I am looking forward to power up my 3rd plane (WM Mustang 46) with a 4 stroke. The instructions for the plane call for a 0.46 2 strokes but don't know what would be the direct equivalent into the 4 strokes. Need help on this one and also would like to get your advice on which brand of 4 strokes would be best to buy.

In the .70-.80 range

Saito .80 OS .72 are usually reccomened sizes for 4s Check the instructions they usually give the range for both 2s and 4s. If yours doesn't you may need to make modifications to get it to fit and or balance since they are usually igger and heavier then the equvilent 2s

I think heavier than the 2 S won't be a problem since I have read many times that warbirds usually require more weight in the front to balance... It better be fm a powerfull engine than fm adding lead...

A Saito .72 will only add an ounce and provide plenty of power. If you'll check the ads for fun fly planes, you'll see a lot of Saito .72s in the .46 size planes. It only weighs a little over 18 ounces and turns a 13-6 prop. For loads of power, get the new Saito .82.