Need Application for this Oil Pump Please ===

[Bill C.]

NOS Oil pump with pickup assembly.
Part number 3946023 Group 1.652.

Also ---
part number 3860376 is cast into the oil pump.

Want to see if this is a regular pump that could be used on a LS5 engine.
Want to be sure it is not some HV-HP pump - don't need to fail the PV in Kissimmee for this.

Thanks in advance

[Joe L.]

Re: Need Application for this Oil Pump Please ===

NOS Oil pump with pickup assembly.
Part number 3946023 Group 1.652.

Also ---
part number 3860376 is cast into the oil pump.

Want to see if this is a regular pump that could be used on a LS5 engine.
Want to be sure it is not some HV-HP pump - don't need to fail the PV in Kissimmee for this.

Thanks in advance

Bill-----


I can't find much of anything on GM #3946023. It was an oil pump and it was a successor to GM #3904838 and GM #3879643. I can't find anything on those pumps, either. The GM #3879643, for which I can find no predecessor, was released in later 1965. The GM #3946023 was discontinued without supercession in July, 1968. So, this series of pumps did not have a very long life.

It may have been an over-the-counter-only pump. The fact that it was discontinued without supercession in 1968 would kind of point in that direction. I can't imagine any 1965 PRODUCTION application that would have had its oil pump discontinued without supercession in 1968.

Most of the standard and high pressure big block pumps of the day have the same pump body, internal gears and cover. The difference is in the pressure relief valves. I don't think that any high volume pumps were being manufactured by/for GM during the period that these pumps were around. My guess would be that it's either a standard pressure or high pressure pump and the reason for the hard-to-find part number involves the attached pick-up screen.

You can check the pump easily for it's pressure and volume rating. Remove the cover and take out one of the gears. Measure the length. If it's 1.15", then it's a standard volume pump; if it's 1.3", then it's a high volume pump.

To check pressure rating, remove the pressure relief spring from the cover. If it's 0.422" OD and 2.5" free length, it's the standard pressure spring. If it's 0.313" OD, 2.438" free length, and with a stripe of green dye, it's the high pressure spring.

Let us know what you find out.

[Bill C.]

Re: Need Application for this Oil Pump Please ===

Joe,

the pump is on ebay - I have to buy the pump to be able to check it out.

I would imagine, based on your technical response, that HV is unlikely, but maybe HP. That I can cure pretty easily with a spring change.

I will look into purchasing it and making the necessary adjustments.

Thank you for all of your assistance !

[Joe L.]

Re: Need Application for this Oil Pump Please ===

Joe,

the pump is on ebay - I have to buy the pump to be able to check it out.

I would imagine, based on your technical response, that HV is unlikely, but maybe HP. That I can cure pretty easily with a spring change.

I will look into purchasing it and making the necessary adjustments.

Thank you for all of your assistance !

Bill-----


I looked at the pump. From what I can see of it, it looks like a standard configuration, standard volume pump. Just like I figured, the reason for the odd-ball part number is the pick-up. The screen section of it is standard 65-74 used for most (but not all) applications. However, the TUBE SECTION is of a configuration I've never seen. I don't think it's for any sort of passenger car pan. Likely, it's some sort of truck pan configuration, possibly MD or HD truck. It's also very possible it was designed for use with a special deep sump, big block pan that was once available over-the counter but NEVER used in PRODUCTION.

As you surmise, regardless of whether it's a standard pressure or high pressure pump that can easily be changed by change of the relief spring.

I can tell you, for sure, that this pump assembly was NEVER used for a PRODUCTION L-88 application as the seller claims. The 1969 L-88 pump assembly was GM #3946026. This pump definitely had a different pick-up than the 3946023 although the remainder of the assembly might have been the same.

[Michael H.]

Re: Need Application for this Oil Pump Please ===

Bill, Joe..

If the pump has a "dropped pick-up" as you describe, it's the one designed to be used with the GM "over the counter" dropped sump oil pan for drag racing. If I remember correctly, the sump section of these pans was extended (rewelded) down about 2".
The process required two oil pans. The sump section of one was cut near the bottom and the second was cut 2" higher. The taller section was welded to the 1st pan.

I think the oil capacity was increased by a quart or two.