I've seen cat converter compared by cfm flow rates, but don't know what is sufficent for a good breathing 350 or 383 with twin cats/duals. I've seen 450cfm on some seems to be the high end.
But now I'm looking at some from Pypes, and they rate them as 5.9 liter and 6000 lbs or 5.0 liter at 4500 lbs???

I like the Pypes ones cause they are very small since I have a limited area to put them on duals, but not sure how they compare to others.

 

You'll need about 2.2 cfm per horsepower(at the flywheel). If you use two cats just divide that number by two. This is just to get an idea...

 

Thats good to know. So with around 500 flywheel hp I'd need at least 2 500+ cfm cats....that where the question comes in...
I see some cats with advertised cfm rating....while others list it as something like 4500 lbs capacity??? How do you compare that?

Here's a prime example..the Powermax is in cfm, the Pypes on the same page is in lbs.
http://www.rpmoutlet.com/powercat.htm

 

Well I think I figured out the flows for all the ones I'm considering, who knows if they are at the same pressures/temps.
Pypes - 450 cfm for around $90
Dynatech Power Cats - 396cfm for around $150
Random Techs 7000 - 598cfm for about $175

So I think I'm going for the Random Techs if they will fit.

 

Have you looked into Carsound/Magnaflow cats? They're on EBay and were decent priced last time I checked...

 

The MAgnaflows are 13" and 16" long, I won't have enough space to put them on I don't think with LT headers and have them before the support "bump" on the driver side without them hanging down a couple more inches. It looks like I'm going to have 11" or less to work with there.

 

The lb rating is to help insure that the converter will pass inspection. The cfm rating is to give you an idea how much restriction the cats cause. In our dyno tests, the mini cats only cost about 2.5 hp on a 225 rwhp car. Also, look at the cfm ratings of cats. They outflow most chambered mufflers, so if flow is a big concern, start looking at the mufflers as well as the cats.

 

Where can I find Pypes cats? Or any comperable flow for the price cats?

 

Search for 'Pypes' on google

 

http://www.pypesexhaust.com/mufflers.html