Catalytic converter

[1TUFF89]

Has anyone recently purchased a new catalytic converter? I have replaced the entire exhaust system except the converter. My truck has over 140,000 miles so legally I shouldn't have a problem. I have only looked at them on the net but have noticed Dynomax high flow converter seems to be popular. Any input would be great.

Chevy's RULE!

 

[Todd78/87]

I bought two for my 85 from here: http://www.discountconverter.com/universals/index.htm
Then in a "dream" I had

,,, I gutted them, cut my mufflers off, slid the cats up the pipes, clamped them, then clamped the mufflers back on.

Todd 78/87

Alaska Bound

 

[CrazeeBush]

Wouldn't it be difficult to run a true dual with the transfer case in the way? Those cats aren't small and I'd think it'd be difficult to plumb it around the t-case. Just a thought.

Although I'd imagine that aftermarket are MUCH smller than those huge pieces if crap they put on at the factory.

-JoSH
[email protected]
http://josh.coloradok5.com

 

[1TUFF89]

If you're just asking - yes, I guess it would be hard to run a true dual exhaust with the t-case in the way. If you're saying that because I said I replaced my exhaust system I only have one cat on the driver's side. I was told that if it came from the factory with one cat you can't change that. I have dual exhaust behind my Flowmaster muffler going out each side behind each rear tire. I will only be replacing the stock converter. What happened is ever since I replaced the y-pipe (along with a new manifold) I have a "hissing" sound when I give it the gas. Apparently the pipe is not perfectly tight inside the converter pipe although it is clamped on tight. I wanted to have it welded together to stop any and all air leaks, but figured if I'm getting it welded for good I should go ahead and replace the cat. I wouldn't want to weld everything up and then have to replace the converter later.

Chevy's RULE!

 

[CrazeeBush]

Forget a high flow cat, just get any one and gut it.

-JoSH
[email protected]
http://josh.coloradok5.com

 

[TexasK5er]

what is the best way to gut them???

Nail It!!!!

 

[Todd78/87]

It's not TO hard to get that right pipe in there... both my 78 and 85 have true duals. I put the right side cat further twards the rear on that side, also turned it vertical to avoid evaportating the gas in the gas lines on the frame rail.


Todd 78/87

Alaska Bound

 

[6.2Blazer]

Why would you buy a new cat only to gut it? The newer original equipment, and especially the high flow aftermarket, converters really are not that restrictive. Gutting one and just splicing it into the pipes will often cause a lot more restriction due to the air tumbling around when it hits the big open space.

 

[Todd78/87]

Because it must visually pass inspection here in MO.... and there is no empty space,,, I slid it 3 feet up the exhaust pipe,, the pipe went completly through it.

Todd 78/87

Alaska Bound

 

[GMC4by4]

1tuff89 seems to have 2 blazers. One '77 and one '89. I know on this list it seems blasphemous to keep your cat but the way the new hi-flow cats are built, they are hardly restrictive at all. I like driving my truck, not smelling it. The '77 will benefit from a new hi-flow cat over the stock one. The '89 will run worse with a gutted cat. The computer controlled engines require a small amount of backpressure to run right. I am running a stock 350 with a hi-flow 3" cat and a Magnaflo muffler with a 3" in and twin 2.25" outlets. It has a nice low rumble, keeps the air clean AND runs better than it did before the new exhaust. So flame away!!

-Rick

 

[HarryH3]

The newer catalytic converters don't affect power enough to worry about gutting them. Many of them flow almost the same as a piece of straight pipe. Colorado tests your emissions at various RPM's so you might not pass with a gutted converter, even tough you pass the visual inspection.

There's been some talk of making vehicles pass a test where they have to run on a chassis dyno at various loads and RPM's, similar to how the EPA tests them. You'd have a very hard time getting past one of those tests with gutted cats.

<font color=black>HarryH3 - '75 K5</font color=black>
http://ThunderTruck.ColoradoK5.com

 

[Todd78/87]

If Mo had an emmisions test, I wouldn't have gutted them,,, some states don't have any kinda of inspection, like Kansas. So it all depends on where you're at.
I wouldn't make the general statement that "the high flow cats out now, flow almost the same as a piece of straight pipe" or even "very well". There may be some that do, but most of them do not. I have collected data from the drag strip on a few different cars with different set ups. One in particular a buddy of mine had a high flow cat and could never run a 12.xx run... always in the 13's (about 50 runs, not all at once ). He finally gutted his cat and has been in the 12's ever sence. With a best of 12.68 @ 115. That's a lot of restriced power. Granted, it was on a forced induction car, which will make more of a difference then on an n/a car, but there is still hp there to be had.
All engines need some degree of back pressure to run right, but if you have an exaust that is applicable to your car or truck,, there is still plenty of back pressure without a cat.
Some places already have that cassis dyno testing. Not sure what states, but the Supra guys talk about it on the list every now and then.

Todd 78/87

Alaska Bound

 

[Jeff427]

Todd78/87, Your 78 was equipped with a cat? I have a 78 that was factory equipped with duals and no cat. The factory exhaust hangers are still riveted to the frame.

 

[det45]

Recently I replaced the exhaust system in my 1989 K5. I stayed with the single exhaust system but used 3" pipe starting from the crossover all the way back to the tailpipe. The catalytic converter is a CATCO with a 3" inlet and oulet. The muffler is a three chamber flowmaster with 3" inlet/outlet. The truck runs great and has a nice tone to it, (sounds like duels). The converter cost me $95.00 via JC Whitney, the flowmaster was $75.00, and the rest of the system including labor was about $120.00 Going with the single exhaust and 3" pipe is an improvement over the stock system yet retains enough back pressure to keep things running well. By the way I could see daylight through the Catco converter. That tells me they are made with a very low restrictive design.

 

[Todd78/87]

No, Jeff it doesn't have cats,, but it does have duals, that was in reference to it being hard to put true duals on them., I meant that I have duals on both, but put the cats on the 85.


Todd 78/87

Alaska Bound

 

[Jeff427]

Thanks for clarifying that

. I was starting to get worried that I was going to have to retro-fit my Blazer with cats that it never had

. So far Michigan doesn't require emissions test though, but I'm sure that it is only a matter of time

.

 

[jarheadk5]

Random Technologies (www.randomtechnologies.com)makes "Super-High Flow" cats that have always gotten good reviews. MANY applications. Four Wheeler just reviewed them very recently on a Chevy big-block dually; one of their conclusions was that if you're getting a hi-flow cat, upgrade the rest of your exhaust too. Hi-flow cats won't help when there's other restrictions in the system. They are also much lighter than stock. One of their 3" in/out cats is in my near future.

Semper Maintenance!

 

[Eagle86K5]

Don't get me wrong ya'll. But the cats were added to vehicles for a reason. To reduce the emissions in the air, the stuff we breath. We have scientists warning us about global warming and I cannot remember such warm winters as we have had the last few years. I will run the cats and do my part to help keep the air breathable.

<font color=green>

Eagle86K5

<font color=red>
Masonry...It's a Good Thing
2B1ASK1

 

[Todd78/87]

Other studies show that cats do more harm to the air than good... so who do you believe??????

Todd 78/87

Alaska Bound

 

[Eagle86K5]

Ok....we could probably "debate" the point, but I still would run them cause of the law, I am the last one that would want to be the first to go to jail over a felony emmissions charge...hehehehehe

<font color=green>

Eagle86K5

<font color=red>
Masonry...It's a Good Thing
2B1ASK1