KB Hypereutectic pistons have a lower pin location and a higher top ring location. Because the higher top ring location leads to greater expansion of that particular ring it requires a greater gap. I used KB on a BB Chevy build a few years back and if memory serves KB specified the top ring gap on that particular engine around .025 while the other compression ring was in the .017 range. I had assembled the short block completely before I read the fine print on the KB paperwork and realized I had set the gap way too tight. The KB instructions (at least at that time) specifically mentioned that failure to set the top ring gap correctly could result in exactly what happened to you.
A sure fire way to see if your engine assembly guy screwed up is to check the gap on the top ring of the rest of the engine and if its the same as the other compression rings, then you know he didn't read the directions and you've got a case for him to fix it. Good luck.
On Thursday, November 7, 2013 6:53:57 PM UTC-6, Paul L. http://1962to1965mopar.ornocar.org/ml-lennemann63.html wrote:
To recap for everyone: On the eve of the Geezer Drags I drove my car to Rich K's house to socialize a little. The engine started to miss, which was pinpointed to #4 cyl. Discovered that the neg. electrode had been hit by something and bent over. There was also a bit of a noise in the engine. Since I am now retired as of last week, I took time today to pull the head off. Discovered that about 1.5" of the top ring land had broken off of the piston. So looks like the engine is coming out. This is disappointing in that I probably only have about 1500 miles on a fresh rebuild. And it has only seen 5K rpm a hand full of times in that time. The pistons were new KB Hyper-eutectic's.
Somewhat surprisingly there was no debris left in the cyl., and no apparent damage to the head. Still need to check the make sure that the valve seats are not damaged. I'm attaching a picture.
Paul L.
63 Sport Fury
440/727
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