Hi, bought melling 10778 oil pump for my 502 gen6 project, rod bearing clearances are 0.0031", mains 1-4=0.0023", 5=0.0035", plan is to polish the 1-4 main journals to get 0.003" clearance. should i go with Std volume pump/ blue spring, instead of my 10778 25% hi-volume pump? oil pan is stock 8qt.

Jani,
You cannot polish that much off a crankshaft and still have it be straight and round. I would get a set of bearings that will give you an extra thousandth clearance and go with it. I have never had an issue using a regular Melling M77HV pump. How are you measuring the clearances ?

I've used 10778, 10778c and M77HV.. For some reason I like the M77HV the best. Pressure seems to always be consistent and what I expect to see on a build. Seems idle pressure was better.

thanks Bill, i also tought to go with clevite HX +.0001. But that would take me to 0.0033" clearance, why not if it aint too much. Measured with micrometer and bore dial gauge.

What kind of pressures you have? Spring colour? Bearing clearances? Oil?

My last engines I set mains up .0030-.0034 1-4 and rear was .0004 increased front to back, melting select HV with shimmed spring, 80 psi of pressure and ran flawless I was always told by marine guys more clearance and mire oil for endurance engines, I never had issues with them clearances

I run them a little loose. Rods 0.0028', mains 0.0030-2" Rear 0.0034", stock spring Mobil1 15w50 60-80 psi. (80 cold) I also run 140°F water and 180°F oil. (165°F oil thermostat)
Also, I am not an engine builder, this is what has worked for me.

Ok, i have exactly the same oil pump. So you shimmed the purple spring to get 80psi. What kind of pressure you see, at hot idle and Cruising speed?

What is stock 502ho/hp500, oil pump?

Get a set of the HX bearings and only use one half. You will run you standards in the lower (cap) and the HX in the block. Will gain you .0005"