[machine shop tom]

Originally Posted by Red1993GMCSierra

The high volume oil pump will most likely fix your problem, but if you do that you need to get a bigger oil pan, because the high volume pump will suck the standard size sump dry and then you'll lose all oil pressure until the oil comes back down.

Uh, no, and probably not.

tom

[lg1969]

so much volume of oil will flow through an engine if the bearing are set to the proper clearance if you use a high volume pump. There will be oil in the oil pan no matter how much oil is circulating. The tighter the bearing are, the less volume oil it will need. Any extra volume is released through pressure relieve valve.

[kc8oye]

it is possible at high rpm for a high volume pump to suck the pan dry, as the oil is sucked up and pumped out under pressure, but has only gravity to return it to the pan.

the high volume pump will indeed be only a bandaide to an engine that is worn, but it's $20 and afternoon's labor to change it and breathe some more time into a worn engine.

What brand is the gauge? I've had bad gauges right out of the box using 'parts store' brand gauges like SunPro. (been so happy with my AutoGage and Autometer stuff)

also, low oil pressure at idle isn't really a concern, unless it drops below 4psi.
according to chevy.

my buddy bought a corvette brand new in 1976, and it has ALWAYS shown 'zero' on the gauge while idling, but the warning light stays off, and checking it with a good gauge show it makes about 5-6 psi at idle.

so long as you meet the minimum of 10psi for every 1000 rpm you are fine.

[oldbogie]

Originally Posted by kc8oye

it is possible at high rpm for a high volume pump to suck the pan dry, as the oil is sucked up and pumped out under pressure, but has only gravity to return it to the pan.

This is unlikely unless the bearings are completely gone and the clearances are huge to where the pump can actually deliver its rated volume. In the end a high volume pump in an engine with normal clearances only serves to increase operating pressure at lower RPMs till there is enough pressure with increasing RPM to open the bypass valve.

A high volume pump with pressure relief set to 60-70 psi in an engine with normal OEM and even high side race clearances cannot push its volume capacity thru those clearances. The excess volume is simply vented at the pump by the pressure relief valve, it doesn't end up circulating thru the engine.

At some theoretical point if there were no pressure relief valve the pressure would keep rising, but the oil escaping the clearances would eventually reach a point where even the additional pressure can't force a greater quantity out and the pump will stabilize the system simply by being unable to intake any more oil than is escaping the clearances. However, in the real world the filter housing will explode or the press-in galley plugs will be blown out before the pump's inlet stalls.

It is common on Chevrolet high volume oil pumps used on wet sump competition engines to drill the pressure relief passage that is internal to the pump from 1/4 inch in its OEM size to 3/8's inch to facilitate venting more oil so the relieve valve when full open will hold 60-70 psi without stalling the pump inlet. This OEM vent route is internal to the pump where the excess volume is just put back to the pump inlet within the casting. This thrashes the oil something fierce and gets it really hot. Stalling the inlet is not stalling or locking the pump, it's just the situation where more oil cannot be admitted to the pump than the amount flowing in the galleys and out the bearing clearances and bypass valve. Also, with high volume pumps the pressure bypasses on wet sump competition engines it becomes necessary to dump the flow out of the pump housing rather than simply back to the intake side of the gears as the OEM design does because this cycle greatly overheats the oil going into the pump. This external, to the pump, venting of the bypass stream requires control of where the bypassed oil goes. This requires the addition of impact barriers and flow directors to absorb the energy of the bypass flow and direct into the pan so it doesn't contact rotating components nor disturb the flow into the pump inlet tube. This is why so many engine builders eschew the use of high volume pumps, they feel the power to drive these pumps isn't worth the gain in low RPM flow. They also feel that the extra heating of the oil serves no useful purpose other than to increase the size of the oil cooler.

Most competition engines increase the pan capacity either thru a deeper or a wider pan depending on the available space between the suspension components and/or the ground. This is not done to keep the pump from drawing more oil from the pan than can return to it. It is done to insure that vehicle maneuvering will not cause the oil to escape the inlet and to provide enough volume that the oil has time to de- aerate before being sucked back into the system. Entrained air with the oil is extremely destructive to pump parts and bearings at high pressures and RPMs so giving the oil time to "relax" is very important. By having more capacity it just gives any molecule a little time to rest up and cool off before going in again.

Bogie

[kc8oye]

hrrm. .makes sense.. guess my chevy book was a little off base.. oh well.

