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Trackerrrr 12-01-2010 02:19 AM

Putting catalytic converter on older car?
 
Hi all,

I've been kicking around the idea of picking up an old car like a '64 Chevy Impala with a 6 cyl engine with a 1 bbl carb to see what kind of mileage I can squeeze out of it. Yeah, I know they aren't the most efficient cars ever made but I like to try just to shut the naysayers up. Anyway, the one thing I hate about older cars is the STINK out the tailpipe. I'd like to put cats on to eliminate most of the pollution, but can you put a three way cat on a carbed engine? Is this a good idea? Another thought I had was to adapt a two bbl fuel injection unit from an S-10 which might work better.

SentraSE-R 12-01-2010 02:45 AM

Just a guess, but a '64 Impala is such a gross polluter, my guess is it would clog a cat in 100 miles of driving. Do yourself and all the air-breathing organisms in the world a favor, and let that dinosaur rot in the junkyard. A carbureted '64 isn't capable of burning close to stoichiometric. It lacks the oxygen and temperature sensors and feedback systems needed to control its emissions, and to prevent the cat from being destroyed.

cfg83 12-01-2010 02:53 AM

Trackerrrr -

Welcome to EM! While I'm no expert, I am *guessing* that a 1964-tech Chevy would poison a catalytic converter because it wouldn't have the right "mix" of emissions for the cat to function properly.

But I don't know, so I asked Wiki :

Catalytic converter - Wikipedia, the free encyclopedia
Quote:

History
The catalytic converter was invented by Eugene Houdry, a French mechanical engineer and expert in catalytic oil refining who lived in the United States. Around 1950, when the results of early studies of smog in Los Angeles were published, Houdry became concerned about the role of automobile exhaust in air pollution and founded a special company, Oxy-Catalyst, to develop catalytic converters for gasoline engines - an idea ahead of its time for which he was awarded a patent (US2742437). Widespread adoption had to wait until the extremely effective anti-knock agent tetra-ethyl lead was eliminated from most gasoline over environmental concerns, as the agent would "foul" the converter by forming a coating on the catalyst's surface, effectively disabling it.
The catalytic converter was further developed by John J. Mooney and Carl D. Keith at the Engelhard Corporation, creating the first production catalytic converter in 1973.
...
Three-way
Since 1981, three-way catalytic converters have been used in vehicle emission control systems in North America and many other countries on roadgoing vehicles. A three-way catalytic converter has three simultaneous tasks:
Reduction of nitrogen oxides to nitrogen and oxygen: 2NOx → xO2 + N2
Oxidation of carbon monoxide to carbon dioxide: 2CO + O2 → 2CO2
Oxidation of unburnt hydrocarbons (HC) to carbon dioxide and water: CxH2x+2 + [(3x+1)/2]O2 → xCO2 + (x+1)H2O
These three reactions occur most efficiently when the catalytic converter receives exhaust from an engine running slightly above the stoichiometric point. This point is between 14.6 and 14.8 parts air to 1 part fuel, by weight, for gasoline. The ratio for LPG, natural gas and ethanol fuels is slightly different, requiring modified fuel system settings when using those fuels. Generally, engines fitted with 3-way catalytic converters are equipped with a computerized closed-loop feedback fuel injection system using one or more oxygen sensors, though early in the deployment of 3-way converters, carburetors equipped for feedback mixture control were used. While a 3-way catalyst can be used in an open-loop system, NOx reduction efficiency is low. Within a narrow fuel/air ratio band surrounding stoichiometry, conversion of all three pollutants is nearly complete. However, outside that band, conversion efficiency falls very rapidly. When there is more oxygen than required, the system is said to be running lean(as all the fuel got burnt,the emission of CO and hydrocarbons are minimized)and thereby, the reduction of NOx is favoured, at the expense of CO and hydrocarbons. When there is excessive fuel, the engine is running rich; the reduction of CO and hydrocarbons is favoured, at the expense of NOx.

CarloSW2

Trackerrrr 12-01-2010 02:55 AM

I suspected the carb would be the sticking point for a cat. Too many variables and inability to control the air/fuel ratio closely enough.

BrianAbington 12-01-2010 04:53 AM

In alot of newer cars they put a cat under the hood as part of the exhaust manifold.
If you had a shorty header and attached the cat right to it this may help get the temp up in the cat getting to the light off temp easier.

If the header is thermal coated and wrapped...this will help to keep more heat in the manifold it self.

Then do some research to find a cat that starts working at a lower temp.

I'd maybe go for a smaller car like a nova, or fairlane.

They are alot lighter, had a straight 6 available, and I have read plenty about people changing the rear gears and averaging upper 20's to lower 30's for hwy MPG's

I think you could get one of these cars even with a carb to pass modern emissions testing.

