Author Topic: What are these marks on the harmonic balancer?  (Read 1454 times)

1967RS/SS

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What are these marks on the harmonic balancer?
« on: March 28, 2013, 07:06:20 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?   

1967 RS/SS L-48
Van Nuys 01C
Joe

CNorton

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Re: What are these marks on the harmonic balancer?
« Reply #1 on: March 28, 2013, 07:24:02 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.

69Z28

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Re: What are these marks on the harmonic balancer?
« Reply #2 on: March 28, 2013, 08:08:04 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.
GaryC

'UNRESTORED' 1969 Cortez Silver X33D80 Z28

1967RS/SS

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Re: What are these marks on the harmonic balancer?
« Reply #3 on: March 28, 2013, 09:44:41 PM »
Ok, then do i just set those marks to 0 and that is TDC or would i need to still find TDC?
1967 RS/SS L-48
Van Nuys 01C
Joe

z28z11

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Re: What are these marks on the harmonic balancer?
« Reply #4 on: March 28, 2013, 09:56:32 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 -

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Steve 
1968 Z28 M21/U17 BRG/W
1969 Z28 X77/M20/VE3 LeMans/W
1969 L78 X66/N66 Cortez/BVT
1969 Z11 L48/M35/C60/C06

69Z28-RS

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Re: What are these marks on the harmonic balancer?
« Reply #5 on: March 29, 2013, 01:51:43 AM »
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.. :) ..  and don't forget that the crankshaft is rotating twice per rotation of the cam, and that makes ONE cycle of the engine.
Gary W / 09C 69Z28-RS, 72 B 720 cowl console rosewood tint
69 Corvette convertible, silver/black 350 hp,
60 Corvette white/red, 72 Corvette coupe, '70 Mach I 
90 ZR1 red/red #246, 90 ZR1 white/gray #2466
72 El Camino, '55-'56-'57 Nomads, '55-'57 B/A Sedan