1981 C3 Catalytic Converter - Going Gold

[Michael H.]

My Original Existing Converter #8999338 Has Small Holes And Has Scpraped The Ground No Major Gash.....i Have A Gm Ac Replacement Kit New Part Number 25056672. Can The Old Unit Be Repaired? What Type Of Deductions Will The Replacement Part Give Me?

[Edward J.]

Re: 1981 C3 Catalytic Converter - Going Gold

Mike, years ago there use to be a replacement sheilding for those style convertors, if thats all thats destroyed, the shell its self of coarse is the whole convertor, maybe Joe L. will chime in ,and he can tell you if its still avaliable.there are also companys that use to refurbish them, but being its so old they may not do those styles anymore.

[Jack H.]

Re: 1981 C3 Catalytic Converter - Going Gold

The judging assessment process is pretty straight forward. Compare the service replacement part to the factory original using a 5-axis universe: Finish, Date (if applicable), Installation, Configuration and Completeness.

To the extent the replacement part differs from the original, deduct 20% of the available originality points for each of the axis considerations that differences can be seen.

[Michael H.]

Re: 1981 C3 Catalytic Converter - Going Gold

Mike, years ago there use to be a replacement sheilding for those style convertors, if thats all thats destroyed, the shell its self of coarse is the whole convertor, maybe Joe L. will chime in ,and he can tell you if its still avaliable.there are also companys that use to refurbish them, but being its so old they may not do those styles anymore.

Thank You Ed, The damage is on the unit it self. The replacement came with upper and lower replacement media and plugs. It looks identical except for part number stampings.

P.S. Thank you for your photo attachment Fantastic 1972!

Mike

[Michael H.]

Re: 1981 C3 Catalytic Converter - Going Gold

The judging assessment process is pretty straight forward. Compare the service replacement part to the factory original using a 5-axis universe: Finish, Date (if applicable), Installation, Configuration and Completeness.

To the extent the replacement part differs from the original, deduct 20% of the available originality points for each of the axis considerations that differences can be seen.

I'm glad I was good in math....The original is not in great shape and the replacement looks identical (although i was not good at the picture game whats different here) except for part number stamping.

[Edward J.]

Re: 1981 C3 Catalytic Converter - Going Gold

Mike, don't get rid of the origianl convertor, save it as the shell can be repaired by mig welding a repair plate to the area damaged, and if the media is still inside sometimes the media gets blown out with holes If its the judging points your looking for the original is the way to go.

If the sheild is still on the convertor and theres a leak Ive seen the shells crack, and thats a easy fix. if rusts the issue then welding a repair plate maybe the fix.

Is the replacemnet convertor part# on the top half of the convertor? if so this would make it hard to see it. which if everthing else is correct , you may not see a deduct.

[Michael H.]

Re: 1981 C3 Catalytic Converter - Going Gold

Mike, don't get rid of the origianl convertor, save it as the shell can be repaired by mig welding a repair plate to the area damaged, and if the media is still inside sometimes the media gets blown out with holes If its the judging points your looking for the original is the way to go.

If the sheild is still on the convertor and theres a leak Ive seen the shells crack, and thats a easy fix. if rusts the issue then welding a repair plate maybe the fix.

Is the replacemnet convertor part# on the top half of the convertor? if so this would make it hard to see it. which if everthing else is correct , you may not see a deduct.

Great Ideas - Going to cleanup existing...Thanks Mike

[Michael W.]

Re: 1981 C3 Catalytic Converter - Going Gold

How much of the converter can actually be seen during judging? Keep in mind that the car is sitting on the ground (maybe grass) and the average weight, height and eyesight of most judges .

[Joe L.]

Re: 1981 C3 Catalytic Converter - Going Gold

My Original Existing Converter #8999338 Has Small Holes And Has Scpraped The Ground No Major Gash.....i Have A Gm Ac Replacement Kit New Part Number 25056672. Can The Old Unit Be Repaired? What Type Of Deductions Will The Replacement Part Give Me?

Michael------


GM #8999338 was the original SERVICE catalytic converter applicable to your car. The original PRODUCTION converter was GM #8999579, although the SERVICE and PRODUCTION converters might be identical in all respects.

GM #8999338 was discontinued from SERVICE in July, 1983 and replaced by GM #8999035. The latter was discontinued without supercession in April, 1994.

I don't know what a GM #25056672 is applicable to, but I can't find any indication that it's applicable to a 1981 Corvette. It is listed as a catalytic converter but it was discontinued without supercession in August, 1993. It was applicable to some Chevrolet application, though. The strange thing is that, when it was available, it sold for about 1/4 as much as most other converters at that time. Although it's not shown as a "repair kit", if it actually was a repair kit, it's not one that I show as being applicable to an 81 Corvette.

Might it work for your application? I don't know.

As far as a repair for your existing converter, you might try Kansas City Converters (www.kansascityconverters.com). They can rebuild and repair original converters.

