Gary,
On the subject of flat collectors: I designed my
headers so that the 4 1 5/8" tubes were aligned side by side
(horizontally). I then welded the touching edges together,
Using a thin cardboard templet, I made a flatten cone that wrapped
around the 4 pipes. The length from the end of the pipes to where
the cone was to mate to the header flange was roughly 8 or 9 inches.
I cut a flat piece of sheet metal to match the templet and
wrapped it around the 4 side by side tubes. About 3/4" overlap
over the tubes. I tack welded it using a torch, and then used
the torch to heat up the sheet metal between the tubes. I then
gently hammered the hot sheetmetal down into the V area between
each tube pair. I completed the weld with a torch. If I do
another I will use my mig welder as it is much faster and cleaner
than a torch.
By the way the hole through the frame for the tail pipe
is not large enough for 2 1/2" EMT. The holes in the frame were
a little rusty andI therefore took a section of 3" EMT
(cut on a bias to match the frame angle)and welded it in the
frame in place of the original crude hole that was hacked in
there by Roots. The 3" EMT is large enough to pass the 2 1/2"
EMT tail pipes without touching. If you build a crooked
version and the pipes touch then I recommend asbestos matting
to cut down the rattle. There was asbestous 1/8 x 2" x 4"
mats on some 351C motor mounts back in the 70's. Other safer
material could be used as long as it can take the heat.
Speaking of safty. EMT is zinc plated just like galvined
sheet metal. When you are welding or brasing to zinc plated material
the zinc will burn to a white powder. It makes it hard to weld
but more important, if you breath the vapors for long you will
find that the next day you will assume that you have a bad case of flu
complete with a lot of chest conjestion and coughing up
"green grimy gopher guts". Always use a strong fan when welding
on zinc plated material. Also note that the brass rods used in
brasing also have zinc in them so when you overheat the brass
you have the same problem even if the base metal is not zinc
plated. The fan is a real problem when using a mig welder with
argon or co2 as the gas gets blown away and it messes up the weld.
Jim Barrett Tiger II and others.
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