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post #1 of 5 (permalink) Old 10-18-2012, 01:09 PM Thread Starter
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Camshaft Position?

i'm new to the forum, and new to the cobalt. this is my girlfriends car, it's a 2007 cobalt LS, 2.2l ecotech.

it recently blew the headgasket, so i went about tearing the motor down to remove the head to send to the machine shop.

first mistake i made(was in a big hurry...) i didnt make sure the car was at Top dead center on the compression stroke.

so now i need to figure out HOW to get the crankshaft and pistons to top dead center on the compression stroke, with the head removed.....i could just put it at TDC, but how do i know if it's on the compression stroke? does it matter?


after i do that, i can install the newly machined head, gasket, and bolts.
but then i need to figure out how to get the camshafts back in the proper positions.

what i'm wanting to know is how the heck do i tell where the cams are(position wise...) i'm pretty sure i can do this, if i knew which valves were open/closed at the position they should be in, which is the intake sprocket diamond at 12 o'clock.


or could i just, put the #1 piston at TDC...then install head and rotate cams until all valves are closed on cylinder #1 then install timing chain properly and call that TDC on the compression stroke?

---------- Post added at 12:09 PM ---------- Previous post was at 12:07 PM ----------

i'm totally new to DOHC engines, i have rebuilt a few old Toyota motors, 20R,22R, and 3vze.
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post #2 of 5 (permalink) Old 10-18-2012, 02:34 PM
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Well I think this is the position of the crankshaft for top dead center to line-up cams.




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post #3 of 5 (permalink) Old 10-18-2012, 05:58 PM Thread Starter
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So does crankshaft position not matter? As long as it is at TDC? (5 O'clock)
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post #4 of 5 (permalink) Old 10-18-2012, 06:10 PM
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From my understanding because it's a 4 banger if you place the crank gear at this position it is in the proper sequence to line up your cams as long as piston one is at "TDC". This is the only time they coincide.

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post #5 of 5 (permalink) Old 10-19-2012, 04:46 PM Thread Starter
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So, after I got all timing chain components installed correctly, green mark on intake cam, red mark on Exhaust cam, and crank sprocket.
Installed guides and tensioner as well(per chiltons manual)

Then I rotated crankshaft clockwise several rotations, and when I put it back to TDC, none of my chain links line up with my marks on the cam and crank sprockets.
Are they supposed to????? Everything is still in the correct spots, crankshaft at 5, while intake cam is at 2, and exhaust cam is at 10.

If I count the teeth, my chain is 4 camshaft teeth off of where it should be.



So basically, JUST my chain needs to be rotated clockwise about ~2".....
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