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Old 02-07-2011, 01:39 PM   #1
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Default finding TDC compression stroke with a broken timing belt

I have searched and havn't stumbled on an answer to this question: My timing belt broke while engine was running, so engine is now obviously out of sync.

If my thinking is correct, the timing mark on the crank sprocket will align 2 times when trying to set the #1 piston at TDC, once on the compression stroke, and once on the exhaust stroke. So I need to know how I can determine if I'm on the compression or exhaust stroke when it's at TDC. It would seem that I can't use a compression gauge since the cams are not connected to correctly close the valves for it to show any compression.

Any suggestions? Or if I missed a thread on the topic, can you point me to it? Any help is appreciated.
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Old 02-07-2011, 01:44 PM   #2
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the crank doesn't care which stroke it's on. the cams do.

and since they have markings on them....
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Old 02-07-2011, 01:50 PM   #3
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There are marks on the timing pulley of the crank. Also, the key on the crank will be 12 o'clock if you cant find it. The cams will also be at 12 o'clock. If all pins are at 12, you are set. Or there is the old trick of sticking a screw driver in the Cyl 1 hole, then cranking the engine BY HAND!!!!! BY HAND!!!!!!! until the screwdriver rises, then once it stops rising you are at TDC. I know of a dumb redneck that cranked his starter while the screwdriver was in there, breaking it off, and holing a piston and screwing up the head. Sometimes common sense isn't so common.
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Old 02-07-2011, 07:16 PM   #4
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TDC is TDC, doesn't matter what stroke you're on. The cams decide what stroke you're on.
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Old 02-09-2011, 09:33 PM   #5
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Ok, thanks guys. Just wanted to make sure I wasn't going to be 180 out somehow.

I've got one other question now tho. When you are aligning the cam timing marks, do the cams try to fight you a little? Or do you go with the neutral position they seem to fall to, even though it looks like the marks aren't EXACTLY lined up?
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Old 02-09-2011, 09:55 PM   #6
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The cams will fight you a bit. Put a wrench on each of the cams (on the hex part obviously) . . . cross the two wrench handles. . .and take some vice grips and clamp the two wrenches together. Now the cams wont move on you.

Like what revlimiter did:

http://revlimiter.net/blog/2009/09/n...g-belt-change/
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Old 02-09-2011, 10:19 PM   #7
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ok, cool. Good tip, thanx! Now if my friggin timing belt would just get here I can get my baby back on the road!
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