cdrod

I'm planning to build a daily driver starting with a '71 Cutlass Supreme (love the wide chrome body molding on these cars). Motor and trans will be 355ci with 200-4r trans and 3.42 or 3.73 rear gear. Here is my question, should I put catalytic convertors on this car to be more environmentally responsible? I plan to build for fun, spirited driving (lots of low RPM torque) and will never see the track. Can the cats bolt right to the header collectors?

oldcutlass

Why, so you don't upset the Prius owners?

MDchanic

You're kidding, right?

- Eric

cdrod

I know ya'll think I'm crazy! 20 years ago I wouldn't have even posed the question - LOL. I live in Houston, TX with a population of 2.5 million people and plenty of traffic. Combine the exhaust of all these cars with the pollution from the oil refineries, and you have a pretty nasty recipe for poor air quality. Every so often we get what the weatherman calls a temperature inversion which traps the pollution. You can see the brownish-yellow haze on the horizon.
Not sure that I would bother with cats, but I thought it would be interesting to get some opinions from this forum.

Rickman48

Cats are designed for low compression, lean mixture, low RPM cars, with retarded cam timing, computer restricted ignition timing, and 195* thermostats, all things unproductive for a high-performance Olds!

cdrod

Richman48, I buy that line of thinking for the majority of production cars, but That doesn't seem to fit the latest crop of muscle cars that have cats, like the new Camaro, Challenger, Mustang, etc. I thought cat convertors cleaned up the exhaust gases exiting the tailpipe.

m371961

No offense, but if you are that concerned then ride a bicycle or get a new car.
Please do not give the greenies any ideas about modifying old cars for pollution requirements. That said, keep it well tuned, maybe computer controlled EFI, and it will not be as bad as some will claim.
Then, since you are doing your part, I won't feel guilty in my old trucks.

Sampson

Dude! There are very few of these cars left. There are even fewer driven daily. The environmental impact is minimal. If this concerns you please go buy a Prius and sell the Cutlass! No offense meant.

DoubleV

Agreed, though I would replace the word 'minimal' to 'almost non-existent'.

oldcutlass

X2 on cat's for newer performance cars, however not on old cars.

m371961

The new HP cars do it with cats, O2 sensors that control the fuel/air mix with computer controlled fuel injection, timing, and idle air control. You can do it on an old engine to some extent, but not just throwing on cats.

cutlassefi

WOW!!!
I'm sorry but you don't have a clue. You guys need to open your minds a bit.

Low compression, really? Why don't you take a look at the compression ratios of the cars today, they're routinely at 10.0:1 or better, really?

Retarded cam timing? Really? How about the newer stuff being on low/advanced intake centerlines with wide lob seps. That means the exhaust valve opens much earlier, why? To let hotter gases enter the cats. Cats are all about heat in order to work right.

Low rpm? Check out the redline on some of the newer stuff, my '07 Dodge revs to 6500 easily. How about a new Vette? 6000rpm+ plus a blower.

For the record, I installed cats on my EFI'd 350. With the EFI I can run it at close to stoich which is lean enough to run cats. With it being a convertible it's nice to have nostalgic looks and no fuel smell, I love it.

And furthermore for the record, when you floor it on a new car, it runs on another fuel map that is typically in the 12.0:1 air/fuel range and below. That cools the cats for a bit before it goes back to stoich at virtually every other load and throttle setting. The EPA does not require new cars to make emission standards at wot.

Man you all gotta get out more.

m371961

I was waiting for you to chime in. I don't know the newer stuff well, but the manufactures found ways to get performance and good emissions. It was just that period in time when the regulations kicked in and it took time for the technology to catch up that performance suffered.I believe it was the emission regs that pushed the move to fuel injection as they are easier to control with a computer than a carb.

hookem horns

I drive the Cutlass way too little to worry about the enviornment, but I was thinking about the same thing to get my wife more involved since she does not like the fuel odor. Sounds like not really feasible without going to EFI which is beyond my hobby budget. I'm in the process of swapping a holley for a quadrajet thinking the smaller primaries may help a little on a stock-ish 350 other than headers.

rcorrigan5

Catalitic converters weren't required on factory production cars until the 1975 model year. If it's not required, I wouldn't put it on.

Randy C.

cdrod

cutlassefi,
I've read many of your posts and respect your expertise. I'm not some crazy tree-hugger, but if I can lower the emissions and reduce the nasty exhaust smell with a couple of $80 catalytic convertors, it seems like a worthy pursuit. Is it worth the money and effort to install dual cats on my "proposed' daily driver to achieve these goals? I knew that cats need hot exhaust gases to work properly. Will the exhaust gases still be hot enough to activate cats if I installed them behind the header collectors? Keep in mind this will not be a high rpm racing motor, this will be my 'grocery-getter" and will seldom see more than 4000-5000 rpm. Thanks!

joe_padavano

Really? Like the ones on the new ZL-1 Camaro or the new Boss 302?

Sorry, but you're really showing your lack of knowledge about modern cats. New monolithic cats have no more restriction than a section of straight exhaust pipe. Installing them in the exhaust will not noticeably hurt performance. The bigger problem is controlling what the cats see on the input side. If the exhaust is too rich at the inlet to the cat, the cats will overheat and melt down. This is why the 307s have the switching valve on the A.I.R. system that diverts air from the exhaust ports to the cat to cool the cat and prevent meltdown.

Modern high-flow cats from companies like Pypes Exhaust won't measurably increase exhaust backpressure and will help lower emissions.

TripDeuces

Prius, bwhahaha

redoldsman

Air quality is certainly a concern for many of us and I know it is a problem in Houston. I am sure you car is in great condition and very well tuned which in itself does a lot to reduce emissions. Then I assume this is a hobby car. How many mile will you drive the car in a year? The affect on the air quality would not even be a hair on a nat's butt. Again, your concern for air quality is admirable but go without the cats.

Napoleon1991

Lol, i love it.

chip-powell

I actually looked into this before getting my '71. Everything depends on where you live. I live in Maryland and if I wanted my '71 to be a "daily driver" instead of putting historical tags on it, I actually would have had to make those kind of changes. I would have had to put shoulder seat belts and a catalytic converter on it or it would not pass the emissions inspection.

Your best bet is to call the DMV and ask. However, most states have a loophole in the laws regarding historical tags. Technically, you are only allowed to drive the car a few days a week, but they don't say which days. So, unless you get pulled over by the cops 3-4 times in one week, you should be fine with historical tags

Here's an added bonus (at least in Maryland)...historical tags are usually much cheaper than regular ones.

coppercutlass

You already did the enviorment a favor by not letting that car rot into the ground. Plus you didn't buy a car with a ton of plastics which will never breakdown for millions of years so they will pollute to make and pollute to break em down. People who drive Priuses don't realize how much pollution is actually created in the production of that car . specifically the process for making the batteries. Then not to mention properly disposing of them or re working them etc. That's could change as I think hybrids are going the lib route.