[alfa] Cat converter woes and questions

[Jon Pike <jhpike@xxxxxxx>]

Digesti..

I'm having a bit of problems with my cat installation.. and as a result 
I have a few questions.

I have an original cat.. flat cylindrical box, has CISAM on it and an 
Alfa looking part number.. but I've just noticed that there is an arrow 
on one of the flange ends, pointing in to the cat.  This happens to NOT 
be the side where the exhaust was entering.  Has this thing been on the 
car backwards the whole time?  This would put the temp probe port at the 
rear (of the car)side of the cat, rather than the forward side, which 
would seem to make more sense, but I don't know what "correct" was.  I 
know the orientation probably dosen't matter, but the angle of the 
flanges seem to be sligtly different, and the cat will not (I think) be 
flat  to the bottom of the car, if you flipped it 180deg and turned it 
around.  My example also has a bowed inward face on the current 
orientation's  "top", and it bows outward on it's "bottom" side.

So, question number one, anyone know about the ancient, orginal 70's 
cats and which way should be which?

I also have an aftermarket cat, which I'm trying to get to fit properly, 
and having some trouble there. It looks to be a standard universal type, 
with flanges  and a temp port welded on, and one side of the heat shield 
shell cut off.

It also fits slightly rotated to the body of the car, and rubs. I had to 
pry the car heatshield up and away from the cat for it not to be in 
solid contact.  Possibly it would have clearance if it wasn't rotated 
that same 10-15 deg that it looks like the original cat's flanges are 
different.

I don't think I can turn it around, due to the other side would be 1/4" 
or so higher, due to the unremoved heat shield shell on that side of the 
cat, making the clearance problem worse.

So, it looks like it was made for the wrong orientation?  This is why 
I'm wondering about the original orientation...  I'm trying to work out 
this problem with the manufacturer, as well as for my own situation.

Next actual question, regarding heating in cats..  I did drive the car 
for a few hours with the new cat, both without and with the airpump 
running.  I had pre set up the Spica on a analyzer to pretty close 
(1-1.5% CO) to the right mixture.
Unless it's changing (famous flat spot on cam follower problem?) it 
should be prett close to a good mixture.  But I'm getting "color", oxide 
coloring from the heat on the steel shell of the cat. 
Question is, how much is too much?  It started out turning a straw 
yellowish color, and after adding the air and a trip of another 20mi or 
so, it was moving on to a pinkish with slight blue tinge on the body 
with the brick area still yellow.  Am I overheating the cat?  I haven't 
driven it since, and will take it off and put the old one back on.

An aside.. I posted earlier asking about what kind of exhaust note a new 
cat will add. From my short drives, I notice a very nice, deep note.  
Seems the box of the cat does add some resonance despite the "stuffing". 
I do like the result.
Wish I had some flanges handy to compare with a straight test pipe.

Sure beats the big, flat, snare drum original, that buzzes, rattles, and 
probably has a few leaks to boot!

And a final question..  does anyone have a source for pre-made cat 
flanges? I know now that the bolt pattern is 3 hole, equilateral 
triangle, hole edge to hole edge is about 2.4", center hole is somewhere 
around 1.9-2.0". (the aftermarket cat used 2.0" and liberal welding)

Each flange is a bit different, here's my measuments for future reference:

Early 2L (72-74) manifold to downpipe

Bolt spacing - 2.25"
Hole size    - ~1.6" (pipe OD is 1.55")

77 (and assumably the rest) Spica cat flanges

Bolt spacing - 2.4"
Hole size    - ~1.98"

Center muffler to tailpiece muffler flange

Bolt spacing - 2.6"
Hole size    - ~1.98"

Jon
77 Spider
Irvine, CA
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