geezel

I read somewhere that you can determine when the #1 cylinder is at TDC on the compression stroke by watching the #6 cylinder rocker arms. Specifically, when the #6 intake valve is just beginning to open, you are at TDC on the #1 cylinder. Is this correct?

outhouse

No its not correct.


Piston rising to TDC compression stroke both valves are closed.


Piston going down both valves are closed, then piston rises on exhaust stoke to get exhaust gasses out


Intake stroke, just past TDC intake valve will open to bring in fuel mixture before rising on compression stroke.

geezel

So how to I determine #1 cylinder TDC compression stroke by observing valve events?

geezel

How about this method;
If you have the valve cover off, you can inspect motion of the rocker arms. For a stock camshaft the intake and exhaust valve motion is mirror image. This means intake and exhaust valve will be open the same amount at TDC, and the rocker arms will be at the same height.

08mojo

Take the spark plug out of #1 and put a pen, dowel rod, or similar in the spark plug hole (whatever you use needs to be long enough to not fall into the cylinder, but rather rest on top of the piston and still stick out of the spark plug hole).

Rotate the engine over and watch the dowel rod go up and down with the piston. At its highest point, you are at TDC. To make sure you are on the compression stroke, watch the valves. When the intake valve opens, you are on the intake stroke, and the piston should be moving down. Keep rotating the engine over and watch the dowel rod. As it starts rising, watch the intake valve--the intake valve should start to close, which ensures you are on the compression stroke. Once the dowel reaches its maximum height, you are at TDC on the compression stroke.

Michael_D

EVC > IVO > IVC >

Soon as exh starts to open, go back the other direction - split the difference. Pretty tough to get the piston exactly at TDC without a dial on it... You can eye ball it if you have a bore scope.

outhouse

You cannot

geezel

So posts #4 and #6 above are incorrect?

Whis9

Just do it through spark plug opening like mentioned earlier


http://www.cpgnation.com/finding-top...ter-made-easy/

outhouse

4 incorrect
6 correct but 6 states it is not accurate.


You cannot use rockers for tdc period

outhouse

$60,000 question is why ?

geezel

Just for getting the lifters on the cam base circle for installing rockers. #6 Is probably plenty accurate for that. I know which lifters to install once cyinder #1 is at TDC compression, rotate 360 degrees and install the rest.

outhouse

You are overthinking it.


Just spin it around until both rockers are all down.


Its not even required so anywhere close to bottom and you will be fine.

08mojo

rio95

When exhaust valve starts to open install that cylinder's intake rocker. When the intake valve is closing, stop just before it does and install that cylinder's exhaust rocker. This is the easiest way in my opinion.

Your question wasn't really geared toward what you're needing to do. Base circle and TDC are two different things.

atljar

Although, I have always watched the intake valve open fully, and then just start to shut when doing the exhaust valve.