# Do I Really Need to Start My Project With the #1 Piston at TDC - Compression Stroke?



## potlatcher (Jun 6, 2014)

I am in the process of replacing the head on my '87 D-21 with the Z24 engine. I have my Chiltons and have been using it a lot as I try to step through this project. One of the first things it said to do was to ensure the #1 cylinder was at TDC on the compression stroke before beginning. I set the cylinder at TDC and proceeded to remove the head. Just yesterday, something on this forum made me realize that I didn't make sure it was TDC on the compression stroke - I'm certain that I'm actually at TDC on the exhaust stroke.

So, here's my situation. I have the head fully removed and ready to replace with a refurbished head. As advised by Chiltons, I marked the timing chain and camshaft sprocket before removing the sprocket so I could line them up again. I placed a wooden wedge down inside the timing chain cover to hold the chain in place until I'm ready to re-attach the sprocket. I have not yet touched the distributor or oil pump. At this point, I see two possible paths forward:

1) Continue on as if nothing is wrong, but just keep in mind my situation and make sure that I mentally add 180 degrees to any further instructions about the distributor and/or cam shaft re-installation.

2) Hand turn the crank shaft 360 degrees and hand turn the new cam shaft 180 degrees to bring them back to TDC. As I do this, get a helper to re-insert the camshaft timing sprocket into the chain and remove the wedge, and then hand turn the sprocket as I turn the crank so that it doesn't get messed up either. Once back at TDC, I can replace the wedge, set the sprocket aside for now, and continue on as if nothing had happened.

So what do you think is the best way to proceed?

Thanks in advance...
Potlatcher


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## jp2code (Jun 2, 2011)

I'm not sure (not a mechanic), but I'd go with leaving it alone until you get it installed.

Keep that in mind, though. So, if you have cranking problems after getting it all back together, it could be that your timing is 180° off.

I would think that if you moved it now, you might never be able to get all of your internal parts to line back up the right way.

Again, I do not know for sure on this.


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## saudade (Apr 10, 2010)

You will not be able to use the factory timing marks. If you're *CERTAIN* you marked the locations of the chain and sprocket, and are *CERTAIN* nothing has moved, you should be OK.

Don't mess with the dist or oil pump drive.

Here are a few shots from my hg change.


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## potlatcher (Jun 6, 2014)

*Crankshaft pulley removal?*

OK, thanks for the posts so far. As I'm making progress, I found I need to remove the front cover to access the timing chain after all. My question now is how to remove the crankshaft pulley while keeping the crank at TDC? My truck has an automatic transmission, so it isn't as simple as putting it in gear. I thought about holding the pulley with a strap wrench while I remove the bolt with a socket and breaker bar. Is there another way to hold the crank still while removing the bolt?


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## rogoman (Dec 16, 2004)

You can remove the starter and use a large screw driver to the teeth of the flywheel to hold the crankshaft from turning. Also try a high torque air wrench instead of a long breaker bar.


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## CMax03 (Jan 17, 2009)

No if you're removing the head the placement of the #1 piston @ TDC can be acheived with the Cyl head off before reassembly!!!!!


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## royl54 (Jun 22, 2014)

Just finished my timing chain it is advisable to put the a/t in neutral before hand turning crank. also to get the crank pulley bolt off i wrapped two old belts around the pulleys around the front tension bar and twisted them tight with two 1/2" 8" extensions. had a assistant loosen the bolt with a 4 foot cheater bar


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## CMax03 (Jan 17, 2009)

royl54 said:


> Just finished my timing chain it is advisable to put the a/t in neutral before hand turning crank. also to get the crank pulley bolt off i wrapped two old belts around the pulleys around the front tension bar and twisted them tight with two 1/2" 8" extensions. had a assistant loosen the bolt with a 4 foot cheater bar


A breaker bar and bump of the starter loosens it in a jippy! If you're doing a head gasket you don't need to remove all that! You just need the magic wedge!


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