Because I am crazy, have no money and like to build stuff I had this wack-a-doodle idea.

The problem:
I need an air compressor that has a specific input (I decide where the air that it is compressing comes from)

Solution 1:
Buy a compressor for 500+ dollars.

Solution 2:
Use a gas motor as an air compressor.
The ignition sequence of a typical 4 cylinder 1 3 4 2 therefore I should use either 1 and 4 or 2 and 3 as the power cylinders because the crank position and firing position are 360 degrees apart therefore I could use the same cam and crank.

A HEAVY flywheel would help, perhaps two recessed flywheels bolted together?

A carbeurated (SP?) engine would be easier as I wouldn't need an ECU of any sort. Therefore an older b18 ish motor running cyl 2 and 3 so as to share heat??

If I am running the engine REALLY slowly (~500 RPM) would the oil pump still be able to provide effective oil pressure? Or do I need to build an external oil pump?

Carbs would also be easier as I could more easily modify the manifold to only have fuel going to cyl 2 and 3 while porting 1 and 4 to where ever I want.

What do you all think? How about a mechanical injection system?

Thanks to all!!

Andrew
(yes I am crazy)