Today, it is common to use or request the use of torque plates during the honing process. But, if your chosen machine shop does not use these, it's best to find another source. It never hurts to ask probing questions. And when it appears you're getting misinformation, you can always revert to the approach Smokey Yunick frequently took. That was, "Keep talkin' 'cause it ain't often I get to listen to a genius." Works just about every time.
This is a top of the line crankshaft from SP Crankshaft. The Irvine, Calif., based company
Hot Honing Hot honing is a technique where the block and honing fluid are heated to the operating temperature of the engine. The block is then honed at this temperature, providing a more cylindrical bore when the engine is running. To properly develop the correct technique for hot honing, a considerable amount of time and work is required. The block must be mapped at operating temperature and the hot honing technique adjusted to give a similar result. We recommend that you discuss this, somewhat at length, with the provider of the hot honing equipment or machine shop you elect to use. The results from this process may yield a few horsepower. This is very specialized work and may not be a good value except for the extremes of motorsport such as Cup racing. You must judge that for yourself, although the process has proven to be beneficial, correctly applied.
WristPins In today's circle track engines, the best solution for a wristpin is to run a high-quality steel pin with a DLC coating. The pin is run directly against the steel pin bore of the rod and without a coating. Cup pins for open class motors are as small as 19mm. Pin lengths tend to be short so the pin is as stiff and light as possible. As an example, a 20mm diameter by 45mm long pin with a 4.5mm wall is common in open Cup engines.
Top-Guided vs. Bottom-Guided Connecting Rods Most high-speed, circle track racing engines today guide the rod from the top, not the bottom as in stock production engines. The advantage of top-guiding is that the packaging of the pin towers can be moved in around the small end of the rod. This allows a shorter, lighter pin and a stiffer piston-rod-pin assembly. Top-guiding works most efficiently with a box-in-box-style piston and usually requires an integrated design of the piston, pin and rod. It will result in a lighter, stronger package which provides better stability to the piston, thus improving piston ring seal.
A NASCAR-style billet piston by JE. Je pistons
Top-guiding also requires that bore angle, bore spacing, and mains are all correctly located. The linear dimensions of the crank shaft must also be correct. For steel rods, the side-clearance for the small end of the rod to the piston should be no more than 0.125mm. The side clearance for the big end of the rod should be no more than 1.0mm. Typically, the small end of the rod will be smaller as well, and a 17.75mm small end width with a 20mm pin is comfortable.
Some Summary Thoughts By now in this Series, you've probably noted that we're not focusing on traditional subjects with equally traditional comments. Rather, we're digging into informational bites that skirt around what you've previously heard or read. That's not to say such prior information from other sources has not been useful. Certainly it has likely been. However, and from its beginning, the charter of this Series was to pull in fresh information you should probably consider or (best case) put into practice. For the most part, charts and graphs provided are actual case histories, or at least based upon them. So they're not hypothetical. That tends to bring reality and experience into play.
Our expectation is all this will become even more interesting when we get into discussing components keyed directly to the sensitive areas that make significant power and add durability to a given engine package. That's upcoming in the following parts of this Series. Don't spin out.