Thinking of putting a 46 fx w/davis head on a piper j3 arf-any suggestions?

Swings a larger prop. More Power. Betterfuel economy. Different fuel. Different smell. Quieter operation. Fewer field Accessaries needed.

I contemplated doing it myself, but never got aroung to it. Although a fellow club member converted all of his engines and really liked it. Don't expect a lot of speed. Flying a Cub I quess you don't need that.
Diesels are very popular in England.
The only tough thing is learning to adjust the head for the proper combustion pressure.

GO FOR IT !!!! [&:]

Diesels are really messy. Make sure you use a diverter tube to keep the exhaust off the model.

Is this diesel the same type found at the gas stations?

I learned to fly using a diesel engine,at times the fuel is hard to find,smells bad,hard to start in cold weather,messy all over the plane and can't wash out the black exhaust stains from clothes or shoes,hope I'm never around diesel planes again,and no it's not the same fuel at a gas station.[:'(]

Replacing the head on a glow engine allows you to burn model diesel fuel instead of glow fuel; but unfortunately you do not obtain all the benefits of a diesel engine. There are a number of other differences -particularly with carburation. There is also a risk - diesels run at double the compression ratio of glow engines and so there is considerable extra stain on the engine, especially on the crank pin. A number have been known to fail. Why risk a good engine for questionable results?
Diesels are great, (I have several), buy an engine designed for that purpose.
Model diesel fuel is not the same stuff as at a gas station; but a mixture of kerosene,oil and ether. plus a little 'ignition improver' additive

My biggest suggestion:
Buy LOTS of stock in 409, Windex, or Simple Green