My understanding was that the sealed block was disposable at some point and that would be a $600 rebuild vs $4-500. if your referring to having the head rebuilt isn't that about the same? what do you get for $150 that sounds a little too good to be true. if there is no power advantage yet there is a quality/rebuild $$ advantage why not let the l206 run with the clone? the minimum it would do is force the builders to drop their prices to be competitive. i'm interested in saving money and not sending so much money overseas.
You "can" dispose of it if you choose, but there is no reason to unless you experience catastrophic failure. The short blocks do get better over time because of the very conservative build specs and ring package used. We had an engine that was from the very first run of LO206s win a feature this year (FWIW, the series still allows old seal engines where they run.)
Too good to be true? I dunno - ask our customers.
A "freshen-up" consists of Removing the head, cutting/touching up the seats and valves, cleaning the cylinder and crankcase, new head gasket, new valve springs, ultra-sonic clean the carburetor, align the carb and intake, set the coil air gap and ignition timing, set the valve lash per your engine and class, bench tune the carburetor, new inlet needle, new bowl o-ring, new valve cover gasket, new 3910X plug, new fuel line, new fuel filter and probably another item or two I'm missing, but that's the general deal for rebuilds on these engines. I think most builders are on the same page as we are. Same level of work and same price ($150+-.)
The power is found primarily in the head and carb tune. Most club racers have their 206s gone through once a year (over the winter.) National level competition is obviously a bit more often.
If you want the engine dyno tuned, it's an add'l $85 (incl. fuel and your choice of oil.)
We get $200 labor alone to rebuild a clone, and I'd rather not touch them.