Oil pump options and questions

[williestreet]

Starting to look into some low oil pressure issues. I am hoping it might just be a bad pressure sensor and will try to get a mechanical gauge on to confirm pressures tomorrow.
I was looking at the Melling site to review their options and they list 3 different High volume pumps.

Does anyone know the difference between the big bock style vs the small block style? They are all listed as working but does the big block style need a different oil pan ?

I haven't replaced one before. Is there anything else required to swap one out or just one of the pumps listed and the intermediate shaft they require as well?

Any advice or tips from those who may have done a High volume swap on a 305?
Thanks.

 

[Ricko1966]

There's no reason for any more pump than what gm put in it. High volume pumps are harder to turn, harder on distributor gear,cam gear, and oil pump drive. If you have low oil pressure, find the real cause. You can spin in rod and main brgs with the pan off if oil clearance is the problem.

 

[fast 99]

Standard pumps work fine. High volume pump as a repair crutches another issue. If 4x4 pan is easy to remove. Roll new main and rod bearings in. Have done that successfully on many customer vehicles. It is a bit of a gamble and messy. Only alternative is yanking the engine for o-haul.

A HV pump in a GM SB or BB my opinion has no downside. I have never seen a failure caused by that style pump. Ford SB is a different story. Recommend using a HD pump drive shaft with the steel collar not the plastic one.

If 2wd pan removal is more difficult due to clearance. Might just rebuild it depending on overall condition.