I put a normal prop on backwards will it push...? Probably a dumb question!

No it wont because it will not change the direction of the slant, but it will kill you thrust by roughly half, If you need a push setup then you need a pusher prop.

99% of the time there are no "dumb questions". If you had asked if it would be a good idea to arm your trainer with napalm and drop it on small animals and children then that would be a dumb question. However on this same subject... pusher setups. When the airflow is not bing run over the engine are there any cooling concerns with pusher setups; ie. use a higher oil content/ dont allow to idle for extended periods? I am thinking about getting one of those pusher planes too.

A normal (tractor) prop can be used as a pusher if the prop is installed backward AND the motor's rotation is reversed, easily done on electrics but not on most glow engines.

Think of a prop as a screw, can you screw a normal nut on a bolt that has a left handed thread by turning it around?

Good point BLE

Stang, I've never changed fuel or had cooling problems with a pusher.

And while you do need a pusher prop, another VERY important point to make is this:

The pusher prop needs to be installed "Backward" - That is, the printing on the prop needs to face the direction the prop is moving.

Many people make the mistake of putting a pusher prop on with the front of the prop facing the back of the plane. This is totally wrong.

The printing is on the FRONT of the prop, and must face the FRONT of the plane!!! Therefore, it will look "Backward" on the engine.

So if I wanted to reverse my glow engine would I just start it in the opposite direction?

It won't run that way UNLESS it's an old Cox reed valve engine.

do ya got a link on that napalm thingie.

No, the crankshaft timing is all wrong to run in reverse. If you have an engine that's got a removeable front housing then turn it the way I've just done one of mine for the photo. That gives crank timing that's almost identical to the original when run in reverse. One caution though, it's best to only do this with a ball raced engine because with a plain bearing engine the prop driver gets pushed back hard against the crankcase by the prop thrust and that seals it against any oil that should get past to lubricate it. Eventually it'll wear back the crankcase and then the crankpin can start rubbing against the back plate.

Actually, once my instructer was kickstarting his engine and it started and ran backwards! He throttled up to taxi out of the pits but his planes went backwards. A little jiggling of the throttle put it in forward and it worked right after that.
Karter

A propeller mounted backward is also less efficient because the blade "airfoil" is incorrect.

Some manufactures such as K&B offer reverse rotation crankshafts for a few of their engines thus making them good as pushers if desired.

Thanks to all for your input! I think the easiest to do is just to buy a pusher prop., although downunder your idea is great, I am not so sure I could succesfuly complete that also I only have one engine that leaves me no room for mistakes! Thanks again.