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Classic/Antique Car Repair/Rochester 4GC choke question

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Expert: Paul Wilczynski - 10/9/2009


Question
Paul:  I have a Rochester 4GC, #7026121, on my 56 Chevy Bel Air and have just tried to replace the automatic choke element, which I was told was bad (the choke would not close when the engine was cold, making it very difficult to start in the morning.)  I manually closed the choke when the engine was cold, then replaced the element with a new one, making sure that the hook on the spring faced the right way and was right up against the lever from the carb.  I put it all back together, but when I started the engine, it bucked and spouted smoke from the tailpipe, like there was no tomorrow.  The choke would not open, even after I kept the engine going and filling the neighborhood with smoke.  Numerous efforts to find the problem have been unsuccessful, so I'v manually opened the choke again and set the element spring 90 degrees out of the way until I can find out what's wrong.  Can you guide me through this and give me some advice on what I'm doing wrong?  thanks a bunch.......Bob

Answer
My experience with these is somewhat limited--my '55 Nomad had one and once it was properly rebuilt it ran fine.

Is the element cover adjustable by rotating it? If so, I'd back it off until the choke was just closed at ambient temp. Make sure your heat riser tube is open and its connection to the exhaust manifold is solid--it's transmitting heat and has to do so quickly for maximum economy and best state of tune.

Last, be sure the choke butterfly pivot shaft runs smoothly--if it's cranky or stiff, it will never work properly once the motor is hot.

--Paul

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Paul Wilczynski

Expertise

Most questions involving vintage car restoration, mechanical and body, paint and upholstery. Parts sourcing. Extensive experience in wood-bodied station wagons, British and French cars of the '40s through '70s. Rolls-Royce Silver Shadow, Sunbeam Alpine and Tiger, Citroen Maserati, VW Beetle, 1955-65 Chevrolet (especially Nomad station wagons), Corvair.

Experience

Wide-ranging and long-term. I owned a restoration shop in the 1970s, continue to dabble in vintage exotics. At one time, had a seven-car collection of contemporary exotics which I had restored and maintained myself. When I was 18 years old, I designed a woodie kit for the VW Beetle, which I developed into a product which was featured on television and in over 100 magazines and 25 books at last count. I still own and drive one of my creations. I owned a design and fabrication consultancy from 1982-2002, specializing in show car fabrication for manufacturers including Ford, Mazda, GM, Subaru, Mitsubishi, etc. Since 2003, I have been a department manager in Industrial Design, and a full-time instructor in automotive design and fabrication at the university level. My students go on to design automobiles as staff designers for major auto manufacturers worldwide.

Organizations
Western Automotive Journalists, Industrial Design Society of America.

Publications
Long list of magazines and books, including Playboy, VW Trends, VW Greats, Hot VWs, and European automotive magazines.

Education/Credentials
I teach design and fabrication at university level. My education is in Industrial Design, University of Illinois (1966-1970).

Awards and Honors
Many awards for restorations in local concours and shows.

Past/Present Clients
Mazda, Ford, GM, Subaru, Mitsubishi, Honda, Toyota, Chrysler, Mercedes, Porsche.

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