I wouldn't think even if the cast aluminum was thick enough it would be safe to bolt a steel hub to it without worry the cast aluminum fracturing from the bolt holes. but I have machine Tecumseh cast aluminum flywheel before and was very impressed how solid and dense without any voids after machine the starter teeth off.
Li'l Popeye do you have the ability to harden the stock cams? if so you could also run set of stamp 1.3 rockers. that would help the performance by using a stock cam. also might be able to get away with not harding the cam by a couple different ways. I know from the pass some guys ran stock cams in there builds with 18 pound springs and didn't have a problem with eating up the lobes,but anything more you could chewy up the lobes. cams are not harden very well from the factory. 18 pounds could still work with 1.3 rockers if there is no coil bind and set at the correct spring height. engine should pull good up to 5000+ and at that rpm your not going to float the valves and it wouldn't hurt to run a good zinc oil. make a good little hot rod engine with just stock parts and couple mods.
Li'l Popeye do you have the ability to harden the stock cams? if so you could also run set of stamp 1.3 rockers. that would help the performance by using a stock cam. also might be able to get away with not harding the cam by a couple different ways. I know from the pass some guys ran stock cams in there builds with 18 pound springs and didn't have a problem with eating up the lobes,but anything more you could chewy up the lobes. cams are not harden very well from the factory. 18 pounds could still work with 1.3 rockers if there is no coil bind and set at the correct spring height. engine should pull good up to 5000+ and at that rpm your not going to float the valves and it wouldn't hurt to run a good zinc oil. make a good little hot rod engine with just stock parts and couple mods.
Hardening stock cams; there might be companies that are able to do so, but I'm not going that route (for now). Like you mentioned; "make a good little hot rod engine with just stock parts and couple mods."
There are no roller lifters available for these engines? I can't seem to find any. There are roller rockers, but no roller lifters.
"and set at the correct spring height": What's the correct spring height?
How I look at it:
The engine is designed and manufactured for stationary purpose at max 3600rpm, with a small diameter stock carb. a highly reliable powerplant.
I don't need +8000 rpm's. So 18Lbs springs will do the job.
I replaced the stock rod with a billet one and the heavy steel flywheel with aluminium, as an insurance and the aluminium flywheel also helps throttle response.
Right now:
I will take the 14cc cylinderhead and mill some material away around the valves, as to me that looks obstructive for proper flow. I know chamber volume will increase, but according my quick calculations it will stay below 15cc (my calculations are not always good, so I will measure the chamber volume when I'm done milling).
I will replace the dished piston with an aftermarket flat top piston, which is 20 grams lighter. This will help against vibrations.
I will replace the stock, thick GX160 headgasket with a thin GX200 headgasket.
Compression ratio will be 10,7:1 (if chamber volume will reach 15cc).