There are two operating systems used by Perry for their pumps and it is not sufficient to say it has a Perry pump. The two types are the ossilating pump and the other is the regulating pump.

The Ossilating pump depends entirely on it being mounted in specically on the engine back plate or the engine mount but not the firewall. It requires that it be mounted in the plane of the propellor rotation to be able to function. The regulating pump requires a pressure tap in the crankcase to operate the pump diaphram.

Now with the Ossilating pump there is the requirement to keep the pump wetted out during storage by keeping a loop of fuel line between the inlet and outlet with fuel in it during storage even just overnights. If you do not do this that tiny bouncing ball will sieze and stop bouncing and this can an will cause running problems.

You say you have the "fuel tank level with the carburator" What does that mean their could be three inchs differance there and OS is very specific about this, check their info on thank heights and do what ever you have to do to accomplish this and there will be no need for pumps.

Tank/spraybar height or relationship in any inverted situation is critical and very important to the success of the installation.

John