FP to CS conversion O-320-B2C

BruceMe · #1 11-14-2017, 06:52 AM

I've broken down my O-320-B2C for overhaul and the opportunity to buy a CS prop came up. At first glace this looks doable as the B2C has the rear governor pad machined out and the flange port plugged. But after careful planning, this model is not listed in Lycoming Service Instruction #1435. I suspect this is because this crank shaft is solid.

I'm in an overhaul, can swap cranks?

Thanks!

-Bruce

scottmillhouse · #2 11-15-2017, 10:07 AM

On my RV-9A I put in a 1991 Lycoming O-320B2C from a Robinson Helicopter. It had a hollow crank and was easy to switch to a CS with the pump bolting up, line to the front and the rear crank plug added. The other challenges were it had a conical mount so the motor mount was a special order from Vans and I had to change out the sump and intake to move the aft carb to the middle to get nose gear clearance and add a fuel pump gear and pin in the rear accessory housing.

BruceMe · #3 11-16-2017, 03:54 AM

Sounds like I'm mistaken about the crankshaft being hollow and the engine not being capable of conversion. This time, I'm glad I'm wrong. Sounds like there's a C/S prop in my future.

Now just getting all the parts and making sure fit right.

Here's my flang... I am currently swinging a Catto 2-blade wood/composite with 7/16" bolts. The hub for the prop looks to have four of the six wholes drilled out for the flange lugs, but two are the size of the bolts.

The prop...

My Hub...

Can this be machined (prop/flange) to fit?

-Bruce

BruceMe · #4 11-16-2017, 04:39 AM

I believe this thread covers my answer...

http://www.vansairforce.com/communit...+flange&page=2

"The new CS is a R flange prop. The crank is setup as a K flange crank. The Hartzell manual says that a R flange prop can be installed on a K flange crank or a R flange crank. This was never an issue before because the FP spacer has counterbores all the way around it on the back. The new CS prop has one bolt hole that has no counterbore and it must be installed in one of 2 locations on a K flange crank. My bushings just happen to sit a little proud in those to locations. I was super cautious when installing and noticed this. Not sure if someone in a hurry would have even noticed it."