bypass cat and muffler???

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faster4231

faster4231

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Is it possible to run a straight pipe from my manafold or do I have to keep it from the cat back? I want to just have a single pipe all the way back. 75 duster slant 6 225 . I know emissions wise it is not suggested but is it possible, or will I not have any back presure and the engine will fail?
 
Check your states laws about having your vehicle inspected. Most states have come to realize that since older cars make up such a small percentage of vehicle miles per year it's pointless to test them. California I believe is one.

Now as for your cat. Is it the original? If so it probably quit working long ago, and should be replaced. Is it the old school flat "stop sign" looking unit (pellet type)? If so it is highly restrictive and should be replaced. Modern honeycomb cats cause virtually no restriction, and aren't terribly expensive.

You could also run without it. Your engine would likely run cooler, and get a little better mileage. Not sure I'd run without a muffler. A stock unmuffled slant won't sound more powerful, it'll just sound like it needs a muffler.

Anybody who says you "need" backpressure doesn't know their a$$ from a hole in the ground, much less anything about cars. Backpressure is, and always will be the enemy.
 
+2 for above staement
i am 100% an advocate of cats in high performance cars (i know it is only a slant six) if collectively we ran cats the EPA would be off our a$$es and crushing so called clunkers would stop. (alright at least slow the pace) i run a 2.2l turbo daytona( 300 HP ) that is running a cat that can flow enough for a 7.5l displacment engine and it passes with flying colors everytime. total cost on it 75.00 at the local parts store !!!!


Norm
 
I agree with running the cat, now that I know the newer ones run virtually presure free I will start shopping, about the exhaust, I want a flomaster sound without the cost of headers and a complete cat back, I can't seem to find headers that are not 599 a peice. I know its a micky mouse job but I've heard storys that it can work till I can come up with the money
 
I agree with the cats, now knowing that they make them now with little to no resistance I will def be shopping, in regards to removing the muffler, any other way to get a deeper sound with out headers? 225 slant
 
trial and error on muffler choices scrounge around craigslist someone is always selling a used flowmaster or something or other buy it for cheap try it don't like it sell for same and try another. for the most part v8 /6 4cyl muffler choice will produce the same results with a deeper tone than stock, just don't expect it to sound like an 8 hahahaha. open pipe will not sound badazz hahaha

Good luck
Norm
 
I remember reading an old hot rodders trick was to run 5 cylinders through one pipe & one cylinder through another single pipe. It was said to make the car sound like a "Stuka Dive-Bomber." Sounds worth a try! :-D
 
Take off the stock one and keep it. Go to the muffler shop and have them bend you one up with your choice of muffler. If or when you need to smog it change back to the stocker with the cat on it.
 
Hey Burntorange70 , I like that 75 duster/ 72 demon you have going on. How did you convert that front end? I have been trying to get rid of that 5 mph bumber I have in front but doesnt seem that too much else fits, steel that is not fiberglass. Any pointers?
 
It is a bolt on thing. But you need all the parts like the fender, hood, bumper,bumper mounts, grill, and the rad support for it to work. Could also change to a 70-72 duster front end. A 70-72 Duster/Demon rear bumper and mounts can also be swapped on with a little work to the mounts. IMO it looks a little better and the bumpers are a lot lighter than the later ones.
 
Unless you are required to smog the vehicle by the DMV. I would eliminate the cat and muffler, run a single 2.5 inch all the way to the rear bumper. If your car is in good tune with good ignition it will probably produce minimal emissions. Mufflers are pointless on a full exhaust with a motor below 300 hp. I run no muffler on two cars, one is a 5.4 260 hp. It is mellow and nice out the bumper.
 
overboost said:
+2 for above staement
i am 100% an advocate of cats in high performance cars (i know it is only a slant six) if collectively we ran cats the EPA would be off our a$$es and crushing so called clunkers would stop. (alright at least slow the pace) i run a 2.2l turbo daytona( 300 HP ) that is running a cat that can flow enough for a 7.5l displacment engine and it passes with flying colors everytime. total cost on it 75.00 at the local parts store !!!!


Norm
Click to expand...

100% advocate of cats in high performance cars ? Whaaaat ?

You are the first guy I have ever heard say that. Interesting.
 
faster4231 said:
I agree with the cats, now knowing that they make them now with little to no resistance I will def be shopping, in regards to removing the muffler, any other way to get a deeper sound with out headers? 225 slant
Click to expand...

I went to a low restriction turbo muffler and a 2¼" pipe on my 73 /6. I also went to an oversized exhaust manifold w/o a heat riser. The bigger pipes definitely deepen the sound. Although at highway speeds, the exhaust noise is no worse inside the car than a stock system.

If I had to run a catalyst, I'd probably do the same thing except go to one of the straight thru Dynomax mufflers, or maybe even a glass pack.
 
Johnny Dart said:
100% advocate of cats in high performance cars ? Whaaaat ?

You are the first guy I have ever heard say that. Interesting.
Click to expand...

We have such a hard time with the epa and the carb board that if we did it it shuts the a-hole politicians up and you will never feel the difference in hp if chosen and placed properly. i am by no means a greenie i love old stuff but if we force them to take notice that our cars are NOT major polluters and we can make a better world for future hot rodders. the old school cats were a joke. the high flow cats i use are obd2 compliant and flow well . i run turbo cars so no restriction in the exhaust means faster spool and no horsepower loss. i have run the car back to back with and without flogging living heel out the car and never noticed any change in drivability,egt's or butt dyno results.

Norm
 
They started making buggy builders use CARB compliant motors. So now all the motor builders have CARB motor packages. They do not run as well or make as much power as non CARB motors. Some like the Subaru motor builders are having a hard time even making a CARB package that works. Bottom line, Smog parts are no good for a performance motor.
 
Burntorange70 said:
They started making buggy builders use CARB compliant motors. So now all the motor builders have CARB motor packages. They do not run as well or make as much power as non CARB motors. Some like the Subaru motor builders are having a hard time even making a CARB package that works. Bottom line, Smog parts are no good for a performance motor.
Click to expand...


that is horse hooeey and cop out they just need to put more development time in.

Norm
 
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