Monte Carlo (SS) Exhaust FAQ

Submitted by: Stu, Victor, George D, and Steve B.

Last updated: Wed Jan 17 1997

     There are two basic ways of modifying a crossmember to accept a dual
exhaust.  A hard way, but probably a stronger way, and a much simpler way.  I'm
of the opinion that either way will work since the crossmember is not a REAL
stressed member, not like the frame, but don't go too nuts modifying the
     The Hard way:  This method does involve removing the crossmember from your
car, need to unbolt the 4 frame bolts and the trans bolts.  First off, you
need to estimate where you will be making the cut.  I suggest installing
your headers and then eyeballing where the cut will be.  Then you take out
the crossmember.  You need to reinforce the crossmember to make up for the
loss of the metal.  So I used channel steel which fit over the crossmember
and welded it in place.  Next, I broke out the torch and referencing off the
marks, cut a big, wide notch into the crossmember.  Make it wide enough to
make up for any mistakes you might have made.  Also cut pretty deep into the
crossmember, at least 1/2 way through to create a reasonable amount of room.
The extra height added by the channel steel on the crossmember required a
little floor pan mods, mainly jacking up the crossmember and allowing it to
self clear itself fit 3" under my crossmember, so you can stuff a whole
bunch of exhaust under your car.  Pictures of this method can be seen on the
monte homepage.
     There has been some email regarding the x-member the past few weeks if you
want true duals on your Monte.  IMHO, this should not be a problem.  All you
need is to find a good welder and for ~$20, he will use a combination of
heating and impacting to create a C-shape in the crossmember under which the
driver's side of the dual system will run. No cutting, no welding, no trans
removal, no loss in strength.  A 30 min. job on the hoist.  Basically heat
the crossmember till its nice and red and then break out BFH and pound the
crossmember to gain the additional clearance.
     When he's done, it should look like this:

          rocker  |                   ___________                | Trans
           panel  |__________________/           \_______________| 

        There are a slew of non emission headers for g bodies with sbc, so that
shouldn't be a problem.  I have used the headman and the dynomax headers.  I
really didn't like the headmans, but they were kinda old, so maybe they
redesigned their headers.  They dynomax headers I had were ceramic coated, I
love the ceramic coating, makes checking the spark plugs easier.
        As far as true duals for g body, I can only think of Torque Tech 
off hand.  They make some nice mandrel bent 2.5" and 3" exhaust.  But any
competent exhaust shop can bend you up an exhaust for the car, and can
probably do the crossmember mods (the easy version).  

Emissions legal Cat back systems:

To my understanding, of emissions laws, anything after the Catalytic
converter doesn't need any CARB/E.O. approvals, and you can do what you
want.  Here's a list of mandrel bent systems for the G-body.


2.25" dual cat back, Aluminized mild steel, True SS exit, tailpipes
polished, DynoMax turbo mufflers, 
P/N: 17423
Price: $230 Hooker:

2.5" Dual cat back, Non-coated mild steel, Super comp mufflers, 
Exits like GN,
P/N: 16810
Price: $260 (Summit)

ATR (Applied Technology & Research) Stainless Steel: 

2.5" dual cat back, Stainless Steel with stainless core muffler wrapped with
aluminized mild steel (similar to walker ultra flow).  Exits like GN
Price: $495 

2.5" dual cat back, Stainless Steel with stainless core and external
muffler. (a little quieter than the one above)  Exits like GN
Price: $695 

3" single cat back, all Stainless Steel. Exits like GN, but only on
passenger side of car. (very loud)
Price: $395 

 2.5" Dual cat back, alumnized steel, Super comp mufflers, 
 Exits like GN,
 P/N: 16810
 Price: $260 (Summit)

Torque Technology:

3" dual cat back, Aluminized mild steel, Exits like GN, Flowmaster 3 chamber
Price: 471.00

Turbo City:

2.5" dual cat back
Price: ??

Emissions legal Headers: 

In order for headers to truly be emissions legal, they must have CARB/E.O.
approval.  For header manufacturers to get CARB/E.O. approval, they must
have a complete system from exhaust manifold to y-pipe. All of the factory
emissions equipment must remain intact and be functional, i.e.: A.I.R., heat
riser valve, O2 sensor.  Also, the manufacturers must do testing for *each*
specific application.  Only a few manufacturers have done this, and to my
knowledge, Edelbrock has the only emissions legal Tubular Exhaust System for
the G-body.  I have heard rumors that Headman has an emissions legal system,
but I'm not sure if they have a system for the G-body.

