That’s a good idea for a short straight edge test. I’m not sure what the physics is, maybe some form of lowest energy configuration, but it seems like it would have to be very straight. Best I think to use a thin wire, like 30 non-insulated AWG solid wire attached to a small rock. That way the wire won’t be able to kink as much. Carpenters use the string method to make straight lines, but they are making them over a long distance compared to the length of a cylinder head.
I think this has the Cummins engine in it (Chinese made, I think). Maybe Cummins.com support could help locate a service manual. The place I normally go to for service manuals didn’t have on for the Foton.
If it is Cummins, I believe the engine has a big C on top of the engine cover.
Ah, here is the Cummins manuals you can download. I do not know if they have your engine listed. Of course, you engine could be an older Foton… before they put in the Cummins diesel.
It could be warped head, cracked head, miserable gasket (after all it’s chinese) but I’ll check one thing first. Go And dry the fuel tank. I mean remove the lid if possible and go dead dry with it. Then you can get a sample of fuel of known mass and test it. You’re looking for water. With petrol it works so that you’ll get say - 900g of fuel, add 100g of alcohol to have full 1kg, and wait. Once an obvious separation line develops after several hours, you suck out the alcohol with a syringe and measure its mass again. If it’s significantly more than before, you had a ton of water in the fuel tank and now it’s bound to the alcohol in your sample. And as water goes, it’s incompressible, and can go as far as destroying the engine completely. I’m not sure if the same will work for diesel though.
Depending on a type of an engine, you may also have faulty injector or an oil leak that will cause accumulation of liquid in the piston chamber. Once that happens, again - fluids don’t like to compress and will find a way out of the engine through the weakest spot.
This may be or may not be helpful, but water in the fuel tank is one of the less uncheap things to check first I think.
It is not a Cummins. I was hoping that it was a cummins “copy” but it isnt. It is a model N485 engine made by Quanchai. They have a website, but no where to download any manual or documentation. The closest PDF file i found on the net is an N485J Still a chinese engine but not made by Quanchai…
Some Foton trucks here do have Cummins engines. I believe foton started by putting together off the shelves parts and gave it a name. It is so hard to find parts, esp these older models… I read somewhere that the N485 was mainly used as generator engines…
Or maybe use a guitar… 
It has taught wires, right… Lol…
But i think not everyone has a guitar lying around… So a string would probably be the easiest…
Wont the miniscule amount of water that came through the diesel injector evaporate with the combustion?
If it’s a small amount, it should. Typically, there is a tiny amount of water in fuel all the time, especially once longer in tank, or/and with alcohol mixed fuels. But you never know. It’s a bit more dense than fuel and doesn’t like to evaporate as well as fuel. If the pump sucks a nice blob of mostly water in to the piston, it will not ignite and will accumulate in the piston instead, while the engine misses a beat. As the piston goes for the compression cycle, with enough water, it could shoot the gasket, shatter the piston, break the crank shaft, bend the piston rod… Water is very ugly stuff even in tiny amounts. One of the reasons not to run the fuel tank dry, as water tends to be at the bottom. It could also get in through the air intake. I remember finding good quarter of a liter of water in my trucks air intake after one heavy storm express drive. The drain have clogged, allowing the water to accumulate. Luckily, I figured it out soon. Otherwise I risked shattering the engine to pieces.
I found the following, but I have no clue as to whether that engine is similar to Yours.
Could it be possible that You could get some needed info by contacting that company?
Yep. That’s his brother…
I have not seen those email addresses, will try to contact them now.
Thank you so much Asterix for digging.
You’re welcome. I’m probably just a bigger spade than You. 
Sorry, you did say that. I was thinking that was the Cummins
factory city. OK, I wonder if these are the head bolts, so the
guys might know how much torque they can take? [https://circled.com.au/quanchai-cylinder-head/5912-qc-cylinder-head-bolt-ii.html
](https://circled.com.au/quanchai-cylinder-head/5912-qc-cylinder-head-bolt-ii.html)
N85-03016A
Head bolt Quanchai 102mm.
M12x1.75
thread. 102mm length. 16mm spanner
Yep. The bolt shown in that website sure looks like the bolts on my truck. I will try and contact them too. I remember going to a website where i entered the dimensions of my bolts and it gave me the recommended torque. That’s where I settled for 80 ft lbs.
At least now i know where I can buy them and not worry about breaking them due to over torquing. I’ll torque it to 110 this time. Thank you mperry!
Hey, don’t thank me yet. We don’t know if it works, but will keep happy thoughts.
How long did the last repair last? Maybe pop in and drop a line if it works?
BTW, what type truck is it? They make some interesting ones, from flatbeds to smaller box trucks. (The engine company seems to specialize in inexpensive generators.)