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Discussion Starter #1
Hi everyone, my second post here. I got a freshly rebuilt engine bored to 426, every thing is lined up perfecly, the timing is good, the valve lash is perfect. When i try and turn it with a ratchet and everything addembled (sparkplug on too), i got no compression, its super easy to turn the engine over. I was wandering if it was normal or something is wrong. (FYI the decompressor mechanism is disassembled.) Thanks
 

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Discussion Starter #2 (Edited)
Think ive found something that isnt helping. When I put the engine on TDC and I put the timing gear in, align it, then put the cam on and finally, when I install the cam tensioner back on, then cam rotate a little bit backwards. Dont know how to fix this but it’s very annoying. Do I need to replace the timing chain? Or the tensioner?
4314
 

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The cam chain is worn, but not enough to prevent it from running, just a slight loss of performance.

Not much info provided: Did you bore a stock cylinder or install a kit? If you bored a stock cylinder, did you get the special 88-89 mm Cometic or Vertex head gasket? Regardless of the valve clearance setting, did you clean and reseat the valves when you installed the new valve seals? What do you mean the decompressor is disassembled? It's either been removed or disabled. If it was removed, who pressed the cam sprocket flange off and back on?

Do a cylinder leakdown test to find out where the compression is going.
 

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Got the spark plug in? LOL... Back the tension off the rocker arms completely, spin it over and see how it feels. If it still has no compression, gotta be something up with the rings.

Did you check ring gap before installing? They fit well? Possibly the wrong & piston rings for the bore.

-DallanC
 

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+1 on checking the valve seats. A worn or broken seat, or bent valve would also explain where the pressure is going.

-DallanC
 

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Discussion Starter #6
Head was rebuilt last year, and yes spark plug was on hahaha. But i did a test where i removed the head cover (the cover with the rocker arms) so valve would no longer open. Crank it a few time with my ratchet and definitely feel more compression in there.
 
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