Marcho Polo

I've been told countless times that running an engine for extended periods of time with only open exhaust manifolds (stock, not headers) will cause burned exhaust valves. Is this true or not.


My pre-cats are clogged. I need to get to the muffler shop 15 miles away. The car won't go over 20 mph right now. I'm thinking of unbolting the front y-pipe and trying to drive down there, but even the muffler shop guy said not to.


What do you think?

ralph

i think "open exhaust" in the case of burnt valves refers to running the car with no exhaust manifold (or Header) at all. Cutting at the y pipe shouldn't be a problem. It might be loud, but it shouldn't hurt anything.

VMAX451

I've heard that too, not sure why it would though. Maybe the lack of backpressure would result in too lean a mixture and hence a burned valve :confused: ? I'd be more worried about fumes and possible fire hazard. And your o2 sensor would be out of the loop I would think. I guess I'm not sure, just rambling...

scorp508

Hmm.... 15 miles. You have AAA gold?

Marcho Polo

:cry :(

nope. Already thought of it! When I lived in California, a friend of mine had AAA and I think I used more of his towing than he did!

88L98

with the header style vette manifolds, you will be fine. they are long enough. im not 100% sure on this, but i believe burnt exaust valves was something more of the past having to do with leaded gas and the type of metal used in the exaust valve. i think i remember reading that this situation has been pretty much eliminated, but the info seems cloudy so id find out a little more.

Aggravated4life

Id be more concerned about heating things up under the car with a open exhaust with just the factory shorties in place.
If your car wont go over 20mph, something is not right.If your cats are truly clogged,they will glow RED and get very hot.
You may even have a clogged main cat if its this bad.
I would suggest you unbolt the rear Y pipes and exhaust and punch out the main cat if its really clogged on visual or unless ts already gutted.
Leave the front Y pipe on and go drive and see if it runs any better.
My cats clogged a few years back and wouldnt move too well.Had to gut the main cat out until the new one arrived(on back order) and when i did that, it screamed back to life.
I drove around a few days with the back exhaust off and just the gutted main cat and front y pipe still attached.

Burning valves from a lean exhuast was more true for older carb cars.
With a properly running TPI and free flow exhaust, it shouldnt be a problem if the 02 compensates for that leaner condition or you ahve a prom burned for everything.

But taking your front pipe off leaves the o2 unplgged and who knows.The heat from that alone can prob melt the firewall or the plastics there and the fumes will come inside the car.
Btw, I thought a code 45 could make the car run in limp mode until fixed.it wouldnt have any power to go.Maybe im wrong on that one.

Good Luck and let us know what happens.

Radio Joe

I had always heard you may burn the valves if you ran the engine with NO exhaust manifolds on it.......

Jay Axson

If your worried about it, why not have it towed?

GS Ragtop

I wonder if the issue is after shutdown, very cool air could hit the valve with only manifolds in place? Maybe somebody warped a valve and believed the cool air was the cause...

Brad

Shark ssn591

I agree w/ Jay... Have it towed, you'll never know if it was worth it untill you break something... Consider it insurance.
In the amount of time it took for you to ask & wait for reply's you could have had your Vette back. If you are worried about the $$$ then the muffler shop guy would be expensive in my neighborhood (they cannot bypass any emission stuff... they are obligated to install new cats)

QUOTE: "nope. Already thought of it! When I lived in California, a friend of mine had AAA and I think I used more of his towing than he did!"

Maybe AAA would be a good Christmas present for yourself.... seems your history suggests it is worth it. :yesnod: :yesnod:





[Modified by Shark ssn591, 6:04 AM 11/27/2001]

TIMSPEED

Craig,
Don't worry about it man. As long as you keep the manifolds on, you'll be ok. Just don't go TOO long, and don't go when the weather is BONE cold. Try to go when it's around 70-80º outside. I drove my truck around for a while with just the race headers on it. It was just AMAZINGLY loud. No worries though. (And that motor is OOOOOOOLD)

Nathan Plemons

I drove my car with my long tubes for 2 days without the catback. People race cars open headers all the time, I think you will be alright, just drive straight to the shop and don't drive around too much.

I drove mine to the shop just to find out that he couldn't do it that day, and had to drive it back home. I then had to drive it back to the shop again. Probably around 30 miles total.

BTW, the 02 sensors shouldn't really be a problem either. When I drove mine I only had one connected, the other was in the glove box. The car ran just fine, not even a check engine light. It was just LOUD!