Daul Cat Question

okay Im contemplating converting my car to dual cats. The car is an "86 but the motor has been change to a 350TPI. Now my brother inlaw works at a
performance shop and I asked him if there are any aftermarket set-ups that are just y-pipe and not header y-pipe combinations. He said no and I'm better off sticking to just one cat because two cats are more restrictive.... Now I'm no genius but that statment goes against all ever ever learned...... lets face it if you put 2 straws in your mouth and blow theres going to be less restriction then if theres only one. So what should I do I'm hoping you guys can help me not make a mistake. and If duals are better is there any aftermarket set-up available thanks TOM
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I would have to agree with you that dual cats would be better, but unfortunately it's not legal to convert your car from single to dual cats. The "hot" legal setup for your car would be to replace the stock cat with a high flow aftermarket cat, then buy an aftermarket cat-back exhaust system.
Gary

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Maybee it is restrictive. after all there is some kind of filter inside the can. if only one side of the motor is running through it then that would be half the presure to force the gasses through the filters. Maybee it does need two banks of the engine to force the gass through at a stady flow. ? dunno I do agree with the Straw idea though. Why not do away with the Cats.
Regards Wombat.

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wrote:

Replace the 2-1/2" cat with a 3" one like I did. There's plenty of flow through the 3" unit. My pipes from the exhaust logs are 2-1/2" each side to the Y-pipe, then the 3" cat., then a Flowmaster 3" cat back exhaust. American Thunder is what Flowmaster calls it, I think. Maybe that's the system in my 68', either way you can upgrade the exhaust to handle it and won't have to worry about the constricted area that you'd have to run 2 pipes down. The last thing is that the system uses all of the original mounting points.
...Ron -- 68'RS Camaro 88'Formula 00'GT Mustang
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Well These are all good points but the thing is I've already Put a 3inch Dynomax superflow cat on there and a 3inch Edelbrock Performer RPM cat back coated with JetHot. Problem is that the stock Y-pipe, has a big crack in it and is leaking pretty good at Idle so I'm guessing that its probably really pouring out at high RPM even though the majority of the exhaust note is coming from the rear.... Your probably thinking big whoop change the pipe right. But the cars seem to have way more balls with the crack and I know Mac makes a nice single cat y-pipe, but hears the thing... 1996 formula Single cat' rated at 275hp '96 T/A daul cat 285hp.... And think about this if your forcing out say 3000cubic cm per min' through a 6"X10" cat// or the same amount of cubic cent-per-min through two 6"X10" cats thats double the amount of flow. I would think???? Tom

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wrote:

Take a look at the page below.
http://www.pontiacstreetperformance.com/psp/exhaust.html
Find someone who can use all of the information about your engine and drive train and have them design the system that will work best with what you have. There is more to look at than just the cm3 of the pipe, you have to look into how well exhaust gasses will flow through those pipe with the least amount of restriction.
Most of the sites I've read have said that a 3.5" equals a dual 2.5" but the sites I was reading had vehicles that were talking about engines that exceeded 400 hp. I've put in a dual exhaust on an 83' Z28 and it was the most difficult fitting system that I've ever had to put in.
...Ron -- 68'RS Camaro 88'Formula 00'GT Mustang
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I installed a full dual exhaust with headers and dual cats onto an '84 T/A. The local inspection people said it was okay because a later model F-Body came from the factory with dual cats. Thankfully there was no sniffer test in the area because there was no way it would have ever passed. Sure, a later model came with duals, but the two 2 1/2" cats I installed couldn't have possibly gotten hot enough to light-off and clean the exhaust. Not to mention there just isn't enough room under the floor to fit all those parts. It used to scrape and bottom all the time.
My recommendation:
Edelbrock T.E.S. headers and Y-pipe. Stock H.O. 2x3 oval catalytic converter, or a high flow aftermarket 2 1/2" 3" Flowmaster cat back exhaust
That'll be 50 state legal, very high flow, and you can sleep well at night knowing the emissions won't kill any spotted owls or desert tortoises.
-rev
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(Update) Well after all the help and throwing around different senarios I've come to the conclusion that it'll be more of a headache to get daul cats on the car all for maybee a few more horses, not really worth it if you ask me. I ordered the High flow Y-pipe from Mac Performance today and the way I look at it this pipe alone will out flow the stock one by far and probably wouldnt have gain more than a couple give or take if I had gone through the trouble of setting up dual cats. Thanks for the help TOM

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Tom wrote:

time. Making everything else flow better is a little bit of waste if you don't do the same with the cat.
--
Cy Welch
89 Camaro RS 5.0 TBI
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