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To build up the header, Chris first mocks it up using welding rod to get the tube paths and lengths down. Then, he cuts out sections of Burns U-Bends to follow the path of the rod. When he has the sections cut out, he cleans the ends off inside and out of any oxidation. This ensures a clean weld.
Next, Chris tack welds the sections together with a tig welder. He can then go and verify the fit of the tubes on the car. If the fits are off, it's easy to lightly grind the tack welds off and start over without too much trouble.
Once that the correct dimensions are confirmed, it is time to seam weld the tubes. Chris back purges the tubes with argon gas to ensure that the welds do not get oxidized from the inside as well as from the outside which is shielded by argon dispensed by the tig torch head.
To back purge the interior of the tube, Chris uses wadded up aluminum foil to block the insides of the tube from the air.
Chris feeds argon gas to the inside of the tube through the foil with a hose connected to the argon tanks regulator. The trick is to run a slight positive pressure inside the tube to keep air out but not so much pressure that it can blow the weld down as you are trying to lay the bead.
With the tube full of argon, Chris proceeds to weld the tube together. After a few hours of this, you get an awesome header!
He completed header is a thing of beauty. The primaries are done in 3 steps of diameter. At the flange they are 13/4″, then they step up to 17/8″ and finally 2″ before the collector. The steps reduce reversion at high overlap and also spread out the tuning peaks for a broader powerband.
6 comments
Great series. I guess you weren’t making enough power to warrant a closed deck?
Yes, its a naturally aspirated engine so no need for a closed deck.
Nice! Over 300hp out of a sewing maching size engine. Only thing missing is some video of the car on track.
15inHg of vacuum? That’s more than 7psi, was it not 15inH2O or 15kpa?
I would take those HP #s more serious if they weren’t for churche Dyno.. it’s been knows for years their Dyno read high. Very high… 50hp plus.
Multiple car have Dyno there and at other Dyno to prove church read high..
Not anymore they have been using a different calibration for a few years now and their numbers are in between our dyno and a typical dynojet.