AO

BTW, what Imo000 suggests will be very loud, but fun!

whitefox

I could really use a lift for the exhaust, its hard to test things out because theres only a certain time of day and area where I can actually open the car up.

Imo000

It sure was. I had to do this on my ’93 LT1 Trans Am. This was the only realistic way of testing it. The dealer suggested it, so I tried it and sure enough it was a clogged cat. A justifiable opportunity like this only comes every now and then, so make sure you make it a good one.

Fabio421

Thats the spirit

Jim R.

Ross,

I am by no means an angel behind the wheel, but think about this. You are a 17 y/o kid driving a red sports car with open headers at speeds above 100 mph............

Be smart and be carefull. Only 3 outcomes: you find the problem (or not), you make a high speed driving error with a 20 year old high mileage car and new driver skills, or you get busted. I don't know about Florida, but in NY they would impound your car and arrest you on the spot. Just something to keep in the back of your head.

Like I said, be smart, be carefull. And yes, I have been well over 100 in my old '75 'Vette with a very well built small block and open 1 7/8" headers at about 20 y/o. Lucky I didn't get caught, it was a LOT of fun, and I probably still have hearing damage from that car.

flamesuit on

Jim

anonymousagain

no flames Jim, actually it's sound advice...and exactly what I told my 17yr old with his '80 as well!!

Not to justify it, but there IS a big difference between accountability if I did it, as opposed to if my son did it. Still a gamble for either, but age matters when something doesn't turn out perfectly and it has to be cleaned up or reconciled.

Sounds like cats are clogged - Good Luck !!

whitefox

Alright I'm going to go out and drop the exhaust... and make a run this afternoon.

Darien

H-pipe

dr bob

Vacuum guage. It's a LOT quieter, cheaper and easier, faster, definitive. Reduces risk of attracting attention an 100+ too, so add in savings on attorney, towing/impound/storage, bail, and cigarettes for Bubba. Subtract the two free meals you'll get before your bail arrives, maybe open exhaust is the better way...

whitefox

I havnt dropped the exhaust yet, I dont understand where I am supposed to pull the vacuum from?

Also, when I get to around 100mph and it starts to hesitate, if I let off to 3/4 throttle it will slowly accelerate but still hesitate. Its an on and off sort of hesitation. If needed I can mount a camera and let you guys diagnose it.

Ron_H

If you're going to need to bail out, make certain that you have a stash of cash on your person, or you own real property in your state. Forget credit cards or atm cards. Don't ask me how I know.

whitefox

When you're under 18 there is do not set a bail for you, don't ask me how I know.

dr bob

Ross--

There's a four- or five-way 'tee' that grabs vacuum from the check valve on the brake booster. Little hose runs from the tee, through a little plastic in-line check valve, then a hose between that and the fitting on the brake booster. Get another tee and put it between the inline check valve and the brake booster fitting. It will take another small piece of hose to do that. Then your vacuum gauge attaches to the new tee with a hose. Run the hose up through the top of the hood at the base of the windshield, through your just-barely-cracked window, and put your vacuum gauge on the dash where you can see it without crashing into something. (Very Important...)

Go drive around normally, and observe the action of the gauge. Vacuum will be none with the engine off, then go to somewhere around 16-17" at engine idle. You can see how the gauge moves with load, a little load means less vacuum, a lot of load can mean no vacuum. You'll also notice that the gauge almost pegs when you run on a trailing throttle. As you accellerate to a given speed (load), you'll see that vacuum drops as you accellerate, then comes back up as you reach your target cruising speed (load). At higher speeds (loads), the vacumm will be less.

Looking for the clogged cats you noticed at 100, you'll accelerate to that speed and back off the throttle some so that you are just holding the speed. How's your vacuum? If you still have good vacuum, accelerate to a slightly higher speed and look. Repeat this process until the car won't go any faster. Assumiung that your previous 100 mph data point on level ground is good, you will find a point where you are at part throttle, max speed, and zero vacuum. With the advertised top speed somewhere in excess of 155, you should have plenty of pedal left when you hit that "wall" at 100, and your diagnosis will be easy. If the vacuum is zero at that point on a cruising throttle, your cats are probably toast.

If they are toast, dispose of them safely. There's a long-lost lister near the Cape who considers toasted cats a delicacy.

whitefox

Are bad cats a common problem?

Fogey1

Run chronically rich for a while and you can end up with a melted catalytic substrate that will effectively clog the cat. That's what happened to me in a non-Porsche.

I dropped the (double) cat and spent half an hour with a steel rod breaking up and removing the substrate. Somewhere I have a bucket of clayish stuff mixed with platinum. Turned the cat boxes into resonators.

If I had it to do again I'd probably just knock some "breathing" holes through the substrate.