"William H. Hiatt III" <william@hiatt.net> wrote:
: Well, based on results from other people, I'm going to take the third cat
: off of my 4.7L. Now, I got the following questions:
: 1) I'm just going to cut it out, shouldn't be a problem right?
Shouldn't be - depending on what tools you plan to use. :-) I
had a pretty easy time with a Sawzall when I did the muffler on
my Dak (as long as you have the proper blade). After helping Andy
with the muffler on his Dak and having to break out the plasma cutter
when I realized I didn't have the right blade for the sawzall, I
decided to get one of those chain style cutters. (Note to self: do
not lie underneath a plasma cutter again!) ;-) I've got a chain
style cutter on order from JC Whitney for about $20. If it works
as advertised, it should be a very useful tool indeed.
: 2) I want to make it so I can bolt that sucker back on for smog testing if I
: need to. Is there a problem with bolting exhaust pieces back on? Just as
: good as welding, right?
Bolting together isn't as easy to get a leak free seal as with
welding, but its still OK - most exhaust systems are bolted together.
: 3) What size straight pipe do I need to buy?
Depends on if you really want to use clamps or not (see below)
: 4) What are the best exhaust clamps to buy for this? I'm just going to
: straight pipe it and use clamps to switch the muffler in and out. Where do I
: get the clamps?
My recommendation would be to get 6 exhaust flanges, weld 2 to the
pipes on your truck, two to the straight pipe and two to the cat.
(The straight pipe and cat pipe must be the same length.) then,
replacing the cat with the pipe or vice versa is just a matter of a
couple of gaskets and some bolts. My Dak is set up this way. If you
don't have a welder, you should be able to get a local exhaust shop
to do the work.
However, if you are set on clamps, I would give the "band clamp"
style a shot. I used them with good success on my Dak in the past.
They're just under $8 each at JC Whitney, stainless steel. Those
clamps won't crimp the pipe and will make it easy to take the exhaust
apart. With a standard exhaust clamp, you have to be VERY careful or
you will crimp the pipe and they are stuck together just as tightly
as if they had been welded. Often, it is nescessary to tighten
those clamps down tight to seal the pipe, so using them on a system
you want to take apart is risky.
As far as the offroad pipe goes, that's the easy part. What you
can do is stop down at Autozone (any parts store really) and pick
up an "exhaust resonator" This is a 1.5-2' pipe that has both ends
expanded. Get a pipe which has ends that are the same ID as the OD
of your stock exhaust pipe. (Probably 2.5") Measure the resonator,
and subtract the depth of the ends. Measure this same distance on
your exhaust system where your cat is located, and cut the stock pipe
at these two spots. (Such that the cat will be cut out.) Now, the
resonator will fit right in place of your cat, your stock exhaust
pipes will fit into the ends of the resonator, and you can use the
band clamps to seal everything up. You might also want to smear some
copper RTV or equivalent on the connections to help the seal a bit,
and help to prevent having the pipes rust together.
Now, here's the tricky bit... What to do with the cat? The
problem is that its the exact same length as the cut, so the
pipes won't overlap - there's nothing to clamp to. One option
would be to try to just hold it in place with a band style
clamp. This might work just to get it to the inspection station
and back. (Though if the inspection station saw what you
were doing they'd probably not be too happy - and justifiably
so.) :-) Another option, and this one will take some luck...
Find an exhaust pipe with the same OD as the ID of your stock
system. Cut this pipe so you get two sections of about 5-6" long,
and do the exact same thing I just described except slip one
of those pipes into each joint first. That should greatly
increase the strength, and I wouldn't have any qualms about driving
around like that. Yet another option is to take your cat
to a muffler shop and have them weld a couple of ends onto it.
These ends should have the same ID as the OD of your stock
exhaust system. (You're basically replicating the straight
pipe (exhaust resonator) except its got a cat in the middle. :-)
I hope that gives you some ideas. :-) Good luck!
---Jon-
.---- Jon Steiger ------ jon@dakota-truck.net or jon@jonsteiger.com -----. | I'm the: AOPA, DoD, EAA, NMA, NRA, SPA, USUA. Rec & UL Pilot - SEL | | '70 Barracuda, '92 Ram 4x4, '96 Dakota, '96 Intruder 1400, '96 FireFly | `----------------------------------------- http://www.jonsteiger.com ----'
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