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Old 09-16-2010, 12:20 PM   #1
billetproofcustoms
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TDC and timing chain question

OK, confused still about TDC and timing chain relation, my 350 is on a stand right now almost finished with the build, the motor #1 cylinder is at tdc on the compression stroke, dot on the crank cam gear is at 12 o'clock, my question is this, I have been told that in the #1 cylinder TDC compression stroke position, the cam gear dot is actually at 12 o'clock also, otherwise you are 180 degrees out, the next revolution of the crank lines the dots up (cam 6 and crank 12 o'clock) which is TDC for #6 cylinder. (companion cylinder), as it sits right now at #1 TDC compression stroke, where should the dots on my timing chain be? I got this info from the "real fixes real fast" youtube channel, it is video #5 (engine rebuild video) at the end of that video in case any of you need to reference it in order to HELP me out...LOL...please help..
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Old 09-16-2010, 12:32 PM   #2
Restrorob
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Re: TDC and timing chain question

Leave the crank at TDC #1 cylinder (dot at 12:00) and rotate the camshaft gear so the dot lines up with the crankshaft gear dot at 6:00 position......
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Last edited by Restrorob; 09-16-2010 at 12:34 PM.
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Old 09-16-2010, 08:13 PM   #3
LONGHAIR
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Re: TDC and timing chain question

You are combining things and making yourself crazy.
For get the distributor for a second.
When the crank do is up (12:00) the #1 piston is at TDC. Now, the cam dot determines whether it is on the compression stroke or the exhaust stroke. The cam and crank can never be "180 degrees out" from each other. They are connected by the timing chain and the crank rotates twice for every single rotation of the cam. Every single rotation of the crank moves the cam half way. One time the dots are together, the next time the cam's dot is up at 12:00
The "variable" factor is in the distributor. You are correct in your statement about the cam dot in relation to the rotor. When the cam dot is up at 12:00, the rotor should be pointed toward the #1 terminal of the cap.

The "180 degrees out" comes from someone just turning the crank around to the TDC mark on the harmonic balancer and "assuming" that it is at the correct stroke.
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