Hi,

Sure sounds like you have piston compression blow by!

If the engine has been that mistreated as you say then the rings are not seating in the bore any longer.
There is very little tension made into piston rings as they are supposed to spring out and even rotate.
The idea of kerosene as a detergent is really cheap but RUNNING the engine on it, in this questionable state, is gambling with gunk going about and that could wipe out lower end bearings.

I would have suggested using a cleaning solvent and filling the cylinders and letting it soak down to the drain pan and out. Rotate the engine by hand and add more until you know all the cylinders are emptying.

It seems to me there could be a rusted cylinder or even scored bores up for grabs. A gentle lubricated cleaning might be too late at this point and if so, you need to do a compression leak down test to give us a hint.

There are engine cleaning additives like Rislone or Marvel Mystery oil that maintains some lubrication while cleaning gently over time. It takes a while to undo what time has done.
That’s one thing you seem to have plenty of by letting the machines sit so much.
Seven years, I hope it was indoors?

Todays oils are the best we have ever had, for several applications in many industries, but a new engine they cannot make.

Good luck with all your project cars!

Phil.