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Old 24-11-2017, 14:10   #1
er9
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how do i find TDC if i cant see timing marks?

would love to adjust my valves but there simply is no conceivable way i can see the timing marks the way my engine is installed and the space i have in engine bay.

Is there a way to figure out which valve to set by the motion of the rocker arms?

i get confused from youtube videos as they all seem incomplete and do not explain in enough detail how to do this for someone who never has. Books are not much better. they all assume you can see the timing marks or are too vague.

if my #1 pistons intake valve is completely compressed (fully open) then my #1 piston is at its lowest point of its stroke is my # 4 pistons intake and exhaust valves at TDC at this point? If so is this when i would adjust the gap on #4 piston intake and exhaust valves?
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Old 24-11-2017, 14:19   #2
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Re: how do i find TDC if i cant see timing marks?

Yes, rotate the engine (the proper direction!) The intake valve will open (go down), before the exhaust valve moves you will be in the slack zone. You can rock the engine rotation back and forth to make sure there is no movement for either.
More accurately: Turn the crankshaft clockwise while you watch the rockers on #1 cylinder. At or just after TDC you will see the rocker push down the exhaust valve. Then, as the exhaust valve closes you will see the intake valve open. At this point the crank is moving past TDC-exhaust. With more rotation the intake valve closes, the crank is near BDC on the intake stroke now. In about 180 degrees more crankshaft rotation (half a turn) you will be at TDC compression.
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Old 24-11-2017, 14:25   #3
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Re: how do i find TDC if i cant see timing marks?

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Originally Posted by er9 View Post
would love to adjust my valves but there simply is no conceivable way i can see the timing marks the way my engine is installed and the space i have in engine bay.

Is there a way to figure out which valve to set by the motion of the rocker arms?

i get confused from youtube videos as they all seem incomplete and do not explain in enough detail how to do this for someone who never has. Books are not much better. they all assume you can see the timing marks or are too vague.
Not sure why you need to see the timing marks to adjust the valves. Rotate engine until both valves are fully closed and the existing valve clearance is at a maximum. Reset to desired value.

Having an engine with a decompression lever is helpful .

Curious - what engine are we discussing?
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Old 24-11-2017, 14:56   #4
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Re: how do i find TDC if i cant see timing marks?

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Not sure why you need to see the timing marks to adjust the valves. Rotate engine until both valves are fully closed and the existing valve clearance is at a maximum. Reset to desired value.

Having an engine with a decompression lever is helpful .

Curious - what engine are we discussing?
thats how the kubota manual describes the procedure.

kubota manual referenced timing marks for finding valve TDC.

Universal 5432 (kubota v1501)
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Old 24-11-2017, 15:27   #5
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Re: how do i find TDC if i cant see timing marks?

I've done the valves on many different engines and never used the marks. The marks are only good for the number one cylinder anyway. Rotate the engine until the intake rocker becomes loose. When both valves are fully closed, you are usually near enough TDC, you can move the rockers of the cylinder and feel them move the amount of the current clearance. Set the 2 valve clearances and rotate the engine for the next cylinder. 2 cycle diesels are different as are overhead cam diesels.
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Old 24-11-2017, 15:45   #6
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Re: how do i find TDC if i cant see timing marks?

I've found this useful on my Yanmar:

1. Using a 17mm wrench, loosen all four injection line one turn at the injector. This will prevent the engine from starting while you are barring it around. Remove the valve cover.
2. Bar the engine clockwise from the alternator end of the engine. This is #4 cylinder end. Bar the engine until the exhaust valve opens (goes down) and begins to close (move up) on #4 cylinder. Continue barring until the intake valve on #4 cyl. just begins to move (open). STOP. This puts number one cylinder at TDC compression.
3. Adjust #1 cyl. (flywheel end) exhaust and intake valves, #2 cyl. intake and #3 cyl. exhaust.
4. Bar the engine 360 degrees. Now adjust the valves that were missed in step #3. The exhaust on #2 cyl, the intake on #3 cyl and the intake and exhaust on #4 cyl. I usually chalk or mark the valves that are first adjusted in step #3. Then adjust the ones that are not marked during this adjustment cycle.
5. Tighten the high pressure fuel lines , put the valve cover back on and start .
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Old 24-11-2017, 17:39   #7
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Re: how do i find TDC if i cant see timing marks?

