HighHopes85

Just wanted to let people know that AC Delco seems to have changed some numbers around.

The previous filter known as the PF25 may now appear as a PF454.

The previous filter known as PF35 may soon be 'filtered out' and replaced with PF1218S.

The PF25/PF454 is still the smaller of the 2 filters. Using a tape measure, I esitmated their volume to be just over a half quart.

The PF35/PF1218S is still the larger of the two filters. I estimate their volume to be just under 1 quart.

FYI, -85Y

SWCDuke

Other than the smaller physical size, the PF 454 has a built in anti-drainback valve (The PF25 does not) , which is not an issue with a vertical filter mount (pad on top) like most vintage Chevy V-8s, but it's quite useful for horizontal or "upside down" mounts that can allow oil to drain back to the sump without the anti-drainback valve. I've already started using it on my Cosworth Vega, which is a horizontal mount.

The size difference between the 25 and 454 does not necessarily mean the 454 has less filter area. Filter capacity (particles) and pressure drop across the media depends a lot on the internal design of the pleating.

The primary application for the PF454 is the late model 8.1L medium duty truck engine, so if it has enough capacity and efficiency for a large commercial truck engine, it should be adequate for our cars.

Duke

NASCAR314

I have seen a AC "PF35L" filter for heavy duty truck applications, the filter is much longer than the PF35, probably 2-3" longer. Catolog list it for GMC pick-ups big-block motors as an optional filter.

Is this number changing?

Thanks,
Tom

clem zahrobsky

PF-35L are the same length as PF-35 the only difference is the type of filter media used. a lot of the new AC filter now have a anti drain back valve to prevent the filter from emptying out if not mounted with the open end up. :chevy


[Modified by clem zahrobsky, 12:39 PM 3/28/2003]

71coupe

Actually, the PF35L is slightly smaller than the regular PF35.
Are they still selling the 'L's?

clem zahrobsky

i have both the 35 and the 35L on the shelf and they are the same in every dimention and yes they still are available thru AC delco. :chevy

black bart

I have been using the 35L it cost more than a 35. I ask why the difference in the price and was told that the 35L filtered better than a 35 :rolleyes:

clem zahrobsky

the 35 L has synthetic media filter material. since water will not swell the pores smaller compared to paper in std filter it can filter to a finer level. years ago i built a all alumimum BBC for a racer that had a cheap after market block. this block leaked water into the oil and would cause the paper oil filter to swell closed and since the oil filter bypass valve was blocked the oil pressure would fall from 70# to 30# by the end if ther nite of racing. the next day the ower would drain out about a pint of water from the oil. using a 35L filter the oil pressure would not change even though the water was still getting into the oil. :chevy


[Modified by clem zahrobsky, 10:02 PM 3/29/2003]

pablocruise

ahhhh! Excellent info. Thank you! Just last night, I went to the autozone for oil and filter and was "wth? 454?" I also use the 35 longer one on my C4. They only get very minimal scrapes from the road. Very minimal.

66427-450

After a ton of research, I went with the long screw-on Mobil 1 filter for my new BBC replacement engine, it cost's a couple bucks more...... but looks, on paper, to be well worth it (it came down to the Mobil 1 or the K&N, and I can get the Mobil 1 filters at auto zone). I can't see spending 9-10K$ on an engine, then going with an inferior filter because it's 5$ less.

PS: sounds like AC made a hi-perf/premium filter, but discontinued it recently

arnold

Actually Clem, doesn't the anti drainback valve help even if the filter is mounted in a vertical position, by preventing the block oil passages from draining?

SWCDuke

Only if the filter is mounted "upside down" or horizontally. In the case of the old Chevy V-8s, the filter is mounted vertically with the pad on top, and the oil can't drain back, so an anti-drainback valve has no effect.

Duke

arnold

Filter orientation has little to do with the need for, or help from an anti drainback valve, although a non vertical filter orientation would be a worse situation. Oil is gonna drain out of the block/crank passages regardless of how the filter is orientated. Gotta disagree with you on this one.