oil pump help

[Jim Hanig]

Originally Posted by Mike Pearson

Go with billet. I had a cast iron pump shear off at the base. No more passenger type pumps for me. Worth the little extra money.

Mike what do you think caused the shaft to break? I have raced chevys for 50 + years and never had a melling, chevy pump fail. Jim Blair does low pressure pumps Pierre s.d.

[Adger Smith]

In the 44 years of doing this engine building I have seen pumps break off a few times. I don't think any of them were the pumps fault. I've seen pumps used after a catastrophic engine failure fall off from being cracked and the builder did not inspect it, or toss it just in case there was a strike or problem. I've seen them fall off because of the engine going into sever detonation. There the problem is the tune or the tuner. I have seen a lot of them subject to failure that we tossed out upon tear down of the engine. Most of them had fretting at the point they met the main cap. That fretting indicated in operation they were vibrating like a tuning fork . Most of the time I changed the balancer on an engine that had that problem and had the owner change his tune up. I usually checked the balance of the engine internals. I've also had a couple of circle track engines that had the pumps fail after a hard wreck. Again not the pumps fault. Early on the necks of most SBC and BBC pumps were weak, but that has changed quite a few years back Melling strengthened the neck of their castings.
I'm not saying they ever fail on their own, but I feel the ones that do might need a little more investigation to determine the cause instead of tossing the carnage aside and quickly placing blame.

[Ed Wright]

If Adger says differently, I will defer to Adger. But, why would anybody think they need a high volume oil pump? I never understood why they are even made & offered.
I took a break from drag racing for a couple of years about 1972, to build my business. I was closed too many week days for travel. I had helped a couple of local dirt track guys, and decided to try that, because it was just Saturday nights right here in town. At the time they weren't allowed dry sumps. 310" limit, wet sumps & carbs. Most were using high volume pumps just because after 25 to 50 laps oil pressure at idle dropped to 15 or 20 psi. Big deal. They wore brass dist gears & camshaft oil pump drive gears like crazy.
Oil filters always full of that that crap as well. I just used the std volume Moroso blueprinted pump from my last C/SM engine, same short block I started with. Zero problems. Just changed the heads, Carillo rods, cam & oil pan. Won some A features the first year.
I changed the pumps in the engines I helped guys with. Had a sharp local machinist cut the gears old camshafts, and put them on the cams they had killed, press fitted with a dowel pin. Stopped all those issues. Bearings stayed nicer without that crap going through them.
I, and a LOT of us, use Larry Stewart LOW volume pumps now. My second choice would be the Moroso blueprinted pump.

[Ron Gusack]

Please help me understanding the whole volume issue. I've always thought this:
Pressure is what determines how much power is required to turn the pump.

Pressure is determined by excess volume and the bypass spring.

If you have a HV pump with the same pressure under the same conditions as a SV pump, the same amount of power will be required to operate the pump. No???

If I put a lower pressure spring in my HV pump, wouldn't I pick up some power??

I just tested my M77HV vs the 22150 Moroso race SV pump. The HV pressure was 70 and quickly dropped to 65, then 60. The Moroso was bouncing between 55 and 50. The HV has the bypass oil returning to the pan and the Moroso doesn't. I'm assuming the bouncing is because of the return differences in the caps. I need to figure out how to drill the cap on the Moroso SV and retest. This was with 10-30 oil at 46 degrees.

[Ed Wright]

Ron, from what I saw with the local circle track cars, I would say you are mistaken. I posted what I observed. More power required to run the big pump is the only thing I know of that would wear gears like that. Old as I am, I haven't seen everything yet.

From your description of the oil pressure you are seeing, I would say you problems other than the pumps. I just put a new Moroso std volume pump in my spare engine, which I recently sold. Oil pressure was solid at 60 psi all the time. Hot or cold (5W20) idle or WOT. You have something wrong somewhere.

I have an old rear main cap, with a gauge on it. I bolt my pumps on it, drop it in my parts washer, and spin it with a 1/2" drill to see where the relief valve is set. Whatever it shows there, is what it shows in the car. My thinking is solvent, being thin, would be similar to hot, thin weight oil.
I noticed solvent spraying out from the area where the pump mounts. The machine marks was the culprit. Also, some do it where the end plate mates to the main housing. I have a surface ground plate I use with wet-or-dry sand paper in the parts washer for sanding piston tops to correct the deck. I started lapping the oil pump mount, end of the housing, end plate, and pull the dowel pins from the rear main cap. I lap all the machine marks from those four surfaces. Stopped the leakage. I prefer my oil going into the oil galley. I don't see how excessive leakage those two places could help anything. Some machine marks are worse than others. Hope this gives somebody something to look at.

