Question for you guys - I'm getting ready to take the distributor out of the vehicle and I'm needing to put the engine in TDC compression, and I have the notch on the crank pulley lined up with the indicator on the block but I'm not sure how to tell if it's the intake or compression stroke, and I don't have the valve covers off yet. The video was saying I could tell because it gets harder to turn the crank as it comes up to TDC on compression, but I've turned this thing over several times and I can't tell enough difference to make the determination. Is there any other way to tell, and secondly, if I get it wrong and take the distributor out when it's 180 degrees the other way, is there a way to fix that later? I saw in some of the videos that you need a scan tool to really get the spark dialed in afterwards anyways, but I want it to be as close as possible before taking the distributor out, and give it the best chance of running well when I put it back together. Can I pull the power steering pulley and other parts and valve covers, before taking the distributor out, so that I can tell by looking, before removing the distributor, does it have to be done in that order, and there's a different way to make sure it's in TDC compression? Thanks folks.
With the crank pulley mark aligned, you will either be at (1) top dead center (TDC) of the
compression stroke of the #1 cylinder or (2) TDC of the
exhaust stroke of the #1 cylinder.
These strokes occur 180 degrees apart on the camshaft and 360 degrees apart (1 full revolution) on the crankshaft, since the crankshaft rotates two times per every one revolution of the camshaft.
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So, if you are accidentally at TDC of the
exhaust stroke of the # 1 cylinder, simply rotate the crankshaft one complete revolution. Align the mark. The #1 cylinder will then be at TDC of the
compression stroke.
During compression stroke, both the intake and exhaust valves are closed.
During exhaust stroke, only the intake valve is closed; the exhaust valve is open.
Therefore, remove the #1 spark plug and place your thumb over the spark plug hole. Have someone turn the engine. If you feel air push your thumb off the spark plug hole, then you're at TDC #1 of the compression stroke.
The reason being, the only path for the air to escape the combustion chamber when it is at TDC #1 of the compression stroke is through the spark plug hole, assuming your valves are not leaking.
If you are 180 degrees off, then you will not feel any air coming out of the spark plug hole. Instead, it will exit out the exhaust valve opening since the exhaust valve is not closed during the exhaust stroke.
@TommyJ1980 Another helpful tool is a TDC whistle. Thread it into the spark plug hole. When you are at TDC of the compression stroke, the air exiting the spark plug hole will make a whistle noise.
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