Jeep Engines - Oljeep

OFF-ROADING AND RACING 479At this point, you start getting specific as far as parts areconcerned. Each engine is unique. The specificsubstitutions are listed in the engine chapters of this book.The service manual for the vehicle will tell you how to takethe engine and vehicle apart. It also tells you how to put itall back together. This book tells you how to modify it tomake it go faster/quicker at the drag strip.We’ll assume there is nothing wrong with the truck that youhave. This allows you to put together a basic list of partsrequired. Obviously, you need gasket sets and bearings.You will also need headers, new pistons and rings (probablyoversize), a race ignition (electronic), and a low restrictionair cleaner for the base plate to use as an ideal entrance. Youalso need a fresh set of valve springs and a “stocker” cam.As far as the basic engine building goes, refer to the‘Engine Assembly’ section of Chapter 4, 4.0L Powrr TechIn-Line 6. Be sure to hone the block with a honing plate.One of the keys to making good power in a stocker is thevalve job. It must be good, but also legal. It’s usually bestto send this out to a professional. If you have a carburetor,you’re also going to need some carburetor jets. Stockersmake more power and, therefore, need more fuel from the“stock” carburetor.Now you need to switch your attention to the chassis. Thefirst thing is to weigh the whole vehicle. This lets you knowhow much weight to take out to get down to theclassification weight. While you are weighing the vehicle,push the front wheels off the scale and weigh just the back.This allows you to calculate the weight distribution. Truckshave basically poor weight distribution if no ballast is added.For chassis parts you’ll want a race torque converter and arace manual shift valve body (assuming automatictransmission). You need to get a Sure-Grip rear axle and alower gear ratio. You’ll need racing tires and lightweightwheels. A balance weight set will be needed for the torqueconverter. At this point you can start building up your newrace truck. As you can see, any racc project is really twoprojects. One is the engine and the other is thebody/chassis/drivetrain. Each one is important to makingthe race vehicle successful.Super StreetSuper Street is an entry level category (similar to SuperGas) with a 10.90 second standard (quarter mile). It is forfull-bodied cars only (full fenders, hood, grille, roof,windshield, and functional doors). Any automotive engineis permitted.Basically, a 10.90 bracket is quite simple to define ingeneral terms. With a 10.90 second elapsed time in thequarter mile, we can calculate thc weight-to-power (W/P)ratio that will allow this performance level. The actualW/P ratio factor is a function of the type oftransmission - manual or automatic. The W/P ratio for theautomatic is ,146; manual is ,140.To simplify this discussion, we’ll assume that everyone has anautomatic. This allows us to calculate how much horsepowerour engine has to make to obtain our goal of 10.90 seconds.As long as we stay in this category, our required power levelis ,146 multiplied by the total vehicle weight.For example, if a vehicle weighs 3,200 pounds, then thehorsepower required would be 467. Total weight refers to thecar’s weight added to the driver’s weight. The NHRA uses170 Ibs. for the average driver’s weight. For best accuracy,you should use your driver’s actual weight. So, if our carweighs 3,030 pounds and our driver’s weight is I70 pounds,then our total race weight (vehicle weight) is 3,200 pounds.We can also figure that if we had a 2,330 pound car and thesame driver, we’d have a total weight of 2,500 pounds andwould need 365 hp to go 10.90. Are you getting the picture‘?We saved 100 hp in engine output by taking 700 pounds offthe car. On the other hand, if our car weighed 3,530 pounds,our total weight would be 3,700 pounds and the powerrequired would be 540 hp. It is obviously easier (and lessexpensive) to build a 365 hp engine than a 540 hp engine.In many cases, it is cheaper to reduce the weight of the carthan it is to build-in extra horsepower. Plan your project forbest performance-per-dollars spent.ConsistencyConsistency. Ask any bracket racer what it takes to win andthat’s the answer you’ll get. Consistency. Everybody knowsit, every racer says it. But for the beginning bracket racer,how do you become consistent? How do you get consistentto the point of cutting a Five-0 light (300 second) andrunning the same E.T. every time? Welcome to BracketRacing 101. Class is in session. Let’s dissect “consistency.”We’ll assume that your vehicle is in good mechanical shapeand you can find your way to the race track. The problemis, the vehicle won’t run consistently. Your reaction timesvary from ,501 second to calendar years, and you always goout in the first round because you’re off your dial-in. Whatdo you do now?First, lets look at reaction time. Why is cutting a Five-0light important? Simple. In bracket racing, anything yougive up at the starting line you can’t get back. You “breakout” if you do. Look at it this way-a vehicle traveling at100 mph is moving 146.7 fee per second, or 1.467 feet per100th of a second. If you cut a ,560 light against youropponent’s S10, and you both run right on your dial-ins,you will be 7.3 feet behind him at the finish line(approximately). To close this gap, you must break out.Five hundredths at the starting line means you lost by halfa car length.. .. I.