Quote:
Originally Posted by kenbo View Post
I've found this useful on my Yanmar:

1. Using a 17mm wrench, loosen all four injection line one turn at the injector. This will prevent the engine from starting while you are barring it around. Remove the valve cover.
2. Bar the engine clockwise from the alternator end of the engine. This is #4 cylinder end. Bar the engine until the exhaust valve opens (goes down) and begins to close (move up) on #4 cylinder. Continue barring until the intake valve on #4 cyl. just begins to move (open). STOP. This puts number one cylinder at TDC compression.
3. Adjust #1 cyl. (flywheel end) exhaust and intake valves, #2 cyl. intake and #3 cyl. exhaust.
4. Bar the engine 360 degrees. Now adjust the valves that were missed in step #3. The exhaust on #2 cyl, the intake on #3 cyl and the intake and exhaust on #4 cyl. I usually chalk or mark the valves that are first adjusted in step #3. Then adjust the ones that are not marked during this adjustment cycle.
5. Tighten the high pressure fuel lines , put the valve cover back on and start .
thanks for detailed response. next time i will think of disconnecting fuel lines. for today i just shut off the fuel line which is close to the injection pump. glad it didnt start, my vice grips would have gone flying.

thats pretty much how i ended up doing it except instead of doing several valves (half) at once i did it piston by piston. took a little longer but i just wanted to be sure i did it right as it was my first valve adjustment iv'e ever done.

didnt have time to bleed the fuel lines and start her. will do that tomorrow. fingers crossed. hopefully #4 piston will fire after this or else i guess its onto injectors.
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Old 24-11-2017, 17:44   #8
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Re: how do i find TDC if i cant see timing marks?

Dr. Google, Rule of Nine valve adjustment.
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Old 24-11-2017, 18:30   #9
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Re: how do i find TDC if i cant see timing marks?

Seems to me if you rotate the crank with the valve cover off, watching a particular cylinder, when the exhaust valve closes and the intake just starts to open you're pretty close to TDC between the exhaust and intake strokes. If you rotate the crank another 360 degrees, and the valves don't move after the intake closes, then you're at TDC between the compression and power strokes. Adjust away.
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Old 24-11-2017, 18:52   #10
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Re: how do i find TDC if i cant see timing marks?

Quote:
Originally Posted by kenbo View Post
I've found this useful on my Yanmar:

1. Using a 17mm wrench, loosen all four injection line one turn at the injector. This will prevent the engine from starting while you are barring it around. Remove the valve cover.
.......
Is it just me or does the first step seem superfluous; I can't image a diesel starting while barring it around.

I don't speak from experience as I have always had decompression levers on my engines so the issue never arose.
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Old 24-11-2017, 18:52   #11
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Re: how do i find TDC if i cant see timing marks?

"rule of 9" might work on normal 4 bangers, but what about 1, 2, 3, or 6 cylinder engines? Or even 1-2-4-3 firing order?
Just go to where both valves are moving, rotate the crank360 degrees and set them.
Purists will say you're not on the absolute heel of the lobe, but -sheesh- it's not an F1 race engine either.
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Old 25-11-2017, 07:13   #12
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Re: how do i find TDC if i cant see timing marks?

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Is it just me or does the first step seem superfluous; I can't image a diesel starting while barring it around.

I don't speak from experience as I have always had decompression levers on my engines so the issue never arose.

It is if you have a cranky to start diesel...if not, maybe not so much.
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Old 25-11-2017, 09:03   #13
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Re: how do i find TDC if i cant see timing marks?

I've never disconnected fuel lines to adjust valves. I have had some diesels that would start with a mere mini tap of the starter though!
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Old 25-11-2017, 12:27   #14
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Re: how do i find TDC if i cant see timing marks?

Considering the fact diesel engine "ignition" occurs due to the heating of rapidly compressed air, I just don't see the possibility of a cold engine "start" occurring when simply barring over slowly to adjust valves. Have you ever tried to manually start a cold diesel with the crank handle? 'Nuff said.
As for "cracking" the fuel lines, well, if you don't mind fuel oil running down the engine and into the bilge, go for it. This sounds like a foolish idea to me.
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Old 25-11-2017, 15:50   #15
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Re: how do i find TDC if i cant see timing marks?

The easiest way is to adjust valve that is NOT compressed. In other words, if a rocker arm is compressing the exhaust valve on a cylender you can adjust intake valve. keep doing this while turning over engine and all valves will be adjusted. It's simple, keep it that way!
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