Conversion kit for catalytic converters

When driving the car, it gets too hot in the motor bay. Catalytic converters are attached to the exhaust manifold -there is another catalytic converter under the car. At any case , we would like to get rid of these converters in the motor bay and replace them with straight pipes. We believe there was such a conversion kit available, but we forgot where to find it. It was a few years back. Can anybody help us ? We would be very thankful. Our email is

An SL Mercedes? Getting too hot under the hood? Have you stopped by the dealer’s to complain?

To replace cat converters with straight pipes is illegal. Doable by any shop that does custom exhaust work, but illegal.

What makes you think the motor bay is gettng too hot?

I assume this is a mid-'70s 450SL, right? Then it’s time to roll out my broken record - you’ll get more reponses on a very specific question like this on one of the SL-specific forums.

And I think the thing you want to replace with a pipe is a ‘thermal reactor’, kinda like a cat, but not exactly.

Back in late 70s and 80s, you could readily purchase “catalytic converter test pipes”. These pipes were simply straight pipes that fit the dimensions and connections for the converters in use. The “test” in the name and the instructions for use were to make them seemingly legal.

The instructions that came with these pipes read something like:

Use this pipe to see if you have a faulty or clogged converter.
Remove your converter and replace it with this test pipe.
If it corrects the problem, you know you have a faulty converter.
Remove the test pipe and replace it with a converter.

As you can imagine, many people used these “test pipes” as simple “replacement pipes”.

The market for these pipes has dried up - for obvious reasons.

Problem is, the 450SL’s ‘thermal reactors’ were bolted right onto the exhaust manifold, so it’s a very unusual kind of part they’re looking for.

It has tolerated the heat for 30 years, now, all of a sudden, it’s getting “too hot”???

Chances are, these things stopped working long ago, and they are producing no additional heat. If you remove the “smog pump” they will indeed become inert…If you are going to “de-smog” the vehicle, you might as well do it right and clean EVERYTHING off…Cats, pumps, EGR, the full Monte…

“Test Pipes” disappeared when the EPA banned there manufacture or sale and made “tampering” illegal…

I’m still wondering why the OP thinks the motor bay is getting too hot.

It is a 1976 450SL. Do you know where I can buy a “thermal reactor”?

Sorry, I don’t. This was a very poor system, the thermal reactor right in the engine compartment caused problems with baking out the other engine components, BMW has the same problem with 530i model of the same era. Ask the question on, and look for answers to questions like this, some may be labeled ‘W107’, the model number for this series.

Normally I discourage removing pollution equipment, but this is an exception, if your state would allow it. Do you have to get it emissions tested? If so, I might even try to figure out if a later 450SL catalytic converter system would work, but this might require a replacement fuel injection system.

I agree with mountainbike. After 34 years it’s now too hot under the hood?

Have you tried the dealership? MB is good about keeping old parts available, at a price ($$$$$).