If you have a Y pipe setup new style cats and bumping up the diameter like the others have said is money well spent.

If you have true duals you can have an H, X or nothing at all you wont feel any difference powerwise maybe a slight difference in exhaust pitch if anything at all.

 

Magnaflow makes complete exhaust systems for 68-74 vettes with a Tru-X pipe but nothing but mufflers for the 75-82's.

 

They don't yet, but I was on their website, and if you look under "coming soon" they have new stuff for other C-3 years also!!!

It doesn't matter to me, because I have a '71. I just thought I would let others know!!!

 

You would be wise to check your local smog laws. Here in San Diego county, and possibly most of So Cal, we cannot change from a "single" exhaust and cat to true duals- even if we agreed to add a second cat! My best remedy was to buy new 2 1/2" stainless steel Y pipes, hone out the the single connector, add short 3"connector, to a 3" Magnaflow cat, to another 3"short connecter , to the rear 2 1/2" duals, to the flowmasters. The Magnaflow cat appears to have no restriction. Hot Rod magazine recently did some dyno testing with 2 small bullit cats, and lost only about 5 HP at very hi RPM. Goo luck with you conversion.

 

Magnaflows website looks like they have cat back systems coming for 80-82's, not true duals, nothing for 75-82's but the current muffler selection, and a 80-82's Y pipes. We on the forum should lobby Magnaflow for a true duals with the Tru-X pipe and Magnaflows with the single 3 in straight out exhaust tips or dual chrome tips for the 75-82's like the Magnaflow for the 68-69 small block system (check the website). It looks and probably sounds awesome!

 

im guessing that they will only trip about it if they look under and if they even know that the car was suppose to have a Y pipe insted of duals. Most of the time the smog test only station dont look under the car. As long you have the cats thats all they care about.

 

The issue with most of this smog **** crap is that they look under the car and any appreciable variation to the stock system is immediately rejected as it has not passed the whole EPA crap testing standards same as what GM had to do to make the things in the first place.....this goes on a car by car basis , not the engine, so just because you maybe think a V8 in a truck or something exhause would be fine in a vette, the .gov in their infinate book learning wisdom sez NO.....

hate to see you spend tons of bux and work only to get kicked in the teeth with that crap.....

The header guy was Schoenfeld, either the father or son, but the fellow I talked to had that last name....point being, they are in the business, and not the largest advertiser out there, and probably for a REASON, in that the magazines will print all sorts of about aftermarket parts being worth X hp or Y improvement when in fact that's true only with ABC improvments as a combination of efforts, and they make it sound as if just changing one aspect of things will gain you 150 hp and imply that OEM designs are idiotic by comparo....

Magszines and advertising do not make a car go faster, necessarily....



OH, edit....so lets not go all negative on the proposed changes....just that there are certain troubles needed sorted out, and the gains are worth it as even 20 hp is some 10% cripe, that's a hell of a gain....people have spent 50X that money for less results....

 

Maybe it would be a good idea to do a whole new exhaust system and save the old setup in case you wanted to install it for a day or so once a year or whatever.... Just so you could compare the difference.

 

I believe that the smog test is every 2 years in the pollution crazed state of CA so why don't you just swap the front y pipe, cat and rear y pipe section in every 2 years and then put on the true duals with the 2 front pipes and 2 rear pipes right after the test. The mufflers will work with either setup! Shouldn't take you more than 2 hours every 2 years and just think how good you would get with the swap. Beat them at this stupid game! Totally ridiculous!