back ground of working on cars and building motors all my life. My dad and his ex-brother-in-law campaigned a 500cid Hemi powered Challenger to many wins in the 70's and has been building motors since the early 70's. Now that that's out of the way, here goes.....

High Volume vs. High Pressure
In an engine, oil pressure is created by the clearances between the crank, rods, cam, lifters, and the bearings/surfaces they run on. Manufactures have specific tolerances they require for these clearances to create the proper oil pressure for the motor and provide the proper lubrication to the system.

A high volume pump moves more oil through the system, creating more pressure. At the same time, it also places increased loads on the timing set, camshaft, distributor gear/shaft, and a few seals. A high volume pump (with the exception of a situation where increased flow is needed such has a turbo charger or super charger that require pressurized lubrication) is just a crutch for an inexperienced or incompetent engine builder. Most of the excess oil is dumped back into the oil pan through the pressure relief valve creating more heat in the motor and decreasing the life of the oil/seals.

A high pressure pump is a OEM volume pump that uses a stronger pressure relief spring to hold higher pressures rather than cutting out and dumping it in the oil pan. These are recommended and used by the OEM's for high performance use. This type pump was used in the Z28 Camaro's 302 and LT1 350 in the late 60's and early 70's.

Most engines do not have the capability to return the excess oil a high volume pump moves to the top end (ie cylinder head/lifter galley) and during use at high RPM or off camber the engine can starve for oil and destroy its self. Also, in some applications (Ford most notably) the excess stress added to the system can cause it to break the oil pump drive and leave you stranded without any oil pressure. The excess oil running out of the engine onto the crank shaft and out of the bearings also causes power loss due the the oil hitting the crankshaft and creating excess "windage" and aeration of the oil, reducing the lubricity of the oil. Alot of guys use them in race motors, but at the same time, using mechanical lifters and oil restrictors to limit the oil getting to the lifters and top end, further reducing the oil volume demands of the engine.

There are exceptions to this, as before mentioned. A turbo or super charger that requires pressurized lubrication from the engine and tapped off in the proper location is a good example of a need for a higher volume.


:rant off:

[Dieselram]

I'm with terry,, If i see a race motor running more than 40-50lbs cold at idle,, i am not a fan and we usually send them back.. i've seen alot of wanna be engine builders who build a motor and say look it has 80lbs of oil pressure at idle... My usual response to that is.. well lets see how long this lasts.... usually not very long.. It took blowing 3 motors before i could convince my old race team it was a BAD thing..

[tsmall07]

I had contemplated putting a dual filter oil filter system to my old '96 and I was told that I would need a high volume oil pump. I guess my He was wrong about a lot of things (he thought he was an expert), so I'm not surprised thats wrong too.

[TerryD]

well, a dual oil filter system is kinda useless unless you're planning on extending your oil changes and running in some terribly dusty or an environment in which the motor is likely to get a lot of dirt inside it. just use a good quality filter like Wix or Purolator Pure One (my personal choice).

[Andrew]

I went ahead and put a high volume pump in my 258, after reading and debating it. It kinda bugs me that at a cold idle it seems high (~60 psi). Once warm, it is 10-15ish at hot idle, and will come up to 50psi when revved.

I did a lot of reading, and the general consensus was that (asides from ancillary systems that requiring oil), when running increased bearing clearances, that's when you need the extra volume.

On my 258, I had to put a new crank in it because the MonkeyNuggetTard previous owner stripped out 3 of 6 flywheel bolts on the flange. I had the new crank polished but not ground. It came out on the small end for standard bearings. In theory I am running a larger clearance on my bearings than would be factory.

IIRC the pump I am running is actually scaled up. It achieves the extra volume by having a larger chambers.

I didn't rebuild the motor entirely, so it is kind of an experimental motor anyways. I don't have high expectations for it. Only one I've ever worked on as I've been a Honda/Volvo driver my entire life. Still never seen the inside of a Volvo 4 cylinder.

[TerryD]

well, larger chambers/taller gears is how they acheive the extra 20% of oil moved. If you are running a HV pump and only have 10-15psi at idle I'd say your motor is trash.(no offence intended) A stock pump should have about 20 at an idle, and HV pumps usually produce upwards of 40+ at an idle. The next motor you build, get the clearances right and use a stock pump. The HV one is just wasting power and money.

[Andrew]

The bearing clearances are in spec, just as large as you can go. 15 psi at a hot idle appears reasonable for that motor. Most people are happy with 10psi running heavy oil. I am running 10W30. The Jeep I6 rule of thumb is 10psi for every 1000 rpms (don't know if this is "factory" or just lore).

Anyways, if my pressure is actually low for that motor with a HV pump, I would wager it is due mainly to old cam bearings. I basically just threw another crank in there to get it running again. The previous owner had a bad habit of F'ing things up, and there's a good part of that motor I didn't have anything to do with. It's got this annoying knock that I think is a wrist pin (best guess anyways). The motor seems to run better than I deserve. It is intended to be a temporary thing. 351W is looking likely this summer funds permitting.

Anyways, I was aware that this motor had issues, and the HV pump was intended as an experiment in conjunction with the largish bearing clearances. The motor runs fine except for the knock which is exactly the same as it was before the new crank.

EDIT: It appears the factory spec is 13psi warm.

[TerryD]

well, if you do a 351W you might check out verticalTRX's 79 F-150. We built one for it a few years ago. His makes some awesome torque and there are vid's of it somewhere on here. Do not run a HV oil pump on a ford. They drive the pump with a 5/16's hex rod and the HV pump will cause the motor to snap that rod, leaving you w/o any pressure. Also, pay the money to have the heads worked over for the stud-mount chevy style rockers, worth the money, Vert (matt) wishes he had listened to me now. He used the screw-in stock mount style. PITA to adjust and not as good a design. Any questions, feel free to ask, I'll help what I can. I'm more of a Chevy guy, but for my first Ford motor, I think it does good.