Gurgle and a hiss!

[Eternal]

Did a bit of engine maintenance today. Sprayed a bit of wd40 into each inlet port of the pistons and turned it over a couple of times just to make sure the inside was not going to rust.
But to my horror could hear a hissing/gurgle sound so removed the sump as it was only on by a couple of bolts and listened again. It sounds like the compressed air/wd40 is pushing its way through the piston rings. Is this something to worry about or is this the standard kind of thing for an engine that has been sitting for 6 months?
Oh and the engine was find when i removed it from the car and never missed a beat. 66km on the clock.