Ever since I developed headers for 55s I was always fielding questions about exhaust scavenging effect on headers. I've never been the best at explaining it in a typed out reply or post. So Today at the shop we had one of your 63 long tube headers just about finished up. Just before we welded on the third Y collector we shot this video to demonstrate how our header scavenging works.

For all of us car nuts out there, we've hear about scavenging alot, but have you ever seen it? So we shot a quick video to share with you guys.

http://www.youtube.com/watch?v=pDQXsfeZGwk

 

Now I know...very interesting...some lucky guy is getting those headers!

 

headers looks very nice but I fail to see anything to do with scavenging effect, what I see is vacuum being created

can you make another video showing the inside of the header, I want to see how clean the welds are where the flange meets the tubing

 

What you are seeing is indeed a vacuum. Based on the scavenging theory that the pulse of one cylinder will help suck out the exhaust gases of another.

Does this pic help? I might have something more close up for ya. I'll check and see what I got. My brother takes most of the photos so better ones could be on his computer.

 

I really like the welds and the cleaned up tube-to-flange area on MBH's headers. At first I was wondering what the heck you are trying to demonstrate until I saw the guy using the blower into one of the tubes creating the scavenging effect on the other tubes. Great work!

Cant't wait to see and hear them on bhamg's car this Thurs.

 

Nice JOB

 

LOL, OWNED.

Josh

 

Famtastic job Hooley.. So talk about air flow, I just installed the Kleeman TB's and got so much flow It blew the weld off one side of my muffler I fixed the weld today and went to play.. The yellow triangle bulb will be the next thing to burn out Gotta say man , I think I have the baddest sounding 63 thanks to the MBH LT's and Renntech Mufflers.. Thanks

 

Thank you,informative.

 

here is a good read.
http://www.ssheaders.com/header.htm

 

interesting video....

 

that pics help, but very little. I would like to see a light or flash onto the flange-tubing conncetion to see the welds. And then another shot on the merger side after the collector looking in, thanks.

 

Were you just getting headers, or headers and tuning? Any before/after dynos yet? I'm sure it's a nice change from stock manifolds.

 

Right now he should be on the road back to Vegas. I'll let him post up his numbers. First and foremost, bhamg is very nice guy. Very kind and likable. Without giving to much away, our dyno testing included this:
Stock runs
Stock ECU, headers, test pipes, with secondary cats intact
ECU,headers, test pipe, secondary cats intact
ECU, headers, Primary cats and secondary cats intact.

With that said I'll wait for bhamg to post if he so chooses.

 

Can you say what tune was used for this test?

 

I can't wait to see the numbers....

 

Very cool; hope he posts - sounds like valuable data (especially A/B'ing the first two).

 

How is it possible to retain the primary cats with the headers installed?

 

No offense but I think the video and it's relationship to "exhaust scavenging effect" is a bit misleading. My understanding is that header primary tube diameter, and more important, primary length are tuned to a specific RPM. Pulses are created in the primary tube by the opening and closing of the exhaust valve. A negative pressure wave naturally develops after an exhaust charge leaves the primary. The science and art of header engineering is to adjust header length so that the negative pressure wave reaches the exhaust valve at the optimum working rpm. That is what creates "exhaust scavenging effect". It does no good to tune headers for 7000 rpm if the engine spends most of it's working life well below. "Long tube" headers work so well on the street because the maximum "exhaust scavenging effect" takes place in the middle of the engine working RPM. This creates a much better torque curve, which is very desirable in a street application, verses a race engine requirement of maximum horsepower with little regard for mid-range torque. Simply blowing air in a tube does create vacuum, known as the venturi effect. Every carburetor and perfume sprayer uses that principle. Tuning negative pressure waves in the exhaust primary tube is what creates exhaust scavenging. Hopefully your long tube headers were designed using the scientific formulas available and then fine tuned on the dyno for a specific torque range. If so, I'm sure they are winners!

 

If I had read this first I wouldn't have bothered. A VERY good explanation of exhaust design

 

One test that would have been cool to see is a stage 1 tune, on the stock exhaust. Then install the headers. Obviously with the throttle body being able to open all the way that would net you more power from the throttle body, then see what the headers do. In this case there was no stage 1 file made. With a state 2 file tuned for the headers, its not a good idea to run that file on the stock manifolds.

Dyno-Comp installed aftermarket cats. So the primary cats used are not stock, but the secondary cats are stock.

 

I came across this picture, Maybe this helps more.

 

No followup until the weekend but lots more power and an unreal exhaust note...OE quiet on the highway but unleashing a wild guttural howl on full throttle. I have more of everything engine/exhaust-related but with absolutely no loss of civility. Great, great crew at Dyno-Comp...Hooley's headers are a work of art!

 

How civil is your cold start?

 

What tune are you using?