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Classic/Antique Car Repair/compression test 1954 belair

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Expert: Paul Wilczynski - 3/23/2009


Question
HI PAUL, IVE JUST COMPLETED A COMPRESSION TEST ON MY 6 CYL 235 54 CHEVY. ALL CYLINDERS READ BETWEEN 105 AND 110 P.S.I. THIS WAS A DRY READING WITH ENGINE HOT. IS THIS READING ACCEPTABLE FOR THIS YEAR AND MAKE VEHICLE? HEAD WAS COMPLETELY REDONE, BLOWS BLACK AND BLUE SMOKE. THANKS

Answer
Vito:

If you do a cylinder leakdown test, you'll find that you've got blowby past the rings. Yes, you'll have to tear the block down and do the cylinders, too. Might as well do the bearings, oil pump, and timing chain, while you're at it.

Many engines wear (top end vs. bottom end) at an equal rate. The old 235 (and its predecessor, the 216) was one of these, and additionally, it was a fairly high-wear motor; often 40K was about all you got out of one, especially if they were lugged and run in dirty environments.

When you sealed up the top end by giving it a valve job, you didn't do the equivalent (rings) to the bottom end, and all of that nice, new compression is sucking cylinder wall oil right past those old, tired rings into the combustion chambers, on every piston downstroke. It's also running rich, as there's reduced volumetric efficiency and compromised ignition function with good valves and bad rings. Hence the colorful smoke!

Bad news, I know, but if you want to be right, break out the hoist and socket set!

--Paul

Classic/Antique Car Repair

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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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