I hope you don't live in California, though. In California, as of 1/1/09, if a catalytic converter for ANY pre-OBD-II (i.e. pre-1996) application is replaced, it must be replaced with an OBD-II certified converter. It's not even legal to install an NOS converter on such a car and any repair shop regulated by the Bureau of Automotive Repair (which includes all repair shops in the state) cannot legally and likely will not install any non-approved converter. All approved converters for pre-OBD-II applications must be OBD-II certified and clearly show an embossed "Executive Order" number.

[Jake D.]

Re: 1981 C3 Catalytic Converter - Going Gold

Shortly after we took delivery (Feb 10, '81) of our "81 four speed car, there was a recall on the convertor. I went down to the Chevy dealer we bought it from (Bill Jacobs in Joliet, Ill.) and asked to be allowed to do the change myself. The parts guy said, "sure, just bring me the old one". He gave me a new convertor and some clamps that were in a "kit" and sent me on my way. I installed the convertor, and returned the old one to the dealer. I think there was a bulletin on this recall, if anyone has a way to check it out. What the numbers were, I don't know, and the car is long gone.

[Edward J.]

Re: 1981 C3 Catalytic Converter - Going Gold

Jake, GM did have a recall on there convertors in or around late 81 in involed quite a few cars not just the corvette, in he beginning they may have been replacing them but lator on we took the upper and lower plugs out of the convertors and measured the contents and swiffed through it to removed the powdery residue that was clogging the convertors up.and installed the correct measurement of pellets.

I was a chevrolet mechanic at that time and I remember doing his recall to many cars.

[Michael H.]

Re: 1981 C3 Catalytic Converter - Going Gold

Shortly after we took delivery (Feb 10, '81) of our "81 four speed car, there was a recall on the convertor. I went down to the Chevy dealer we bought it from (Bill Jacobs in Joliet, Ill.) and asked to be allowed to do the change myself. The parts guy said, "sure, just bring me the old one". He gave me a new convertor and some clamps that were in a "kit" and sent me on my way. I installed the convertor, and returned the old one to the dealer. I think there was a bulletin on this recall, if anyone has a way to check it out. What the numbers were, I don't know, and the car is long gone.

Thanks Jake, Great info.... Do you know anything about concrete? Just asking we have a contractor in the area (Chicago) with your last name that is a good concrete contractor.

[Michael H.]

Re: 1981 C3 Catalytic Converter - Going Gold

Michael------


GM #8999338 was the original SERVICE catalytic converter applicable to your car. The original PRODUCTION converter was GM #8999579, although the SERVICE and PRODUCTION converters might be identical in all respects.

GM #8999338 was discontinued from SERVICE in July, 1983 and replaced by GM #8999035. The latter was discontinued without supercession in April, 1994.

I don't know what a GM #25056672 is applicable to, but I can't find any indication that it's applicable to a 1981 Corvette. It is listed as a catalytic converter but it was discontinued without supercession in August, 1993. It was applicable to some Chevrolet application, though. The strange thing is that, when it was available, it sold for about 1/4 as much as most other converters at that time. Although it's not shown as a "repair kit", if it actually was a repair kit, it's not one that I show as being applicable to an 81 Corvette.

Might it work for your application? I don't know.

As far as a repair for your existing converter, you might try Kansas City Converters (www.kansascityconverters.com). They can rebuild and repair original converters.

I hope you don't live in California, though. In California, as of 1/1/09, if a catalytic converter for ANY pre-OBD-II (i.e. pre-1996) application is replaced, it must be replaced with an OBD-II certified converter. It's not even legal to install an NOS converter on such a car and any repair shop regulated by the Bureau of Automotive Repair (which includes all repair shops in the state) cannot legally and likely will not install any non-approved converter. All approved converters for pre-OBD-II applications must be OBD-II certified and clearly show an embossed "Executive Order" number.

Joe you are the Sultan of numbers! Thank you for your time. I will be calling Kansascity Converters. I think the converter kit may have been for other GM products. It came from a guy who's Uncle had an 1981 but never installed it then passed on and left in basement. Probably did not work???

[Tom B.]

Re: 1981 C3 Catalytic Converter - Going Gold

Shortly after we took delivery (Feb 10, '81) of our "81 four speed car, there was a recall on the convertor. I went down to the Chevy dealer we bought it from (Bill Jacobs in Joliet, Ill.) and asked to be allowed to do the change myself. The parts guy said, "sure, just bring me the old one". He gave me a new convertor and some clamps that were in a "kit" and sent me on my way. I installed the convertor, and returned the old one to the dealer. I think there was a bulletin on this recall, if anyone has a way to check it out. What the numbers were, I don't know, and the car is long gone.

You are absolutely right. I changed the converter myself on this recall also. In fact I put one of those test tubes on it when I took the converter off several months before the recall. It was also a few years after the recall before I got around to putting the new converter on. I'm sure I still have the paperwork around here someplace for the recall. I never throw anything away that relates to the '81.

Tom

[Michael H.]

Re: 1981 C3 Catalytic Converter - Going Gold

Long Time still looking for a 1981 Converter. I tried Kansas City But apparently they have gone out of business.....Bummer! I have been searching and ran across a company called Smithcat. Called a week ago told me they could rebuild to OEM except for stamped part number. After driving 100 miles to drop it off they told me they did not think they could rebuild it. So back to the search for gold.