Frank Lee 12-01-2010 08:44 AM

My '84 Tempos came with carbs and cats.

mcrews 12-01-2010 10:20 AM

In 1979, I had a 1966 mustang coupe with a 1bbl 200ci straight six, automatic 3spd and a 2.87 rearend ratio.
I installed clifford headers that were 3 cyl on each header then did a "y" pipe into a 2 1/4 pipe w/ a single muffler, then 'y' piped uot to the two GT exhaust tips.
I was running E-70 radial series tires on the 14inch rims.
I had purchased a trip computer from jcwhitney and got it all calibrated. (yeah I was into ecomodding in 1979!!!)
I consistantly got 28+ mpg on the road.
I had to put a rebuilt long block in and went to have it smogged (in California). the results were less than 10% of the allowable level. It barely registered on the machine.
What really surprised me was that with the rebuilt engine I could actually 'chirp' the tires on take-off.

Ryland 12-01-2010 10:35 AM

The carburetors that are going to allow you to do this are going to be complex, the early 80's Honda civic pulled this off with a carburetor but it was with a mess of vacuum lines that very few could figure out.
The nice thing about the type of car that you are talking about is that the engine block for it most likely stayed the same for the next 30-40 years, other then getting a few more holes for sensors and a refinement in quality control, so you might be able to put an updated engine in that would bolt right in.
In my mind fuel injection is going to be the way to go, not just because it burns cleaner but because it lets you use less fuel by giving better control and that is what you want.

UFO 12-01-2010 12:54 PM

If you convert the engine to fuel injection, you could fit the exhaust with a converter. Fuel injection has been developed to the point where anyone can do it now, and cheaply too. Megasquirt comes to mind.

DonR 12-01-2010 01:07 PM

I have an awful Carter BBD computer controlled carb on my Jeep. The vaccum diagram is just as complicated as the electrical diagram. Alot of guys end up putting on a Ford Motorcraft 2100 or MC-2150 stand alone carb & still pass emmissions tests. Husquavarna also put some catalytic converters on 2 stroke chain saws. So running a cat with a fairly simple carb is certainly doable.

I would look into some emmissions systems of some very early cat equiped vehicles & see what all was required. Most cats are killed by running rich, the unburned fuel burns at the cat causing the substrate to melt, plugging them up. This robs power & makes the car hiss everytime you hit the gas.

Someone else had mentioned some Clifford Performance products. They specialize in straight 6 parts. They sell cams for torque

A 4.3l v-6 is only slightly larger than the 230 cid 6 that chevy used & may bolt into where the small block v-8 would go. All the modern bits to help with emissions & fuel economy.

Good luck

Don

roflwaffle 12-01-2010 03:44 PM

Quote:

Originally Posted by Trackerrrr (Post 206970)
I suspected the carb would be the sticking point for a cat. Too many variables and inability to control the air/fuel ratio closely enough.

You can control it fairly well post combustion (smog pump) by either developing your own control unit for a smog pump/1 wire oxygen sensor so the cat could work or finding a system (I think it's called a FFS in emissions lingo) from an ~80s/90s engine of similar displacement and retrofitting that. Given all the work involved I think a conversion to TBI w/ megasquirt would be easier, cheaper, and also improve mileage.

PhilA 12-03-2010 01:04 AM

It's possible but a headache, carbs and cats don't mix well.

My Briggs & Stratton engined generator has a catalytic converter (apparently now required for CA) and a small carb but I think that works well as it's a narrow range engine- constant RPM, not a particularly variable load.

Lada used carburettors and catalytic converters through until the 90's, with enevitable problems as the carbs wore and got out of tune. They moved onto computer controlled SPI after that.

That being said, with the right setup and good conditions it's possible to "clean up" an engine- friend of ours had a 1977 Ford Fiesta with a 1.1 litre Kent engine, and a small Solex carburettor, mechanical CB points etc and it ran cleaner than a lot of cars WITH a catalytic converter, well maintained, with readings that had the tester check his machine on a few other cars to make sure it wasn't broken.

Best bet on an engine of that vintage would be fuel injection that can be mapped on a rolling road, to aid a 14:1 burn- but then factors like plugs and valveseats become an issue as you may end up burning the fuel hotter than designed (weaker mixture), especially with today's unleaded+ethanol.

I'd say go for it though, get the car running a good mixture and fling a couple cats on it, as close to the engine as possible to keep them hot.

Totally possible, and it would mean that "hulking dinosaur" need not be "scrapped" ;)

--Phil

4more 12-03-2010 11:34 AM

hello more of a lurker than a poster but i like this topic
If I'm correct converters came factory on cars in i believe 1976 +-
fuel injection came on cars full stream 1986+-
also i have heard of many people with older cars getting 20 plus mpg with 6cyl.
and Hot Rod mag. got a 67 Camaro they saved from the crusher in 1993 and got it to pass Cal. emmisions.
1967 Chevrolet Camaro Drag Car - Hot Rod Magazine

rmcelwee 12-03-2010 12:44 PM

There are a lot of old unused cats laying around. You could just pipe a couple up on the exhaust and see what happens. Probably wouldn't cost that much (assuming you can weld) and you would get to actually see what happens instead of just guessing.

bikin' Ed 12-03-2010 02:20 PM

A Classic
 
If you can just "pick up" a 1964 Chevy you're either very wealthy or very lucky. They are in great demand. I'd restore it and sell it. Somebody will keep it, mostly in the garage, and it won't pollute and will burn hardly any fuel. The $$ you make could go a long way!:D

Ang84Indy 12-28-2010 02:42 AM

I think it's a great idea. I would install a fuel injection system that uses O2 sensor, get it tuned properly, then add the catalytic convertor (to avoid damaging it during set-up).

