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Originally Posted by RedBarchetta
Is it possible that the builder did not take the .015 decking into account?!?  That's not .0015 (thousandths); .015 is a significant amount.
-Dean |
Um....actually, .015 is fifteen thousanths; .0015 is one and one-half thousanths. Either way, it wouldn't have made a difference, because those gouges in the piston tops are deeper than 14 thousanths of an inch.
As regards where the piston is sitting assembled - you will need to know exactly the dimension between the TDC stroke centerline and the top of the deck (deck height), and then know what the assembled piston/rod combo is. Compression height of the piston is that dimension from the centerline of the piston pin to the top of the piston; the measurement of the connecting rod, center-to-center, plus the compression height of the piston, as measured against the aforementioned deck height, will tell you exactly where the piston is in the hole. All kind of moot, since there is no doubt whatsoever that the valves were hitting the pistons, meaning the cam was the wrong choice for the short block as assembled.
However, there might be some real credibility to the crank key issue - since the valve was contacting the piston, this means there was a BIG load put on the cam to stop turning as all lash was removed and something had to make up for it....either by flexing or by going to the weakest link which just might be the crank key. I am surprised that maybe a pushrod didn't bend - actually, I'm kind of surprised they ALL didn't bend - but strange things do happen.
Still. All in all, your builder has some serious explaining to do, especially since you have a video showing that there was no clearance at the time of the build.