Size doesn't matter.

Well, at least in reference to connecting rods.

There was a recent article in National Dragster regarding a test conducted by Reher-Morrison Racing Engines on a 500 inch Chevy Pro Stock engine. In this test, they built and dyno tested several different engines with the only variable being the length of the connecting rods (and the piston compression height, of course). Can you believe it? They found that the rod length didn't result in much, if any, HP differences. Long rods, short rods, it didn't seem to matter. They concluded that the most important thing that the rod had to do was to connect the pistons to the crankshaft.

I have found that this is old news to a lot of engine builders. Apparently the great myth regarding "rod/stroke ratio" is just that, a myth. I don't know where or when this "long rod" theory began. Some say it was something that Smokey Yunick started, or some tech article in a magazine. Whatever, many people have put a lot of faith in the "long rod is better" theory. The theory has something to do with the piston "dwelling" for a longer period of time near top dead center. Like most theories, there are always other theories that basically counteract each other. Like, "whatever goes up, must come down", or "every action has an equal and opposite reaction".

Being in the Stroker Kit Engine business, we get to hear customers and prospective customers discuss the merits of different "rod/stroke" ratios. The consensus with some of these people is that "longer is better" (we're talking about connecting rods, now), and in many cases they are willing to settle for a smaller displacement engine that has a "better" rod/stroke ratio. Hey, whatever the customer wants, right? If they are willing to trade less horsepower for a longer rod, no problem for us.

Here are a few examples of different OEM engine combinations and their rod /stroke ratios:

302 Small Block Ford (1.70:1)
351Windsor Ford (1.70:1)
350 Small Block Chevy (1.63:1)
 

Are these rod/stroke ratios "good"? Does anybody know for sure? Does it matter?

Let's do some comparison testing for fun. In this test, you have to pick which engine you would rather have for your performance car.

First, if you were going to pick a Small Block Ford powerplant, would it be a:

302 SB Ford (1.70:1), or a 289 SB Ford (1.78:1)?

For the Chevy fans, how about a 350 SB (1.63:1) or a 454 BB (1.53:1)?

For the Chevy SB Stroker Motor racers, would you favor a 350 (1.63:1) or the ever popular 383 (1.52:1)?

For the Ford Stroker Motor racers, how about a 302 SB (1.70:1) or a 347 SB (1.58:1)?

If you selected the larger displacement engines in each case, you get an "A". If you selected the larger rod/stroke ratios in each case, you will be required to go to the back of the classroom and face the corner (large, pointed hat included at no extra charge).

But if you still want a big rod/stroke ratio engine, we offer the 221 cubic inch Ford Flathead for your approval (1.86:1).

Before we get off the subject of connecting rods, let's discuss another great myth; connecting rod design.

Since we are only willing to settle for the best, should it be the "H-Beam" design, or the "I-Beam" design? If you said "H-Beam", you may be part of a vast group of racers that seem to have been programmed into believing that an "H" is stronger than an "I". Here's a question to ponder. When they construct a high-rise building, do they frame the building with I-Beam girders or H-Beam girders? If you selected H-Beam, guess again. Why, because the I-Beam design is a stronger (and lighter) design. Maybe this is why the NASCAR Winston Cup engine builders (even Smokey) use I-Beam rods almost exclusively.

Does anyone think that those big aluminum rods inside of John Force's 6000 HP engines are more of an I-Beam or H-Beam design? Do we even need to answer this question? In fact, has anyone ever seen an aluminum H-Beam rod? I don't think so.

Another great myth down the tubes.

But, despite all of these facts, and because we feel that the customer is always right, we will be happy to sell you a smaller displacement, long rod, (H-Beam design) engine. If you're happy, we're happy.