Dumb question from a Valve Ajustment Noobie

[Gunter]

mthomas58,
You'll need to give that distributor some TLC like cleaning and lube on the weights, springs and pivot points.
Don't forget a few drops of oil on the small felt under the rotor.

[rnln]

oh no. I am not so sure now.
My car has 3 marks just like that picture above and the pic from tech article I place below here, there is no numbering on mine, not even "Z1". I used the first mark on the right (like Z1 on the article), and the rotor matched the distributor's point correctly base on the book. Now the question is if I should base on the first mark on the right, or 5 degrees to the left of the last (3rd) mark?
Anyone know?

Originally Posted by porschenut

Yeah, about 5 degrees left of there.

[Gunter]

Keep in mind that TDC for #1 and the rotor pointing to the notch could mean that you're on the exhaust stroke, NOT the compression stroke.

You may have to go another turn for compression stroke.

Wiggle the rockers on #1 intake and exhaust. Should be loose for compression stroke.

[rnln]

??? Now even more confused, although not realated to the marks on the crank pulley. I thought when you are at TDC, both exhaust and intake valves for that piston should be at the most loose point, and you can adjust both of them at the same time?

[Wayne 962]

When adjusting the valves, the engine doesn't need to be *exactly* at TDC either - just both valves completely closed. If the adjustment is normal, this means a little click when you rock the valve back and forth. Little click - barely noticeable, and even sometimes difficult to do because of the oil suction effect on the two flat surfaces between the valve and the rocker foot.

-Wayne

[2.70Racer]

Since you have the engine out, now is a good time to learn how the cams and valve actually work.
First the engine rotates clockwise. Always turn the crank clockwise.
To find TDC for #1 or any other cylinder, simply remove the sparkplug and place a compression gauge in the sparkplug hole.
As you slowly turn the crank clockwise look for the compression gauge pressure to rise.
Remove the comp gauge when the pressure just begins to rise. then carefully insert a medium size screw driver tip into the cylinder.
Slowly continue to rotate the crank clockwise, while feeling for the top of the piston with the screw driver.
When the piston pushes the screw driver fully up you are at or near TDC Compression stroke.
Remember the compression must begin to rise, this is the compression stroke.
Some folks can reach in and feel the compression with a finger plugging the sparkplug hole.
Also remember the piston also rises to the top when in the exhaust stroke.
With the exhaust stroke there is no pressure developed in the cylinder.
Both the exhaust valve and intake valve are closed during the compression stroke.
They close over 100 degrees before TDC and remain closed for over 100 degrees after TDC. Thus it isn't required to be exactly on the TDC mark as Wayne pointed out.
Once you have identified TDC compression you can adjust both valves.
A helpful exercise is to slowly rotate the crank clockwise from TDC compression while watching the valve action.
About a half turn past TDC the exhaust valve will open and remain open until the crank returns to the TDC position. This allows the burnt air/fuel mixture out of the engine. This is the exhaust stroke.
Near TDC EXhaust stroke the exhaust valve will close and the intake valve will open. The intake will remain open until the crank is just past BDC.
This allows the fresh air fuel/mixture into the cylinder. This is the intake stroke.
The intake will close just past BDC and it will remain closed until the next intake stroke.
With both valves closed the air/fuel mix is compressed just prior to firing.
These are the four strokes of a four cycle engine. Intake, Compression, Fire, Exhaust.
Try it and you will find you really don't need the crank marks at all.
You really need to understand the four strokes and the valve/piston inter-action, then things like adjusting valves will be simple.
Have fun,

[rnln]

When I search for my TDC, I lifted up the distributor's cap to look at the dist rotor, and turn the crank's pulley. When my crank pulley look likt first pic below (first mark without numbering/lettering. And the dist/rotor look like second pic, I am at TDC. Now I can adjust both intake and exahust valves for piston #1.
Turning the crank pulley almost 1/2 a turn (120 degrees?), I hit another single mark on the pulley, I am at another piston (#6 I think). Now I can adjust both intake and exhaust valves for this piston... and go on to next piston by turning the pulley another 120 degree for another mark. Am I correct?

At first mark like this pic, but ther eis no numbering/lettering.


The mark on housing isn't at the middle of the rotor, but at the right corner of it. Pic morrow from Mark's post earlier.