I run an 8qt pan myself with a trap door (for drag racing)
I typically keep the oil on the 1qt low mark on the stick to keep it away from the rotating assembly. I also have the correct deep-pan pickup so there are no issues with oil starvation. it's a moroso pan with the correct moroso pickup.

i got very lucky, the block I rebuilt (done totally on the cheap) was in great shape, the only thing it needed was an over-bore from a piston getting rusted into the cylinder from rain water. all the rod and main bearings checked out on the 'tight' side of good with the plastigauge, it makes awesome oil pressure with a o.e type pump.

[machine shop tom]

Some engines may "live" at 4-6 lbs at idle, but I think that's living on or over the edge. Something with 11:1 compression will not like that, specially with higher clearances. Also, "idle" may mean 600 to 1100 rpms, depending on cam, convertor, etc. I don't like to see less than 10-15 at a dragged down in gear idle (around 700 rpm). As far as anything off idle, 40-50 is good, anything more is not necessary, although some have kittens if the oil pressure gauge is not pegged at 7 grand.......

tom

[OLNOLAN]

Hey, This thread is from March 2009.

[machine shop tom]

Originally Posted by OLNOLAN

Hey, This thread is from March 2009.

Yep, the dreaded ZOMBIE THREAD !!

QUICK, GET YOUR MOSINS!!

I allowed it because oil pressure threads are so rare...................

tom

[kc8oye]

you make a good point Tom.. it all depends on what the engine was designed to do.. a lazy 350 small block in a 76 vette doesn't exactly live a hard life and is problaby just fine with really low oil pressure

my video I have shows my engine idling on 40psi but that had to be with the oil still cold, I really don't remember my oil pressure being that high.. may have also been on the dino oil. but I make about 46psi @ 2250 rpm on the freeway and that keeps me feeling good

on a slightly related note.. Tom.. where do you stand on plugging the oil filter bypass? do it? don't do it? I was contemplating doing it for my mild 350 once it get it back in the same state as I am :>

[machine shop tom]

Originally Posted by kc8oye

on a slightly related note.. Tom.. where do you stand on plugging the oil filter bypass? do it? don't do it? I was contemplating doing it for my mild 350 once it get it back in the same state as I am :>

If it is only going to be driven in warm (no less than 45ƒ), it's not a bad idea to plug it if you let the engine warm up a bit before jazzing on the throttle. If it's to be driven in colder conditions, I'd leave it unplugged.

tom

[kc8oye]

hrrrm.. that makes it tough lol. If I was still in michigan I'd leave it unplugged heh. I'm not sure if Texas winters technically qualify as 'cold' LOL

[Skybow23@gamil.com]

I have a 87 gmc Jimmy and I just put a new motor in it. It's a 350 not sure the year. But it's bored over 60 and rv pulling cam. Forged flat top pistons and full release values, e five heads. Not sure about how big the cam is tho, but I am losing oil pressure and it wants to die when I am at idle and when I give it a real quick shot of gas, at idle. It Boggs down and if I do that and stay on the gas it back fires and shoots fire out the tbi. And I have good pressure in all cylinders. It dies down when it gets hot. When I drive it and come to a stop I have to keep on the gas at a stop light. I changed the oil sending unit. And has a new pump put it in when I put the motor in, well before i put it in. But I am just lost. I don't know what to do. Do I need to make it a carb motor or what??

[lg1969]

Originally Posted by Skybow23@gamil.com

I have a 87 gmc Jimmy and I just put a new motor in it. It's a 350 not sure the year. But it's bored over 60 and rv pulling cam. Forged flat top pistons and full release values, e five heads. Not sure about how big the cam is tho, but I am losing oil pressure and it wants to die when I am at idle and when I give it a real quick shot of gas, at idle. It Boggs down and if I do that and stay on the gas it back fires and shoots fire out the tbi. And I have good pressure in all cylinders. It dies down when it gets hot. When I drive it and come to a stop I have to keep on the gas at a stop light. I changed the oil sending unit. And has a new pump put it in when I put the motor in, well before i put it in. But I am just lost. I don't know what to do. Do I need to make it a carb motor or what??

You should take this and create a new post and start a new thread.

[Jmmc]

Maybe i misunderstood. Was this a fuel injected engine. Because an NA engine and a FI engine use two different camshafts. You can not use a carb on an FI engine.

[kc8oye]

Originally Posted by Jmmc

Maybe i misunderstood. Was this a fuel injected engine. Because an NA engine and a FI engine use two different camshafts. You can not use a carb on an FI engine.

SAY WHAT!?

of course you can use a carb an EFI engine.. the cams aren't THAT different.
the EFI Computer is rather sensitive to cam changes, especially if it's a TBI engine, and that is probably where most of his trouble is coming from.

but swapping to a carb, also means having to replace the computer controlled ignition with one that isn't.

you also have an issue with fuel pressure if you keep the electric fuel pump