I did not hear back on your numbers brother , however recently woods ported a quad port 357 xp . I ran with a conservative .018 squish , 141 duration & 13.5 deg. of blowdown & achieved a 500+ rpm gain over stock with a minor muffler mod & goobs of low & midrange torgue . The overall compression with the crank stuffers wa. pretty well unaffected . I still run 91 octane with Saber @ 44:1 . Very strong firewood saw. P.S. I usually use a 10 deg. raduis on all chamfers including the transfers .
Sorry NNW, been busy trying to get my new (stupid) P320 XTen running right. Mags keep jamming-up with 200 gr HC. Sig sucks.
Anyway, the 3120xp:
Exhaust opening = 98 deg ATDC, duration = 164 deg.
Intake duration = 135.7 deg
And oops, looking at my spreadsheet on the engine, squish is actually 0.580mm = 0.0228" (still kinda tight for the compression and squish-band width of 9.5mm)
I've been thinking of getting it just a hair tighter.... but calcs indicate that it's already too tight. No indication of detonation with the fuel being used, though.
Blowdown is just a hair over 22 degrees.
Transfer duration is 120 deg.
Nothing too radical, though I don't know if I want to try 93 octane as before. Seems to run smoother and harder on 100LL for the time being. And Aviation fuel is no more expensive than the available non-alcohol 93 pump gas around here.
I've been thinking of increasing intake duration to around 140 - 142 deg.
The head, piston deck, and intake and exhaust ports have had the 350 deg baked Cerakote Piston-Coat applied and it does seem to help with keeping the heat inside the combustion chamber rather than getting the piston undersides and head too hot.
I use pretty cool plugs -- B10HS.
Funny (not), I have the engine apart again, checking things out. I purchased an OEM piston last year to put on the shelf for a snowy day. I just weighed it and it's a whole 2.3g lighter than my messaged and lightened OEM piston that I had been running. WT....? Measured it all over and found some of the webs are slightly thinner, but the big surprise was some minute cracks in the casting right at the window/skirt corners just under the lower ring, on two sides. Bugger. Good luck exchanging that piece of junk AL.
The OEM rings (junk) that I had in there lasted maybe 1.5 hrs. Initial gap was something like 0.445mm, should have been closer to 0.21mm. I ran them anyway because I couldn't find any G15H cabers at the time. Everyone was selling those F-Cast rings.
The thing ran really powerful for about half hour straight out of the shop (typical break-in stuff, short bursts up to roughly 11000rpms). Then the rpm's started slowing down roughly 200-300 rpm's lower (tinytach). No big deal though. After 1.5 hrs, took the pipe off and saw minute scratches on the cylinder on the intake side. Fug!
Took the top off and found minute scratching on the exhaust side too. Double fug! Ring gap grew to 0.650mm on both rings! Max-gap replacement time should be around 0.60mm. These husqvarna OEM rings suck. They're lazered 'KO B8' for Komarov s.r.o. The circumferential exterior edges of the rings looked a bit chipped in some places, but not really localized to the ports. Initially the edges were quite sharp, not chamfered.
Finally got some G15H cabers in yesterday. Nicely chamfered edges. Gaps acceptable at 0.253mm.
Crankcase has been thoroughly flushed, all bearings look and feel good, seals are 1.5hrs old, so going to slap on the rings and see how she goes. Again.
Anyone know where I can find a Meteor piston for the 3120, or should I just get another OEM at inflated cost?