Coolant loss after rebuild

We're a bit flabber gasted at the problem right now, looking for some additional troubleshooting angles.

On my 71 CJ5 with <4k miles on a rebuilt Buick 225....
Carb bolt dropped out into Pistons 2/4/6 causing extreme damage to the pistons & slight dings in a few valve seats.

Phase 1:
Disassembled block, replaced all 6 pistons & rings. Honed cylinders, no bad gouging.
Had passenger side head valve job & surfacing performed.
Cleaned all mating surfaces & used all new gaskets. Only used loctite for bolt thread sealant. Torqued heads to 80 ft-lb (spec is 65-85) which was the upper end of the 3/8" ratchet's spectrum
Started vehicle up. Tons of coolant in the oil after <15 minutes of running. Cylinder #6 was pristine (aka... steam cleaned) and part of cylinder #4 (rear 1/4) was clean. Ash/soot build up on rest of piston & #2.
Checked for surface flatness with straight edge, nothing seemed out of wack.

Diagnosis 1:
Used a 1/2" (0-150 ft lb) torque wrench at 85 ft lb to see if heads were torqued appropriately. They were probably closer to 70 ft lb than 80, so I assumed that might have been the issue. Just to be safe, I uninstalled the head and recleaned all mating surfaces. Then torqued down to 85 again.

Phase 2:
Ran engine for 60 minutes and same problem as before. Still same coolant issue in cylinders 4 & 6. Double checked torque and they are at 85 ft lb.
Pressure tested cooling system and has a slow leak. Could hear it in the passenger side, but can't figure out exactly where.
Performed cylinder leakdown test with cooling system tester attached. I was curious if pressuring each individual cylinder up to 90 psi would pressurize the coolant system. It did not.

Diagnosis 2:
Didn't notice any cracks in the cylinder head but possible, so dissembling tomorrow.
Do I need to do some additional thread sealant? No bubbling around the threads while the coolant system was pressurized.
Any other guesses? It didn't leak until after it was surfaced and the area they machined was not the entire surface, just the outer third.

 

Did the shop magnaflux the head when you had it resurfaced? I agree with Patrick, sounds like a cracked head, I'm assuming that you've eyeballed the gasket and made sure its not leaking. I'm curious though , why did they only machine the outer portion of the head, and not the whole thing? Have you taken a straight edge to it to make sure that its been machined evenly and that it's not warped or twisted and that the surface is perfectly straight?
Posted via Mobile Device

 

WOW, and I thought I had problems getting mine running after a complete rebuild

 

My first thought is a cracked head but your comment on the surfacing keeps bugging me. I would go to another shop at this point and have it fully checked. The first shop may be fine but probably should have recommended magnafluxing after seeing the type of damage and they may have improperly set the head and angle milled it (pictures?). A second opinion will help you decide what to do next.

 

w3srl FOR THE WIN... cracked wall in cylinder #6. After the honing, it only looked like there was a slight scratch in the cylinder. After getting the cylinder in BDC position, I could see the crack had propagated to 4" long and had rust around it. Oddly, there is a guy 1 exit down with a 67 Commando he's parting out. Getting the entire engine on Saturday for $100. Assuming his cylinders all measure within spec, I'll just swap all my components on since just had a rebuild 4k miles ago. Since I'll be swapping out the crankshafts. Do I need to also get oil seals? I'll replace bearings with excess wear of course. Any other small things to watch out for?

Thanks everyone for the help with diagnostics & guesses. Hopefully this will help someone else in the future:

If you've got white smoke & a lot of coolant in your oil (white, frothy, latte mixture), then probably a cracked cylinder wall.... dammit