Closed exhaust vs. cutout or open headers

[Winston Wolf]

I have 1-5/8" primary headers with 3" collectors, 3" cutouts, and 3" full exhaust/Dynomax 3" mufflers.

 

I saw no change in MPH/ET in back to back runs open vs closed. This is in 500 HP upper 11 sec small block.

 

There was a difference with 2-1/2" though.

[Andy's Auto]

Thats odd Wolfie, or good, not sure. Malibu runs .2 quicker on open headers. But it is not a street car with open headers, slicks, and race gas. But I am starting to use those 5 gallon blue cans of Sunoco just to get the lead and not ethanol. Turns out everything in leaded 100 is good for an old engine that makes a few hp.

[Chevyss]

Your lucky to be able to find Sunoco fuel. Us up here in the frozen north aren't as lucky. Of course when you live in BFE they have to pipe day light to us from time to time.

[Andy's Auto]

That is the downer Royce. Those cans that are piling up can only be had at Murrays Speed and Custom or the track itself. We used to have a pump at an In Da Hood gas station, but the quality is iffy at best. And you need a sidarm to get it safely. Industrial district during the day, drug dealers, thief, and other stuff when the sun goes down.

[CrazyDavey]

I can get pump VP100 here at some local stations. Before that I was using Sunoco but that place went out of business....Davey

[Montemedic]

Andy, I believe that you can order either VP or Cam 2 and have it shipped directly to your shop. It comes in either 5 or 55 gallon pail/drum. They will not sell to individuals, trade or business only.

[Mom's Car]

Hey Andy (or anyone else in the Southeast).....If you need/want VP Fuel my cousin Mark Klein in Ft Lauderdale is the Southeast Distributor

[Winston Wolf]

Thats odd Wolfie, or good, not sure. Malibu runs .2 quicker on open headers. But it is not a street car with open headers, slicks, and race gas. But I am starting to use those 5 gallon blue cans of Sunoco just to get the lead and not ethanol. Turns out everything in leaded 100 is good for an old engine that makes a few hp.

 

I would say if it doesn't loose any power, it flows like it is suppose to for the engine's needs. Keep in mind I also have an H type crossover. The guy that did my exhaust work promised it would work, and it appears he did not lie. I wrote him a letter on my track findings that I see was on his wall the last time I had to go there.....

[680HPStroker]

You are in the same power area I'm in and there was nothing to gain by going open from my every day closed system. That system is a 3.5" into 3" Torque Tech system. My system necks down to 3" just in front of my Dynomax mufflers. I love it. The power is there, the tone is there when you want it, but when just cruising I don't have to yell to have conversation with either a passenger, or someone on the cell.

[CrazyDavey]

there is a point, especially in larger displacement engines, where if the motor is not overpowering the muffler system then the volumetric capabilities are not being utilized to their potential. There are several reasons for this such as wear, mis-match of components and inefficient cam timing or profile.

 

If for example the intake valves are opening to late or closing to slowly then the cylinders are not being properly packed for maximum volume and combustion pressure. Ramp design is just as critical as choosing the correct duration and lift characteristics.

 

With open headers listening to the radio or conversation is not really an issue (hopefully you're at the track) but a well conceived exhaust system certainly is beneficial for street activities. That said if you are pushing 500+ c.i. and you open the headers with no gain something is not right....Davey

[wallaby]

 

 

"Did you get all that, Max?"

"All but one part, Chief"

"What part didn't you get?"

"The part after "There is a point"..."

[CrazyDavey]

it's rod bolts....

[714024SP]

Meanwhile, at Crazy Davey Racing...

[wallaby]

LMAO

[John Burns]

Make the power through the pipes! Diddling with cut-outs is a hassle in my book. I recommend a bigger pipe to the muffler (the hot gas needs more pipe there but not as much down stream). My Camaro is well into the 10s with 3" pipes to 3" mufflers (20" case) and 2.5" tails- I used torque techs reducer to neck down to 2.5 after the muffs.