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TDC - Is this Top Dead Centre


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#1 luke240ZED

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Posted 08 October 2012 - 03:00 PM

With the timing markings here and on the compression stroke and my dizzy rotor here.

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Is this where I need to be for TDC?

Cheers
Luke

#2 Scoota G

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Posted 08 October 2012 - 03:36 PM

Looks like somone has set it 180 Degrees out.

#3 luke240ZED

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Posted 08 October 2012 - 05:45 PM

If it was 180 degrees out wouldn't the rotor be facing in the opposite direction from no.1 spark plug?

#4 Scoota G

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Posted 08 October 2012 - 06:45 PM

They swap the leads around to suit. To get it back where it should be you remove the oil pump, remove oil pump drive and turn around 180. It's been documented on here in another thread.

#5 luke240ZED

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Posted 08 October 2012 - 08:19 PM

Thanks Scoota, i'll have a look.

#6 Six_Shooter

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Posted 09 October 2012 - 01:23 PM

LOL.
I always laugh when someone says "the dizzy is 180* out."

While it may be common to have the #1 spark plug lead in a certain location, you can in essence have it placed anywhere around the circle of the dizzy cap, as long as the rotor also starts the firing order from the same point.

Something else to think about, is that the crank turns twice for every rotation of the cam, AND the dizzy, so you may actually be at TDC of the exhaust stroke (just as the exhaust valve closes and the intake valve opens). The best way to verify this is to remove the cam cover and make sure both valves are closed. Alternatively, you can remove the spark plug, and bump the engine over with your thumb over the hole feeling for compression, as it does build compression, this would be TDC of the compression stroke, and you can then finish turning it to TDC, of the compression stroke by hand.

#7 zeds4ever

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Posted 15 November 2012 - 07:45 PM



            For what its worth, if the dissy has been pulled apart & the upper section has been put back 180 dgrs out you will also have this problem.
           
            Stands to reason that  if the bottom of the motor hasn't been touched then it  has to be the dissy.
     
            Might also mention that if you fit a 280z elctrnc dissy you also have to use the 280 base plate otherwise timing will be out.

            Am easier way to find TDC without to much hassle is to remove the #1 spark plug then rotate motor so that timing mark lines up & relevant   
            piston is at the top of stroke you can use a torch to visualize or a  long screw driver  thru the plug hole.                         
                           
                                                                        Regards: Alan.

#8 nizm0zed

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Posted 15 November 2012 - 08:22 PM

An easier way to find TDC without to much hassle is to remove the #1 spark plug then rotate motor so that timing mark lines up & relevant   
piston is at the top of stroke you can use a torch to visualize or a  long screw driver  thru the plug hole.                         
                           
                                                                        Regards: Alan.



Something else to think about, is that the crank turns twice for every rotation of the cam, AND the dizzy, so you may actually be at TDC of the exhaust stroke (just as the exhaust valve closes and the intake valve opens). The best way to verify this is to remove the cam cover and make sure both valves are closed. Alternatively, you can remove the spark plug, and bump the engine over with your thumb over the hole feeling for compression, as it does build compression, this would be TDC of the compression stroke, and you can then finish turning it to TDC, of the compression stroke by hand.


As six shooter just pointed out, the crankshaft rotates twice for every single rotation of the cam AND the dizzy.
While you can remove the plug and see the piston reaching the top (or use a soft probe to feel it)
It'll only tell you that the crank is at top dead centre, not whether its TDC compression, or TDC exhaust, which are 180 degrees apart from one another on the cam and dizzy.

#9 Zedman240®

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Posted 15 November 2012 - 09:11 PM

Best to get a small torch and check both cam lobes for #1 cylinder are making a "V". both pointy ends pointing up. There is also a small mark on the distributor body showing number 1 position. Between the cap and body.

#10 neRok

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Posted 16 November 2012 - 09:42 AM

LOL. I always laugh when someone says "the dizzy is 180* out."

While it may be common to have the #1 spark plug lead in a certain location, you can in essence have it placed anywhere around the circle of the dizzy cap, as long as the rotor also starts the firing order from the same point.

This man speaks the truth. The leads do not have to in the exact position (for example, #1 doesnt have to be at 3oclock), you just have to have the leads on the correct post for the particular position of the crank. So dont bother disassembling anything, just put the leads on to suit.




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