When 2 years ago I rebuilt my 90 due to 8 (8!) spun bearings, I noticed during the disassembling procedure that this part (3952301 - 1968-2000 Small block 1968-1990 big block Engine Oil Filter Adapter 305,350,396,400,402,454) was with the fluctuating valve completely stuck (with the actuating spring compressed and the round little valve/plate trapped in a diagonal way in its bore.
Refer to this link to see the pic of the piece part # 3952301. http://www.paceparts.com/product.asp?0=0&1=0&3=115
I thought that a lack of oil was the cause of the spun bearings and that this stuck valve was one of the causes of this decreased oil feeding to the engine.
I bought one of this prior to start the rebuild. The car now (since the rebuild) has this adapter.
If you read the description of this part:
“This adapter mounts a spin-on cartridge oil filter on all 1968-2000 small block chevy engines Gen I and all 1968-1990 Mark IV big block engines .Not for use with 1988-2000 4x4 trucks(that used a right angle adapter) or vehicles that use an oil cooler. This adapter does not require a gasket, it mounts directly to the engine block. It contains a filter bypass valve. . Requires two attaching bolts P/N 3951644.
…seems that it is not intended to be used with car that has an oil cooler.
Hummm, my car hasn’t an oil cooler, but it has an oil cooler spacer/adapter with an out line and a return line. (I don't know if this oil cooler spacer/adapter is stock or added by the previous owner) Actually there is a rubber pipe that comes out from the out line and it return to the return line, without (in the middle) any oil cooler.
Is this part 3952301 necessary? All of us we have this part on a SBC cars? I have to remove it, in view of the fact that I have an oil cooler adapter upper the oil filter? What’s the purpose of this part with a self adjusting valve?
Thanks

 

The thing that seems like a spacer, with the "Out" and "Return" line, sounds like somebody took off the factory oil cooler that used to be there, and put an aftermarket one on it, and now it's gone too. I'd get rid of all that.

Use the other thing you bought, that you screw the oil filter onto. You don't particularly need an oil cooler. The factory oil cooler was actually as much a "warmer" as a cooler anyway; it ran coolant through a similar block that mounted there, and had lines about like heater hose to carry the coolant to it.

The bypass valve being stuck open won't directly cause low oil pressure. Its purpose is to open whenever there's too much pressure drop across the filter (cold oil, plugged up filter, or whatever), in order to allow oil to bypass the filter and flow to the bearings. Unfiltered oil is better than no oil at all. However, the valve being stuck open all the time, means that the oil didn't flow through the filter like it was supposed to; so the filter wasn't very effective, and constant dirty oil may have contributed to bearing wear; which will cause low oil pressure and spun bearings.

 

That bypass valve is necessary. 90-92, I believe had the oil cooler lines installed with that block inbetween the filter. The rubber of the hoses often leak, so some people just bypass that, the way yours is. Although, if I were going to bypass it, I'd probably just remove it altogether. Actually, the warmer the oil is, the better your engine will perform. Up to 220º is acceptable, after that, conventional oil just gets too thin. If you are using synthetic, then it is usually good to around 300º.

 

Thanks, so you suggest to remove this oil cooler adapter and retain the part with the valve?

 

Yes.