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July 18, 2002


I picked up my rebuilt carburetors from Jerry Mong on Tuesday, but had to wait until today to install them because I was waiting for a set of manifold gaskets and heat insulators from CARS, Inc. I had my repainted air cleaner ready to go and refilled it with a pint of motor oil per the service manual. A few drops of blue Lok-Tite on the carburetor studs and I dropped the carburetors in place and tightened them down.

Carbs 2.jpg (151103 bytes)
Freshly rebuilt carburetors installed with restored oil-bath air cleaner.

These Strombergs are quite remarkable pieces of engineering. They do most of the things our modern fuel-injection systems do, but mechanically instead of electronically. They have different idle strategies based on engine temperature, a unique lock-out that prevents large throttle openings and heavy loads until the engine is properly warmed up (I think only Lexus currently does this on their cars), and an automatic choke for easy starting in almost any weather.  Here's how it works:

Carb Diagram.jpg (79704 bytes)
A is attached to the butterfly in the top of the carburetor. It is controlled by
a heat-sensitive spring (like in a house thermostat), which is fed heat from
a stove pipe in the manifold. As the manifold heats up, the butterfly opens
wider, moving the stepped idle cam, B. As the engine warms up, the cam
rotates clockwise, reducing idle RPM. C, though you can barely see it, is a
small rod that prevents the throttle from opening more than 40% or so until
B opens up to the second step. D is the throttle rod that connects the carb
to the accelerator pedal. E is a fulcrum that activates the accelerator pump,
and it is attacked to the linkage using another cam-shaped plate, which causes
the accelerator pump to dump extra fuel into the carburetor when the throttle
is first opened. Pretty neat, eh?

I fired it up after the carbs were installed. After some cranking to prime the carburetors, the engine sprang to life and settled into a nice, even idle. Wicking the throttle was smooth, not stumbly as it used to be, and with the open exhaust, it really sounded healthy. Again, there was a lot of smoke from burning crud, as well as some smoke in the exhaust (which I suspect is from an overfilled crankcase--the service manual calls for 10 quarts while the owner's manual calls for 8--which is it, guys?). There's still some fine-tuning to do on the carbs, since it was a little rough and even low idle was a little fast. I also think it's running rich (I could smell fuel in the exhaust). I didn't have time to do it all, however, because I believe the thermostat is sticking--the gauge pegged itself pretty quickly, though the radiator didn't seem very hot. I'll check that next. I also think it'll run better with an exhaust on it--a little backpressure is good for smooth idling. I should probably powerwash the engine as well to get that gunk off that's causing all the smoke. We'll see what happens next week.

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Last modified on 02/06/2005

Thanks, Fidget!