1948 Farmall Cub Restoration - Final Assembly - Major Set Back 

It looks as though the head bolt holes have water in them which means the holes are connected to the water jacket. If that is the case, the head bolts need to be sealed when they are installed. Otherwise, water will infiltrate via the head bolt hole.

I have worked on old vehicles and restored a few as well. It's not abnormal to have set back, I'm sure you will figure it out. Some of the other commenters have some good advice. I have faith you will have it up and running soon. Please keep us posted on this if you can. I'm curious with what you come up with. Thank you for the video.

Im an 80 year old RETIRED mechanic and I know coppercoat on the head gaskets USED to be the GO TO sealant for head gaskets but todays gasket makers tells us NOT TO USE ANY TYPE OF GASKET SEALER on the Head Gaskets and that was the first thing I noted was coppercoat on the head gasket

This might be a stupid question, but did you use a straightedge to check both the top of the block as well as the head to make sure they were straight? If the head is warped as you suspect, it would possibly show up with this test. I would suspect the head as well since the water was in all of the cylinders. If you have a good machine shop nearby they may be able to plane the head. They should also be able to deck the block to ensure a really good mating surface.

Maybe a crack between the thermo siphon system and the actual engine block?

Did you put pipe dope around head bolt threads? water coming up bolts from water jackets.

Use copper paint on the head gasit and can used for 2 time. I do it all time 1943 farmaĺl

Good luck. Maybe have the head checked out.

I.ALWAYS USE COPPER COAT SPRAY BOTH SIDES OF HEAD GASKET. AND WIRE WHEEL THE HEAD BOLTS AND COAT THEM ALL WITH BLUE PERMATEX SILICONE. FIRST CHASING THE HEAD THREADED BOLT HOLES .WITH THE BOLT FOR THAT HOLE TO MAKE SURE ALL IS GOING TO GO SMOOTH...HAVE FUN

i would never use any sealent on the gasket no need to use any gasket sealer on any head gaskets but thats not your problem ...

Rectorseal 5

did you bring the head and block to a machine shop,, even if you use a stright edge on the head and block you may never see a worped head or block,, iv machined a ton of blocks and heads and ever body all ways says O O O its stright ,, i would use the bearings headgasket valves if you never cranked it over ... did you use a skuffie pad on any of the surfaces, id say looks like heads cracked .. no water in crank case .. id guess its the head