Um... They ALL have side exhaust. We're talking about the intake.
I used OS engines because the high-performance car camshafts fit in them. No other brand of engine has a cam that will allow it to rev high enough to be practical for r/c car use. Using this cam, I've got more than enough power for my applications.
Believe me, I'd love to use a Saito or YS, but it's a practical impossibility at the moment.
Damon Palm's 2011 Race Rigs (the ones that have all the guts in them):
Thump RC 4 stroke "GSC10"
X-Factory X-6 Squared
Traxxas Slash w/ STRC LCG conversion
THUMP RC -The only 4 stroke race conversion-