oil pump help

[Ron Gusack]

433 BBC bracket/index car. I want to switch from my HV pump to a standard volume to pick up a few hp. I have a Moroso 22150 pump that I bought in '09 and never used. I called Larry Stewart but he isn't making pumps until he can find a suitable machinist. I've also thought about a Schumann with an external bypass return. I don't think I need a billet, but I'd like to hear your thoughts on which way to go?

[Adger Smith]

Ron,
You only need enough volume to overcome the required flow of your clearances.
This Melling might be a good choice for you: 10774
10774Standard volume performance upgrade for M-77.
The housing and cover are CNC machined and phosphate coated.
The lower pressure spring is included to reduce pressure if desired.
Includes intermediate shaft with steel guide.
Uses 3/4” press in screen.

[Ron Gusack]

My current pump uses the cap as the pickup and returns the bypass oil to the pan, which has always seemed like a good thing to me. That Melling doesn't look like it has the grooves in the cap and wall of the body. Is anti cavitation over rated? Somewhere around here I have detailed info on how to drill the cap to get the bypass oil straight back to the pan, but I haven't been able to find it. Is it not necessary?

[Signman]

Ron PM sent

[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.

[Alan Roehrich]

I switched to Clay Valley Racing pumps. The last Schumann pumps I bought did not look nearly as good as they once did, which saddens me, as they had a really nice product for a reasonable price.

[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.