Edelbrock TES (Tubular Exhaust System) CARB/E.O.#D-215-1:

LG4 engine, Non-coated,
P/N: 6878
Price: $305

LG4 engine, Ceramic coated
P/N: 7978
Price: $475

L69 engine, Non-coated,
P/N: 6879
Price: $335

L69 engine, Ceramic coated
P/N: 7979
Price: $505

   And now the forever asked questions about mufflers.  Generally, Montes take
an offset/offset configuration.  There are a huge amount of mufflers which
can fit the car.  But the question that everyone has concerns the Flowmaster
and the Dynomax Super Turbo mufflers.  
    First off, there are many things which effect the sound and volume of the
exhaust.  Most important are probably cubic inches, cam, headers, exhaust
size, converter, and tailpipes besides the muffler itself.   Any changes of
these will make an effect on the sound and volume of the exhaust.  But the
muffler probably does play the biggest role in the tone of the car.

Flowmaster 2 chamber vs. 3 chamber:
    Yes, Flowmasters are louder than the stock exhaust, but generally speaking
the 3 chamber mufflers are streetable while the 2 chamber ones are pretty
loud, so you might want to think about that before you go that route.  As a
side, in a test of mufflers done by a Ford magazine, they didn't find very
much power difference between the 2 chambers and the 3 chambers, the
difference mainly comes on the very top end.  Contrary to popular belief,
they are affordable, should be around $50 a piece if you order from a major
mail order place.  
     To characterize the sound of Flowmaster, I would say they sound very much
like open headers, just quieter.  They have a certain crackle to them, like
open exhaust.  Flowmaster work on the baffled system, so there is no
fiberglass to blow out.  So, they should sound the same the day you put them
on to years down the road.

Dynomax Super Turbo:
     The dynomax has a different sound from the Flowmaster, they tend to have
a deeper, more muffled tone.  Hard to describe, but I would characterize them
as being more refined, less crackly than the Flowmasters.  Beware, when you
first put them on, they will be pretty quiet.  But since they are fiberglass
filled, the will get louder the more you use the car.  These mufflers tend
to be cheaper, around $30 from the mail order shops.

Exhaust Size:
      The stock monte exhaust is 2". But the stock design monte exhaust comes
together into one cat and then splits into two pipes.  This is not the most
conductive to making lots of power, but probably must be retained to pass
emissions.  So generally speaking, for a stock monte, 2" may be more than
enough.  But if you're getting a new system, you might as well step up in
size, since they allow you make more power later.  But remember, the y pipe
is still the choke point no matter how big you make the exhaust.  But don't
let that scare you, people have used the y pipe with dual 3" exhaust and
still made tons of power.  My rule of thumb is at minimum, get a 2.25" or
2.5" exhaust.  I tend to lean towards the 2.5" since there usually isn't a
big price difference.  2.5" on a stock 305 might be kinda large, but you
might as well.  
      For true dual exhaust, I would suggest 2.5" when you get near the 300 hp
level.  3" when you get around 400 hp.  These are general rules, I had a
dual 3" on a motor making around 350 hp.  I didn't notice too much of a loss
on low end, but then it was geared to eliminate low end problem.  I still
made a ton of low end.

Catalytic Converters:
  For those who need to run, or at least pretend to run cats, there are a
variety of options.  The simplest thing to do if your cat goes bad (or even
if it doesn't) is to hollow it out.  Cats are made up or certain rare
metals, platinum, palladium, etc. (which is why they're so expensive) on a
ceramic honeycomb.
  The most common cause for the cat to go bad is an over rich condition.
So if you're tuning a carb on a car with a cat, be careful about running it
too rich.  Also, if your o2 sensor goes bad, the motor will often go rich,
which may end up killing the cat.  Going rich will cause the substrate
material to melt and end up clogging up the ceramic honeycomb and generally
causing a large amount of back pressure.  Also, physically hitting the cat
can cause it to break.  So watch it when you ramble speed bumps and other
might spot opportunities.
  Federal law says you can't change your working cat unless its gone bad or
you have at least 50k miles on it.  If you cat does go bad, these are the
symptoms: If you bang on the bottom of the cat or if you floor it, you may
hear some rattling of chunks inside it.  Unexplained loss of power is a good
one.  Especially if you floor it and it feels like there is a boat anchor
tied to your rear, the engine will labor to make rpm's and it will just run
like crap.  Rotten egg (sulfur) odor.  Not necessarily a bad cat, but if it
is consistent, it is bad.  The exhaust note will change, the engine temps
will go up.  Also, the cat gets very hot.  The passenger side floor around
the cat would get very hot.
  Its pretty easy to breakup and take it out, broomstick should work.
Remember to take out the broken chunks after you're done.  Remember, running
no cats on an originally cat equipped car is only legal for off road
applications.  For those who would like to keep a working cat, Summit Racing
sells a hi flow cat which people have used and liked.  Its a PFP
brand and should be able to be had for under $100.  Call for specific part
numbers.   If you have a 3" system, Random Technologies makes a real high
flow 3" cat; supposedly the least restrictive on the market.  Not too much
more restrictive than a straight pipe. It's $200 though.

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