Andy
Yes many pistons were changed without balancing and often they got it wrong to start with and comes down to a good bit of guessing and if you get it right its so satisfying. I restored a 1905 Rover 780cc 6HP single cylinder car engine the balance was was a bit lucky with a new rod of different design and lighter piston, however taking masses of weight of the reciprocating mass is like loosing quite a chunk off the flywheel weight so effects idle.
Well think they said normal running 24mph was 900rpm but could be run be run up to 1200rpm that gave 28mph and returned 40 mpg, Well with a bit of experiment with the induction length we could better 40mph and got 70mpg but at a cost of low down torque and getting it nice to drive knocked it back to its original 28 max with still 50+ mpg in all conditions.
I also found a bit of interesting or what was used early on was Masked ignition where the plug sits in its own combustion chamber, and it works, a engine can use vast quantities of oil and not fowl its plug, and if taken to extremes will only run a engine at well below -20 degree and above will overheat. My 1905 Rover wasn’t fitted with the Masked plug chamber later on it just appeared, A mr Alfred Feaviour got commendation on improvements to early aircraft engines and later sold as plug savers which I have one this was also used in cylinder heads from small equipment to car engines. I was asked to a old tractor that its mag wasn’t good and noticed it back plug sat up not on one of the plug savers but three so don’t think that cylinder would have been doing much. photo of a very lighten rod by rust and the un-masked 05 plug with the later 06? later, so Rover, emergency aircraft generator and one of the plug savers.
