Greetings all I am finally working on car as snow is due here in Idaho. Question: The engine compartment is overheating from the Catalytic Converter (I think)....the engine is not internally hot but the rear fire wall wiring almost melted and almost caught fire from heat coming from the CC...The muffler at rear of car is cold.
Zinc additive and Sea Foam was added to engine (engine was rebuilt about 10 year ago before I bought it.... did it destroyed the CC? I am going to take the thing off myself and put on a straight pipe. Does this sound like the CC is the problem before I go through the exercise of cutting it out? I cannot take the car out of the driveway the firewall and anything above the CC gets blazing hot real fast. Engine starts perfectly well, runs great for the little time I run it. Manifolds are also looking like internal heat is building up badly, they look scorched.
Thanks for your assistance.
Blocked exhaust engine will usually run fine just won't make power and will make the the exhaust hot. Cats can easily plug up if the engine wasn't running right at some point. Don't overlook the muffler either. Original mufflers had an insulation material in em held in with a steel mesh that can rot and let the insulation plug up while still looking new on the outside.
Get did of the convertor and the stupid cast iron box in front of it that the exhaust pipes are going into. I have a 76 and put a 71-74 exhaust system with the resonator and it is free flowing and quiet and has a lot more mid range torque.
Sounds like your cat is clogged to me.
Quote from: 76eldo on December 12, 2020, 11:37:16 PM
Get did of the convertor and the stupid cast iron box in front of it that the exhaust pipes are going into. I have a 76 and put a 71-74 exhaust system with the resonator and it is free flowing and quiet and has a lot more mid range torque.
Sounds like your cat is clogged to me.
You are aware of course that you are telling the OP to break federal laws.
good luck neighbor. I feel your pain, we have snow here in Spokane,~
Bob, do you have to do an emissions test to license your car in Boise? If you do, you will probably be required to have a catalytic converter on the car. NAPA, and other automotive parts jobbers, have universal catalytic converters that cost around $100. If you have a wire-feed welder, or an oxy-acetylene torch, you can install it yourself.
Daryl Chesterman
If ZDPP or similar was put in the oil, there's a slow loss, ~5%/1000 miles, that occurs and would go out through the breather/PCV to intake. Zn will coat the catalytic surface and render inoperative. That's why they got away from or reduced the levels of some of the old additives going forward.
Any lead replacement gas additives will also be bad here. But '76 is well into the low compression daze negating its need. One used to be able to buy the pellets to recharge the early cats, but I haven't kept up with that stuff. There was a plug in them. Lots of them were stolen when the metal prices spiked in that period due to high demand for new. The current ones are quite compact compared to the early versions. {aside;I later worked with one of the inventors of the GM cat convertors, now deceased.}
Excessive heat; Sounds to me like your heat shield is missing or rotten(floor?). They put shields in, then found they could cause fires if parked over combustibles, like grass, etc.
ps: They don't like to run too rich either, as more fuel means more heat.
Removing the cat on a 76 car is breaking federal law?
Better call J Edgar Hoover on me then.
I’m in PA and antique registered cars are exempt from any emissions testing.
Lack of an inspection where you live doesn't change the law.
I don't think there is a direct bolt in option available for these cars so pretty much no matter what you do there will be custom work. I'm sure you could do it with flex pipe and band clamps but someone that can bend and weld would be ideal.
Its been a while but pretty sure the engine side was a flange that bolted to the crossover manifold thing. Wasn't the rear a flange too? And there pretty much wasn't any pipe between the body and flanges so you can't easily re use them.
Quote from: 76eldo on December 13, 2020, 12:18:12 PM
Removing the cat on a 76 car is breaking federal law?
Better call J Edgar Hoover on me then.
I’m in PA and antique registered cars are exempt from any emissions testing.
I really tried to keep quiet over that one.
Just like Mike, I'm in Florida with NO inspections and nobody peeking under the car to see if the cat is there. I pull them off of every pre-77 car I have ever had.
