ZR-1 Oil Filters

[James W.]

I have been researching the correct oil filter for ZR-1s. I own a 90 with 14xxx miles and the JM shows a PF970, black label, no "Duraguard" and was used in 90 to 91. My understanding was that in 92 (maybe 93) the filter went to a PF970C that had "Duraguard" on the label, no barcode. Marc Haibeck's site (zr1specialist) notes that this filter was factory-installed on his 93. I have gotten other information, however, that later model ZR-1s also came with the PF970. Sooooooooooooooooooooo, I don't have all the judging manuals for the Zs and would like an informed answer from the gurus here.

Thanks for the time

Jim

[Joe L.]

Re: ZR-1 Oil Filters

I have been researching the correct oil filter for ZR-1s. I own a 90 with 14xxx miles and the JM shows a PF970, black label, no "Duraguard" and was used in 90 to 91. My understanding was that in 92 (maybe 93) the filter went to a PF970C that had "Duraguard" on the label, no barcode. Marc Haibeck's site (zr1specialist) notes that this filter was factory-installed on his 93. I have gotten other information, however, that later model ZR-1s also came with the PF970. Sooooooooooooooooooooo, I don't have all the judging manuals for the Zs and would like an informed answer from the gurus here.

Thanks for the time

Jim

Jim----


1990 Corvettes with ZR-1 used oil filter AC PF-970. This filter was painted black but only for PRODUCTION-LINE installed filters. In those days, the black-painted oil filters were used to later provide a visual "cue" that an oil filter might never have been changed (e.g. if there was a warranty issue). The filters did use a label which I believe had black printing on a silver background. I don't think the "Duraguard" was found on these labels.

I do not think that SERVICE AC PF-970 filters were ever available in any color other than blue. The labels were also different than those used on PRODUCTION filters.

For the 1991 model year, or at least sometime during the 1991 model year, the filter changed to the AC PF-970C. This filter was painted black in both PRODUCTION and SERVICE and I believe the labels were the same although they may have varied over the 91-95 period.

So, what's the difference between a PF-970 and a PF-970C? I don't know. I used to know what the "C" suffix denoted but I've forgotten it.

Below are pictured a SERVICE PF-970 filter from 1982 and a SERVICE PF-970C filter from 1992. The label on the PF-970 is different than any label ever used on a ZR-1 Corvette; this style label was long gone by the time the first ZR-1 was built, but the filter is otherwise the same as the SERVICE PF-970 filters once available for 1990 Corvette ZR-1's.

So, why was a PF-970 available in 1982 if the ZR-1 was still 8 years away? Well, the PF-970 had other applications. Its first application was 1982 Chevrolet Chevettes with 1.8L diesel engines. Later, it accumulated many more applications, all diesels except the Corvette ZR-1.

Also, the PF-970C replaced the PF-970 for SERVICE of 1990 Corvette ZR-1's.

[James W.]

Re: ZR-1 Oil Filters

Joe,

Thanks for the definitive reply. Marc Haiback did an article on filters where he cut them open, counted pleats, filtration surface and evaluated the drainback, as these cars can have an issue with tensioner chain rattle, if the wrong filter was used. For every day use it seemed the Bosch 3401 was best, with the Mobil1 close behind. I just wanted to know what was supposed to be on my engine, even though I can't find a PF-970, I can find a PF970C (with Duraguard on it). Probably won't get me any more points than a current GM service filter.

Thanks again

Jim

[Tom H.]

Re: ZR-1 Oil Filters

Can't remember for certain, but wasn't the "C" for the filters with the Check Valve ??

[Joe R.]

Re: ZR-1 Oil Filters

Tom,

Give that man a "STAR"!

Yep, the early ZR-1's had a little problem with noise and the PF-970C cured the problem (sometimes).

The filter on the ZR-1 is upside down on the top of the motor and when shut down the oil ran back to the pan. You just gotta have a filter with a one way valve when you drive a ZR-1.

MOST ZR-1 owners knew about the problem early and jumped for other filters on the market with the valve.

JR

[Tom H.]

Re: ZR-1 Oil Filters

Yep ! I remember the upside down filter well !! We sold as many ZR1's as anyone in the USA back in the day. I was one of the early registry members and was there in April of 95 when the last one rolled off the line. The ZR1 was one of my all time favorite Corvettes.

