I just got my engine back from the rebuilders. 1965 Pontiac 389 They have crank timing Mark at tdc on the front pulley. The distributor is not installed.

The problem is that I don't know if piston 1 is firing or exhausting

Is it true that if the timing marks on the cam gear and the crank gear are lined up then Piston 1 is firing??


  • Welcome to Motor Vehicle Maintenance & Repair! Commented Oct 1, 2019 at 20:19

2 Answers 2


If the crank and cam are both aligned , it is TDC firing. While the crank rotates twice and can be either TDC firing or exhaust , the cam only rotates once and is at TDC firing every time its mark is aligned with the crank mark .


Best option is to remove spark plug from #1 cylinder and turn over the engine while your finger is in the spark plug hole, when you feel the compression pushing your finger out that is the compression stroke, now continue to turn the engine slowly until the mark lines up on 0 degrees on the timing cover, now set the distributor in aligning the rotor with the #1 plug wire on the cap, this will get it very close to start the engine.

I usually set the timing mark on the cover at 10 degrees (instead of 0) before top dead center prior to stabbing the distributor, this gets the ignition timing more optimal for starting right away.


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