GMT 800 & Older GM General Discussion 2006 & Older Trucks | General Discussion

finding TDC

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Old Oct 12, 2011 | 11:43 AM
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Default finding TDC

i finally got the heads and valley cover on without breaking anything. now for the pushrods and rockers. ive read in my haynes manual that the #1 piston needs to be at TDC to torque in. 1345 ex. 1278. rotate 360 degrees torque in.2678 ex. 3456. i cant afford a piston stop and degree wheel. so im going to have employ the screwdriver method. ive never done this, so how do i know when #1's at TDC using the screwdriver.does it need to be on the compression stroke,if so how can i tell that, and whats the effect of rotating the crankshaft 360 degrees...

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Old Oct 12, 2011 | 09:03 PM
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i estimated it as best i could, and got everything torqued down. should get the rest of it together tomorrow. then find out if it starts...holds together.
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Old Oct 12, 2011 | 09:38 PM
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Its pretty simple to just look and see TDC. Rotate the engine over untill you see number 1 coming up. once it is up, move it back and forth, you will be able to tell where TDC is.. It is going to stop, then start back down.. Find the happy spot..
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Old Oct 12, 2011 | 10:39 PM
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say you`re off a cunthair either way, a big deal?
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Old Oct 13, 2011 | 12:24 AM
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I don't use the TDC method. I use the adjust exh when the int is closing, and adjust the int when the exh is opening. That seems to be the easiest for me.
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Old Oct 13, 2011 | 02:01 PM
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maybe Im just ignorant...but I thought on LS engines, you just tightened down everything and you were good to go. No adjustment needed like on the older SBC engines.
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Old Oct 13, 2011 | 02:07 PM
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^^^ Correct.. I did not use this method either, as they are self adjusting lifters.. Tq them to 22 ft lb and roll with it.. I did however crank the engine over some, then go back over things..
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Old Oct 13, 2011 | 03:46 PM
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You just don't want to tighten a rocker down when the pushrod is all the way up because it makes it easier to rip the threads out. I have done it before though and nothing bad happened.
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Old Oct 14, 2011 | 10:45 AM
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thanks guys
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Old Oct 14, 2011 | 10:47 AM
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Yea tighten them all, rotate crank 90 degrees then go back over them
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