Finding TDC

[jessedukhia]

Ok, I know my harmonic balancer is correct. When the mark is it at zero. The rotor points two ways. It either faces at the number two cylinder or at the number one. I am thinking that when it points at the number 2 cylinder area, that is the exhaust stroke and when it points and the number one that's the compression stroke? 350 sbc

 

[Opie Knievel]

I'm not sure which engine you have but this is one case where that doesn't matter. I'm gonna assume that you either have a small block Chevy or a GM V6. Both are cam in block engines with a distributor. Timing works the same way on both.

To complete the 4 stroke cycle the crankshaft must complete 2 revolutions. This means that your timing marks on the harmonic balancer will line up twice. Only one of the 2 times is correct though. You are right. When the balancer marks line up and the rotor is pointing at the terminal on the distributor cap that the #1 plug wire attaches to, you are at TDC on the compression stroke of the #1 cylinder. If your marks are lined up on the balancer but the rotor is pointing at a terminal other than #1 you are at TDC on the exhaust stroke or what is referred to as 180° out of time. This is assuming that the engine is in running condition and that the plug wires and timing hasn't been messed with.

I hope this helped. I know sometimes I confuse people with my explanations. If you have any more questions let us know.

 

[pontiacgp]

if you need to fine the compression stroke remove the #1 plug and stick your finger in the hole ( on a cold engine) and you will feel the compression stroke, stop there and you'll probably have to back up the engine a little to get it on TDC on the balancer.