Tech Tips Provided by Andy Jensen

March 2005 Tech Tip: Engine Rebuilding Basics

      It’s here! 2005, and the rush is on to get ready for the ’05 season. Whether you’re a circle tracker, drag racer, or street performance enthusiast you probably have something you’re getting ready for the spring.

      No matter what kind of racing you’re into or what your goals are for the ’05 season, when it comes to horsepower, all racers have the same thing on their mind. How can I get the most power for the least amount of money without sacrificing reliability? This is especially true with guys that are just getting started in hot rodding or running an entry-level class at the racetrack, so this article will be geared more toward them.
We’ll assume that you already have an engine to work with and that you’re going to do a good stock rebuild on it such as having the block bored and honed, the connecting rods resized, the crankshaft reground and a valve job on the cylinder heads. This is all stuff that must be done to ensure that you have a good sound engine to work with.
Now we can start to think about increasing the power output, so we’ll go over it in order of importance and what will give the most horsepower per dollar.
At the top of the list is cubic inches. Anything that can be done to increase the size of your engine such as boring more out of the cylinders or offset grinding the crank or even robbing the crank from a larger engine that can be made to fit into yours without a lot of hassle and expense is a common way to increase engine displacement. Of course if you’re running in a limited class you can’t go over the displacement limit, but you should be right on it.

      Next on the list is compression. If you’re boring the block you’ll need pistons any way so shop for something that will increase your compression ratio. If you can’t find an economical piston to increase your compression ratio, check into decking the block or cutting the heads. Sometimes this is the most economical way to go. Again, compression ratio is limited by the fuel you’re going to run or by the class rules that you’re running in.
Now that our short block is as big as we can afford to make it and has as much compression as practical, let’s go to work on the heads. Many people will argue that the heads should be first in line for performance modifications and this is a good point, but I feel that you need a good sound short block with a reasonable amount of compression to take full advantage of cylinder head modifications. Before you spend any money on your cylinder heads make sure they are a good casting and have a large valve size for that model of engine. Many engine manufacturers made different versions of heads to fit the same engines and some are more suited for performance applications than others. So before spending any amount of money on heads, make sure you have something good to start with. Once you’re sure you have the right heads, we can start working on them. One of the most economical ways to improve performance is with a competition three-angle valve job. Another popular modification is to increase valve size, but this is more costly because it involves buying new valves and the machine work to have them installed. Also if the port is not opened up to the correct size and shape for the larger valve, the performance gain will be minimal.

      Another economical way to increase performance is to port match and bowl blend the ports. In most cases a well-shaped valve bowl on a stock size valve will out perform an oversized valve that has not had the bowl bending done.

      This should cover what machining operations the beginner needs to be concerned about. Things like the camshaft, intake manifold and carburetor need to be carefully chosen for the specific engine application. However, these subjects will have to wait for a future installment of tech tips. If you have any questions please feel free to call the shop, we will be happy to help you out. Until next time, good luck.

      Well, I hope this info helps you to determine what’s best for your needs. If you have an idea for a future tech tip, just email them to andy@jensensenginetech.com