[Joe L.]

Re: ZR-1 Oil Filters

Can't remember for certain, but wasn't the "C" for the filters with the Check Valve ??

Tom-----


It's possible. However, there are several things that would make it puzzling.

First, I believe that the PF-970 does have a check valve (i.e. anti-drain back valve). In fact, I think I've seen some tests in the past which indicated that the valve in the PF-970 worked better and more reliably than the valve in the PF-970C.

Second, there are quite a few AC parts lines that use the "C" suffix for part numbers. Among them, many PCV valves (but not all) use the "C" suffix (e.g. AC CV736C, AC CV746C). Many air filter elements (but not all) also use the "C" suffix (e.g. AC 98C, AC 350C, AC 163C).

Third, there are many current oil filter models that use an anti-drain back valve but use no "C" suffix. For example, the PF-52, PF-1218, PF-44, and PF-48 all have anti drain back valves, but none use the "C" suffix.

Of course, it's possible that the "C" suffix represents different things for the different types of products. However, it seems sort of unlikely to me.

[Joe L.]

Re: ZR-1 Oil Filters

Joe,

Thanks for the definitive reply. Marc Haiback did an article on filters where he cut them open, counted pleats, filtration surface and evaluated the drainback, as these cars can have an issue with tensioner chain rattle, if the wrong filter was used. For every day use it seemed the Bosch 3401 was best, with the Mobil1 close behind. I just wanted to know what was supposed to be on my engine, even though I can't find a PF-970, I can find a PF970C (with Duraguard on it). Probably won't get me any more points than a current GM service filter.

Thanks again

Jim

Jim-----


I believe the current version of the PF-970C (which is blue) is also shorter than the the original PF-970 or PF-970C. The originals are right at 4-1/4" long.

[James W.]

Re: ZR-1 Oil Filters

Joe/Tom,

The PF970Cs I have are black and the longer can. referring to Marc's site again, he indicates the check valve in the PF970C does not work as well as the PF970, which is why he recommends either Bosch or Mobil1. The Wix filters also come in well. Makes you wonder what the General had in mind sometimes.

Jim

[James W.]

Re: ZR-1 Oil Filters

BTW, if anyone wants to read Marc's article on oil filters it is posted ot his web site - zr1specialist.cim. The information pertains to all oil filters, not just those for ZR-1's

Jim

[Joe L.]

Re: ZR-1 Oil Filters

Joe/Tom,

The PF970Cs I have are black and the longer can. referring to Marc's site again, he indicates the check valve in the PF970C does not work as well as the PF970, which is why he recommends either Bosch or Mobil1. The Wix filters also come in well. Makes you wonder what the General had in mind sometimes.

Jim

Jim-----


I thought I had read somewhere that the PF970C valve did not work as well as the PF970. Maybe the site you mention is where I read it but I don't ever recall going to that site. So, maybe it says the same thing somewhere else, too.

If your interest in the filters is strictly functional and not correct configuration, I think any of the filters will work ok. However, if correctness of configuration is important to you, the AC Delco and the Bosch, even if they are not of original length, are the only ones that have the "flutes" around the end. The Wix and Mobil 1 do not have the "flutes".

[Joan W.]

Re: ZR-1 Oil Filters

I have a '92 ZR-1 and want to know if the thumbnail picture posted by Joe Lucia in post #2 is correct for my application. The Judging Guide states "Original filters do not have the word DURAGUARD or bar codes." Since this black filter says DURAGUARD I assume this would be incorrect. Can someone post a picture of an orginal oil filter for my application?

[Joe L.]

Re: ZR-1 Oil Filters

I have a '92 ZR-1 and want to know if the thumbnail picture posted by Joe Lucia in post #2 is correct for my application. The Judging Guide states "Original filters do not have the word DURAGUARD or bar codes." Since this black filter says DURAGUARD I assume this would be incorrect. Can someone post a picture of an orginal oil filter for my application?

Joan-----


I can tell you this: the PF970C oil filter I previously posted a picture of was manufactured in 1992. Was a filter with the exact same label used on some or all 1992 LT5's? I don't know. However, I do think the "Duraguard" tradename was being used in 1992. I still have the original PF-51 oil filter from my original owner 1992 LT1. I have it around here but I couldn't find it at the moment. My recollection is that the "Duraguard" was on it but I'm not 100% sure.