Ok, went back and looked at the engine catalog in the box. Did'nt reliese that the sf was also a c/l offering. So I have an OS 46 SFabc r/c engine and am thinking about making a stunt engine out of it. Are nva and venturi's available for this set up? Will they run ok? Or just leave it alone? Thanks, Jack

Ok, went back and looked at the engine catalog in the box. Did'nt reliese that the sf was also a c/l offering. So I have an OS 46 SFabc r/c engine and am thinking about making a stunt engine out of it. Are nva and venturi's available for this set up? Will they run ok? Or just leave it alone?

     I haven't personally owned one, but I have spent a fair bit of time helping others with theirs.

    Straight out of the box, with the muffler outlet opened up as much as it can be without cutting off the nipple (we used a Fox prop reamer, right there in the grass in a contest), and typical 46VF props like a 11-4 3-blade or a 12-4 2-blade, it runs very nicely in a constant rich 2 with a lot of power.

    I was also very impressed with the Randy-modified version as a 4-2 break motor. One of the San Diego crew ran it a slightly-cut down Cardinal and I thought the engine was about as strong as an average ST60, although maybe not a really strong ST60. If you aren't into some development work that might be required for the stock engine, this would be my recommendation.

    The knock that you will hear (and I am sure there are 4 people typing this right now) is that it's heavy. That may be, but within reason I wouldn't choose engines based on weight.

     Brett

 

If my OS Catalog is not wrong this engine is quite light with 312g,  8g lighter then an ST G51.


Martin

R/c crank - big prop - run away. R/c crank small prop, no run away. Stunt crank big prop - no run away. How do you want to run it?

R/c crank - big prop - run away. R/c crank small prop, no run away. Stunt crank big prop - no run away. How do you want to run it?

    My version of the RO-Jett 61 has a crank from a quickie 500 engine, and the timing on the 40/46VFcrank is pretty similar. And widening the crank timing on "stunt" cranks was a pretty popular modification for several engines back in the mid-90's. The effect is to smooth out the power delivery in the range of interest. Not that surprising since you want stunt engines to run in the 11000-12000 rpm range in the air. That's not particularly fast by racing standards, but you don't want a "chugger", either.

      Brett

The stunt version had a different crank with about 14 deg less duration. The stunt crank has an S stamped on the counter weight.

Correct, They did that because if you have a lot of crank timimg..as in a bigger port..  the motor runs ratty many times and you see much fuel blowing out of the top of the venturie, makes for a ratty running motor, The only cure is to advance and lower the crank timing , or to increase the RPMs of the motor

Randy