As for the big cast iron collector, I left mine because it was in such good shape. I do the exhaust from the collector back in aluminized steel and it lasts far longer then the car. My car runs better than it did from the factory and is just as quiet.
Get a laser-dot temperature gun. With engine running, if there is a big temperature drop between the entry pipe/exit pipe, then your cat is a goner. With a correctly operating cat, the temperature will be about the same or will increase (due to the catalyst action).
The temperatue gun can also detect a clogged muffler. And, if you have a misfire, you can find the exact cylinder by hitting the exhaust ports on the head. Great tool!
You don't need to eliminate the cat. Gut the cat.
Thanks all, yes it is a Federal Offense to remove it, can I say the Feds can go ____ themselves? I am not an anarchist, just a passionate car enthusiast; There are far more important things that need to get done within our government than worrying about one little converter on a car that gets driven maybe 50 miles a year. We have no inspection in Idaho for older cars so I am clear in that manner. I may try to cut it then gut it out as a "dummy" we will see. I can have someone weld it on.
I am leaving the square connector for now but know getting an older one allows for better flow.
I just checked and cutting on the back side of converter is easy, wondering does the converter fit "over" the exhaust pipe or just attaches with weld to it end to end? It is important to know as I dont have much room from square box to the converter to cut out. I can remove flange from square box if bolts are not too frozen, prefer not to disassemble the whole thing keeping it simple as possible if it aint broke dont touch it.
AS an aside to my prior message.....newer car catalytic converters are being stolen at the rate of 500 a month in Seattle. I jokingly told a friend, maybe I should just take it there, leave it on the street for a day or two....problem solved...alas, they would most likely steal the whole car....not a joke.
Hasn't Seattle cut their police force dramatically?
This is for Seattle.
https://www.youtube.com/watch?v=7TLqfnwFd3o
Quote from: 76eldo on December 13, 2020, 12:18:12 PM
Removing the cat on a 76 car is breaking federal law?
Better call J Edgar Hoover on me then.
I’m in PA and antique registered cars are exempt from any emissions testing.
No emission testing doesn't mean you don't need a CAT converter; Federal law requires all cars that came from the factory with one must still have one, so let us all obey the laws for a change and keep all our health protected as much as possible. EAM
last response made me rethink, what I intend to do is eventually replace CC but need to get oil changed and fresh fuel so a new one wont plug up. In the meanwhile I will put in a temporary pipe where old converter was and drive the car. Too cold and rainy here in Boise now but down the road will get her out and figure out next project of which there are many. Thanks all for your input and having travelled the world, there is no place like America.
My 76 only sees about 500 miles a year.
I have no regrets about losing the convertor and changing to a 71-74 exhaust system.
If I was using it as an everyday car that would be different.
Quote from: 76eldo on December 13, 2020, 12:18:12 PM
Removing the cat on a 76 car is breaking federal law?
Better call J Edgar Hoover on me then.
I’m in PA and antique registered cars are exempt from any emissions testing.
No matter what local testing requirements are, Federal Law prohibits removing or tampering with ANY part of a car's emission systems.
I'm not telling anyone here what to do or not to do, just what the facts of the laws are. If you have no testing requirements fine, some states will STILL look for the parts on the cars. Do what you want.
Greetings all
I finally cut out the CC what a job..figured out how to do it. Cannot see light through the unit, just a little bit, obviously clogged.For now putting in a straight pipe to see what engine does, will eventually replace the CC but think the Zinc and SeaFoam clogged the unit, I forgot engine was rebuilt before I bought it so should not used cleaning additives, however, it did quiet down a noisy lifter.
Shame on me.....if it aint broke dont fix it....learned my lesson. want to share my anxst.. I dreamed about removing the CC, many nights, caused much frustration during the day and being someone who is goal oriented and requires everything to be in working order this was a rough spell for me I was determined to cut the damn thing out, and finally succeeded. My personality is probably not the best for a classic car, however, I have had one most of my later years of life. I appreciate everyone's input on the forum for moral support and guidance. In my management days I always requested input from everyone to make decisions work.
wishing all of you good health, stay safe and more tales coming on "Ella Eldorado" as we move forward to her recovery.
