Osmosis

I am thinking of cutting my cats, but have a few questions.

First, what should be done with the air tubes? I was thinking of letting them vent to atmosphere where they meet the cat.

Second, is there any complication in running the car without the cat's other than emmissions?

Is there any way to pass emmissions with the cat's off?

Thanks for the help!

90rocz

If you really want to go that route, why not just break all of the internals out of them, leave them stock appearing?
I've passed E-Check with "hollowed" cats, if your car is tuned up pretty good, it'd be clean enough w/o the cats...BUT they usually want to visually see them there...if it makes them feel better I'll giv'em the visual..

Osmosis

I want to keep them incase I need to weld them back up for emmissions testing. I would hate to gut them and find that I did not pass emmiissions an now need to drop cash on new cat's! That's why I want to leave the air tubes in place in case of the need to weld the cat's back on.

The main reason I"m trying this is becasue of a wierd problem I'm having with my Z. Reubilt engine, AFR heads, ZZ3 cam, ported intake, 24lb injectors, crane ingintion, ect.... THE car has about the same power as the stock engine! After 1month of the life of the engine, it "opend up" and had tons of power! Well, then I put my supercharger back on 5mo. later. I blew a head gasket. Tore it down, and after the rebuild, the car has no power again?? I runs fine, just no power and gets hot in stop and go traffic. The car starts overheating in 80deg. weather in stop and go traffic. The only thing I have not done is cut the cats. And when the cats' get hot, I'm sure they expand and cause even more of a restriction, thus, MAYBE my overheating in hot traffic and lack of power is the result of restrictive cats? I was told that they were "high flow cats" from the muffler shop due to the 3in diameter. But then, 3 in diameter may not have "high flow Interals"!

I have tried everything!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Wide band showed OK 12.8/1,
Checked cam timming, OK
Valve lash, OK
New ECM, OK
NO results, checked the cat, ONE OF THE TWO, looked oK. The shop said " no need to look at the other since it's not gettin "Hot or sounds like it's broke"
I got to thinking, maybe it's too much of a restriction? So I"m going to cut the cat's to see if that is the problem. IF it is, I'll get some random tech. cats.............EVENTUALLY

dj haf

go to a muffler shop and have them cut out the cats and put some straight pipes in it's place... cost me 80 bucks, 40 a piece actually... dont hollow them out, they don't sound too good hollowed out. weld shut the air tubes and then take off your smog pump equipment cuz you really dont need it. if anything you can still use the shell of the cats and put them over the piping to make it look like you still have cats instead of hollowing them out

Osmosis

I want to leave the smog crap incase I need it for emmissions. Thinking of leaving all iof it so I can put on some random tech. cat's if I must. So leaving the smog pump/tubes on is a must for me. Must I weld shut the air tubes that run to the cat?

90rocz

You can just crush them shut with side cutters.
Did you get a custom Prom burnt, that's a lot of mods for a stock type ECM??
What compression?Timing?Are you seeing any knock or knock-retard??
I'd start with the basics again, go through the ignition, TPS, idle air bleed for starters..

Osmosis

Yea, I have the chip burning kit, an extra ECM, but that is not the problem because when it opend up, I was running the stock chip. The capability to burn the chip gives you the ability to tune to perfection where you gain extra ponies which I hope to do before I drive the thing off a cliff!

97WS6SCharged

As far as the over heating, have you thought about a new radiator or having your old one checked/cleaned out?

Osmosis

Had the radiator checked out too! And it's good. It only overheats when the outside temps are around 80deg F. and I'm in stop and go traffic. That's the only time it overheats? THe cat theory seems to make sence. More heat results in expansion and more of a restriction, adn increasing heat??? I hope, I thinnk?????????????? Open for Ideas and thoughts!!! thanks!!

dj haf

get a new thermostat. if you get a 180 thermo, ground one of the fan wires so that when the car starts, the fan comes on. in 85-90 degree weather, it keeps me around 160-180 degrees. if you dont want to kill your fan just stick in a 160 degree thermo... if you start to overheat, your fans will kick in and cool it down some... and you'll be around 160-180 agrees as well. any way you put it, one of the two ways will help you a lot.

Osmosis

Bro,

TY for the reply! I have a 160 stat in and also programed my chip for my larger injectors and to turn the fans on @ 180deg, and no. 2 @ 195 deg. I also wired a switch to turn them on by demand. I still overhead in stop and go, no power either?

90rocz

Here's what do do when I work on an overheating car.
**Check the specific gravity of the antifreeze mix, "a Prestone-type tester".
**Watch the flow inside the radiator after warmed up, to see if there is a problem with clogging or pump performance.
**Inspect for a "correct" radiator cap that will NOT bleed off pressure into the overflow bottle until cap's Max Pressure is exceeded. Not pressurizing will allow the coolant to "Boil" and not cool effectively. You can tell by squeezing the upper rad hose and see if it blows bubbles in the overflow bottle with virtually no effort.
**Rev the car while watching the lower radiator hose, if it sucks shut, it's missing the spring inside..
**Make sure it has the "Air Dam" under the radiator to direct air up to it...
**You did the T-Stat....
**Make sure the water pump is correct for a "Serpintine" set up, the others will turn BACKWARDS...
**Make sure the fans are working properly...you got that covered...

If you still have overheating you are either running lean, or too much compression, or too much timing advance, or not enough radiator, or have scale build up in the block. You can have the block flushed clean with solvents at a good radiator shop...

Osmosis

90rocz,

i really appriciate the reply! I have done everythig you posted! THe overheating thing is really wierd! When the temp outside is above 75-80deg f, and i"m in stop n go traffic, the temp creeps up and once it hit's 220, it climbs as if I have no fan. BUT BOTH WORK! The wide band showed proper fuel ratio. I occasionally get a code 32 (egr) but have applied vacume to the egr and it holds vacume and the solenoid is new, the vacume lines are good too! Brand new cap, timming is set @ 6deg advanced...i have played wiht that, but nothing!

I'm cutting the cats in a few weeks when i get time! Talked to a guy @ a pro shop and he thinks that may be my problem. Lack of power and a restrictive cat could cause the poor performance and the type of overheating i'm' having????????? I hate my car now!

90rocz

While I have seen the "lack of power" problems with plugged cats, the only thing that usually got hot was the cats. A sure sign they're plugged is them turning "cherry red!" Or vacuum that steadily decreases while idling. But I've only seen that maybe twice in my life...I repair cars all the time...
A stock radiator is going to have a tough time handling the increased heat/power you're making, it might be time to upgrade??..

One other thought, have you replaced your temp sender? I've seen marginally bad one give low and high readings...

dj haf

get headers coated by jethot... it'll reduce the underhood temp enough for your car not to overheat. i notice that every time i step on it, the temp gets hotter and hotter till i let off on the gas and start driving normally. mainly because the headers get so hot it starts to heat up the engine bay.

but if you dont want to buy headers... get yourself a heavy duty radiator. thats probably your real chance of fixing your overheating problem. it's not that hard to install a new radiator though... my grandmother could probably do it for me if i asked her to lol