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Author Topic: What are these marks on the harmonic balancer?  (Read 1091 times)
1967RS/SS
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« on: March 28, 2013, 02:06:20 PM »

Trying to find TDC on my 350 (without a piston stop tool) and found these paint marks.  If I rotate these to 0 will that be TDC?  If not, what are they for?   

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1967 RS/SS L-48
Van Nuys 01C
Joe
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« Reply #1 on: March 28, 2013, 02:24:02 PM »

That's one-half of what you need.  The other half of the equation is the "0" or "TDC" mark on the tab.  Theoretically, when the line on the damper is directly aligned with the "0" mark, the engine is at TDC.  It is not, however, certain until you confirm the true TDC with a piston stop and compare that to the mark on the tab.
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69Z28
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« Reply #2 on: March 28, 2013, 03:08:04 PM »

The mark is for setting the timing as we all know and the white on either side of the mark is just to enhance that mark when the engine is running and the timing light is applied. Way easier to see the timing mark. A common practice that was done as far back as I can remember.
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GaryC

'UNRESTORED' 1969 Cortez Silver X33D80 Z28
1967RS/SS
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« Reply #3 on: March 28, 2013, 04:44:41 PM »

Ok, then do i just set those marks to 0 and that is TDC or would i need to still find TDC?
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1967 RS/SS L-48
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« Reply #4 on: March 28, 2013, 04:56:32 PM »

You'll still need to verify whether the mark is on the #1 or #6 rotation - both valves on the #1 cylinder will be closed if you are at TDC for the #1 piston (you probably knew that, just a reminder). I've started engines before without realizing it; you usually find out quickly enough -

Regards,
Steve 
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1968 Z28 BRG/W
1969 Z28 X77 LeMans/W
1969 X66 L78 Cortez/BVT
1969 Z11 L48
69Z28-RS
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« Reply #5 on: March 28, 2013, 08:51:43 PM »

When the timing mark on the damper is at the 'TDC' mark on the pointer, the piston is always UP at TOP DEAD CENTER, .. BUT.. 
1) the piston might be UP on Compression (which is the one that counts for timing), OR
2) it might be up on Exhaust (in which case the exhaust port will be open). 

Just pull the LH valve cover and observe the rockers as you rotate the engine thru the 4 'strokes'  (intake, compression, power, and  exhaust).  If you've never done that before, it will give you a new appreciation for the engine operation.. Smiley ..  and don't forget that the crankshaft is rotating twice per rotation of the cam, and that makes ONE cycle of the engine.
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Gary W.  /  69Z28-RS, 72 B 720 cowl console rosewood all tint
69 Corvette convertible, silver/black 350 hp,
60 Corvette white/red, 72 Corvette coupe (2), 
90 ZR1 red/red #246, 90 ZR1 white/gray #2466
72 El Camino, '55 Nomad, '57 Nomad, '57 B/A Sedan
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