top dead center

[tmar04]

going to attempt replacement of valve stem seals with head on. how do I determine when piston is fully up in cylinder? thx again to all.

 

[ctjstr]

There are a couple ways. If you have timing marks on your model which show TDC for the #1 cylinder, you can start there. If you know the firing order, you can do the math and turn the engine the appropriate amount so the next cylinder is tdc, e.g. 4 cylinder, turn 90 degrees to get to the next.

Another way; when the valve cover is off, crank the engine by hand with a bar or whatever and watch the valves. Watch for the intake valve on a cylinder to go down, then back up. You know that piston is headed back up and you can estimate that another 20 degrees or so of turning will get it pretty close to tdc.

In reality though, you're normally going to have to pull the injectors or the glow plugs and you can just stick a straw down the hole and feel the piston as it comes up to TDC.

 

[DieselPower]

For starters, what engine and in what? Diesel or gas engine.

 

[tmar04]

sorry. it is diesel, 3t80 in yanmar ym 2500.(JD 850)

 

[oldmech]

Hi! Here My system. First find number one cyl. compression TDC. Two valves tappets LOOSE. On crankshaft Pulley You make 3 lines One is TDC Cyl one The second line 120 DEG.more and the third 120 deg more . So 3 lines 120 DEG.= 360 . You make valves on the first cyl number one TDC. after . You turn exactly 240 DEG. you makes the valves.On number two . After you turn again 240 DEG. You make the number 3 cyl. so 3 X 240= 720 DEG or two turns . (IF Your engine is 3 cylinders and 1-2-3 firing order) Good Luck ! Oldmech