Nuts and Bolts with Buffalo Jim

Buffalo Jim,

A few weeks ago, the 5.7L engine in my 1985 Chevy half-ton pickup developed an engine miss. I took the truck to my mechanic, who replaced the plugs and wires and then said it needed a valve job. The problem is, I had an $800 valve job done less than 20,000 miles ago. I like the truck and don't mind spending the money, but I really don't want to spend it on parts that I just replaced. What do you think I should do?

--Tom G.

To be honest with you, bro, 99 times out of 100 your mechanic would be absolutely right. In fact, his diagnosis may well be correct, but it's also possible that a worn-out cam is causing your engine to miss. I first ran across this problem in the early '70s. A car came in with a miss, so I did what everyone does--swapped out the plugs, wires, distributor cap and rotor. When that didn't work, I ran a compression check on all the cylinders. One of the cylinders came back low, and I assumed the car needed a valve job. It was an easy diagnosis and looked like a straightforward repair--that is, until I finished the job and found that the engine still had the miss.

As it turned out, it was the cam that was fouling up the works. When I finally pulled it out of the engine, one of the cam's lobes had worn down to almost nothing. I replaced the cam and lifters with a new set, and wouldn't you know it, the engine ran like brand new. I ended up eating the cost of the job, but I learned not to do a valve job without first checking to make sure the cam is in good working order.

It's an uncommon problem, but I suspect you might have it all the same. In fact, I've seen it on several Chevy 350s over the past few years. The way to check is to pull off the valve covers and have someone turn the engine over. Find the cylinder that's low on compression and make sure the valve's rocker arm is moving like the others. If it's not, take it back to your mechanic and tell him you need a new cam. Feel free to let the victory go to your head.

Tip of the Week: Automatic transmissions

As everyone who's ever owned a car in Las Vegas knows, heat is the enemy. It will destroy every major component on a car--engine, battery, brakes, tires, paint, interior, everything--but no component is more susceptible to the debilitating effect of heat than the automatic transmission. According to the Automatic Transmissions Rebuilders Association, more than 90 percent of transmission failures are caused by excessive heat. This, of course, is bad news in a city where the summer temperature is only slightly cooler than the earth's molten core.

That being said, there are several easy ways to reduce summertime transmission wear. First and foremost, take it easy on the gas pedal. Quick starts and hard shifts create a lot of friction and heat in the transmission. If you ease off the accelerator for the summer months, your transmission will reward you with longer life and better performance when it's cold enough to punch it.

Also, if it's been a while since your last transmission service, take the car to a reputable shop and have the transmission fluid changed. It's an easy step to forget, but it's absolutely essential--not only because the fluid lubricates the seals and clutches but because the fluid actually helps propel the transmission. Old, dirty fluid will cause the transmission to slip, which is a surefire way to burn up a good transmission in a hurry.

If you haul a lot of stuff or regularly use your car for towing, you should also consider an auxiliary transmission cooler, which routs transmission fluid through a tiny radiator mounted at the front of the car. It's a pretty simple job that will help keep your transmission cool even when you feel like you're about to spontaneously combust.

Buffalo Jim is the owner of Allstate Auto Marine. On his birthday, March 22, he will officially be as old as the hills. E-mail him car questions and birthday well-wishes at buffalojim@lasvegasmercury.com.