Just got the car going a few days ago and currently it's running on open headers(Hedman 68470) and prob will be till next week when I decide to tow(its a trailor queen) to the exhaust shop.

My question though is... I've heard from various people here and there that open headers aren't good on a car. Sure, the Camaro is rarely driven, but how bad are open headers? I'm running on lightly modified engine(in sig), but have heard that open headers can blow valves and such. Reason I'm asking... considering taking the Camaro to the track this weekend to see how it's going. I've only put maybe 15 miles on the car since it's been back together with the open headers, but making a few passes Saturday won't be causing problems, right?

 

Open headers are fine.

 

Here's how the theory goes:

You run the car hard, get it hot, and shut it off. Some of the valves will be open. The hot exhaust valves can be exposed to cool air sucked back up through the open headers. The valve cools unevenly and warps.

There are a few problems with this theory, such as:
- Never been proven (write in to Myth Busters, maybe they'll take it on)
- Can't explain how cool air flows back into the engine - one theory is you catch a cylinder at overlap so you get both exhaust and intake open at the same time
- The heat in the headers will warm any air that flows back into the cylinder. By the time the header heat is gone, the valves will have cooled, anyway.

Much more likely to happen if you don't have any headers or exhaust manifold on the heads. Even then, it would have been more likely back in the soft valve leaded-gas days than it would be with today's better material valves.

The bigger problem running yours open is shorties don't produce good power when open. You should at least have a pipe off of each collector for a couple of feet.

 

I was told your computer would throw a code. That's false?

Also, thanks for that valve theory. I was always taught that cold air was sucked back in but never understood how.

 

I drove around with open headers for a day and had no SES codes. The car would seem to slightly hunt for idle though, which with the open headers made it sound cam'ed. As soon as I connected the Y pipe it idled fine like before.

 

The trouble with open headers is when you run them on an engine that is tuned for a full exhaust, most notably an engine that previously had cast iron manifolds and single exhaust. When you run open headers, the mixture will run lean because of the increase in efficiency of the header. With lean mixture, you get a hotter combustion chamber temperature, and an overly hot exhaust gas temperature. This can cause a burned exhaust valve.

The cure is to make sure the mixture is running in the 12:1 to 13:1 ratio at wide open throttle in order to maximise power and minimize problems with leanout. If you do this, then there is no problem with open headers, other than hearing loss.

 

i ran mine on open hedman LTs for a day..... but i didn't wanna chance an encounter with the law. that was really loud. but no issues here.

 

Burned exhaust valves are an artifact from leaded gas days. About the only way it happens these days is if something gets caught between the valve and seat (like a loosened chunk of carbon) and keeps the valve off the seat during combustion.

Speed density systems ('90-'92 TPI, TBI) and open-loop (non-feedback carb or FI) are sensitive to changes in the assumed parameters, such as exhaust efficiency. So, running open exhaust when tuned to muffled exhaust can cause mixture issues. MAF systems ('85-'89 TPI), on the other hand, just read the air going in - how efficiently the air goes out doesn't affect the tuning. Feedback carb just reads the O2 in the exhaust and adjusts mixture accordingly.