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Old 07-08-2004, 02:57 PM   #1
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Open headers = engine damage?

I have been thinking about getting remote operated motorized exhaust cutouts for quite a while now, but I have some concerns.

I've heard that running open headers can damage you engine...something like burning the exhaust valves Is this something to worry about? How can I prevent it...because I know you can run open headers...tons of street rod guys do it. I need to know how to run cutouts (which will essentially be open headers) without hurting my engine.

Thanks.
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Old 07-08-2004, 05:08 PM   #2
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Old wives tales. About the only down side to open headers is the noise and heat.

If the cam is designed around a restrictive exhaust with lots of duration crutch to evacuate the cylinder, a free flowing exhaust will actually rob you of HP.
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Old 07-08-2004, 11:06 PM   #3
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hmmm... i guess it depends on who you ask. I asked the same question on StangNet, and just about everyone said that it would hurt my valves.
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Old 07-08-2004, 11:44 PM   #4
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Maybe if you ran it open head with any headers you might hurt something. Someone on here was doing just that a month or so ago...LOL. If you have shortie headers you have to run open out the back of the H-pipe. I always run it open out the X-pipe. I once tried it open with just the headers. It ran the same times but it was way louder in the car so I put the X-pipe back on. I don't think you will be impressed with cutouts. Not all of the exhaust will go out of them and IMO they sound like crap. But being you don't have any mufflers now whats the difference.
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Old 07-09-2004, 12:19 AM   #5
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Quote:
Originally posted by Scot_94GT
hmmm... i guess it depends on who you ask. I asked the same question on StangNet, and just about everyone said that it would hurt my valves.
Yup, and if you run your tires with anything but 32 psi air pressure they will explode. If you don't run 50/50 anti-freeze in the coolant system the engine will sieze, and if you run anything but 10w-30 motor oil the engine will explode.

What exactly is going to damage a valve with open headers? The hot gases escapeing past the valves???? That happens everytime the cylinder fires. The rapid escape of gas??? Well cylinder pressure at 1300 psi, it comes out pretty close to the same with 14 psi pressure or 20 psi pressure against it.

Lastly.......... HAVE YOU EVER BEEN TO A RACE????? Every car out there is running OPEN HEADERS. Most tunned MUCH shorter than anything your going to want to run. Outside of dumping shorties against the firewall..... a race header is probably going to have about 20 to 24" of tubing total. To long a tubing package restricts the flow for large displacement/high RPM engines. Even when talking about 2 1/2" primary tubes and 5" collectors.
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Old 07-11-2004, 04:44 AM   #6
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usually running through the H(x) pipe is better and iv'e seen results where running total exhaust vs open headers is better in power and noise, win win i say.
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Old 07-11-2004, 04:49 AM   #7
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I repeat......

I depends on the engine design.

If the cam installed in the engine is designed around a restrictive exhaust, then open headers can have a detriment to performance. The excessive cylinder pressure bleed due to long exhaust event durations and no back pressure will reduce performance.

If the cam is designed around a free flow exhaust, and a restrictive exhaust is installed, then the engine will be constipated, with the air/fuel charge remaining contaminated with exhaust gases that are not evacuated.

There is no one solution fits all, but your not going to BURN valves based on an open header run engine.
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Old 07-11-2004, 05:37 AM   #8
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what i think about the people saying you will hurt the valves is not while the motor is runnint.. i have HEARD that cool air coming back up the collector after the motor is shut off can cool the valves too rapidly and then cause them to warp. dont hold me to this though.
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Old 07-11-2004, 07:09 AM   #9
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Ive been racing cars for 20+ years and all my drag cars have been open header cars. Ive never had an exhaust valve problem.

LOL this is just too funny. Kinda like dont sit to close to TV or you will go blind LOL
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Old 07-11-2004, 06:33 PM   #10
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Quote:
Originally posted by bigisle87
what i think about the people saying you will hurt the valves is not while the motor is runnint.. i have HEARD that cool air coming back up the collector after the motor is shut off can cool the valves too rapidly and then cause them to warp. dont hold me to this though.
this is what ive heard as well....the people at stangnet are either idiots or they misunderstood you and thought you meant running open head as in no headers at all or open shorties which both are bad ideas b/c your gonna have a ton of hot air in your engine bay causing all kinds of problems...and in that case I guess you might have a problem with your exhaust valve cooling off real fast and warping but even then I dont really see how....now if youre planning on running cut outs somewhere down twoards the end of your h pipe or after your long tubes then I see no problem at all in doing that....it might not be worth it but its not going to ruin your exhaust valves...
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