stock 1974 plymouth valiant 318 muffler/ Cat delete?

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stw1991

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I have a newly aquired 1974 Plymouth Valiant, all original bone stock 318 v8. I recently was working under the car and noticed that it appeared the car had bottomed out at some point due to worn out leafsprings. It appears to have either a muffler/resonance chamber or an early CAT of some kind in the exhaust system, and has a huge folded crese/folded buckled area in the middle and I fear its crushed the innards and creating to much backpressure and not allowing the engine to "breathe". I want to get one of those stainless blanks that you can buy at autozone, cut out that folded muffler/cat of sorts and clamp the blank in place, but im concerned about removing the muffler/cat as I dont want to lose performance due to giving the engine less backpressure. Will this affect my performance? Will I lose or gain any? any help would be greatly appriciated!
 
Make sure your area and state don't require smog equipment for licensing before you get crazy

"Reducing backpressure" is not an issue except that if it gets dropped enough, you will be running too lean and have to richen up the carb. If it still has the "smog" carb that might well become an issue.
 
Catalatic converters didnt come out until 75 in California.
Not sure what you have, but it sounds like a new exhaust system is in the future.
 
Johnny Dart said:
Catalatic converters didnt come out until 75 in California.
Not sure what you have, but it sounds like a new exhaust system is in the future.
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I find it odd that the op has a catalytic converter in a 74. There is a thread I started about catalytic converters in 74 because I have a late build 74 duster and it also has a catalytic converter.

Either way, like you say .......all that old stuff needs to hit the junk pile and a nice new exhaust needs to be installed. Just found it odd that I am finding a few 74s with cats when I previously thought it was 75+ thing.
 
You just made it. 75 is cut off year for smog in CA. you can delete the entire "thing" and just run a muffler.
 
In 74 they were also getting ready for the cats with the indentation in the floorboard, where the cats would go. If you ever seen a set of bucket seet tracks, where 1 of them was flat, the flat one was bolted over the cat Iindentation.
 
The cats are actually worth a little bit of money at the scrap yard.
 
Dunno about other states, but here in Texas if you register your vehicle as an antique you do not have to have an annual safety inspection.
 
eestatic said:
Dunno about other states, but here in Texas if you register your vehicle as an antique you do not have to have an annual safety inspection.
Click to expand...

here in Michigan there are no annual inspections, just pay the fee, put the tag on your plate and go :D
 
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