496 oil pumps

[ka0tyk]

What’s a good pump? Worthwhile to go hv or hp? I’ve heard of people changing springs and welding the tube on etc. Just looking to add a little more pressure at idle, I’m getting about 25 right now and I don’t know how old the pump is or what it is.

 

[obnoxious001]

Several things can and will affect oil pressure (which is basically a measured back pressure. Bearing clearance, weight of oil, and the oil pump to name a few. Other things can be loose fitting lifters. Sometimes the bypass plunger can stick, and for that reason I disassemble all new pumps to check them out, including making sure the plunger travels freely.

I normally run high volume pumps on most everything high performance, and bearing clearances to suit heavier weight oils. Out of the box the 77HV Melling pump has a good spring in it. Your pickup needs to be securely fastened, either to the pump or main cap with a bolt on bracket, or by welding. If you weld it yourself, or have it done, it needs to be done carefully to keep any welding debris out of the pump, and no semi loose balls of weld that can come off later into the oil pan. Other than just some spot welds, it should probably be pre-heated, and then when the welding is complete the temperature needs to be brought down slowly.

You many want to dump some STP into the oil right now and see if pressure comes up. 1 bottle of STP per 5 qts may bring it up about 10 psi, just to help understand the problem. If you are using a lightweight oil, you could step it up a notch and see what happens too, same sort of idea. What kind of oil temperature are you running? I don't like seeing oil pressure that low, but years ago my turbo engine would drop like that after running. When my oil pan developed a leak I pulled the engine and shimmed the spring, but the more modern Melling pumps should not require shims.

 

[Lavey 29]

Shark tooth Melling or Schumann oil pumps.