All that work and you have not got a test drive in yet? Curious to hear what difference it made.
This vintage converter was filled with little balls so their random nature would mean you were not likely to see through even a new one. Around 80 they came up with the more of a honeycomb design that you could see straight through a new one. I think what they were going for with the balls was maximum surface area and the idea that you could service it by replacing the balls.
Unless you or someone else really went nuts with additives I doubt that is what plugged it if it was plugged. Most likely something else was wrong at some point.
From what I found was that Ford used the Honeycomb material, and GM used the balls.
Bruce. >:D
My question, by removing the converter how much is this changing the back pressure the car is designed to have. I know it is a 500 and it probably could use some extra flow. But how much is to much? Just my 2 cents.
Thanks Wayne
G'day Wayne,
It will change a bit, but I don't think it will be noticeable from the drivers seat.
One thing in performance, one doesn't like back-pressure, which is why we fit dual exhausts where there was a single exhaust, Headers to replace Manifolds, etc, etc.
But, a partially blocked Cat will really hurt performance, and these things are only performing perfectly when they are brand new.
Bruce. >:D
Factory rating in 1974 was 210 SAE Net. 1975 dropped to 190 SAE Net (about 10% less). That's the converter.
Runs better without the convertor and the stupidly designed cast iron box that the two head pipes dump into facing each other.
As previously posted I installed a 71-74 full system on my 76 and it had an increase in mid range torque that was noticeable to me.
Quote from: 76eldo on December 13, 2020, 12:18:12 PM
Removing the cat on a 76 car is breaking federal law?
Better call J Edgar Hoover on me then.
I’m in PA and antique registered cars are exempt from any emissions testing.
What is your complete address so as I can give J. Edgar Hoover a visit for your violation of Federal law; keep healthy! EAM
I’m at 1313 Mockingbird Lane
Has Edgar been reincarnated?
Bruce. >:D
Quote from: EAM 17806 on January 20, 2021, 12:15:17 PM
OK, but what is your city and state so EDGAR can find you? EAM
as seen below his posts ---
Brian Rachlin
Huntingdon Valley, Pa
CLC # 22443
Quote from: The Tassie Devil(le) on January 20, 2021, 06:31:52 PM
Has Edgar been reincarnated?
Bruce. >:D
Not yet!; but his spirit is still looking for Brian (76 Eldo) to help him restore his Cat back on for the good of his health. EAM
I had a 76 Eldo in 1991 when I moved to Florida. The catalytic converter had been removed years before. The car ran absolutely perfect, smooth and quiet.
At the time, Florida had emissions testing. The car easily passed the emissions testing at the tailpipe, but failed the visual inspection, as the cat had been removed.
So I installed a new modern cat and had the car retested. It still passed the emissions test at the tail pipe, but the emissions tripled with the new catalytic converter in place and the car ran like crap.
Somehow, that cat got hollowed out, and put back on. So the end result was lower emissions and would pass the visual test. Best of all, the car ran fantastic w/o it!
Yes, there is that, federal law.
so to sleep better at night, best verify the federal tags remain on our mattresses ... per federal law. 🤦🏻�♂️
Curious with the rampant catalytic converter thefts 😤 I wonder if there has been ONE conviction of this federal law of knowingly removing such emission control device and rendering it inoperable? 🥴 🤔😱
It would seem that if it is getting that HOT the catalyst is actually working and possibly, as suggested earlier ...there is rich run condition that is causing this problem?
The cats do simply 'fail' so I would not be too quick to blame supplements, 99.9 'lead substitutes' have no lead anyway.
I have had many of those OEM pellet cats replaced with modern honeycomb and the performance change was dramatic. And WOW those original cats were seriously ridiculously heavy!!!
I remember a 76 Seville and when it plugged up (no fuel supplements) the car just went slower and slower until it stalled roadside. No excessive heat radiating, I could hear a hissing at attempts to restart it that alerted to the restriction.
