AC917C Date Code

[Floyd B.]

This is a picture of the air filter element from a low miles '98 pace car. I'm pretty sure it is the original filter. I'm assuming the part I've outlined in red is a date code. Perhaps:

7 = 1997
M = December
27 = Date (27th)
N = maybe a location of plant code?

Build date of car is Feb 18, 1998.

[Pete B.]

Re: AC917C Date Code

Floyd... You are on to something.
We have randomly seen what appears to be dates that work, but then there are ones that make no sense.
We have theorized that there may have been several plants that supplied the OE filters.
My 10k mile 99 has the date coding that matches build.
But then my 02 Z06 does not make any sense.
We look for the Grey rubber gasket material and the yellow filter media with the dimples as are in your photo.
Minor deductions for excessive dirt... but don't go trying to clean it.

[Pat F.]

Re: AC917C Date Code

Folks, the late C4 guys have determined that the area you pointed out in red is in fact a date code.
The information has been sent to Tom Barr about research that has been done in this area. It will probably be included in the first revised Judging Manual that date codes are applicable for the C4.
The question I have for this date code is that M is the 13th character. If it was a December date code issue the letter would have been L instead of M.
However, we do not have enough information to make this a positive statement as one of the alphabet letters could have been deleted in AC's date coding. I have seen and have photos of other air filters with the letter M.
Concerning the final letter, D-maybe for day shift and N-maybe for night shift or it could be for a plant designation like on the windows. Again, I have photos of numerous air filters with date codes. The C4, up until around 1993 did not have the date code.
Any comments would be appreciated

[Floyd B.]

Re: AC917C Date Code

The question I have for this date code is that M is the 13th character. If it was a December date code issue the letter would have been L instead of M.

Pat,

As you're probably aware, many of the GM date coding systems eliminate "I" due to its confusion with "1". That is why I assumed M = Dec. However, my speculation is no better than anyone else's.

Thanx

[Pat F.]

Re: AC917C Date Code

Floyd, I agree with you 100%. We thought that that was the reason for the M character indicating the month of December, but we do not have a strong enough data base to make a positive statement.
From what you have displayed the air filter fits perfectly for a February 1998 Build.
The 1993 and prior used ACSPARKPLUG . These did not have the date code. The later air filters for the C4 were AC Rochester.
I am attaching some examples for you.

[Chris G.]

Re: AC917C Date Code

Anyone know the date tolerance on the air filter? A 95 with a 10/94 build date could have and air filter dated what month +/- ? Thanks

[Ed H.]

Re: AC917C Date Code

I would find out the date code of my AC Delco 1097C bearing the numbers and letters (4J17N). I used it twice, one on a 93 ZR-1, and on my
90 L-98. I had no idea that a date code was included in the letters and numbers. Used it anyway.

[Chris G.]

Re: AC917C Date Code

I would find out the date code of my AC Delco 1097C bearing the numbers and letters (4J17N). I used it twice, one on a 93 ZR-1, and on my
90 L-98. I had no idea that a date code was included in the letters and numbers. Used it anyway.

I believe the correct 93 would have A/C Sparkplug on the filter without a date. I know where a new one is that hasn't been posted on line yet if you verify you need it.

[Ed H.]

Re: AC917C Date Code

Chris, thanks anyway. The last award I am going for is Founders for my 1990 at Las Vegas, then onward and upward for a new mountain.