[Ron Gusack]

Originally Posted by Ed Wright

Ron, from what I saw with the local circle track cars, I would say you are mistaken. I posted what I observed. More power required to run the big pump is the only thing I know of that would wear gears like that. Old as I am, I haven't seen everything yet.

From your description of the oil pressure you are seeing, I would say you problems other than the pumps. I just put a new Moroso std volume pump in my spare engine, which I recently sold. Oil pressure was solid at 60 psi all the time. Hot or cold (5W20) idle or WOT. You have something wrong somewhere.

I have an old rear main cap, with a gauge on it. I bolt my pumps on it, drop it in my parts washer, and spin it with a 1/2" drill to see where the relief valve is set. Whatever it shows there, is what it shows in the car. My thinking is solvent, being thin, would be similar to hot, thin weight oil.
I noticed solvent spraying out from the area where the pump mounts. The machine marks was the culprit. Also, some do it where the end plate mates to the main housing. I have a surface ground plate I use with wet-or-dry sand paper in the parts washer for sanding piston tops to correct the deck. I started lapping the oil pump mount, end of the housing, end plate, and pull the dowel pins from the rear main cap. I lap all the machine marks from those four surfaces. Stopped the leakage. I prefer my oil going into the oil galley. I don't see how excessive leakage those two places could help anything. Some machine marks are worse than others. Hope this gives somebody something to look at.

Thanks Ed. The test results I posted was for pumps mounted to a rear cap and in a pan with 46 degree, super thick 10-30 oil. I like the idea of using the parts washer fluid to closer replicate hot oil and I would not have thought of that. I have thought about the various mating surfaces leaking, but didn't really know a good way to fix the problem. Do the pins just pull out of the rear main and press back in? Could I use a piece of glass to wet sand on?

[Ed Wright]

Originally Posted by Ron Gusack

Thanks Ed. The test results I posted was for pumps mounted to a rear cap and in a pan with 46 degree, super thick 10-30 oil. I like the idea of using the parts washer fluid to closer replicate hot oil and I would not have thought of that. I have thought about the various mating surfaces leaking, but didn't really know a good way to fix the problem. Do the pins just pull out of the rear main and press back in? Could I use a piece of glass to wet sand on?

They make a slid hammer style tool for pulling dowel pins. Snap-On makes one.
The dowel pins do go back in. Never used glass. May be fine. I used 280 grit paper, then 400.
I think you have something screwy going on to have oil pressure like you discribed. I've never had one do that.

[Ron Gusack]

Originally Posted by Ed Wright

Ron, from what I saw with the local circle track cars, I would say you are mistaken. I posted what I observed. More power required to run the big pump is the only thing I know of that would wear gears like that. Old as I am, I haven't seen everything yet.

From your description of the oil pressure you are seeing, I would say you problems other than the pumps. I just put a new Moroso std volume pump in my spare engine, which I recently sold. Oil pressure was solid at 60 psi all the time. Hot or cold (5W20) idle or WOT. You have something wrong somewhere.

I have an old rear main cap, with a gauge on it. I bolt my pumps on it, drop it in my parts washer, and spin it with a 1/2" drill to see where the relief valve is set. Whatever it shows there, is what it shows in the car. My thinking is solvent, being thin, would be similar to hot, thin weight oil.
I noticed solvent spraying out from the area where the pump mounts. The machine marks was the culprit. Also, some do it where the end plate mates to the main housing. I have a surface ground plate I use with wet-or-dry sand paper in the parts washer for sanding piston tops to correct the deck. I started lapping the oil pump mount, end of the housing, end plate, and pull the dowel pins from the rear main cap. I lap all the machine marks from those four surfaces. Stopped the leakage. I prefer my oil going into the oil galley. I don't see how excessive leakage those two places could help anything. Some machine marks are worse than others. Hope this gives somebody something to look at.

So you tap the rear main cap that's actually going on the race engine? How else could you determine that there was a mating surface leak. Do you leave the threads in the cap when it goes on the race motor?

