What additives can be use to clean piston head with valve

If the pistons are hitting the valves the engine is either out of time or there isn't enough clearance between the valves and pistons. If the head has been milled flat due to warpage, it is very possible that the valves are now too close to the piston. You will need either a thicker head gasket or pistons with releaf cuts to make room. But since they have already made contact, your going to need new valves at minimum.

the first thing is --did you do anything with the head ( machined flat-checked for cracks)
did you run a thread tap down the stud holes and blow out any oil,water in the holes
did you inspect the valve heads to see for burnt heads
Why did you replace the head gasket to start with
Low pressure between adjacent pistons indicates blown gasket between those cylinders
to do a head job properly, remove the head and check for warps and cracks ( head machined flat) clean out the threads of the studs and blow any thing out of the holes
next check that all the head studs are the same length and insert each stud in the head so that all the studs sit the same distance above the head before tightening down
next tighten down using the correct tightening sequence so that the gasket is evenly compressed
tighten down to the correct tension or degrees of turn as is stated in the specifications
any piston or valve or ring damage would be restricted to the one piston and would not show up in adjacent cylinder

Sounds like a broken ring land on the piston , a hole in the piston or the piston skirt or skirts is or are broken. :( blown head gasket is first chk to do though it's cheap!

the worst that could happen is that it will bend every valve in the head. it's as repairable as a blown head gasket, with the additional cost of new valves, seals, and perhaps valve guides.

Blue smoke is usually an indication of bad rings, which allows engine oil to be burned as you drive. The fix requires engine teardown, pulling off the heads, removing the oil pan, and removing the crankshaft, rods, and pistons. The cylinders may need to be bored, but at the least they will need cleaned up with a hone. The old rings taken off and new rings istalled. If the engine needed bored, then new pistons must be installed. Then, put it all back together.

Hope this helps you

no/loss of compression can be from a few different problems blown piston/piston rings[fix rebuild engine and replace piston parts ]camshaft flattened lobe [replace camshaft]valves burnt/bent carbon build up [remove head and repair/replace valves ] valve springs weak/broken[repair or replace ] head itself cracked [replace ]these are some of the reasons that u can loose compression if ur guy did compression test and determined its the head[valves ] then replace head if car is worth fixing then fix it good luck

FOR ENGINE THAT DIESELING POSSIBLE CAUSES IDLE SPEED TOO HIGH.IGNITION TIMING OFF AND EXCESSIVE CARBON DEPOSITS ON VALVES AND PISTONS.YOU CAN GO TO AUTO ZONE BUY A CAN OF ENGINE CARBON REMOVER YOU ADD TO GAS BUT IF CARBON BUILT TOO THICK ON VALVES HEADS AND PISTONS.THE CYLINDER HEADS WILL HAVE TO BE REMOVED.TO CLEAN OFF CARBON.

That carbon build up is bad!Carbon is what a diamond is made from and pieces of it breaking off will decrease the life of your engine.Also the carbon will heat up and cause premature detonation in the combustion chamber.Just wait till he leaves the garage and clean it off before reassembly.
Take care!

if heads were warped, then yes coolant got into the cylinder/s . so there is your water poured into engine. a bent piston rod cannot be diagnosed, it must be seen. a would run slick 50 into this engine.

clean the tops of the pistons and check for any hairline cracks and damage, if none is found they should be ok