ThirdGenKen

I am going to be getting a custom exhaust built for my 87 Iroc. I am going to go with a single 3 inch into a hooker aero chamber muffler with two 2 1/2 tailpipes. Should I go with a high flow cat or just delete the cat completely?

What are your experiences and opinions on this?

MrBrooks

First thing to consider is your displacement..........~6.3L and you are boosted so actual amount of gases exiting the engine will be 6.3L plus boost. So, that being said, you will be at the ragged edge of the capacity for a single 3' Hi-Flo Cat(most are rated at around 6L). thats before you put any boost in the motor. So....unless you are able to run one off of EACH bank of the motor......it will be a bottleneck.

Second thing to consider is SMOG ****'s...........if you have no inspections where you live you are best off to go without.

Personally......I am going to go with one at each collector when I get the 427sb in......just to make a point.......I personally believe that the power loss will be so small that I may as well make the effort to save some fresh air for my Grankiz Grankidz.....you know what i mean????

ThirdGenKen

I have inspections where I live, but I work at a shop, so someone there will pass it for me. I think I am going to go with no cat. Is a single 3 inch plenty of flow for a 383 stroker with boost or should I go 4 inch exhaust?

hrspwr

iTrader: (3)

I have dual magnaflows and they have not hurt any performance, at leas that I can tell. Worth it in my opinion.

ThirdGenKen

Dual magnaflow cats?

hrspwr

iTrader: (3)

Yes Dual.
The issue is that you have not said what headers or routing you will be doing with the custom exhaust. I have shorties that go into 3" collectors/ypipe with dual cats into a single 3" flowmaster. I am using the stock routing. Cats I used are these:
http://www.magnaflow.com/02catalytic...niversal=59959

ThirdGenKen

I have Edelbrock shorty headers on it now. I think Mrbrooks had a good point, with mine being supercharged and a 383 stroker, I might be better off without a cat.

1991sleeper

iTrader: (-3)

3.5 or bigger mandrel bent
Or dual 2.5

hrspwr

iTrader: (3)

I agree to a point. What is the loss going to be? 10hp?
I think the shorties are more of a restriction than dual cats will be. Unless they are 1 3/4, but I dont think Edelbrock makes them that large.

khulsebus

iTrader: (2)

Use the high flow cats. Car Craft did an article a few years ago, when Frieburger was still the editor and the logo was "Do It Yourself Performance" or something to that effect. Either way, their dyno mule lost 1 hp to dual high flow cats.

MrBrooks

Your best bet all the way around will be to send a PM to DYNO DON. Ask him what he can do that will be adequate for your application. He is making the ONLY shorty header i would even consider running on a blown stroker. You will have to put out a little more $$ for his pipes..........but in the end you cant beat them in the world of shorties.......I would think he can most likely do something custom to in the Y-pipe to make it a dual cat set-up that will be adequate......

ThirdGenKen

Thanks for the input everyone. I will post pics once I get it done.

twowwwerf

Agreed. Single 3" is certainly the bare minimum for this kind of displacement + FI

ThirdGenKen

Do they make headers with 3.5 Y-pipes or would I just have to get an adaptor? Will full size headers fit in a thirdgen camaro?

MrBrooks

http://www.summitracing.com/parts/do...t/model/camaro
or
http://www.edquay.com/camaro/index.html

best option will be the Ed Quay.......1 7/8 primaries at your displacement and blown the huge tube option will be best.....lol
will be a FULL custom Y-pipe to I and out the back....... 3"Y to merge and 4" out the back thru a Hooker Max Flow........ would be the best way to go....IMHO....

http://www.jegs.com/i/Hooker+Headers/520/21609/10002/-1
http://www.jegs.com/i/Flowmaster/389...oductId=744773

ThirdGenKen

Ok. Thanks.