M127: Air intake intermediate piece

[pagodarune]

I am rebuilding my 230SL engine, and I try to restore the engine to look as original as possible.
Between the throttle body and air filter there is a part called intermediate piece in the EPC, see picture. What is the correct finish of this part? Was it originally yellow cad? 

[Benz Dr.]

Yes, it's yellow cad. That part is a throttle body heater.

[Scottcorvette]

That's interesting. I don't have that in my car, should I? Mine is 1964

[Benz Dr.]

Not all cars have it. If you live in a warm climate or only summer drive you probably don't need it.

[twistedtree]

I though they didn't show up until the 250?

[pagodarune]

Dr. Benz: Thanks, I will send the part to plating.

twistedtree: The EPC says that this was introduced with engine no 013981. My car is produced in November 1966 and has engine no 014350.

I don't understand why this heater was added. I thought that you want dense (cool) air in order to get the best performance.

[twistedtree]

Thanks for the clarification on when it was introduced.  I suspect it's tied to emissions controls, but that's just a guess.  In later years it was integrated right into the throttle body.

[Benz Dr.]

From what I can tell, vapors entering the throttle body can start to freeze in colder weather do to the blast of cold air going by the throttle plate. If you get enough icing happening the throttle plate won't close and in certain situations it could cause an accident. Call it a safety device because they wouldn't have done it if it wasn't needed.

I had a throttle body ice up once and the engine wouldn't idle below 2,000 RPM. Not so bad in a standard trans car but in an auto.............

[ctaylor738]

While you're at it, you might want to replace that Nylock nut on the bracket on top.

[pagodarune]

I will replace the Nylock nut with the correct type. While we are discussing nuts and bolts. Does anyone know of a good source of nuts and bolts, where it is possible to buy small quantities?

[Benz Dr.]

Lots of places have regular sizes but some stuff you would need to special order. I use Fastenal but they're probably not in your area.

[ja17]

I've seen the throttle plate ice-up on cold damp mornings. The heater solved the problem. For those of you who remember four barrel carburetors they had throttle plate icing problems also on cold damp mornings.  It only happens shortly after start-up as the engine heat eventually works it way to the rest of the engine bay after the engine warms up.

[Benz Dr.]

Generally, I would agree completely. I have driven my car in some pretty cold weather and well below freezing. Aluminium will transfer heat very effectively but it will also cool just as well. That long plenum chamber doesn't get very warm towards the throttle body end in really cold weather.
 
Actually, now that I remember it the vent line coming from the valve cover froze up and the crankcase pressure pushed oil out of the fitting for the tach cable. When I stopped, I had oil all over the place in my engine bay. After I put the throttle body heater on I've never had a problem like that again. I washed the engine at a car wash which quickly thawed all of my icing problems.

 Late cars have a plastic pipe for venting the valve cover but early cars have metal ones. The metal ones can fill up with rust and crud which is what happened to my car. With little to no opening it easily froze up once the throttle valve iced over.