FinnHammer, I've enjoyed reading your build thread, you are doing some nice work!
Thanks for that video, the presenter does a good job of explaining the situation.
In "Tuning for Speed" Phil Irving gives a formula for calculating piston loads, and I ran some Savage numbers through my spreadsheet.
stock rod, Wiseco piston, 6500 RPM:
2864.04 lbf load TDC 1.766:1 rod ratio
1600.10 lbf load BDC
long rod:
2790.09 lbf load TDC 2:1 rod ratio
1674.05 lbf load BDC
That tracks the video with the longer rod reducing both the load at TDC and also the variance between the TDC and BDC loads.
Piston pin offset can also make some difference in things like sideloads at midstroke.
But as far as the rod, I think the Savage will be one of those "it is what it is" situations.
I've seen some vintage pistons with thick rings that were widely spaced, so fixing that can help to make space to raise the pin in the piston. Also, race pistons will try and bring the top ring closer to the deck to reduce the top ring volume as the gasses above the ring aren't helping the compression ratio or doing much work, but if that is pushed too far the top ring will be exposed to too much heat and fail.
Here's a handy calculator for pistons:
https://www.wiseco.com/compression-calculator/I'm going to play with the ports. I have an Audie Technologies FlowQuik that I will have to drag out of hiding. I've pulled molds from the ports but I should put those photos into a different thread.
Here's some information on the new Ducati 659cc Superquadro single for comparison:
https://www.cycleworld.com/motorcycle-news/ducati-new-superquadro-660-single-...659cc Ducati Superquadro 77.5hp @ 9750 RPM, or 85hp @ 9500 RPM with exhaust changes, 116m x 62.4mm, 46.8 and 38.2mm valves. 110mm rods for 1.81:1 rod ratio (which Cameron considers "shortish") where Ducati twins are usually in the 2-2.2:1 range.
Putting the Ducati numbers into Irving's formula @ 9750RPM and keeping the same piston weight (though I'd expect the larger Ducati piston to be heavier) gives
TDC 4279.47 lbf
BDC 2388.26 lbf
At 6500 RPM to match the Savage calculation:
TDC 1901.98
BDC 1061.45
A short stroke helps too! But if a person wanted a short stroke high revving single, they probably wouldn't have purchased a Savage.
cheers,
Michael