Bassani Off-Road X-pipe

Report on Bassani \”Off-Road\” X-pipe setup for my 2001 Z06
(This was recently posted on the C5 Registry listserve and I
received several questions which prompted some revisions and updates
included here.)
1. Description, quality, fit & finish, price
Bassani makes an \”off road\” X-pipe setup that is particularly
handy for those who want to be able to go back and forth to stock if need
be. It actually consists of two Bassani pieces, the \”front\” piece,
part # C501-2 which replaces the part of the stock pipes with the 4 cats,
and the \”rear\” piece, part #5797X. Each piece contains an
\”X-pipe\” section welded in. Actually, each piece was designed to be
used separately if you want to cut your stock pipes in the middle. But by
combining the two, your stock pipes remain intact and can be bolted back
on.
The two pieces slip together in the middle and clamp tight, and
the two piece assembly bolts to the exhaust manifold in front and the
muffler pipes in back. This way, you jack up the car, remove 8 bolts and
6 nuts, replace the stock pipe with the Bassani pipe, replace 8 bolts and
6 nuts, and go. (See details below.)
I was impressed with the
quality and fit of the Bassani parts. All the mounting fittings and
hangers were in the right places, flanges are thick and flat. Everything
fit just right (except for a slight mis-alignment of the muggler pipe
flanges – see below). You couldn\’t ask for a more quality
setup.
The pipes themselves are made from heavy gauge material
which should improve service life. After extended use, exhaust pipes
become corroded by the sulfuric acid produced when the sulfur in gasoline
burns. Exhaust heat just speeds up this process. Pipes made from thin
material tend to quickly \”rust\” through, although it is not really
rust, the pipe is actually eaten away by the sulfuric acid. The Bassani
pipes should resist such corrosion longer than most.
Bassani pipes
are sold through its dealer network. There is a \”list\” price, but
most dealers discount that price. I paid $310 for the front piece and
$235 for the rear plus sales tax. This price included shipping. It seems
reasonable considering the $1,000 to $1,200 price charged by the
Corsa/Borla-type muffler firms. Shop around, you may find an even better
price.
2. Initial fit problem solved
Earlier I reported
that the original \”front\” piece that Bassani sent did not fit my Z06.
After a telephone call, Sheldon at Bassani asked me to make a measurement
on the pipes. It turned out that even though the piece had the correct
part number engraved on it, it was not the correct part. Apparently the
piece had been mis-labeled during manufacture, and no one caught the
error. This would be easy to miss, as the two parts (LS6, LS1) look the
same and are less than an inch different. After profuse apologies,
Bassani immediately sent me the correct part. I must say their people
were great.
3. Weight vs. stock
Stock pipes with cats:
42 Lbs.
Bassani 2-piece assembly: 27 Lbs.
Weight saving:
15 Lbs.
Neat, eh? Removing weight is like adding
horsepower.
4. Installation details
As I mentioned above,
installing this setup consists of removing and replacing 8 bolts and 6
nuts. However, there are a few details that might be
helpful.
Start by assembling the two Bassani parts. Before mating,
loosely place one of the clamps that Bassani supplies over each of the
junctions. Bassani also supplies a tube of anti-seize compound. I used a
thin coat on the pipe ends before slipping them together to ease
adjustment of the final length after the parts were in place on the
car.
The installation basically involves lifting the car onto jack
stands, supporting the middle of the stock pipes with a jack just behind
the large cats, and removing the 8 bolts and 6 nuts. The stock piece is
now loose and can be slid down and to the rear until it is free of the
manifold studs. Then lower the jack. Balance the Bassani pipes on the
jack, jack it up into the right place while sliding the pipes forward onto
the manifold studs, and then replace and snug up the 8 bolts and 6 nuts.
Slowly tighten the 6 manifold nuts first with the other bolts very loose.
Tighten the 6 nuts evenly a little at a time to slowly pull the pipes up
to the manifold. After the manifold nuts are tight, do the final
tightening of the other bolts. (Don\’t forget to use anti-seize
compound.) Before final tightening, adjust the length of the Bassani
assembly by sliding the two pieces together or apart so the muffler pipe
flanges are in the right place. Then torque everything to the torque
specification in the service manual.
The anti-seize compound comes
in handy at many places. The six self locking nuts that attach the pipes
to the exhaust manifold require excessive force to loosen and tighten.
The force required is so great that sometimes the exhaust manifold studs
bend! After removing the nuts several times (trying different pipes), my
studs were bent! Fortunately, the studs can be removed from the exhaust
manifold and replaced with new studs (see Chevy part numbers below). Use
anti-seize compound generously on the studs and nut threads when replacing
and tightening these nuts. The anti-seize compound reduces the force
required. To remove the manifold studs you need a \”thin\” 15mm open
end wrench. I don\’t have one, and some of the old studs would not come
out, so I reused them.
To use these \”off road\” pipes, you
must remove the rear pair of oxygen sensors and replace them with
\”oxygen sensor simulators\” (available from several vendors, mine came
from Breathless). But Bassani dutifully welded the fittings for the rear
oxygen sensors to the (front) pipes. So you must plug these holes. It is
a metric 18mm x 1.5 plug, unavailable at any hardware supplier.
Fortunately, Chevy has a plug; the part number is listed below. Use
anti-seize compound.
