The 6M has a couple of longer counterweights to cover the MIA ones, while this "works" it's not ideal, look at a Jz crank and you will see it's 7M heritage.
Prepped ie: identical Main, Rod Journals and Thrust dimensions, Balance, Heat treating, Niteriding so getting each crank 100% interchangable.
(clerical error resulted in me having both cranks ready at the same time)
Not sure what the actual hard cut is on both ECU's but either crank is happy to spin to the higher limit, I ran both cranks in the same engine within a 2 week period with the crank being the only change, both were prepped identically and the 7M was smoother across the range until 7500+ where it...
I just unhook the Coils so it can't fire then crank it till I see pressure on the stock gauge, normally you'd confirm flow at the drain but on a ct26 the hardline makes this difficult.
Last time I built a 7M I rang ACL here and they didn't do the race series for M's, this may have changed as it was a few years back Steve.
All I can say is it looks like an FoD issue to me. I'd have expected the loose bearing to be pristine compared to the tight ones as long as it had Oil...
Not enough room between cylinders to o-ring a 7M.....
(exception to this is a figure 8 o-ring around 2 cylinders but very expensive)
Stick with the tried and true route.
ACL don't do M bearings in the race series :(
See if you can find some NDC's, I found when running my 7M hard I had to go to high 2's on the rod bearings and run a 10/60 Synthetic to get any sort of life out of the engines, having said that yours looks like it's had some gunk or crap hiding...
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