Car Shop Mistakes - Don't Do This In The Shop! - Tech File

Second Of Two PartsLast month, we talked about ways to avoid five common errors new racers make behind the wheel. But the track isn't the only place where racers can make mistakes. Here are five quick tips for avoiding costly mistakes back at the shop.

Don't Confuse Your BoltsIn Street Stock racing classes, GM's "Metric" chassis cars are by far the most popular. These include Chevy Monte Carlos, Buick Regals, and Olds Cutlasses. Metric chassis were built from 1979 through 1986 and are so named because GM began using metric fasteners on the chassis during this time period. The problem for racers is that the engine, transmission, and rear end still used SAE bolts (measured in fractions of an inch).

When working on one of these cars, you have to be very aware of the type of bolt being used as a fastener. In many cases, metric and SAE bolts appear to be the same size, but are slightly different. If you try to insert the wrong bolt in the wrong place, it can cause damage to the threads and cause the bolt to fail early. If this is your first time building and maintaining a race car with metric fasteners, you will also need to get used to a new sizing and grading system.

Don't Depend On Your MemoryTaking notes and generally writing stuff down is not why any of us got into racing, but it is a necessary part of running well and winning. Don't depend on your memory for how you adjusted your setup when the weather was cold or what stagger you used three weeks ago. A good record-keeping system should be used for everything from what chassis adjustments were made at every race, to how many laps are on the engine so that you can get it refreshed at the proper time before it fails. There is a reason the best NASCAR Nextel Cup crewchiefs value their bound volumes of setup notes more than their toolboxes.

How you organize your information isn't nearly as important as whether or not it works for you. Remember to track changes during test sessions and throughout every race. Critical measurements and numbers are those dealing with wheel weights, crossweight, ride heights, tire pressures, springs, shock settings, caster, camber, toe, bumpsteer, camber gain, right- and left-side wheelbase, and tread width. You may decide to track other changes as well. Finally, don't forget to recheck your chassis settings when you get back to the shop after a night of racing-especially if the night went well. You may have bumped wheels with another driver, or maybe someone made a chassis change without recording it, and sometimes people simply measure incorrectly. Whatever the reason, if the chassis settings are different than what you think they are, there is no way you can find that "magic" setup again next week. Rechecking all your chassis settings may require extra time in the shop, but it's worth it.

Don't Buy On ReputationIf you are buying a used race car or even used equipment, one of the worst mistakes you can make is to base your purchasing decisions on reputation. If so-and-so has a car for sale that won six races, that's nice, but it doesn't tell you much. If that car is so good, then why is it being sold? The condition of the equipment you want to buy is much more important than its racing history. Has the car been wrecked? How well has it been maintained? Does it have a pretty, new body hung over a used-up chassis that's bent like a pretzel?

Believe it or not, some of the smartest buys can come from the back markers. If the driver wrecks the car every other week, then stay away like the plague. But if the driver was just plain slow, you might have a hidden gem (and there are plenty of drivers out there that are just plain slow). They don't wreck their cars, but they don't drive them hard either, leaving them in sound condition. Often, these are the cars you want.

Don't forget to ask the car owner for any records of repairs or chassis changes. If the team has performed repairs itself, then it is quite possible that important measurements have changed. But if the changes were made by the chassis builder on a dedicated jig, chances are much more likely that all chassis dimensions will remain true.

Don't Make Assumptions With Front-Drive CarsIn the lower classes, front-wheel-drive cars are catching on because they are plentiful and cheap in the junkyards. If you are thinking about building one of these cars for a FWD class, don't assume any of your knowledge from standard rear-wheel-drive race cars will carry over. Now, instead of handling just the steering and braking duties, a FWD car must use the front wheels to turn, brake, and power the car forward. It becomes difficult to figure out how to do all three effectively within the tires' limited traction window.

Sleepy Gomez, SCR's tech editor, built a Honda for oval-track racing and covered the process in previous issues of the magazine. He says that just about everything he learned to help a RWD car handle worked backward on his FWD racer. For example, he found 66 to 70 percent negative crossweight (on the left-front and right-rear tires) helped the car turn and got rid of the push that almost all FWD cars have.

Don't Settle For An Out-Of-The-Box CarbJust because the rules state which Holley carburetor is legal in your class, don't assume they are all the same. Holley carbs are very tunable with their many adjustments, but a carb that has been massaged and rebuilt by a knowledgeable carb builder is always going to be head-and-shoulders better than an out-of-the-box carb. Also, when shopping around for a carb builder, ask to see if he has an engine dyno. A flow bench is nice, but an engine dyno is critical because it is the only way to really test a carburetor. With a dyno, a carb builder can test and tune fuel flow, throttle response, and midrange and top-end power. Good flow-bench numbers don't mean a thing if the carburetor doesn't actually help the engine produce better power. As Gomez says, "I don't care how much stuff he has in his shop for building carburetors, if he doesn't have an engine dyno, he's just guessing."