I want to upgrade my exhaust. What size should I go with?
The stock SS exhaust pipe size (from mufflers back) is 2.25"
If you are keeping your engine set-up stock, without modifying the
exhaust manifolds (to headers), or any cam/intake changes; the stock
exhaust size (2.25") will work just fine. You can increast to 2.5"
and may gain a few HP, but don't expect much.
If you have changed to headers on your exhaust and/or have changed
your cam/intake, you will realize more HP gain by increasing the
size of your exhaust piping. In this case, 2.5" will work well.
If you've swapped engines, and are now pumping in excess of 350HP,
going to a 3" exhaust will be benefitial.
If you go too big in your exhaust size, you will actually hinder
performance. This is one of the cases where bigger is not necessarilly
better. As a general rule of thumb, don't go to 3" unless you're well
over the 300 HP mark. 2.5" is good to the mid 300HP level.
Having a mandrel bent exhaust will also free up a few extra HP from
your exhaust. But keep in mind that the stock exhaust manifolds are
the most restrictive (read HP robbing) element of the engine system.
If you stay with the stock manifolds, the amount of power you can free
up is limited.
Is it possible to put a true dual exhaust on the Monte Carlo?
Yes, although it's benefits for a stock to mildly modified (300HP
and below) set-ups are limited if not non-exhistent.
A few things to remember when considering a true dual exhaust:
First and fore most, find out what your local emissions laws will
allow in regards to a true dual exhaust. If your area does not have
emissions checks, or very limited (non-visual, sniffer only) checks,
you can get away with a true dual set-up. Keep in mind it is
technically illegal no matter where you are in the US. Federal law
prohibits modification of the number of catalytic converters or the
number of inputs / outputs from the stock converter setup. This is
why many exhaust shops will have nothing to do with true dual converstions.
Adding a second catalytic converter is just as illegal (federally) as
not having any converters. Two converters actually will not work to
reduce emissions efficiently since the converter relies uppon operating
temperature, which is significantly reduced if it only 'sees' half the
To run true duals, the transmission cross member will need to be
modified to allow the new pipe to run down the driver's side of the
car. Some have used the stock exhaust cross point on the cross member
for both pipes, but this limits the size of the pipe you can use, and
is in efficient for exhaust flow. There are some write-ups on how
to modify your cross member:
There is also a company that manufactures cross members for true dual
exhaust: G-Force Performance
If you go with true duals, 2.25" pipes are enough to take you well
into the 300HP area. 2.5" well into the 400HP area. Again, going
too large will hinder performance. Remember, each pipe is only seeing
the volume of 4 cylinders, instead of all 8.
Is is a true dual exhaust emissions legal if I use two catalytic converters?
Technically, no. Doesn't matter what your local or state emissions test
requirements are. It's against federal EPA law to modify the number of
catalytic converters from the stock configuration.
Many exhaust shops will have nothing to do with modifying your exhaust
in this way since they can be heavily fined by the federal government
for doing such modifications.
Granted, if your local / state emissions law are lax enough, or non-existent,
you can get away with going true dual exhaust. Going to twin
catalytic converters will not make you any more legal however.
Two catalytic converters (on a true dual exhaust setup) will not work as
well as a single converter to remove unwanted emissions. Catalytic converters
rely on high operating temperature to do their job. By reducing the flow
of hot exhaust gases through the converter by only sending the volumn of
4 cylinders through it will dramatically increase the time it takes to reach
the desired operating temperature.
My Catalytic Converter is making noise.. what should I do?
Chances are, it has gone bad. With the catalytic converter cold
and the engine off, get under the car and give the converter a good
wrap with your fist. If you hear any rattling, the converter needs
replacing and is most likely robbing your SS of power.
Be aware that there are two classes of replacement catalytic converters
on the market:
OEM (Original Equipment Manufacturer) replacements. These are
identical to the stock catalytic converter. They are required
by federal law to carry a heafty warranty period, and thus, carry
a heafty price tag (in excess of $250). If you go to one of the
big name exhaust shops, chances are they will install one of these.
Your bill will likely be in the $500 range once labor is added in.
Non-OEM, aftermarket replacements. These do not carry the heafty
warranty period that the OEM versions carry. The are manufactured
with identical processes and work just as well, and just as long
as the OEM versions. Price on these is typically below $100, and
some times as low as $65.
It will be very evident which type you are looking at based solely
on the price. There are quite a few aftermarket catalytic converter
manufacturers who make replacements for the SS (PFP, Catgo). Shop around
the many mail order performance companies (Summit, Jegs, NAPA) for
the best price.
Finally, there is an aftermarket catalytic converter that matches
the OEM converters in expense. The Random Technologies High Flow
catalytic converter is an extreem performance converter that is meant
for extreem engine setups pushing lots of power. They are expensive
because of the design. Unless you are pushing a lot of power (greater
than 350 HP), you probably don't need this type converter. The normal
aftermarket brands (which often are better flowing than OEM versions)
are good well into the 300 HP range and are the right price.
What kind of headers will fit on the Monte Carlo SS?
The only fully emissions legal (in all 50 states) header currently
available for the 4th generation Monte Carlo SS is the
TES (Tubular Exhaust System). It carries the coveted C.A.R.B.
number for this application. No other header on the market does.
It comes in non-coated version only now (there used to be a ceramic
coated version that was discontinued). Part Number 6879.
Other manufacturers who make headers for the 4th generation Monte
Carlo SS include Headman, SLP and Flowtec. We'll provide more
detail on these other headers and other manufacturers at a later date.
I have a chatter in the exhaust in the lower passenger side of the engine. What is it?
Most likely the EFE (Early Fuel Evaporation) valve which is located
on the exit of the passenger side exhaust manifold down pipe.
Replacement from GM is about $112.
Some have removed the valve and taken out the center butterfly section
and caped off the resulting holes. Removing the butterfly will cause
the engine to take longer to get to operating temperature, but will
not affect ECM performance.
The EFE valve is required as a space bridge between the passenger
side exhaust manifold down pipe and the cross over Y-Pipe. If you
remove the valve all together, you will have an unnatural gap between
these two pipes that needs to be bridged. Some have used an EFE
valve from an F-Body to bridge this gap (no further details at this time).