Usually the reason that the Cat gets extremely hot is that the engine is either running rich, misfiring, or badly restricted. Over fueling and misfires are what kill Cats. To check for exhaust restrictions, connect a vacuum gauge to a manifold vacuum port on the engine, snap the engine to WOT and watch the gauge. If it goes from 15-18 inHg to 1-2 lbs pressure, you have a restriction in the exhaust. Don't just blame the Cat, remove the exhaust pipe from the Cat and repeat the test. If still high, then the cat is restricted. GM used 2 layer exhaust pipes on many applications and the inner pipe will collaspe and restrict the exhaust. Removing the Cat can cause detonation issues because now the EGR does not work properly. If you'r lucky it will ping when under light throttle high load and you hear it and back off the throttle. If you don't, the detonation can damage the pistons, break rings, and break the insulators off the spark plugs. Just a few things to think about before making modifications. Making a change to one thing affects other things: timing, air fuel ratio, etc. The engines and emmission system were engineered to work together. Sometimes you can get by with it, but other times it can cost big time.
PS: I think I forgot to add, if the exhaust checks good or bad, make sure the engine is properly tuned and has no misfire issues.
Especially with the age we are talking about here mufflers are perhaps a more likely place for a restriction. The limited use vs age increases the chances of some sort of critter trying to move in as well as rotting from the inside out. A common muffler design was to have insulation material held in place by a wire mesh. The wire mesh rusts out and lets the insulation get loose and restricts or plugs the outlet.
Quote from: EAM 17806 on January 21, 2021, 10:42:11 AMNot yet!; but his spirit is still looking for Brian (76 Eldo) to help him restore his Cat back on for the good of his health. EAM
Gee, I guess I should've been dead long ago, what with driving pre-70s Cadillacs without convertors all these years. Every car that survives means one less car that needs to be built - any idea how much that reduces pollution? As to EVs, don't even ask what manufacturing a single battery causes. I don't know about you but I take exception to so-called "elected officials" taking private jets on a whim, on the taxpayer's dime no less, while giving us sermons on how to live.
Quote from: Cadillacdave on February 05, 2023, 10:24:26 PMI had a 76 Eldo in 1991 when I moved to Florida. The catalytic converter had been removed years before. The car ran absolutely perfect, smooth and quiet.
At the time, Florida had emissions testing. The car easily passed the emissions testing at the tailpipe, but failed the visual inspection, as the cat had been removed.
So I installed a new modern cat and had the car retested. It still passed the emissions test at the tail pipe, but the emissions tripled with the new catalytic converter in place and the car ran like crap.
Somehow, that cat got hollowed out, and put back on. So the end result was lower emissions and would pass the visual test. Best of all, the car ran fantastic w/o it!
I think the General originally had a one fits all
converter, which obviously was too small for a 500.
A pair of those 2.5 in might work, I have gone for
a 3 in truck converter with decent results. Bruce Roe
The one thing everyone is forgetting is that the Cat is part of an engine system. If the Cat is removed or gutted, it affects other things. The EGR system, timing, and fuel mixture. Without the Cat, the EGR will not function properly. This can cause detonation, heard as pinging under light throttle/heavy load, which can break off spark plug insulators, break rings, or damage pistons. Many times detonation is not heard, but the damage still happens. Is it worth the chance, I don't think so. Usually when the Cat gets extremely hot, it is because the engine is running very rich or it is misfiring. The Cat gets hot because of the excessive fuel. If the Cat or exhaust is restricted, the engine will not develop much power. To check for a restricted exhaust, connect a vacuum gauge that can read pressure and vacuum to a manifold port on the engine. When the engine is idling it should develope 15-18 inHG. snap the throttle wide open. If the vacuum gauge reads greater than 1-2 lb, the exhaust is restricted. If restricted, disconnect the exhaust behind the Cat and repeat the test. If still high, the Cat is restricted. If not, check the rest of the exhaust. Many GM vehicles uses dual wall exhaust pipes and the inner wall would collaspe and restrict the exhaust. Hope this helpc. Good Luck!