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High Flow Cat... What have you used and recommend?

S

smier

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I've been collecting parts for springtime, and next on my list is a high flow Catalytic Converter. I'm wondering what you guys have used and whether or not you would recommend it to others. I did a search and came up with tons if references to them but no specifics so far... My plans are to squeeze every bit of performance and fuel efficiency I can out of mostly stock '91 TBI 350 Blazer. I bought this thing 5 years ago for $1300 as a winter beater and absolutely love it so I decided to give it a second chance on life, now I'm so far in the hole on this one there's no turning back now. I'm running a flowmaster catback 3" single exhaust setup already and I plan on keeping my stock exhaust manifolds. I have to pass a visual inspection only for emmisions where I live because of it's age.
1. So tell me what worked, or didn't work?
2. Easy to install or a pain?
3. Any noticable gains?
Thanks in advance!!!
 
I used a piece of 3" exhaust tubing :haha::haha:

I really don't know much about them, but I have been told they all flow well when they are new so don't spend high $$ on one. I imagine any new one will work 100 times better than the stock one and you'll prolly never notice the difference on a TBI 350 between a top end one and a standard replacement Cat anyway.
 
I run one of the magnaflow universal highflow converters that was legal in CA.6 years ago it was only $60 or so.It`s not the prety spun one it`s the short rectangular one,it goes to the same as you flowmaster 3" cat back with there I think they called it 60 series suv muffler and 3" tail pipe on my 88.The converter has held up 6 years and just passed a smog check.did it ad power I would like to think so.At least its quieter then the beat up pellet converter that was factory and the exhaust is quieter then have the stock muffler and tail pipes with rust holes in them.
 
88-98 sbc shorty headers fit with tiny frame clearence. ebay specials all the time for under 200 bucks.

then flowmaster http://www.summitracing.com/parts/FLO-Y250300/ for homemade ypipe fab up.

do the 3 wire o2 sensor swap in . down in the y pipe area as the 88-98 headers wont work the o2 location . needs to more. plus the heated o2 works better than single wire.

then your 3" cat or non cat and bolt on good 3" in/out muffler .

thay say this is good for a basic solid 25-30 hp.

brian at tbichips dyno run pulls stock to this setup got his basicly 40hp and 50 ft lb of tourqe . on 87 oct gas
 
I just had my brother that works at pepboys order me the cheapest magnaflow highflow cats that they showed in there computer they have been fine for me with no problems they are just a weld in unit. There on my 2001 gmc z71 with a 5.3.
 
Yeah, actually I've gotten a lot ideas from Brian @ tbichips... He's a good guy, he helped me a lot with my old TPI camaro I sold last year. He could have sold me things I didn't need a couple of times, but didn't take advantage of me, instead he helped me for free. I owe him some business so I always give him a recommendation when his name comes up!
The old build description on his site implies that he just bought a cheap noname hiflow cat off of eBay... I was just trying to see if there was a decent, affordable, easy to install setup. Comparable to the flowmaster catback... It was affordable, has held up for almost 5 years, and was the easiest exhaust system I ever installed over the years. It took me longer to cut the old exhaust pipes off. I'm not ready to put headers and a new y-pipe on, I know it would help, but I'm nowhere near ready to upgrade motors yet. I've got a block bored and prepped to become a 383 that was originally planned for my camaro, but that's a long way down the road if ever!!!
 
Cornfield seems to be right, seems the only "High Flow" feature would be the 3" inlet/outlet diameter... So, since I already have a 3" inlet/outlet, I will only realistically gain in replacing my somewhat plugged up 20 year old cat. It would seem that the spun style has less area for exhaust gasses to travel thru and provide a more direct flow, but not a lot of info other than guys calling them "High Flow". What Jeg's lists as "High Flow" Summit and Magnaflow don't? I also read somewhere. That they can no longer put high flow on their packaging? So I'm debating getting a direct fit for $140 or the universal spun style for $100.
 
Well they call them spun because thats how the housing is formed. The internals are actually a called wire cats, or metal cats. Plus the element is shorter, so less surface area for oxygen retention and less restriction. If you have the original "pancake" converter which is a bead type, you WILL notice a large difference between the monolith converters and the bead type. The bead type will clog up and not show any signs of failing, and restrict even more.

Basically just going to a monolith converter will help you out, but if you do some homework you'll find some that may pull just a little more flow out of them. Smooth transitions, larger diameter inlet/outlets, and even larger body's will flow more. Just pay attention to the weight ratings on them. Too small and they will fail quickly.
 
Thanks!!! That was better info than on the actual manufacturers sites... Yes, I have the original pancake style. I figure after 20+ years of use, and my truck used to run so poorly that it's probably not operating at 100% anymore. Plus, everything I've done so far has helped in drivability, power, or mpg... The money saved in fuel at $3+ a gallon doesn't take long to add up, so in a way the parts have been paying for themselves. I figure I'll keep tweaking everything until I'm not seeing any improvements. Thanks for all the info guys!!!
 
I've used Magnaflow and Carsound cats in the past. I think they're the same thing or something now. Figured they both had good reputations so wouldn't hurt considering both times I put a new cat on they "high flow" unit was the same or similar priced as the "OEM replacement" units.

Friend of mine found a set of cats off of a low mileage, newer GM fullsize truck in a junkyard and used them on his truck. Worked fine. Then again Michigan doesn't give a hoot about the emissions just so long as the stuff is all there.
 
Yes, magnaflow and carsound are the same now according to their website. I'm leaning towards the spun style only because it would seem to have a pretty straight thru design for the exhaust flow. I need a cat for emissions, but they don't actually test it. I won't gut it, because I've had Chevys with the cats removed or gutted before, and didn't enjoy the fumes... Especially since we enjoy running around with the rear window down, or the top off.
 
I always just use a test pipe and swap in a real cat if I ever have to do emissions, which I don't.
 
Well, we used to not have emissions testing here until a few years ago, and everybody used to just remove everything. The problem now is you can get an exemption if you keep it under 5000 miles per year, BUT... when you go to sell the vehicle, the new owner can't get it inspected until they have owned it Longer than a year. Let me tell you, try selling a vehicle that can't be inspected. I "found" a way around it, but it took me 2 years to sell a great pickup, and I lost a ton of money. Lesson learned, time to do things the right way...
 
Rumor has it, they will eventually do away with "sniffing" emissions testing and just do a quick OBD-II plug in test. If the engine light is off, and no codes present they will pass it.

Reasons why are because with so many states hurting for money, it will be cheaper for the state to do it that way rather than running full tests the way they are.
 
That's exactly what Pennsylvania does now... It works great, 95 and newer go on the scanner, 94 and older have to pass a visual inspection and everything has to be hooked up and in place. Simple and quick...
 
96 -up = odbII

95 older = non plug in required.

ny has been doing 96-up obdII plug in tests for over 5 years now.

but thay still do visual test of emmisions componets to be there if required from factory .
 
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