Change Catalytic Converter ?
 

I have a 77 coupe.
I recently wanted to change my mufflers to flowmaster series 40's, because they don't sound aggressive enough, even though they are currently performance flowmasters.

Went to the local Muffler guy, he put the car up on a lift and said that my Catalytic Converter (cat) was really really old school. I need to put in a Performance Catalytic converter and redo the piping from the Cat to the mufflers, including the Y-Pipe. He said that the cat was restricting the sound to the mufflers, which are fine he said...:crazy:

Does that sound right ? He quoted me $350 for the job.
Gimme some advice fellas...:willy:

$350 sounds about fair, actually. I'd see if he could make the tubing 2 1/2" from the manifolds all the way to the back. Being that you're in california, if you want to register it as a normal vehicle, you have to leave the catalytic convertor in.

So you agree that if i redo the pipes and change the catalytic converter, it will sound more mean ? :yesnod:

You've never seen how poorly those old catalytic convertors flow have you? Oh man it should be a pretty decent difference.

I'm running long tube headers to sidepipes w/o cats, but I've got glasspacks. It has a very distinct tone now, my girlfriend said you could tell the difference between my car and every other car out at autocross just from the sound... of course I was also one of 2 C3s that even raced. Oh and it's VERY quiet at low rpms now, too.

Um, no! 350$ to weld a high flow cat in there? You can find a bolt in one from Mid America or Ecklers for $120 and put it in yourself, no welding required.

And yes a high flow cat will make it a little bit louder. And if you get rid of those flowmasters, on your car I'd replace them with pipes. Y pipe exhuast with factory rams horns blowing through a cat won't be loud even without mufflers.

http://www.ecklers.com/product.asp?p...&dept%5Fid=157
http://www.ecklers.com/images/vette/31769.jpg

And don't waste your money on new pipes unless you're going to go with duals.

Summit has them too
 

Here is the link for the 1977 direct fit replacement cat:

http://store.summitracing.com/partde...5&autoview=sku

Double check the fitment before you pull the trigger on it.

http://static.summitracing.com/globa...cto-4690_w.jpg

Summit price: $103.69

Or, ya could go with this option, but in California....I dunno...

http://i24.photobucket.com/albums/c3...q/testpipe.jpg

I replaced my 1980 Catalytic Converter with the one in Ecklers. Fit in perfect, took no time to install. Taking out the old one was a different story. After trying penetrating oil, heat, ripped knuckles, dremel, and a sawzall it came off. Check the condition of the bolts before you decide. $350 might be a deal after all.

Well, the whole purpose of going to the muffler guy was to get a meaner sounding car.. If he changes the cat and it still doesn't sound mean, I feel I will have wasted $350. The car runs fine as is...

I really need to be assured that it will sound like a rumbling animal once i spend the money.:smash:

I also have a 77 and recently had to drop the gas tank to change the fuel lines. We dropped the rear exhaust at the back of the cat. Because I am planning on putting on true duels, I have not put the mufflers back on. It is surprisingly quite. It now has a rumble to it, but I would not call it loud. I can't speak to much louder it will be without the old cat, but I can tell you that the old cats are really restrictive and work great as mufflers! Hope that helps.

Hell you don't even need mufflers if you have that catalytic convertor, it muffles it enough. I ran around without mufflers, when the old ones rusted off, for a few days and it wasn't very loud. I tried unbolting my cat... ya right, those bolts WILL NOT come off. I ended up cutting the pipes off to get that SOB off.

....ask me how I know this is true...... :rofl:

The cat will make it louder, for sure. But it won't sound like a rumbling animal. If you want a mean sounding exhaust it all needs to go, especially those Flowmasters. You need, long tube headers, true duals, high flow cats, and decent mufflers. Or just go with some Hooker Sidemount headers. :thumbs:

If you want it to sound like this you'll also need heads and cam. Here's my setup:
http://thumbs.streetfire.net/2E2E2D5...266DE6FEE3.jpgClick here to see Video

Problem: He owns a '77 and lives in California. Long tube headers MAY be legal, but true duals is not. He can do a SINGLE high flow cat and some nice wide Y pipes but that's about it.

The only way you can "legally" get by in California with having a car with open exhaust is by registering it as a vehicle of historic value, like I did. However, even then it's not "legal" to remove the smog BS, but they no longer check for it as you don't have to pass emissions for it. The only way you can get an exhaust shop to work on your car in California and work on the cat forward is to take the plates off and either trailer it in or drive it in on a one day trip permit and say it's for racing only.

I just finsihed my exhaust this weekend. I have a '78 which I removed the old system off of and put a straight dual system with high flow cats from Allen's. It definitely sounds much better! I was told that by a number of exhaust specialists that if you keep the stock cat you won't get any decent sound. More than one told me that if you leave the cat you can run with no mufflers and it actually will sound good. I wanted to retain the stock look from behind. Just for the s/s cats (need two on duals) I spent $250. The complete system all s/s including mufflers was $900. The cats and s/s mufflers drove the price up a bit, but I wanted all s/s.

Torqvette, that is a nice car with a BadAss sound !!!
Love it.. That's sort of what i want mine to sound like...:toetap:

At low RPMs it has this deep growl, and that is fine.... but I want more.. Anyway, I will be getting it back in about 4 hours, will let you know if it sounds good.

Nice Footage torqvette :thumbs: :thumbs:

I live in CA also. I plan to register my car historically when the time comes. But if you don't want to do that you can always throw the manifolds and y pipe back on and shoot it through one side of your exhaust once every two years. As long as I have cats cops can't fine me and I don't have a guilty conscience.

And thanks guys, you should hear it under load at high rpm. That's when it really screams.

Well, good thing is car is back and it sounds fab !!!

New Performance Hi-Flow Cat, 2.25 Inch Y-pipes, FLowmaster 40s mufflers.
Louder than before... and a bit meaner too...
Let's see if I can make a video like torquevette and post it..

Total, total :bs

Read all about it: http://forums.corvetteforum.com/show....php?t=1382340