Oil filter bypass valve

[David L.]

Re: Oil filter bypass valve

Based on my research the adapter with casting "3959104" is GM part number 3951626 and is used with 2 bolts, GM # 3951644
(5/16"-18 X 1 1/8"). GM # 3951626 is listed in my 1970 Chevrolet Parts catalog (Oct. 1970) for 1968 Chevrolet Police models.

Dave

[Joe L.]

Re: Oil filter bypass valve

Based on my research the adapter with casting "3959104" is GM part number 3951626 and is used with 2 bolts, GM # 3951644
(5/16"-18 X 1 1/8"). GM # 3951626 is listed in my 1970 Chevrolet Parts catalog (Oct. 1970) for 1968 Chevrolet Police models.

Dave

Dave------


I believe the GM #3951626 valve was used on blocks designed for a spin-on filter to allow them to use a canister-type filter. I was previously unaware, though, that it carried the 3959104 casting number. For some reason, after the introduction of blocks designed for spin-on filters, there were some applications for which GM continued to use canister-type filters but not with blocks designed for canister filters. Among these were some trucks, taxis and police cars. I've never understood the rationale behind this. However, that did not last too long as in a few years all were converted to spin-on.

The 3951644 (cast 3959104) was also supplied with kits to convert blocks designed for spin-on filters to canister-style filters. The interesting thing is that the kits mostly contained AC Division components (with AC Division part numbers) which were otherwise available separately in SERVICE. The exception was the 3951644 (cast 3959104) which has a Chevrolet part number. The AC Division must not have wanted to get involved in this, probably because the manufacturing volume was too low. So. Chevrolet likely out-sourced this to some other manufacturer.

The GM #3951644 was never cataloged by GM as a replacement for the valves used on pre-1968 engines.

[Peter T.]

Re: Oil filter bypass valve

Thanks Larry and Joe
I just ordered a reproduction bypass valve from Paragon. I got an original, "reconditioned" oil can from Paragon which comes with a filter. I'll have to see what brand it is. I always use Wix filters on our other vehicles. Thanks for the 'startup' procedure.
Pete Terry

[Peter T.]

Re: Oil filter bypass valve

Joe,
Awesum research Joe,

Pete

[Ken A.]

Re: Oil filter bypass valve

Why so much discussion for a part designed for taxicabs & dump trucks that doesn't belong on a Corvette?

[Gary B.]

Re: Oil filter bypass valve

Ken,

Because that's what we do and are good at!

Gary

[David L.]

Re: Oil filter bypass valve

Ken,

Because that's what we do and are good at!

Gary

I agree!......After researching Corvette and Chevrolet parts for almost 4 decades I think that I may be addicted......at least that what my wife and friends tell me.

Dave

[Jeff B.]

Re: Oil filter bypass valve

Should the bypass valve even be replaced in routine servicing? What is the downside (if any) if the spring loses tension?

[Ken A.]

Re: Oil filter bypass valve

Should the bypass valve even be replaced in routine servicing? What is the downside (if any) if the spring loses tension?

Disaster, no oil being filtered!