QUESTION: I have a 1992 Acura Legend with 71,000 miles on it. The local Acura service department recommends a valve adjustment every 60,000 miles. The vehicle is used mostly for in-town driving, 4-15 miles round trip. Is there a mechanical reason affecting engine life requiring a valve adjustment every 60,000 miles?

QUESTION: I have a 1992 Acura Legend with 71,000 miles on it. The local Acura service department recommends a valve adjustment every 60,000 miles. The vehicle is used mostly for in-town driving, 4-15 miles round trip. Is there a mechanical reason affecting engine life requiring a valve adjustment every 60,000 miles?

—George F. Miller

ANSWER: Proper valve adjustment is important on engines that require it. An engine’s valves are subjected to considerable heat and forces that can alter shape ever so slightly, affecting adjustment. The mechanisms that transmit motion from the camshaft to the valves need to be snug, yet loose enough to ensure the valves close fully. Too much clearance causes noise, and too little could result in valve failure due to overheating (if a valve fails to close it can’t properly transfer heat to the cylinder head).

Some engines require periodic valve adjustment and others don’t. Your Legend’s C32A1 engine employs hydraulic valve lifters, which take up the slack, making adjustment unnecessary. Many Honda and Acura engines do require valve adjustment; perhaps there was a misunderstanding regarding the engine application.

Q: Your battery column got me thinking: What’s the difference between a regular car battery and a deep cycle battery?

—Mike Shatto

A: A conventional car battery is classified as a starting, lighting and ignition battery, or SLI battery.. These can deliver a big rush of electric current to crank the engine — almost 10 times that of any other car demand — but are not designed to be discharged deeply. A deep-cycle battery, used in RVs and other specialized applications, leans opposite. Their cells, made up of a sandwich of plates, are optimized for smaller electrical loads and a much deeper depth of discharge.

If one were to deeply discharge an SLI battery — say, by forgetting to turn off the headlights — more than a few times, battery life will be dramatically shortened. It’s best if these batteries aren’t discharged more than about 20 percent of capacity. In normal use, starting and running a typical vehicle, this doesn’t happen.

A deep cycle battery may be damaged in a different way, should it be used to crank a large engine. These batteries can be gently discharged down to about 50 percent capacity perhaps 500 or more times before wearing out. They are great for powering lights and accessories between charging opportunities. Deep cycle lead-acid batteries are also used for solar energy storage and low tech electric vehicles. Marine batteries offer a compromise of the two qualities.

NOTE: I recently attended a training seminar oriented toward engine diagnosis. I was reminded, yet again, of the importance of maintaining clean and correct oil in engines employing variable valve technology. (Valve lift and timing are varied depending on operating conditions.) These engines use engine oil as a hydraulic fluid for the valve altering mechanisms and typically employ fine screens to prevent particles from fouling things up. These screens and mechanisms are prone to plugging up with gunk and can be obscenely expensive to service.

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ABOUT THE WRITER

Brad Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose, Calif. Readers may send him email at under-the-hood@earthlink.net; he cannot make personal replies.

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