Exhaust/Cat Converter

[Strife]

I had intended to replace my center muffler on my 380SL because during an o2 sensor replacement (I couldn't get it out even after using both kinds of O2-sensor nut-rounding tools), the shop observed that it "leaked" - and would repair it for $800.

So, I bought the center muffler and the other fittings, seals, and hanger rubber needed. I replaced the rear muffler about 2 years ago, so that was OK.

I cut off the clamp bolts between the CAT and the center muffler, and discovered:

1. The seal was just a little debris on the bottom of the inside of the pipe:

2. the CAT converter flanged lip was partially rusted off.

So, I was a little worried about success, but I put the proper seal and tightened the new bolts/nuts. This (barely) worked, because the car is MUCH quieter.

Unfortunately, when I put some smoke down there to look for leaks, I discovered that the CAT to LH manifold pipe seal is iffy, and even worse, the CAT had a hole in it near a weld. It's small, but still...bad.

So, I have a much quieter car and a strange exhaust rattle has disappeared (basically ,with no seal, the bolts were just holding the center muffler and CAT in "alignment", that's all). This car , with new f/r subframe rubber and motor mounts/torsion rubber, is about as tight and good-feeling (albeit somewhat slower) than my 560SL, which had lived a much more pampered life.

Questions for anyone who has replaced one of these:

1. How "bad" are aftermarket CAT converters? I've read:

(a.) They use hardly any platinum and don't last
(b.) Because of (a.), the engine has to be absolutely in perfect tune at all times or they will be quickly made ineffective anyway
(c.) They are "all" made by the same (crummy) company.

True/False? Any comments?

I am not interested in putting in a "test pipe" or anything like that. And I am definitely not interested in getting an OEM converter (I've heard, 4 large bills).

When I get a replacment, I'll install the new center muffler and put in new seals for the front of the CAT as well as the back. The LH down pipe to the CAT itself looked good, especially after I cut off what was left of it's heat shield

[ScottinSoCal]

Originally Posted by Strife

Questions for anyone who has replaced one of these:

1. How "bad" are aftermarket CAT converters? I've read:

(a.) They use hardly any platinum and don't last
(b.) Because of (a.), the engine has to be absolutely in perfect tune at all times or they will be quickly made ineffective anyway
(c.) They are "all" made by the same (crummy) company.

True/False? Any comments?

I just had the cat changed on my 78. Since it was just done just recently I can't speak to the longevity. It definitely changed the exhaust note. The V8 rumble is more pronounced now. Some people might like that, I don't so much. I may try to find a cat off an old wreck and see if I can get it changed.

It was only $250 to have it installed, and it was the only way it was going to pass emissions. When the old one came off it was all broken up inside and partially melted. The car is much better breathing now.

[ctaylor738]

I would have a chat with Timevalve. They sell cats in stainless with a warranty.

[redsl]

If you buy an after market be prepared to cut and weld the pipes. I have to cut the pipe in two places that comes down off the driver side manifold. It did not clear the oil pan (added piece to make longer) and did not reach the other pipe by the converter(added piece to make longer) to bolt it up. I did purchase the driver side pipe w/o the converter as I have the car registered as a classic and it has one converter already on it. But good luck, they say direct bolt on! NO WAY

[Roncallo]

I hava a bolt in from DEC. It does bolt right in without any mods, however it is a pice of crap. For the 560SL they simply replaced the muffler and cat with 2 tiny $39.00 universal cats. My recomendation is good used junk yard unit if you can find it. An OE is about $4000.00 WTF? My Bosel muffler also sucks. Its loud and obnoxious. I stole the OE muffler of my other car that I am no longer using. I intend on doing a full heat shield reconstruction and O2 bung grind off and weld to repair my original OE cat and muffler.

[jr811]

79 450SL about 10 years ago I just replaced my Cat. with a straight pipe
Runs great - cost about $25 Jim