C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Could the timing marker move..?

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Old May 9, 2011 | 10:57 PM
  #21  
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86PACER
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That balancer does not look slipped by eye.

Indeed factory setting is 6 degrees. The middle point of the deep notch on the timing tab is Zero. 8 degrees should not really cause problems. But set it back to 6 degrees anyway and see if anything changes. Obviously have the EST wire on the firewall unplugged during this and reconnect it when done. Disconnect the battery for a few minutes to clear the code the EST wire will automatically set.

Since the timing tab is almost always rusted and unreadable, I set my adjustable timing light's **** to 6 degrees then I just line up the balancer mark to the deep notch (Zero) of the timing tab. This puts me right at factory specs regardless of weather or not I can see the numbers on the timing tab. As long as I know where Zero is I can set it.

Make sure you are really hooking up your timing light to the #1 plug wire. #1 Cylinder is the front most plug on the driver's side.



Find Physical #1 Top Dead Center:

If you are on the #1 wire and you're still having trouble and are doubting your balancer mark then you need to find physical TDC without using the balancer. Someone needs to put their thumb over the spark plug hole (#1 plug removed obviously) while the engine is being rotated by hand with a ratchet/socket on the crank bolt. Turn clockwise. When pressure is felt at the plug hole it means you're coming up on the Compression stroke.

Stop and now use a long skinny wooden dowel such as a chopstick inside the #1 plug hole or one of those long skinny wooden hand held flag poles. It must be long enough that it cannot fall inside the cylinder and one piece so nothing can fall off of it. Wood won't scratch. As you slowly rotate the engine the rest of the way up the compression stroke by hand you will see the stick rise up then begin to fall back down. Set the engine to where it's at the maximun top of it's travel just before it starts to go back down. You can back up conterclockwise a little bit if you have to. This will be TDC on the Compression stroke. Now you should see your balancer timing mark line up exactly on the center of the deep Zero notch of the timing tab. If it's not lined up and you are TDC on the Compression stroke and not the Exhaust stroke the balancer mark is off plain and simple. It has to be lined up with Zero at #1 Compression TDC period.

If it's off scribe your own temporary correct mark with white chalk and then set your timing at 6 degrees to that new mark. See how the car runs now.

Last edited by 86PACER; May 10, 2011 at 03:00 AM.
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Old May 9, 2011 | 11:38 PM
  #22  
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Awesome!! I'm going to do what you suggested and check TDC and see if the mark lines up to the zero notch tomorrow.

Thanks, I will let you all know what I find.
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Old May 10, 2011 | 07:28 AM
  #23  
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The wooden stick method is interesting but will only get you to about +- 10 degrees as the piston dwells at TDC and the crank is turning but the piston movement is in thousandths of an inch. Moroso and others make a tdc stop that goes in the sparkplug hole. You can make one as well out of an old spark plug with a piece of tubing welded or brazed to it that has a longer reach than a standard plug and will touch the piston about 10 or 20 degrees before tdc. Use either one. The idea is to remove all the plugs so the engine turns easily install the stop in #1 plug hole and turn the engine until it contacts the stop and make a mark on the damper. Turn in the other direction until it contacts it again and make another mark. Halfway between is tdc. If this is not very close to the factory mark(2 or 3 degrees) buy a new damper as the old one has slipped and is going to fail at some point. Before you put the new damper on use a ***** punch and make a mark on both the outter ring and the crank hub that line up with each other so you can check the damper at a later date
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Old May 10, 2011 | 10:44 PM
  #24  
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Ok guys good news and bad news, using the stick method I was 12+ and 12- degrees on the rising and falling of the piston. This to me means that the mark was at 0 degrees like it should of in between. I was hoping it would be off so something could be wrong I could fix but then again I wasn't looking forward to replacing that balancer.

I am going to get a new timing light and change the timing to 6 degrees and see what happens.. I really don't think my balancer has slipped given the photo evidence and checking it with the stick in spark plug #1.
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Old May 29, 2011 | 03:48 PM
  #25  
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Ok all, yesterday I set the timing to 6 degrees and the car started shaking and idling bad again so I set it to 4 degrees.. same thing shake/idle bad then I put it to 0 degrees and now the car idles great again...

Not sure where to go from here. I guess I'll just leave it a 0 even though factor is supposed to be 6..... as it runs horrible at 6 degrees timing. Only thing is i'm getting 8 MPG probably because the of the timing. The car has new injectors/cat/oxygen sensors so I'm not sure why it get such bad gas mileage.
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