Hey there....welcome!
try this thread for starters
http://www.rcuniverse.com/forum/Engi...2255693/tm.htm
For RE, there are older K&B 3.5 engines out there..... some older OS 25 DF engines too. Sometimes can be had for a bargan. Very good engines.. both respond very well to pipes.
NovaRossi 09-20 is outstanding. Currently available
Irvine XR-15 is a real nice engine
Rossi use to have both .15 and .21 size engines - look around a bit.
Older Cox/K&B/Ron Young .15 engines are out there. Excellent power... use to use these for QM15 racing. Check around with the Free-Flight guys and some of the older pylon guys.
There are a few Nelson .15 engines still out there. Not throttle capable, but very powerful.
MVVS has a a few engines in the size range....they use to make a RE years ago...... not sure if its still available.
The Jett FIRE .25-35 engines are the top of the list in performance. $260 roughly... plus pipe. Can be tuned to exactly the rpm/prop you desire.
A few import engines available from SC and SY.
Check with the FF guys for excellent sources for any of these size engines....
I hope this is helpful
Bob