I am learning how to adjust my valves for the first time on my new 1981 LUV 4WD with the 2.2L Isuzu diesel engine and have two questions.
1. Should I believe the valve clearances on an Isuzu sticker on the hood of the vehicle or the clearances in the Series 11 Shop Supplement (which contains the diesel engine info?)
2. What's the best way to turn this engine? There doesn't seem to be much space to work in at the front of the engine or from underneath.
I don't want to overcomplicate things here but . . . Isuzu gives the general valve-lash specs for a cold C223 engine as: Intake 25 mm (.010") and exhaust 35 mm (.014"). You will find some slight variations in these very general specs. Anything close to that will be fine for most purposes. But - there have been many arguments about this for many years - dating back to the early 1900s, Henry Ford, and Model T racing.
Many people tend to adjust their valves to quiet the engine down a bit - especially when they get a bit loose and noisy. The true meaing of valve-lash specs is to get the valve timing where it was designed to be. So - to be technical, an engine adjusted for best performance is likely not to be pefectly in specs with the general lash specs as posted. An engine tuned to run it's best is adjusted with a degree wheel and the said clearance is totally ignored. Remember, the looser a valve is adjusted, the later the valve timing. The tighter the adjustment, the earlier the timing.
Since few people are willing to spend time with a degree wheel, valve-lash is a shortcut that puts an engine in "the ball park" to run well enough.
So - to be very technical - intake valves are supposed to be adjusted so they just start to open 32 degrees BTDC and close at 60 degrees ABDC. Exhaust must just start to open at 65 degrees BBDC and close at 29 degrees ATDC.
I don't use a degree wheel by the way. If I was entering some sort of contest ,I would. Any race engine - where everything needs to be perfect - is always adjusted with a degree wheel.
I find it kind of interesting. Back around 1918, there was a race between two Ford Model Ts. The race was based on a long standing argument about valve-lash adjustment. The guy who adusted with a degree-wheel won the race.
For your valve-lash adjustment going by clearance specs, you do so by getting the engine at TDC of the compression stroke for #1. Then adjust I and E on #1, just I on #2, just E on #3 and none on #4.
Then turn the crank one full turn and do the following:
Adjust none on #1, adjust E on #2, adjust I on #3, and adjust I and E on #4.
To turn the engine, I usually stick a socket and wrench on the crankshaft bolt. Another way is to remove the glow-plugs and then turn easily by hand.