How to Connect Headers to Cats

I have installed two sets of Melrose LT headers in C5\’s.
These go in with minimum hassel
and work great. To
finish the job you need the following items:
3\” \’U\’ bend.
Four 3\” header flanges
Any decent 110 MIG welder w/mixed gas (use nothing larger than .022 MIG
Skill saw w/ abrasive cut-off disk (Home
One coat hanger
Put the car on a lift or jack stands.
2) Remove the
\’H\’ pipe.
3) Cut off the head pipes right at
the front of the cat.
4) Re-install the \’H\’
5) Cut and bend the coat hanger to simulate
the bend radius and length of the short
section of
pipe needed between the collector and the cat.
Use this to locate a section of your \’U\’ bend, mark it and cut out
the section.
7) Trial fit the piece and trim to fit
with about 1/4\” (total) clearance while held in place.
8) Weld three 3/8 UNC nuts to the back of one of the header flanges.
9) Position this flange on the collector and rotate until you think you
can get a wrench on all
three bolts during
assembly. Leave about 1/2 of the thickness of the flange sticking out
from the collector.
10) Weld the flange to the
collector from the aft side on the inside diameter. Keep the weld
bead small.
11) Bolt another header flange and
gasket to the one you just welded on the collector.
12) Position the short section of 3\” pipe in place inside the bolted
header flange and the
13) Tack weld the pipe to the flange and the cat.
14) Repeat this process on the other side.
Remove the \’H\’ pipe with the tack welded flanges and pipes.
16) Seal weld the pipe to the cat and to the header flange all around on
both sides.
17) Re-install the \’H\’ pipe, cat
back mufflers etc.
18) Drop the car back to the
19) Enjoy your new found power with pride
and satisfaction of doing it yourself…
If you
have any questions, get back to me by email.