[Ed Wright]

Originally Posted by Ron Gusack

So you tap the rear main cap that's actually going on the race engine? How else could you determine that there was a mating surface leak. Do you leave the threads in the cap when it goes on the race motor?

Ron, I think I said I used an old main cap. If I had a piece of aluminium plate on hand at the time, I would have made a test fixture from that. The cap is tapped for a pipe thread, with a hose and oil pressure gauge screwed into the oil passage. It ain't purty, jut a quickie with what I could find at the time, about twenty years ago. Works, so I still use it. I just don't get it out and show it off. :-)

I am not a professional engine builder. I just cobble my own crap together, and have helpped a couple of other guys in the past. Someone like Adger differs, I defer to them.

[Adger Smith]

Ron,
You seem to have a good grasp of what is going on and
you are close on the cause of pressure. (sorry this gets long)
Look at the way it works with your garden hose.
Yea, one of those cheap soft plastic garden hoses.
You have it hooked up to your house/city water supply.
Open the valve wide open at the house end.
You are now flowing the set volume (through the valve as a flow orifice)
Behind that valve/orifice you have a pressure, say X.
Then on the hose side of the orifice/valve you take a pressure reading and find out it is X minus. (lower on that side)
Your end of the hose is wide open and there is nothing on it to slow the flow, Volume. You screw on one of these twisty spray nozzles and the pressure on the hose goes up (the soft plastic also swells) because you have cut the volume of the free flow. As you cut back on the volume to an orifice the same size as the house valve the pressure on the hose side is less than the house side of the valve. When the volume of the spray nozzle equals the volume of the house valve the pressures on the hose and house will be equal, too.
How much pressure and volume will it be?
That all depends on the source. How much capacity the source has and if there is a bypass in the system.
Now we are at the oil pump.
You said"Pressure is determined by excess volume and the bypass spring"
Yes and No. For all practical purposes you can turn any automotive pump in a free flow situation and utilize 100% of it's volume and have 0 pressure and not have any bypass activity.
Now put tight bearing clearances and tight lifter bore clearances on the end of that free flowing pump. AHA! you have pressure, resistance to flow volume. Vary the clearances and you vary the "Require flow volume" which will limit the volume out of the pump and increase the pressure till it kicks the bypass in the pump open. The excess volume then bypasses and the output is held at what the bypass regulates the pressure and volume to.
Start by determining what your required flow volume is. Do you have tight or loose clearances? Then figure out what pressure you want or need. Don't pump any more oil at any higher pressure than you absolutely need. It will take more power if you go up on either one. It may not be 5 to 7 HP, but it is power.
The way I first started approaching what was required was to consider what the engineers designed for the original engine. They are going to over engineer whatever they do by a certain percentage. If you have reasonable clearances the flow demand will probably match the flow capacity of a stock pump. Keep in mind the flow capacity of the pump varies with RPM. Ever wondered why the pressure drops when you slow the rpm down? The pump flow capacity gets less and the flow required by the engine clearances stays the same so there is not enough excess volume to work the bypass.
The trick is to get the least amount of loaded pump to flow the required oil volume at a low pressure to keep the bypass from over working.
1. Why is a Hi vol pump needed. "Market Demand" The avg person has no idea what is going on, but they don't want the pressure to drop when the engine speed slows down.
2. Hi Vol might be needed in some extreme cases of clearance or "Required Flow"
3. The end user usually equates engine health with hi oil pressure.(it Ain't so)
Now to the anti cavitation. It is my opinion that when you have too much pump gear size and are working the bypass too much the gears will cavitate. They will build real high pressures on the outside of the gear teeth and the low pressure on the inside causes air bubbles. The cavitation slots in pumps are there to reintroduce higher pressure oil to the low pressure areas.
I think it is a crutch. If you have a pump that is matched to your system needs you don't need them. Again the customer doesn't know or understand why the pressure drops when you are at idle. So they do cause problems of misunderstanding with customers. At this point I might add I don't like a system that is over pressured or has too much volume. It can get you into trouble with oil aeration. Air in oil doesn't lubricate or cool the parts & air can negate some of the effects of chemicals that are in the oil. If you experiment with your pump system and run only what you need you can save a little power. (Each engine and combination has it's own requirements)