Horsepower and the Short Block Assembly

We want to build horsepower, and the block is the vault the houses all the parts that must contain the power in that we are creating. If you are building your engine for competition then please research many blocks to make sure you make the right choice. You will want to avoid any that may have thin areas in spots that undergo much stress.

After you have chose a block to build, check the main bearing housings for alignment and have them sized to fit pretty tight as far as bearing crush is concerned so that the chance of spinning a bearing is less likely. Be sure to check and double check the crush before the final assembly.

The bore is yet another critical point to consider, and often overlooked. You may want to consider taking a close look at the machining process and how it works before deciding on a machine shop to do the work. Some machines for boring align off the old bore and if there is any error it just repeats it over again. The way to correct this is to have it bored on a machine the centers off the mains, rather than the old bore. The faces of the block should be squared up and true with the mains as well. Follow the manufactures recommendations that produce the rings as to the finish of the bore. This will all help reduce friction and maximize horsepower.

If power is the primary concern, then a bigger bore and shorter stroke usually will satisfy the need. This will allow for bigger valves and allow the engine the getting a bigger breath. If emissions and fuel consumption are a concern this may not be the answer. This would lean more towards a smaller bore with a longer stroke.

Crankshafts are vital as they transfer the power to the transmission. The grade of crank needs to match the power you plan to pump out of your engine. When you plan to maximize horsepower you must give great consideration to the bottom end or the short block assembly. Cranks are available in three grades that I am aware of. Cast being the least expensive, Forged is in the middle, and billit is the most expensive. the cast iron cranks are less costly and may be alright for a fairly stout street engine, but wont handle the power and abuse that competition will bring on. Forged will have more strength and depending on cost, you may be further ahead to have some surface hardening done and gain the same strength for less money. It pays to do your homework on these parts as you can spend a sizable amount on your rotating assembly. Billet is by far the strongest and very expensive. It is made from a block of steel. For most of us the forged is about as good as it is going to get, and there are many good companies offering the parts we need. The less friction you have the more power you are going to transfer out of you engine. The goal is to get the power to the pavement. Horsepower without traction is useless.

There are good and bad to every aspect of maximizing horsepower. Increasing the stroke means increased speed of the pistons, reducing the RPM band. If you are just building for max horsepower gains with no restrictions or rules to play by then the benefits of gaining more cubes with a longer stroke by far out weigh the loss of RPM potential. The stroker motors are a popular choice of many horsepower hungry people all over.

Not enough can be said about connecting rods. They are the most often weakest link and cause catastrophic failure, time and time again. The important thing here is the rod/stroke ratio. What we need to study is rod angulation and friction. The rod length divided by the stroke will give the rod / stroke ratio. There many valid arguments and theories on this topic, but I will share my idea on the subject. It is in your best interest, when trying to achieve maximum horsepower gains to use a shorter rod and gain the cubes, your compression ratio climbs and there are less negative effects with a shorter rod. On the other hand a longer rod is more efficient mechanically, so you have the information to make a decision as to what will work best for you.

Pistons are yet another vital part of the rotating assembly. Pistons are made of three materials that I know of. They are categorized in order of performance, high performance being first with High silicon aluminum, The ever so popular hyper eutectic cast, and the forged piston. If you want good parts you have to spend the money or you will be disappointed when if comes apart after you spent all that time and money to build it. Just do it right the first time and enjoy your toy for a long time.

Rings, bearings and lubrication systems are just as important as the block and crank. By Minimizing friction you will allow the engine to spin with less resistance and create more horsepower gains from you efforts in the top end. Horsepower is a adrenaline high for many of us. It is expensive to build power, but we will do it anyway because we have horsepower fever as we like to call it where I come from. It is like a disease that never goes away, it always pops back out sooner later. Be safe and have fun making that expensive noise.

Palange&Son Racing, Terry Shade ( Shade Racing Engines )