On the stock pipes, the rear flange is
threaded to accept the (metric) bolts that attach the muffler pipes. The
Bassani part is not threaded. I purchased four comparable size bolts and
self-locking nuts from a local hardware store (not in a metric size,
though). The fit of the flange on the rear Bassani pipes and the muffler
pipes was a little off, but pulled together when I tightened the
bolts/nuts. The two pipes flexed a little to fit. So far so good. Use
anti-seize compound.
Finally, when everything is bolted up and you
have adjusted the length of the Bassani 2-piece assembly, position and
tighten the clamps Bassani supplies to keep the two pieces fixed together.
For my car, the \”shortest\” length was the best fit. Use anti-seize
compound on the clamp bolt and nut. (For a really neat job, have the two
pieces welded together after adjusting the length.)
5. Additional
note on \”Oxygen Sensor Simulators\”
On my 2001 there are four
oxygen sensors, or two pairs, the \”front\” pair which screw into the
two exhaust manifolds, and the \”rear\” pair which screw into the pipes
just behind the large cats. It\’s this second \”rear\” pair you need
to simulate if you remove the cats. Otherwise you will get \”cats not
working\” trouble codes.
The front pair are used in \”closed
loop\” by the computer to keep the mixture at stoichiometric, that is, at
equal amounts of fuel and oxygen. The front pair are essential for the
correct function of the engine. On the other hand, as far as I can tell,
the rear pair are only there to be sure your cats are working correctly,
and to give you a bunch of trouble codes if they aren\’t.
The
fittings for the front pair of oxygen sensors are in the exhaust manifolds
and not of interest to you. The rear pair of oxygen sensors holes are in
the *front* Bassani \”off-road\” X-pipe part. Why they put these
fittings onto the pipes puzzles me, because the computer would go wild if
you installed the rear oxygen sensors there with no cats. There are no
fittings for oxygen sensors in the rear Bassani pipes.
6.
Additional Note on \”Fit\”
Above I mentioned that the rear X-pipe
to muffler flange fit was a \”little off\”. In a week of driving the
car, I have noticed a \”tic-tic-tic\” under moderate acceleration and
somewhat more noise that just after installation. I suspect that there
may be one or more exhaust leaks that I need to fix, possibly at the \”a
little off\” fitting, but work has kept me out from under the car.
I\’ll update this report when I find out what\’s going on.
7.
Additional parts I needed
The first three parts are available from
your local Chevy dealer. My dealer had to order all three (delivery in
about 4-5 days). The price is a little high, so only replace the studs
and nuts if they are damaged. Take one of the muffler pipe bolts to a
hardware store and get four equivalent-sized American bolts and self
locking nuts to attach the muffler pipes.
Part
Part # Quantity Price ea.
———————— ———
—— ———
Manifold stud 012562640 6
$3.55
Self-locking nut 010255857 6
$1.80
Oxygen sensor hole plug 025509274 2
$3.33
Bolts & nuts for
muffler pipes N/A 4
ea. ~$.50
8. Exhaust sound
The improvement in the
exhaust sound was remarkable. At idle and below about 2,000 rpm there is
almost no difference. I can cruse along at 1,800 rpm at 75 mph and listen
to the stereo. At this speed, wind noise is the largest distraction.
This is in line with my observation that the un-muffled Mosler prototype
with stock Corvette engine at Daytona was very quiet at idle (and not that
loud at full song).
Above about 2,200 rpm at more than 1/4 throttle
the engine begins to emit a real **rrraaaaappp**. It is *not* like the
classic V8 rumble. Apparently the firing order change raises the
frequency of the emitted sound in a manner that is very pleasing to me,
much like the old V12 Ferraris. At WOT it is a **much** louder
RRRAAAAAPPP!
This raises another issue. Apparently the stock Z06
*mufflers* really don\’t \”muffle\” that much. (Its probably the same
with the stock C5 mufflers.) It appears that a substantial part of the
Corvette \”muffling\” job is done by the cats. This may explain why
Borla/Corsa is unable to produce any more HP – there isn\’t that much
restriction in the stock mufflers to start with. IMHO, replacing the cats
with the Bassani setup (~$550) makes it unnecessary to spend $1.200 on the
Borla/Corsa solution, and I believe (but can\’t prove yet) that you do
get more HP.
9. Performance
This is a tough question. In
theory the Bassani pipes should yield 15-18 hp. That\’s in theory. GM
said that loosing just the \”pup\” cats yielded 5+ HP. These pipes have
been on my car less than a day, so I\’m not sure yet. The engine seems
to run better and have somewhat more power, but that RRRAAAAAPPP makes it
sound so good that it would be easy to fool oneself. I don\’t have a
dyno, so I don\’t have any hard data to give you. After a couple weeks
when the engine has a chance to \”relearn\” the increased flow
characteristics, I will update this report.
P.S. I am not
associated with Bassani in any way and own no stock in Bassani. I\’m
just a satisfied user of their parts.
Keep waving!
Jim
Green
jgreen@robotvision.com
2001 Z06, \”Arrest Me\” Red/Modified
Red, Halltech TRIC+MAG+throtle body heater bypass, lowered 1\”, Bassani
off-road X-pipe, Doug Rippie roll/harness bar, 6-point harness, braided
stainless break lines, CAGS eliminator, stay tuned, more to come.