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TDC screwdriver test

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Old Dec 2, 2018 | 02:29 PM
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Default TDC screwdriver test
While finding TDC on my small journal 327, something odd happened. When it was at TDC I put a screwdriver into the plug hole and felt the top of the piston. Then, if I angled the screwdriver so that the end of it pointed up, the screwdriver went all the way into the cylinder. I can't fathom how a long screwdriver can go that far into a cylinder at TDC. I know it's TDC because the timing is set correctly and the car runs fine. Any idea how that could happen? I know nothing about what pistons this car has, it's a mystery 327.
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Old Dec 2, 2018 | 04:27 PM
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How long is the screwdriver shaft? The bore is about 3 3/4" off the spark plug hole inside.....4" inch bore.

Jebby
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Old Dec 2, 2018 | 10:02 PM
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Look at the right triangle. 4 inch across, 3.25 down. A 5.1 inch hypotenuse. (sp)? So most of a 6 inch screwdriver shaft would go in.
Last edited by derekderek; Dec 2, 2018 at 10:03 PM.
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Old Dec 2, 2018 | 10:33 PM
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Originally Posted by derekderek
Look at the right triangle. 4 inch across, 3.25 down. A 5.1 inch hypotenuse. (sp)? So most of a 6 inch screwdriver shaft would go in.
Not at TDC. But methinks he is at BDC.
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Old Dec 2, 2018 | 10:52 PM
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Originally Posted by 62corvette

Not at TDC. But methinks he is at BDC.
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Old Dec 3, 2018 | 01:29 PM
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Originally Posted by The13Bats
To verify, loosen the distributor cap and see if the rotor is pointing to #1 (or if 180 off #6)
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Old Dec 3, 2018 | 04:42 PM
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actually, piston is at tdc both places. at bdc on 1 or 6 when pointing at 4 or 7.
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