I have a bunch of engines that I have collected through the years and I am trying to decide which one to put in the D-7 I'm building. The SF .40 has a big case-same size as an OS .46FX, The Fp has a smaller case but with the same displacement. Are the Sf's more powerful than the FP's or just bigger?

The SF engines have ball bearing supported crankshafts, while the FP's have bushings. The FP is a good line, but the FP 40 will not have as much power as the SF 40. Also, the SF has a two-needle carb while the FP uses an air bleed carb. The two-needle is a much better carb.

Sandy T

I have a .45-46? SF that is pulling great after 10+ years of abuse and neglect. I know that dosen't speak to your power question. But it's a great engine, starts right up and goes.

The SF was a predecessor to the FX and then the AX

The FP was a predecessor to the LA

Whats the difference?

About 6yrs--ball bearings--and $20. [sm=lol.gif]