Hyperflow cats installed (Tom Clark in Pennsylvania - 7/17/2005 via "TCLARK" at Fchat)


Yesterday I installed the hyperflow cats on the 348 as provded by Daniel at Ricambi America. For any shade tree mechanics out there who are going to attempt this, allow me to share my experience. As has been posted many times before, soak all the existing bolts a couple of days prior to starting, with a good penetrant in order to ease removal.

I had done a lot of searching far as jack points for the 348. One thread had pictures of a 348 on jackstands. When I saw that picture, I thought there is no way in hell I'm going to be yanking on a wrench under that car while it's up on jackstands. The solution was to build a set of ramps that had a shallow angle that I could simply back the car onto and chock the front wheels. Extreme stability, no chance of a mishap.

Before you start, go to your local mom and pop hardware store and buy 4 bolts 4"x5/16" along with 4 nuts and 8 washers. You will need these to reinstall your new cats. Details below.

Next, comes disassembly. Several previous threads have stated that you must remove the exhaust, bumper and airbox. Other's have stated just the opposite. Here's my take. My car is of the single can exhaust type, so all comments apply to that style only. The twin can exhaust may be different.

1: Remove the two heat shields
2: Remove the 4 bolts that secure the exhaust hanger bracket to the frame,
do not remove the exhaust. This will allow enough movement of the ex-
haust for removing the cats.
3: Remove the 2 bolts on the exhaust side, and the 2 bolts on the engine
side of each cat. You will need 13mm open end wrenches and 13 mm
ratchet with extensions. Some aren't too bad to get at, some are a
real b!tch.
4: Remove thermocouple sensors from the exhaust side of each cat. I think
it was a 10mm open end wrench.
5: Unplug the connectors from the O2 sensors. If you follow the cable from
the O2 sensor, it splits into two separate connections that snap in just
below and in front of the air box. You can, albeit with some difficulty,dis-
connect them without removing the air box.
6: Remove the cats with the O2 sensor in place. The previous removal of the
exhaust bracket bolts will allow sufficient movement of the exhaust so
that the cats can now be removed.
7: Remove the O2 sensors. All that is needed is a 22mm open end wrench.
As repeatedly stated on fchat, these are indeed very fragile sensors. Han-
dle with extreme caution. I don't know if it would have been possible
to disconnect the O2 sensors from the cats while they were still on the
car. Perhaps hacksawing a 22mm wrench would have allowed sufficient
clearance in the very tight spaces. If it is possible, skip step 5 above.
8: Install the O2 sensors in new cats. Since everything is very accessible at
this point externally ground the O2 sensors just to be safe. It has been
noted on this site that some of the 348 electrical gremlins are due to
inadequate grounding. Simply secure a 12AWG wire to the outside body
of the O2 sensor with a small hose clamp. The other end of the wire goes
to any good grounding point on the frame.
9: Scrape off any debris remaining from the old donuts where the front side
of the cats will reattach
10: Install the new cats using the 4"x5/16" bolts on the engine side of each
cat, and the old bolts on the exhaust side of each cat. The springs and
bushings can be removed from the old unused bolts and be used for the
4 new bolts. The reason the new bolts are needed is that the hyperflow
cats have a much longer bellmouth or flare at the end of them. This pre-
vents the two halves of the coupler from getting as close together as
was on the stock cats. See the second picture below. Sorry for the
crap photography. Both cats are shown with the coupler pushed as far
forward as possible. You can see why a longer bolt would be necessary.
Oh yeah, don't forget to put the new donuts on.
Reinstalling the new cats was the most time consuming part of the job.
It takes a little time to get the couplers in the exact position in order
to be able to get clearance to retighten the bolts. If I were to do it
again, I think I would take a picture of the couplers prior to removal so
as to more easily orient them correctly when it was time to reassemble.
11: Reinstall the thermocouple probes. Reconnect both O2 sensor plugs for
each cat at the front underside of the airbox. Reinstall the heat shields.
12: Make sure no tools are laying anywhere inside the engine compartment.
Shut the hood, jump in the car, fire her up and check for exhaust leaks.
If you haven't yet, crack open a cold one and listen for a few minutes
before you shut it off. In my case, you could crack open a few because
it was pouring down rain with intense lightning. Oh well, the test drive
will have to wait.

Thanks to all who have posted threads on this. It's the previous threads that
gave me the "stones" to attempt this. And of course, thanks to you Daniel.

Pic 1: Car on ramps capable of supporting Kirstie Alley

Pic 2: Comparison on flange on old and new cats

Pic 3: One new sleek feline, one old fat cat


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