So did a head job about 8 years ago, and everything ran great until last year she started making a little chuffing noise from the driver's side head with cylinder 3 misfire. Figured gasket blew again, but she still ran fine and wasn't leaking water (that I could tell, no tailpipe water vapor smoke or loss) so let it ride for a few months, then started hearing tapping on the opposite head, which over the next few months got worse and started overheating with the tapping turning into a thunking and found the oil literally was boiling inside the valve cover. Plumes of white smoke from the valve cover when you opened the oil cap. Never ran it hot for more than 30 seconds, pulled over immediately, etc. After a cool down, she'd run again for about 15 minutes with light tapping, and then overheat again, make thunking noises and boiling the oil in the valve cover. Never any white smoke out of the tail pipe.

Got it home, checked cylinder pressures and every cylinder was way low. Not surprising, as when I rebuilt initially, I didn't do a valve job on the heads, nor change the lifters, so some pressure loss would be expected but it ran fine, but now cylinder 3 was really bad so figured I definitely had another blown gasket there but didn't understand where the noise on the other side was coming from or how it could be related.

So my diagnosis was that more than likely, the blown gasket on the passenger side wasn't really the main issue, I either had a coolant problem or an oil flow problem in the other head and/or mechanical damage. Strongly suspected a bad stuck lifter, bent rod/valve or internal water leak between cylinders.

So, pulled the heads, and yep, gasket blown at the top (near intake) over cylinder 3 on driver side but no apparent issues on the noisy passenger side head! Other than the known cylinder 3 breach, both gaskets on both heads looked fine. I couldn't see any damage or wear on the passenger head where I heard the tapping then the thunking. Also, none of the piston heads or cups inside the heads were steam cleaned looking, so it didn't seem like water had been leaking into the combustion chambers. I was fully expecting to see a bent rod or valve or lifter on the passenger side, but it all looked fine. Lastly, I pulled all the lifters out and they came out more or less easily with no major mushrooming. Couldn't see any significant wear on the their bases. But their internal pistons were indeed stuck in various positions and not very tight against their retaining clips. I have not inspected the cams on the cam shaft yet. So, since no white smoke out the tailpipe, no steam-cleaned combustion chambers, and no water loss, i'm leaning towards an oil flow and/or exhaust gas escaping issue causing it to overheat and boil the oil.

So to be safe, I completely rebuilt both heads, cleaned out their really gunked up rockers and even changed upper valve seals and lapped all the valves. Got em perfect and down to near zero pressure bleed down. Also, pulled a vacuum check on the head water intakes by blocking off three off the access ports and pulling about 25lbs of suction on the fourth. Suction held fine. I let it test for 15 mins and had zero loss in vacccum. This was the only testing I did for a cracked head, hadn't seen anyone else ever test for water jacket cracks like this before, was just an idea I had as I didn't have any dye on me and had already had them resurfaced and didn't wanna pull it all apart again and mess up the finish, etc.

So, besides the heads, I'm completely replacing all the lifters as I am dubious as to the old one's current ability to adjust to the reworked heads. This is possibly the third resurfacing of these heads (it looked like to me the previous owner had them reworked at least once the first time I pulled em), and they are pretty below spec at this point (total cut loss of about .75mm-1mm on the exhaust side of the head, but only 0mm-.5mm on the intake side) and seriously considered shims but decided not to for now. Just gonna slap em in there again as is and hope for no compression issues. I'm not even sure this rebuild will fix the problem and may have to yank it all apart again anyhow.

So, my question is, anything else I should be looking for while she's all opened up? Anything I should clean/check on the rest of the heads or short block? I did check the block for true considering how many times I've had blown gaskets, and it looks pretty dang flat according to my straight edge and feeler gauges). I mean, could it possibly have just been the oil pump or hell, maybe the water pump this whole time? I'm sure I remember checking for motion in the radiator and and fairly certain it's circulating. Unfortunately I never thought to check the oil pressure before dismantling, but no idiot light had ever come on or thrown a code.

Thanks for any advice
-Mike