Chevy & GMC Vans

Hey guys...a quick question. My Cat is full of holes and smells like rotten eggs, so I was thinking of eliminating it since we live in Florida, where there are no emissions or inspections. The oxygen sensor on my 91 (there is only 1 oxygen sensor) is before the cat, so that shouldn't be a problem.

My question is about back pressure. Will there be enough backpressure with just the muffler and no catalytic converter?

Thanks guys!

Kev

I ran my '94 for well over a year with a gutted cat with no problems or noticeable difference in performance or economy. I don't see you having a problem with it.

In theory, removing the cat should improve exaust gas velocity down the pipe and improve exhaust scavenging from the cylinders. The second the exhaust hits an enlarged chamber like a cat or a muffler, there is a loss in pressure and velocity.
It amazes me that Florida has no emissions testing.

With out any emmissions laws then takeing out the cat will only help ya. In MO we dont have to have a sniffer test on 1995 and earlyer cars BUT if it came factory with a cat or A.I.R. it HAS to be on it to pass visual safety insp. But that dont mean you cant have a hollow shell where the cat used to be LOL

So pretty much the only thing you'll be hurting is the environment.

I was thinking about that, Aaron, but I don't think the lack of a cat will be any worse for the environment than the defective cat it has now...lol. Plus, I had an old Volvo that barely passed emissions back in the early 90s...and then finally the cat died, so I gutted it because they were very expensive for Volvos, and I was stationed in CT where they are very strict. I had to run it through emissions a year latter, and it passed with even lower emissions, even with the gutted cat...not sure how much good they do other than lowering nitrous oxides...which get broken down into oxygen and nitrogen in sunlight anyway.

And I guess Florida decided that since the ever-present winds in Florida scavenge all the gases away (even Miami has clean air!), they didn't want to mess with emissions...or even inspections even! It is also the best place in my opinion to register a vehicle...there are no personal property or motor vehicle taxes in Florida, except for the very first time you register it...you never pay taxes on it again! And most DMV transactions take place at every single town tax collector's office, so you never have to wait for more than a few minutes in line! They have separate offices in almost every town that handle driver's licenses, so again, there is hardly ever a wait in line. Pretty cool state for registering vehicles, if you can put up with a billion old people driving slow, or the nasty humid summers...thank god we are never in Florida in the summer!

Kev

I tried to get my toyota to pass with no cat... it doubled the limit... passed with flying colors with a cat...


Global warming is natural anyways, it is caused by solar flares and sunspots... that does not mean that you should start littering and smogging up the city, but I dont think you should worry to much about not running a cat.

The Cat Is Gone!!! Yay!!!

I replaced the whole exhaust from the head pipe back. Where the cat was is a 2 1/4 inch straight pipe, flared to 2.5 inches to fit over the head pipe, and clamped in place. I used a 2 1/4 inch inlet and outlet round cross section muffler (cylindrical) with offset inlet and outlets to give me more room to work when disconnecting the driveshaft when towing it. The tail pipe I was able to reuse, although I did have to pay the local muffler shop to cut off the old section that went to the old muffler and weld on a new flared piece. I used all new universal exhaust hangers, although I did use the original hanger mounts: I drilled into the bottom of them, and bolted the new hangers to them with grade 8 bolts.

The result?

No more lag in acceleration at all! Its quiet, but throatier than stock. It still does the "purr...purr...duff...purr...purr...duff..." that all non-Vortec 4.3 engines do, but it runs awesome!

Still doesn't start right up though...gonna clean up the throttle body and see if that helps...whole ignition system is new and so is the fuel pump. Takes about 20 seconds of turning over to start right now, with the gas pedal half way down. It tries to start without depressing the pedal, but won't without pushing on it. I'm guessing a very dirty TBI?

Anyhow, good results with the exhaust...still gotta make it start on the first turn of the key!

Kev

Try Lucas Oil Top Cylinder Oil -=- cleans it right out.

You may suffer from low fuel pressure due to a clogged in tank filter or a fuel pump worn past acceptable limits. Drop the tank and replace that pump and filter, bet your problem is gone....

Hey Wagonmaster!

Already replaced the fuel pump, filter, and the pickup sock in the tank...also replaced the oil pressure switch, which seemed to help, but didn't entirely solve the problem: The Astro starts now in 5-10 seconds instead of 30...my guess is the fuel pressure regulator...it doesn't seem to be holding fuel pressure when you shut it down, and acts like you are repriming the lines when starting it up.

Kev

My astro came with a 3" exhaust and 2 1/2" tail pipe on a 4.3. If I had it to do again I would have left my cat on. I was getting 23 mpg before and now get 20 and its a slug used to zip. But thats just my opinion. With 3" exhaust theres not enough back pressure with out a cat.