FP 40 Problem

I put an FP 40 on my rebuilt Vector which seems to run great except in the outside stuff. At the transition from outside to inside on the horizontal eights it tries to die and again on the third corner of the outside squares which makes square eights real interesting and the four leaf is something to behold. Any ideas on what could be going wrong with this? I am running pressure with an 11x5 prop at about 9600 rpm on the ground the motor seems real happy there
Would appreciate any ideas as I am totally lost right now. And also on the outside of the hour glass and vertical eights its the same thing

>I put an FP 40 on my rebuilt Vector which seems to run great
>except in the outside stuff. At the transition from outside to
>inside on the horizontal eights it tries to die and again on
>the third corner of the outside squares which makes square
>eights real interesting and the four leaf is something to
>behold. Any ideas on what could be going wrong with this? I am
>running pressure with an 11x5 prop at about 9600 rpm on the
>ground the motor seems real happy there
>Would appreciate any ideas as I am totally lost right now. And
>also on the outside of the hour glass and vertical eights its
>the same thing

Welcome to the club of discovery on the FP 40. The 35 FP does not do this. The only thing I can trace it to is they, for some odd reason, make the porting of the sleeve wider on the 40 and I figure it is throwing fuel from the crankcase down onto the plug at that transition point which drowns the plug momentarily.

If you run it leaner with a lower pitch prop, it may not be as bad. If you use less oil or more synthetic it may not be as bad.

Or, run it sideways and get a 35 FP (That was always my choice.)

Try a 101/2by 41/2 apc. Too much prop. Enya #3 plugs help. 22% (50/50) either 5% or 10% Powermaster. Which venturi are you running? Which muffler? Try the prop, plug and fuel first. My friend Jack Weston happens to be running an FP35 in his Vector. Excellent match. But an unmodified FP40 (extra head gasket) set up with the fuel, prop and plug I recommended, has run beautifully for years in a Gieseke Nobler. Gieseke himself expressed his approval of the setup at the NATs. He wanted one.

Hot plugs help burn off an extra splash or two of fuel.