Help me Build my Engine

[blykins]

Chris, it's been a while since I've made that post...looks like a couple years now. I've heard arguments each way since then. You know that each piston on the power stroke tries to drive the crank out the bottom of the block.....the girdle would distribute this force along all 5 caps instead of just 1. My girdle is .400" thick and covers all the caps....unlike some others I've seen that just hits the middle 3. In my mind, it would be stronger, but I've definitely been wrong before. It's the same prinicple behind a rearend girdle....the girdle ties in both differential bearing caps together. I guess no one's ever made a 4-bolt differential housing though....

Let's look at it like this...say one piston fires and produces 500 lbs (truly hypothetical situation) of force in a straight vector straight towards the main cap. (This couldn't be possible because the rods & pistons are at an angle to the crank, but this is just an example anyway.) In a 4-bolt block, that 500 pounds would be distributed over 4 bolts with probably a tensile strength of about 100ksi each. In a girdle'd block, the 500 pounds would only be distributed over 2 bolts (again probably 100ksi T.S.), but any deflection whatsoever would be taken up by the other 4 main caps as well, therefore reducing any strain on the 2 initially loaded bolts.

Maybe sometime I can whip up a 3D solid model of an engine block, do some finite testing and post the results.

I guess there could be arguments to each side. One good argument against it is that Nextel Cup engines would be using them if they were stouter than 4 bolt main blocks.....but then again it adds a little weight vs. a 4 bolt main cap.

Maybe we can get KC to chime in on this one...