350 with open headers, is that ok?

Question

i have a chevy 350 bored .30 over...edlebrok manifold, holly 650 carb. msd ignition system. aeromotive fule pressure regulator. .

it has 3" headers. . . is it okay to have just the headers, no extra pipe or cat or muffler or anything. just headers and a y pipe....

or will there not be enuff back pressure.

i no its illegal to do so, i dont care. i just wana know if its gonna mess up my motor or not.

Answer 1

It will run stronger and more HP with the open headers.If you do put an exhaust on,use 2"-2 1/2".The only thing with open headers is the car gets heated inside.I ran my 68 442 with open headers on the strip and road.I got a 10.1",135mph,quarter mile!And that was back in 1978! got some tickets but it was fun and funny!lol

Answer 2

If this helps a few other gearheads stop believing this myth, I feel I will have done my job!



No exhaust back pressure does not cause burnt valves! Running an engine over long periods of time LEAN burns valves! When you run an open header or header into open y pipe, you eliminate the majority of the flow restriction in the exhaust and change the scavenging properties of the exhaust pulse, which will make the carb run very lean, since the carb was tuned with the exhaust restriction in place. This is especially obvious with more radical carbs, since the overlap will allow a bit of over-scavenging of the cylinders - the adjacent exhaust pulse chasing down the header pulls the air/fuel out of the cylinder before the exhaust valve closes. If you run open headers, you need to correct for this situation by enriching the carb to compensate.



If you have an air/fuel meter and a O2 sensor bung on that y pipe, you may want to check the air/fuel ratio if/when you run it, just to be sure you're in a safe range.

Answer 3

Running Open Headers

Answer 4

It won't hurt the engine at all. Thats just an old wives tale, a myth about burnt valves, but you WILL loose torque under 4000 RPM with the open headers. Back pressure is not good, but exhaust needs to be "tuned" to the engine. Too big and you kill air speed inside the pipes which moves your torque curve way up in the RPM range, too small and you choke it up and kill top end HP.





I have tested this many times and my car runs .07 to .10 faster ETs with a full exhaust system than it does with open headers, and I'm talking about a pretty wild 355 engine here. 600 HP, brodix IK200 heads, 249/252@.050" cam, .570"/.579" lift, 3500 stall torque converter, 3.89 gear ratio, peak HP at 7,000 rpm, shift at 7200 rpm. Launch off a two step at 3000-3300 rpm depending on track cond.



My exhaust on this is true dual 3" pipes, 3" X pipe, 3" dynomax ultraflow mufflers. Full lenght exhaust with exits under the rear bumper of my camaro. System probbly weighs 45 lbs



And car still runs right at 1/10th second faster with exhaust, than open headers

Answer 5

Burned valves, maybe poorer performance depending on the application....



If this is for street driving then figure on noise tickets from the cops before you get to the point where the valved will be burned.....



Racing?.... Its probably ok but you do risk causing a fire under the vehicle....



If you don't care about the noise then at least run straight pipes from the headers and have the pipes exit in front of the rear wheels......

Answer 6

No it wont damage your engine, however you may run a bit LEAN if you dont adjust propertly, and you will move your torque curve way way upper in the power band.



You can use a car performance simulator to virtually do this and find out how moving your torque will change your car, try at http://www.nxgtrsim.com

Answer 7

Yes, you valves will not seat right without the back pressure from the muffler/exhaust system. You'll end up burning you valves.