glow to gas
 

I bought a top flight Cessna 182 with 81in wingspan it calls for a .91 to 1.20 4 stroke glow I want to try a 4 stroke gas engine I know 2 stroke gas engines dont have as much power as its glow counterpart does this hold true with 4 strokes. would a saito fg21 which is a 1.26 gas 4 stoke be big enough or should I go up to a 30cc gas 4 stroke

That will fly it scale.
If you want to have some extra power then go with the 30.

I am flying, since two years, a ESM STKA 80" with a SAITO 180 convert to GAZ.
It's very very limit! I am changing the engine with an MVVS 26cc, 2 strokes, I found again in my work room.
An FG21 will be too smal.

Tell that to this guy. He is flying it with the old FG20 !

lets talk numbers and performance:
900 sq in wing
~ 12 lbs
sold as a .60 - .90 2 stroke or .90 - 1.20 4 stroke (glow)
wing loading 30 - 32 oz / sq ft

Those are the numbers, what do you want for performance?

How I describe it is: "Pretty plane flies and lands fast."

I'm sure at the bottom of the performance envelope an FG 14 would fly just fine. When would two much engine be reached? I'm guessing the FG 21 would be my choice for an ever heavy already wing loading.

She will never be fun and easy to hover, so why bother with more than good power?

IMHO ken

thanks for the info ill give the fg 21 a try

To throw in an old-school reference here, take a look at a Zenoah G-23, an engine that has been around a very long time with the dependability record to go with it.