didn't matter, warm or cold, head gasket look good. My thoughts are that the black jell might of swelled up when hot and reduced air flow around the intake valves.

When did the symptoms appear- when engine was warm or cold? Perhaps it was a head gasket issue ???

Machine shop said the only thing he found was a black jell around the valve seats and stems, seals were real bad and a lot of oil around the valve seat area. Guides and springs were good.
Installed another head on another unit doing the same thing and both engines are running real good.

Ya know, we just had a similar problem on a Toyota 4Y. Found a few things wrong.

1. The last time the head was refurbed the machine shop did not tip the valves so the exhaust was a bit longer than the intake.

2. The valve springs were wore out not allowing the valves to return to rest position when the engine was hot.

Engine has about 11K hours on it. Just some thoughts for ya.

Visual inspection showed the valves were saturated with oil and lots of carbon build up on the valve and around the seat. I'll take the head to a rebuilder where the guides, stems and seats can be inspected. I will post the find.

Did you find anything wrong with the old head under examination? Would like to hear what you found- your symptoms were so strange.

After replacing the head the engine runs good, no problems

I am in the process of replacing the Head with one that was working well in a hyster unit. Transmission went out on it. I will post the results when I have tested it.

Im thinking the valves are sticking somehow.

I tried the fuel spray test, it choked off, I changed the PCV valve with one from a working unit, no change.

Just had a Cat with extremely strange symptoms. Engine would run good ( at any given rpm), then suddenly die off, some times to a stall, other times it would catch at the last moment, then run good again. There was no rhythm to it though- turned out to be a faulty PCV valve. I thought of your situation. I simply removed the PCV valve, plugged the hose & ran the engine- symptoms went away. This is of course after checking all the usual suspects & then pulling my hair out- this really stumped me- never saw a PCV do that before

I would do one more test before taking the head off. Make it act up, and as it's sputtering, spray some flammable brake clean in the air intake and see if it trys to run right, to prove it's not a fuel starvation problem. It just seems if it is a valve problem it would skip regularly and not rev up and then slow down and skip.

Thanks, I will make them aware of that.

and consider the reasons an exhaust valve may 'burn' and prepare the customer for purchasing an exhaust system as well as head overhaul.
Also I have seen a few of these where the cam pulley for the timing belt had cracked and or had the key way stripped or key broken... it might be worth checking before the head is sent out.

Valve clearance.012 Job placed on hold waiting for customer to approve head removal.