Comments by "mpetersen6" (@mpetersen6) on "MIND BOGGLING ENGINE GEOMETRY - Rod Ratio Explained" video.

  1. In automotive engines the wrist pin is typically offset 1 to 1.5 mm with the offset trailing the crankshaft direction of rotation. As I understand it this is done to 1) help the piston to begin the downward stroke. And 2) to reduce piston slap. Piston slap can also be reduced with tighter clearances between the piston and cylinder walls.
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  2. One thing to keep in mind here. The F1 examples. These are typically engines that are using bore to stroke ratios that can approach 2:1. In the past I have heard the ideal stroke to rod ratio is around 1.75. Looking at data on the Stan Weiss engine data site the only engine I can find that hits that is an AMC 232. Looking at V-8s the Ford Boss 302 had R/S ratio of 1.7162. The Chevy DZ 302 was 1.8968. Two engines with essentially the same bore and stroke. The other Ford 302 was in the 1.6's. One reason the Fords had the lower ration was the significantly shorter deck height of the Fords
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  3.  @carllinden533  Side load wear and piston slap are two different things. Piston slap is the piston rocking side to side as it goes up and down. The amount of rocking is directly related to the side clearance between the piston skirt and the cylinder walls. Piston skirts actually are not round. they are slightly elliptical with the major axis of the ellipse at 90 degrees to the wrist pin. Also since the advent of modern cnc controled turning equipment the skirt may also be barrel shaped top to bottom. The turning machines i was familiar with used an amplifier to control the tool when cutting the skirt. The service engineer when in house during install had a special tool that he could load in. After machining the skirt would have G & L on one side and Giddings and Lewis on the other.
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