Aftermarket head casting problem or mistake caused by me?

[StarquestMan]

My 88' Mighty Max G54B developed a cracked head this summer that caused it to puke out coolant via the overflow tank, so I had to sideline it until I could get the time and money to get around to fixing it.

I ended up going with an aftermarket head without jet valves and solid lifters from amazon. after installing the new head I started the thing up and noticed it missing on one or two cylinders but figured everything just needed to sorta seat itself and let it run for a bit. i looked behind the truck and noticed it smoking quite a bit but figured it was normal with all the assembly lube and stuff for a new head. after a few minutes though it wasn't clearing up so I shut it off and checked the oil level to find it looked like a chocolate milkshake. I immediately drained the oil and checked the coolant level which had dropped significantly. I used the radiator funnel fitting to blow into the cooling system and found a leak at what i assumed was the cooling line connecting to the base of the stock Mikuni carb. I didn't have any more fresh oil to use in the engine but i wanted to reduce the damage to the bottom end bearings from being coated in glycol antifreeze, so I grabbed a jug of used oil from my other vehicle that was not contaminated and filled up the engine. but when i turned the key the engine made maybe one rotation and made a hard noise that i thought was the engine locking up.

after much swearing and feeling sick to my stomach, i decided to sleep on it and weigh my options the next day with a clear head. the next morning Thought maybe it had hydrolocked, so i puled the spark plugs to find they were all wet, especially the number 4 plug since the engine tilts backward slightly. i then turned it over with a wrench to watch it spray coolant out the number 4 cylinder over the fender. after that relief, I decided to pull the head since i assumed i had a defective casting. as I started in though I realized i had forgot to check the bottom of the carb for pieces of old gasket. sure enough! i had old gasket on maybe half of the area where the coolant goes between the carb and manifold so i cleaned it all up and re mounted it and checked it for pressure by blowing into it again and found no leaks! i then tried to start it several times to no avail, maybe i flooded it? so i let it sit a couple of hours and tried again and it fired right up and ran great! i didnt run it long at all though since i have not put more coolant in.

so thats where i am now but im still confused how the oil got so bad so quickly since the only way i would think it could happen is through the head itself or the head gasket? could so much antifreeze get squeezed past the rings to do that? could the coolant have compressed and blown out the head gasket and into the oil return passage between the number 4 cylinder and the firewall?

[FMS88]

If it ran great after fixing the carb gasket, the head gasket is probably fine and a casting defect seems most unlikely. Do a compression test and pressure test the cooling system. If those test results are fine, start driving it. Keep an eye on the oil and coolant, but I doubt you'll have any problems as it continues to run well.

[StarquestMan]

Thanks for the feedback! ill try and check out the compression today. I did a quick check on cylinders 1 and 4 soon after clearing out the 4th cylinder but i should check the rest. 1 and 4 were at about 145-150psi. next payday ill pick up a cooling system pressure tester.

[StarquestMan]

Ended up getting some fresh coolant put in and have had zero issues so far

[FMS88]

Excellent! Keep an eye on the coolant recover bottle and use the heater. You may need to add a little coolant to the bottle as any air in the system is forced out with each heat/cool cycle. The coolant level should stabilize within a few days of driving. If it does, all should be fine. Driving will also evaporate and force out any coolant that may have remained within the engine after you changed the contaminated oil.