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Another TDC Question

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K5Pappi

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This should be quick and hopefully painless... Before I drop my new motor into my K5 I want to know how to validate that I am on TDC (fire position) without removing the valve covers. I have a TDC plug tool that only tells me when piston # 1 is at its top position, it doesn't tell me if it's in its compressed firing position. I've heard the two following tricks... Do they really work?

- rotate the engine and cover the exhaust port to #1 with your hand and if you feel the air pushing out that's the exhaust TDC and if there is no air coming out then that's the compression TDC
- Pop the filler Cap/Breather out and try and look through the valve cover hole to ensure the valves are all the way up on TDC

Do these tricks work and does anyone else have any other suggestions...

PS - Can you share a link to a sweet aftermarket tilt column that will work for my 84 K5 blazer w/o cruise control?
 
The finger in the spark plug hole works to get you on the compression stroke, then use the damper marks to hit TDC. Pulling the valve cover to check the valves is easy too, just 4 bolts and a gasket.
 
K5Pappi said:
- rotate the engine and cover the exhaust port to #1 with your hand and if you feel the air pushing out that's the exhaust TDC and if there is no air coming out then that's the compression TDC
- Pop the filler Cap/Breather out and try and look through the valve cover hole to ensure the valves are all the way up on TDC
Click to expand...
Air pushes out of the spark plug hole as the engine approaches TDC on the compression stroke, i.e. both valves are closed. On the exhaust stroke the intake valve is still closed, or it would be (at least partially) backfiring. So yeah, put your finger on #1 plug hole and rotate until the pressure pushes it off. Then rotate back and forth until you're sure you're at the center of the highest point, using your TDC tool, drinking straw (sorry CA residents!) or whatever. At this time, verify that your timing mark is aligned at 0.
 
You should be able to feel the compression from the spark plug hole, better than air out the exhaust. Use your tdc tool to verify the tdc marks, then bar theengine over with finger covering #1 spark plug hole you will know you are on tdc compression
 
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