Well.

I got tired of wondering about whether I could turn my SF into a Hanno Special type big prop swingin' powerhouse by copying the port timing and decided to try it out on a used SF ringed engine. Figured I could use the rest of the engine for parts if I dorked it up. I measured (multiple times) the ports on my stock Hanno MkII liner (SF too) and re-read the C. Lee review of the Hanno Special. The liner from the SF was a match for the Hanno liner except for the boost port width and the exhaust port height/timing with that extra width at the top. I had done some 'porting' to model engines in the long dark past and had used small files. This time I broke out the trusty Dremel tool and chose a fine, tapered stone bit to use. I carefully marked the .025" I wanted to raise the ports and the side cuts, put my magnifying visor on and went to work.

Started slow, checking progress often and before long had a pretty good looking cut done to one side. Feeling good about what I had accomplished so far, I proceeded. The second cut was less of a white knuckle experience but turned out a little less 'precise' than the first. Measured and matched the cuts to within about .001" using an old dial caliper and checked the results after washing, rinsing, oiling the liner. I was a bit surprised at the lack of burrs on the cuts and used a few passes of 400 grit paper to polish them up. Checked the timing of the 'twin' exhaust ports by observing their opening while stroking the piston/rod by hand while shining a light (back lit) down the bore. They looked pretty close to me so I reassembled the engine. Had to use two 'parts' engines to get one workable due to a very slightly bent crank I hadn't noticed before and some bad bearings. Was more work cleaning the case, crank and bearings than doing the porting.

Took the engine out this afternoon to give it a try. Set it up on the bench, connected a stock header cut by the previous owner at about 5" long to a MACS 1062 Quiet Pipe and put in a Fox Miracle plug. Took the 13~8 APC off of the Hanno II and put it on the ported SF. Filled the tank with some Omega 10% w/ added Benol to make it approx. 21% oil, opened the throttle and flipped the prop a few times to prime it, hooked up the plug heater and it started the first flip of the chicken stick. Man! I'm liking these OS pumper engines! How come I didn't get some back in the '80s? It ran for about thirty seconds 'cause it was way too blubbering rich. Wouldn't start again.

Took it off the bench, turned it upside down, drained some fuel out and put it back on the bench. Turned the n/v in some and it started after a few flips. After adjusting the mix some it was topping out at 11,200! That's right in the neighborhood of what I got with the Hanno II on this same prop! It was more steady at around 10,800 or so though. The carb is gonna need some more adjusting for idle/transition and it needs some new O rings too. The header length will need to be experimented with to find a nice broad range of boost. Gonna try some different props and a different pipe or two before it's over as well.

Don't know about y'all but I'm happy about these results. Gonna do an old used RF next, I think.

Took some pics of the session.

Terry in LP