Pieces of the pistons dropped down into the crank area and finished off the rest of the shortblock, leaving us with another set of Cobra heads minus a shortblock. The night before St. Louis it dipped into the low 60's here in Detroit when I was testing the car. This change in the weather changed the tune for the worse, which was optimized for the T-Trim in the heat. When the car shifted into 3rd and the R's dropped down to about 6000 the timing was around 28 and the air fuel ratio according to the FP was 11.6ish not 10.8 to 11.0 like usual. This was a dangerous combination and allowed the detonation, which broke the two pistons.
Performance is only down slightly with the less aggressive rpms and tune.
The new engine has spun to the 8000 limiter a couple of times and not missed a lick. The 3rd engine has an estimated 35,000 to 50,000 on it judging from the dark colored staining on the bottoms of the pistons, we pulled the pan to check for loose or spun rod bearings. Currently we are building Joe a Cobra short block with good rods and pistons in an effort to go even faster. But I stubbornly want to continue to see what a stock engine can take. We may even sneak up on the trap rpm and install 4.30s instead of the original 4.56s and see what difference a few hundred rpm make.