The short answer is -- it's not tough.

My PA30 is counter rotated and last year we did a 1967 PA30 to c/r although in that instance the owner located an engine off a PA39 (engine IO320-C1A)

I suggest that you call me -- Pat Barry  (949) 362.1600

I don't know why an engine shop would have a problem with this ..... it requires a new cam and crank, and the propeller, of course. The air speed indicator must be opened up and the VMC changed to 80 MPH or 70 kts, and the panel placard that says 90 mph VMC must also be changed to 80 mph (or 70 kts). Your air speed indicator might welcome an overhaul.

Mechanically, you install an accessory drive to connect to the tachometer cable (that's no big deal). 

The engine is a straight overhaul, so an overhauler should have no objection ..... it's the same overhaul, except with the crank and cam that turns in the other direction. Prop spinner is the same - just a different propeller.

Your props might be standard props, and you could either change the blades in the right side, or you could sell your props and buy new from Knots 2U - they have the STC for higher performance blades which will squeeze a few extra knots out of your plane in cruise so this is an interesting option. You can get them in regular or c/r.

I have the paperwork in one of my computers so if you call me and give me your contact details I'll see what I can do to help you/

It's not an STC requirement ...... the PA39 is the same plane but with a c/r engine so the conversion is simple. It's a log book entry, just like a regular overhaul, noting the change in VMC. 

Pat

I would have to ask why you want to do this? 

In my opinion the downsides out weigh any advantages.

Your performance will be less with counter rotating props.

In addition to the changes Pat has listed I think you will also need to change the flow strips on the wings. These are different for counter rotating engines.

If it were my aircraft I wouldn't waste my money on counter rotating engines.

The PA30 I have had for over 35 years, and it was counter rotated when I bought it. I have flown numerous Twin Comanches and I see no performance difference between the planes that are c/r other than the obvious of the lower vmc. The plane is certainly no slower.

The stall strip on one side has to be relocated - that's simple enough. 

The old props can be sold and I recommend the higher performance props for which Knots 2U has an STC. The engine requires a crank and cam replacement but if these are being replaced at overhaul then the engine can be counter rotated simply enough. 

Put another way - the c/r conversion is not difficult, and the main expense is the propeller, the crank and the cam. The rest is small stuff. The paperwork from Piper to do this change describes it, and it isn't an STC but a minor alteration and can be signed off by an IA. 

If an owner is passionate about improving a PA30 then the c/r conversion is worth considering.

Pat

Hello Pat,

Unlike you I haven't flown enough hours in the CR versions to say I have sufficient experience to compare performance. I have had some owners tell me there is no difference and others say there is a difference. Who do I believe?

I understand the non CR PA31-310 performs as well as if not better than the CR PA31-325, and have been told Piper put the 325 HP engines on the CR Navajo in an attempt to get the same performance as the non CR 310 HP model.

The difference on the Comanche if any is likely to be small and may well be masked between different aircraft by other things like baffles, gear door rigging, aircraft rigging etc.

I don't see any benefit in fitting CR engines. As far as I'm concerned the Vmc reduction is like a mirage, the gains from this are almost imaginary. In real life there is no benefit in my opinion. If you're relying on the lower Vmc speed to get you out of trouble then you have other more important things to be worrying about. All your lower Vmc speed means is you might crash 5 knots or so slower.

Piper put the CR engines on the PA39 as a marketing exercise to help overcome the bad reputation the Comanche had gained due to improper training methods.

In return for having a lower Vmc you have an engine with a prop and accessories which are not so common. For example you land some where away from home to gas up and the right hand starter fails. The one on the left hand engine is pretty common and there's likely to be a spare on the field, but probably not so for the right hand one.

Unlike you I don't see the CR conversion as an improvement. I'd rather spend my money elsewhere. Hence my posts putting an alternative point of view for the original poster to consider.

However each to their own. Some owners see value in having a CR engine and it is for them a worthwhile improvement.

I agree 100% on the Knot2U props. They are worth every cent, plus when I bought some a few years ago they were cheaper than the original props from Hartzell. Go figure.

from Lucky Louque

Ifg you are looking for a LIO-320-B1A,  Bob Cretney has one in Good condition ready to hang on the aircraft. Call him at 214-725-6584 Thanks, Lucky/////