Superturnier 12-28-2010 11:56 AM

I have been dreaming about this same idea for some time, since I don't like either so much the smell of exhaust fumes. And as my old summer vehicle is not so leak tight, some of the smell comes inside the car.

Anyhow I think that the ignition system should also be in good condition to avoid unburnt fuel entering the cat. The fuel in the cat would cause excess heat that can melt the cat.
To minimize this risk of melting I would put the cat more far behind from the engine.

I'm not so sure if the A/F mixture has to be exactly right because also the newer cars run rich when cold and that does not kill the cat immediately. It just doesn't clean all the pollutants 100% Or what do you think?

Well these are just my thoughts, I cannot be sure since I haven't tested it.
Maybe next summer:rolleyes:

Trackerrrr 12-28-2010 01:48 PM

Quote:

Originally Posted by bikin' Ed (Post 207391)
If you can just "pick up" a 1964 Chevy you're either very wealthy or very lucky. They are in great demand. I'd restore it and sell it. Somebody will keep it, mostly in the garage, and it won't pollute and will burn hardly any fuel. The $$ you make could go a long way!:D

You can pick up 4 door models pretty easily out in SoCal that don't cost a second morgage. :)

Cd 12-28-2010 03:30 PM

Why not just look for one with a transplanted 350 with modern day components ?
Even if you find one that has a 350, but it has a carb, you could convert it using pieces from a junk yard.
Cars from that era had horrible aerodynamics, but a large portion was due to the underbody.
You could probably drop the drag down quite a bit with a stealth belly-pan and still have the classic look of the car.

Frank Lee 12-28-2010 06:08 PM

The upper bodies were awful too.

blade 01-16-2011 07:14 PM

i believe you need an egr setup to get heat for c c and alot of them need airpumps you can put a cam in it and tune it and find a shop that does 4 gas checks you can tweek the carb alot to get it to run good and not produce alot of emmisions. keep us informed at what you do iteresting ideas

mechman600 11-13-2011 01:27 AM

Modern catalytic converters can handle more abuse than most people think. It's only when a misfire develops with raw fuel being dumped into the exhaust that they will turn to molten lava while innocently doing their job of oxidizing HC. The cats in the 70's were notoriously easy to damage, which is why 90% of them were removed in the first 5 years of the car's life.

Here's the latest AirCare emission test from the carbed '84 Volvo that I might buy for $500. 350,000 km on the odometer.
Driving HC: 47ppm
Driving CO: 1.14%
Driving NOx:925ppm
Idle HC: 32ppm
Idle CO: 0.61%

Needless to say, a PASS with flying colors. Keep in mind that the Solex style constant velocity carb was notoriously accurate in its fuel metering, as long as the ATF "reference fluid" reservoir was kept at the proper level.

I imagine that one of these carbs would be a simple install on your '64 Chevy six. An aftermarket generic cat would work absolutely perfect. But, a TBI setup from an S10 would also work well, as they are also simple.

slowmover 11-13-2011 10:35 PM

I had plenty of carb'd cars, several with cats. To retrofit isn't as worthwhile at might first seem apparent. The "stink" is associated mainly with a cold motor. Sure, it'll never be as "clean" as one with a cat, but as with the example above, one can build a "performance" motor that is about maximizing BSFC for either town or country driving. Decide what it will be used for, and go to folks like Bruce Crower who have a long history of highly efficient motors going back decades. Conpression ratio, piston quench, bore/stroke ratio, all sorts of fun details to go through. A good five speed would be ideal, IMO, as memory seems to say that in the old days that a V8 with the proper load on it, gear-by-gear, always seemed to be worked a tad harder where it mattered. That made for one internally clean compared to a lazy motor never used hard. Definite stink reduction . . although I for one miss the sweet smell of tetraethyl lead and the sound of a high compression gasoline engine.

One has to learn to distinguish between just well-burnt gas, and a motor way out of whack. Huge difference. All sorts of info in that exhaust.

sc2dave 11-23-2011 07:26 PM

Quote:

Originally Posted by SentraSE-R (Post 206968)
Just a guess, but a '64 Impala is such a gross polluter, my guess is it would clog a cat in 100 miles of driving. Do yourself and all the air-breathing organisms in the world a favor, and let that dinosaur rot in the junkyard. A carbureted '64 isn't capable of burning close to stoichiometric. It lacks the oxygen and temperature sensors and feedback systems needed to control its emissions, and to prevent the cat from being destroyed.

you just adapt a newer style carb with perhaps feedback,properly done,problem solved.No need to let a classic go and rot in a junkyard.


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