differentiating between sb and bb oil pump

[Paul J.]

Rebuilding 230hp '61. I bought a Melling M55 oil pump and the old pump is larger than the M55. Old one is larger, has tag 99HVS, pickup hole is 3/4"and faces toward front of engine. Pickup curves to right side (engine upside down)and up. M55 has 5/8" hole on right side of pump (engine upside down) so my pickup does not fit. Is the M55 the proper arrangement and I need to get a different pickup? Is my old one for a bb?
Paul

[Joe L.]

Re: differentiating between sb and bb oil pump

Paul-----

I don't know what a "99HVS" is. However, I'm quite sure that the "HVS" denotes a high volume pump. High volume oil pumps were NEVER used in PRODUCTION for any small block Chevrolet engine, and I don't recommend their use. High volume pumps have a somewhat larger main body than standard volume pumps due to the longer gears. So, that may be what you are referring to as far as the existing pump being larger than the new M-55. Big block pumps can be adapted to small blocks, but I doubt that's what you have. It's easy to distinguish most small block pumps from big block. The small block pumps have a cover retained by FOUR bolts. Most big block pumps have a cover retained by FIVE bolts.

The M-55 is the correct Melling pump for your application. Assuming that you are using a stock oil pan, the oil pump pick-up screen you need is a GM #3764113 which is still available from GM for about 18 bucks, GM list. You can also use a Melling 55-S pick-up screen.

[Paul J.]

differentiating between sb and bb oil pump

Thanks Joe, that is the exact information I was interested in.

[Paul J.]

differentiating between sb and bb oil pump

Just a follow up on the old pump. It has a 5 bolt cover but maybe that is needed because of the longer gears.