Pt.1 - Twin 660 build: Big Bore Top-End on 25" Felling Saw

To be crystal clear this is really a "swing for the fences" build that I'm not sure will pan-out, as mentioned I have another big bore setup for porting after I've seen how this one plays when in real situations!! Exhaust cracks 106deg ATDC, intake pulls at 101deg ABDC, blowdown was raised to nearly 29deg, squish is 24 with about 5thou freeport -- this was a big the biggest problem-decision with these jugs, you want to squish tigher (on a flat squish-band) but can't w/o freeporting unless super careful with your work, I think I can get sub-25 squish WITHOUT freeporting on the next one, we'll see!!

[@joescissorhands141]

Update: Sadly it isn't "tight" at TDC, once it was broken-in a bit and I was doing gentle cutting it started to accumulate oil at the muffler that I didn't like, it definitely "had pressure" behind it that I've never seen, it's either from a lil freeport or a lil bit of non-sealing sides of exhaust-port, my suspicion is the latter, at any rate the compression was fine and aside from wasting some fuel (and surely stealing *some* charge from the engine function itself) it felt fine, will test it hard at a job on Thur but it needs the other big bore jug swapped-in, I've begun getting that ready and I have a 56mm Hyway pop-up piston (and Stihl D-handle) en route so on Fri or the weekend I'll swap in this other jug and the Hyway, bumping compression higher, eliminating the loss at TDC by both keeping exhaust port width to allow >10thou piston skirting coverage, and leaving at least ~10thou before freeporting, this latter is unlikely the bigger problem but I want both resolved (of course) and if my mapping & math are on point then this CAN be done in a way where I'm 10thou+ from freeport while still: - Having a fully flat squish band, - Having no more than 30-35thou squish clearance maximum (1 regular base gasket, no Moto, no decking just band flattening/polishing) and still fit the parameters (obviously it's still a lower-ring-only build, but that doesn't seem to be a problem in fact it may be desirable for performance despite being negative for longevity/reliabillity, kind of like how I use F.Tec rings during initial break-in and then swap in my Caber rings ;D Which reminds me I better do that before taking it w/ me on Thur >;D