Why not use it?  May not be as fast as a pressurized engine, but I have several old combat designs I am still working fuel feed problems on.   Seems the design doesn't like uni-flo tank setups. 

You should see some of my combos that run on suction,  Renegade with K&B Greenhead 35  Jerkline Special with OS 40,  Sweet Sweep with OS 25 and others.   Gilloutine with OS 40 Manx Cat with Fox 35.   

You should see some of my combos that run on suction,  Renegade with K&B Greenhead 35  Jerkline Special with OS 40,  Sweet Sweep with OS 25 and others.   Gilloutine with OS 40 Manx Cat with Fox 35.   

Those are all nice planes, the Sweet sweep I really like, that is sharp lookin. Maybe sometime i'll try luck at building one. Thanks for that John.

I blew the shaft on the Magnum 36 trying to get a fast engine cheap.  8/6 prop, 20% nitro, wide open venturing 7/16 or more diameter.  Clocked it at 95mph on .018 stainless lines.  Next flight it spit the front of the crank out.  Luckily the 32 crank is the same and I got a spare.

For some reason, probably the smaller bore, I never could get the 32 version to run well.  It was just fussy.

There would be no problem running this motor to fly 75-80 mph.  Just use a smaller venturi, somewhere in the range of 5/16-3/8in. diameter with the needle valve across it.  8/6 or 9/4 APC prop.

One relatively easy way to stiffen up the crank is to fill the front of the crankshaft with epoxy putty, JB Weld or PC-7 or similar.  Wire brush the inside of the crank thoroughly.  Clean it with strong soap and water and then methanol or other solvent.  Mix up some epoxy and pack it into the front of the crank.  Put a bit of a curve down in it starting at the front of the valve and curve it down to the ID at the back of the valve.  If you can, get a look at the inside of an F2D crank.  They do a similar thing with a phenolic plastic plug held in place with a set screw(much more work for a non-machinist).