Q&A for How to Find Your Engine's Top Dead Center (TDC)

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Question

Do I need to remove the distributor before I find TDC?

Community Answer

No, but you will need to take off the cap to set the timing.

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Question

Exhaust valve open on number one on top dead center or closed?

Community Answer

TDC on compression stroke all valves closed, TDC on exhaust stroke the exhaust valve will be opened.

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Question

Do I take out the distributor or leave it in when finding my engine's TDC?

Community Answer

You don't need to do anything with the distributor except remove the cap to be able to see where the rotor is pointing.

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Question

Will these steps work for a truck?

Community Answer

This basic principle should work well for most internal combustion 4 stroke engines (which pretty much any car or truck engine would be).

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Question

Does this work if it is a truck motor?

Community Answer

No. If your motor is seized, you will not be able to rotate it in order to identify top dead center using these methods. You will have to disassemble a seized motor in order to find TDC.

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Question

How do I find the pistons on an engine?

Community Answer

To "find" the pistons, you can follow the spark plug wires from the distributor to each one.

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Question

Do I need to find my TDC if changing the timing chain?

Community Answer

Yes, it's always a good idea to make sure your timing chain has correct timing.

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Question

I have a 1969 400 Pontiac engine. How far should I screw the piston stopper in?

Community Answer

It only needs to be long enough to stop the piston, but it really doesn't matter if it is longer. A deeper or a longer bolt will stop the piston sooner and the length between the two marks will be farther apart. The shorter it is, the closer the marks, which makes it easier to find the center between the marks, in my opinion.

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Question

If the rotor of my 98 Nissan Pathfinder inside the distributor was removed and the distributor was replaced without marking anything, how do I know where to set both the distributor and the rotor?

Community Answer

First, you would find TDC using one of the methods indicated above. Then, drop your distributor in and place the rotor in it. The rotor will be pointing anywhere your #1 plug wire goes in the distributor cap. Then, just install the remaining plug wires following your vehicles firing order. You will need to "time it" after you reinstall all of this.

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