One of my winter projects included changing the oil pan on my 383. While I was at it, I changed the HV pump to a standard M55 Melling with the GM ZZ4 spring.

With 200°F coolant on a 100° day, it idles in gear at 600 rpm with 30 psi using 30wt valvoline. It makes 50 psi @ 1,000 rpm and 55-60 psi above 1,500 rpm.

Bearing clearances were good, but not ideal, running 0.0025"-0.030" on the mains with 0.0022"-0.0025" on the rods. For what it's worth, rod side clearances were 0.012"-0.015".

The HV pump using a stock 40 psi spring made 60 psi at 3,000 rpm and kept climbing with engine speed.

Add me to the long list of those that can say with confidence that HV pumps ARE NOT needed.

So noted.

SO what was wrong with the high volume pump? To much pressure? I've got one that's been in for four years now without any trouble, low pressure spring.

I just replaced one myself. It was loosing and gaining pressure after warm up. Oil pressure would drop to 20 then jump to 60 and on and on. the bypass showed some ware but that was it.

whats the consensus on HV pumps when using roller lifters? Crower specifically with the high pressure pin oiling? I may be old school,but I still lean towards HV pumps.

Originally posted by baddbob71:
SO what was wrong with the high volume pump? To much pressure? I've got one that's been in for four years now without any trouble, low pressure spring. I suppose HV pumps may still have a place in some limited applications. However, my relatively docile hydraulic flat tapped cammed 383 is not one of them.

In Bill Jenkins book, he recommends using a standard pump with 55-60 psi hot oil pressure. If I recall, he was running close to 2 hp/ci and 9,000+ rpm. He implemented some simple modifications to the standard volume pump, one being to drill out the bypass to a larger size and replace the soft plug with a threaded pipe plug. He stated this was necessary to reduce the velocity of oil in the bypass back to the main body of the pump. This was necessary to reduce vibrations that could migrate up the distributor shaft and contribute to spark scatter.

I think there is some merit in Grumpy's logic. A guy over on the Nova site recently posted a pic of a wasted oil pump drive shaft that came from his bone stock 350'78 caprice wagon. He used a HV pump with the 40 psi spring with the stock drive shaft and nylon retainer. This engine likely never saw the high side of 2,500 rpm during its 80,000 mile life. He is a reputable automotive engineer and concluded that the oil pressure bypass-related vibrations wiped the shaft.

I honestly thought I'd lose some idle oil pressure, but so far it seems unaffected. The gear-to-cover end clearance was a perfect 0.0025". I understand that the low-speed performance of these pumps suffers considerebly when this clearance is greater. I never checked the clearance of the HV pump.

Whats the address of the nova site?

Originally posted by Nickel333:
Whats the address of the nova site? http://stevesnovasite.com/forums/