Author Topic: Top Dead Center  (Read 782 times)

0 Members and 1 Guest are viewing this topic.


  • Speedster
  • ***
  • Posts: 291
Top Dead Center
« on: April 12, 2019, 07:55:27 AM »
Hi Chris,
           I need to establish an accurate Top Dead Center timing mark on the harmonic balancer on my corvette.

It has a ZZ3 HO 350 chev crate motor.
The existing TDC mark appears to be no where near correct?
I made up a piston stop tool using a hollowed out spark plug with a welded nut on end and threaded rod.

I have looked at YouTube videos where the engine is hand turned in each direction until the no1 piston stops against the inserted piston stop tool. Each position is marked on the harmonic balancer then disected to give a true TDC mark.

I'm ready to try this but remain cautious, I can't help thinking that the valves could contact the piston stop tool and cause damage, whilst the engine is turned by hand.

The heads are alloy and the plugs are angled.
The no1 plug is angled towards the exhaust valve.

Any advice you could give would be appreciated.
Glen :bow:


  • Rally Licence
  • ****
  • Posts: 762
  • Sponsor & The Mechanic
Re: Top Dead Center
« Reply #1 on: April 12, 2019, 01:02:59 PM »
Hi Glen,
Don't panic, even if you have a crazy cam with .700 lift it will not open deep enough to hit your tool. Easiest way is to do it is to take out all your plugs so you can turn the engine over smoothly. Just be gentle so you dont ram the piston hard against your stopper.
Early small block Chevs have the timing tab attached to the timing case cover showing top dead centre at 2 o'clock, later engines show at 12 o'clock. The marking on the balancer must correspond with the correct tab.
If you get stuck....come for a drive and I will do it for you.

Phone 02 9793 3332
Biggles, The Flying Mechanic


  • Speedster
  • ***
  • Posts: 291
Re: Top Dead Center
« Reply #2 on: April 12, 2019, 03:33:51 PM »
Hey Chris,
thanks for your prompt reply.
I'll give it a go. :pepper:


Phone 02 4627 7600