Q&A with Kit Foster: May 23, 2013

Q. Regarding Glenn Simmons’ trouble with falling sun visors on his Cadillac Allanté (Q&A March 28), I have had this problem also. I found that if you drill a hole next to the rod, close to the end of the visor, and insert a small bolt, with a washer on both sides of the visor and a lock nut, you can tighten up the looseness. It’s not the prettiest solution, but it does work. I recall that some visors used to have a screw at the end of the visor for tightening it up. I’m thinking Ford products with the lighted mirrors.

— Keith Davis, St. Louis Mo.

A. As I said, a little more friction should fix it. Thanks.

 

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Q. Over the last 30 years, most car manufacturers have gone from making inline six-cylinder engines to V-6 engines. I can understand the reasoning behind it — a short V-6 will be easier to fit when mounted transversely in today’s front-wheel drive cars. But I have a hypothetical question: Imagine an inline six and a V-6 engine, both having the same bore and stroke, camshafts with the same lift and duration,  same valve train, same combustion chambers. Now further imagine both of these engines being run on dynamometers. How would one engine compare with the other in terms of horsepower, torque, maximum rpms, and overall efficiency? In other words what performance characteristics were lost or gained by switching to a V-6 design?

— Donald Chepurna, Waterbury, Conn.

A. That’s a very interesting question, and one that’s not easy to answer. The “V” configuration provides a number of other benefits in addition to the shorter engine length for ease of transverse installation. Crankshafts and camshafts are shorter, and thus less “whippy” and, as a result, probably lighter. The casting for a V-6 may be lighter, too, as less “bottom end” is needed. Weight would not affect dynamometer results, but the resulting lighter weight of the car would give better performance. Another factor is engine balance and smoothness. An inline six is the most perfectly balanced engine, whereas V-6s can be quite rough, depending on firing order and crankshaft configuration. Sometimes a balance shaft is added to smooth things out. The better-balanced engine should perform better. I notice that in 1975, Buick offered both a 231 cid V-6 in some models, and an inline six of 250 cid in others. The V-6 was rated at 0.476 bhp per cubic inch, while the inline unit developed 0.42 bhp per cid. Interestingly, the maximum horsepower for both the engines was developed at the same rpm: 4,000. Even though the bore and stroke of the two engines were nearly the same (and both dated from 1960s designs) a lot of other things differed, so it’s not safe to say that the horsepower difference between the two engines was attributable to their respective configurations. Still, it suggests that the ‘V’ configuration is more efficient, albeit modestly so. Are there any engineers among our readers who can comment on this?

 

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Q. In reply to the Chevrolet Fleet Economy question, April 18, Chevrolet offered a special “economy” engine for fleet use from 1935 through 1942. The following is from the 1939 Truck Data book, a guide for salesmen. The engine was available for both cars and trucks.
“THE ECONOMY ENGINE: To meet the requirements of truck users who have ordinary delivery problems, and who desire maximum economy, Chevrolet offers an ‘Economy Unit,’ at slight extra cost, on special order, that consists of the following:

“ENGINE: The engine is identical with the regular engine with the following exceptions: A throttle stop prevents full opening of the throttle, giving approximately half throttle operation. The carburetor has different metering rods and jets. Valve clearance settings vary from regular clearances. Rear axle gear ratio changes on some models. Caution: Do not recommend Economy Engines for heavy-duty models until you have consulted your zone truck manager.”

The description goes on to say the option shows a marked improvement in gasoline consumption under certain conditions, such as door-to-door delivery where there is no overloading and on fairly level routes. It was not recommended in mountainous country, such as Pittsburgh, or high altitudes such as Denver. It would also be used for passenger car taxi cab service. Gas mileage could be increased about 20 percent. It had ample power and speed for ordinary delivery work… Thanks for mentioning the Vintage Chevrolet Club (www.vcca.org). We have an excellent chat site and can answer Chevrolet restoration questions for all years.

— Gene Schneider, West Allis, Wis.

A. Thank you very much for your very comprehensive explanation. The marque- and model-specific clubs are rich founts of knowledge on their respective vehicles.

 

To submit questions to this column: E-mail angelo.vanbogart@fwmedia.com or mail to: Q&A, c/o Angelo Van Bogart, 700 E. State St., Iola, WI 54990-0001.

 

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