Originally Posted by
Pete S-RCU
I have the Evo 7260 radial that I'm putting on a BUSA Stearman.
This is my first radial, so I have a few questions.
I've read most of this thread and didn't see anything about the E7260.
The carb has two fuel fittings on it, one for fuel and another for a primer.
Do I need to use a tee and connect both lines even though I can't reach the primer.
It's a Walbro WT 621 carb.
The ignition has a double connector on it, one for the bat and the other has a square end on it.
Looks like an ignition sensor, but no place to mount or connect it?
Maybe it's used for a tach?
The number one and seven cyl's have a fuel line from the intake pipe to a tee and then to a nylon spacer between the carb and the crankcase.
What is this for?
I'm going to use a 34x12 prop on it.
Thanks for any information......
Pete,
I have an older 7-250, but maybe these things can help you on your way. Here are my experiences:
Fuel system
The pulses from the air intake that the Walbro needs to draw fuel, can be weak. If you have long fuel lines and the engine stops under accelration or in top of loops, it is caused by G forces on the fuel, and preventing the fuel to reach the carb. Use a pump.
Prop
As written above, 34x12 is way to small(pitch) I use a Biela 32x22, which pulls 20% more than a Menz 32x18. To high rpm will give you less pull and a selfdestructing engine. 4000 rpm on ground is a good start. Remember that equal specs on props, is not always the same prop from different brands.
Fuel
I use environmental fuel(which is actually alcohol) Gives less carbon buildup inside engine.
/terje