I started out with an O.S. .91 surpass with pump. Very reliable engine but also pricey. I decided to use this engine on my H9 P-51 so I started the search for a new engine for the 4* I decided to go out on a limb and try a GMS .76 Because of it's very low price. I was a bit skeptical because I have had such good luck with O.S engines. I was pleasantly surprised with the results it is a very powerful engine and has been reliable so far. It is a ringed engine so it takes a bit of break in. Best bang for the buck in my opinion. I got mine from GMSENGINES.COM For only 85 dollars shipped. If I remember right it only took 4 or 5 days to get to Ohio From California.