MACDAD260

Mike, I think you are on the right track with the oil bypass being stuck open or way to weak. Who knows why it is different this year. Maybe the spring just broke or something stupid like that. Try the adapter with the bypass plugged and see what happens. Use a Wix or AC filter for a Chevy V8 and you should be safe. They have a built in spring loaded bypass. Good Luck!

Cord

GregP

I know the large "2 quart" filters by for Chevy by AC, Fram, K&N (and I'd bet the others) do not have a bypass. I'm pretty sure "no" Chevy filters does, but most Ford and Mopar applications do. I havn't cut open the small filters, but have done lots of the big ones and none had a bypass.

-Greg)

Audiofn

Greg P does that mean that they filter has the bypass? Not the engine? I am sooooo confused!!!!

GregP

Audiofn -

Sticking my neck out on the limb ....

Chevy V8 engines have the bypass in the filter adapter that bolts to the block. Merc (at least) puts a bypass in their "remote filter adapter" block that replaces the auto style filter adapter on the block. As such, GM oil filters don't have a bypass in the filter canister.

Ford engines do not have a bypass in the block or the (auto) filter mounting housing, it is in the filter canister itself.

I "think" Chrysler V-8's follow the Ford approach and spec a bypass in the filter canister.

Chevy uses a different thread size (13/16 I think) than Ford and Chrysler, so filters made for a Chevy won't have a bypass in them (they don't need it), while filters made for Ford/Chrysler applications will have a bypass, as that was part of the factory spec for their filters.

All of this my change for "racing" application filters. I know my System 1 filters (which have adapter bushings so they can fit racing, Chevy, Ford and Chrysler filter mounts) do have a bypass in them.

Hope that is at least as clear as the mud at the bottom of my creek

-Greg

MACDAD260

I don't know about the 2 quart filters but, the 1/2 & 1 quart Wix and AC filters DO have a bypass. It is just a spring between the bottom of the filter element and the canister. If the oil cannot pass through the filter element the pressure build up pushes the element against the spring. The spring allows the element to move and the top of the element is no longer sealed against the metal top of the filter where the oil goes in (the outside holes) and comes out (the center hole). The oil will take the path of least resistance and go to the return side, unfiltered. Once the oil pressure is low enough the spring pushes the element back against the seal and the oil is forced through the element and is filtered. It is my understanding that on a Fram filter there is no spring, just a crush sleeve. Once this sleeve is crushed only unfiltered oil comes out since there is no resistance to force the oil through the element. I use AC PF25 or Wix 51069 filters on my riser mounted remote filter housing with the bottom of the filter pointing down. Some filters also have an anti-drainback feature as well. That is the rubber seal that is under the inlet holes. It acts as a one-way valve so unfiltered oil and the dirt trapped by the filter cannot drain back into the engine when it is shut off. That type of filter should be used when the filter is mounted sideways or upside down. The Quicksilver filters have both a bypass and an anti-drainback valve. I think an AC1218 also has both features, however the PF25 &PF35 do not have the anti-drainback valve. You can easily check for a spring type bypass by inserting a dowel into the center of the filter and pushing down. It will move and then return back if it has a spring. I just checked both the Wix and Quicksilver filters for this and they both are spring loaded. I don't have a new AC filter on hand to check but, the AC Filter catalog explains this feature and has a cut-away drawing.

Hope this clears things up. Doug

fred

Thanks for the info...I feel better with my Wix filters.....Fred

GregP

Doug,

You may be right on the small filters, I never ran them. I do know the big ones stop oil flow completly when the element swells, chased a problem for a year of oil filters simply stopping all oil flow.

Do you have a link to the cutaway you talked about? I'd like to see it, as since the oil enters the outside of the filter element, I don't see how high pressure on the outside could possibly "push the element down" to open a bypass. It would make sense if the oil flowed from inside to outside, but it doesn't.

-Greg