top dead center?

[chevyuser74]

my timing mark tab was bent, so i would like to set it right, is there a way to find true top dead center, without pulling the engine apart.

 

[resurrected_jimmy]

pull the #1 spark plug insert wooden dowel and rotate the engine by hand until the piston comes up on compression stroke

 

[chevyuser74]

thats what i figured, just didnt know if it was close enough.

 

[jonrpick]

thats what i figured, just didnt know if it was close enough.

Make sure to rotate it until it stops, then mark the stopping point on the balancer or a pulley. then rotate it the opposite direction and do the same.

The spot directly between those two marks is TDC. They even make a tool just for this that screws into the spark plug hole.

 

[British Slave]

I have never tried thi myself, but it seems like it would work.







How to Find Your Engine's Top Dead Center (TDC)

If you have a car with no timing marks on the crank pulley, here is a really neat, accurate and cheap way of finding the engine's TDC. This is done with the engine in the car and the head torqued down.


Steps

1. Make an indicator from some clear plastic tubing, a jar of light oil, and an old sparkplug.
2. Break up an old sparkplug and attach a length of clear plastic tubing to it (make it airtight).
3. Remove all the spark plugs.
4. Stick your thumb OVER the #1 cylinder spark plug hole. Rotate the engine (see note below on tricks for this) until you feel pressure on your thumb. That's the compression stroke. TDC is at the top of this stroke.
5. Screw in the sparkplug with plastic tubing attached and insert the other end of the tube into a jar of light oil. Continue rotating the engine. Bubbles will appear until the piston reaches the top of its travel. When it starts down on the next stroke, the bubbles will stop and oil will begin traveling up the tube. Stop at a convenient point and mark the tube. Then mark the crank pulley and the engine body at a convenient spot.
6. Rotate the engine backwards and watch the oil recede into the jar. Continue rotating. As the piston continues past tdc and downward it will again suck oil into the tube. Rotate the engine till the oil again reaches the mark. STOP! Mark the crankshaft pulley where it lines up with the mark you made previously on the engine. You should now have two marks on the crankshaft pulley. The midpoint of these two marks lined up with the mark on the engine is tdc. Whoa! Almost like finding South with a wristwatch. Boy and girl scouts listen up.

 

[British Slave]

Here's a video with another version of the above:

http://www.youtube.com/watch?v=Aw7IdW4Qxcc

 

[Fabrimacator21]

my timing mark tab was bent, so i would like to set it right, is there a way to find true top dead center, without pulling the engine apart.

Buy a new one for 4 bucks.

 

[chevyuser74]

Buy a new one for 4 bucks.

have a new one, but because my timing cover is cast aluminum i have to bend it to put it on, which i aligned it when the heads where off, but i bent it when i put the accessory brackets on so i dont have a clue where its at.

 

[chevyuser74]

i got it thanks, i was a whole 2 degrees off.

 

[British Slave]

How did you do it?

 

[chevyuser74]

first i did it the way u posted, and then i did it this way http://www.youtube.com/watch?v=zhafm7F4EPo&feature=related, to confirm it, except i just made a scale instead of paying $40 for one.