What would cause 0 compression on all 8 cylinders  Rebuilt 400 SBC?

Completely rebuilt 400 SBC, all new bearings, rings, cam & lifters, timing set, new heads, pushrod, rocker arms, dizzy, plugs, wires, carb, fuel pump, etc, etc. 

It has ZERO compression on all 8 cylinders and shoots gas out of the top of the carb when turning it over? 

21 Answers

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  • zipper
    Lv 6
    3 weeks ago

    The timing is off, either the values were not set right, or the person doing the pressure check is doing it wrong. But with the gas being pushed out the carburetor the value train is set wrong!

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  • 3 weeks ago

    Someone really screwed up when they rebuilt the engine.

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  • 4 weeks ago

    The culprit would be the timing gears were not aligned properly. Those two dots have to be next to each other. The camshaft gear dot is at six o'clock and the crankshaft gear at twelve o'clock with the #1 cylinder at top dead center. 

    Even in newer double overhead cam engines, there are timing dots in various locations and the #1 cylinder must be at top dead center when those dots are lined up. 

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  • 4 weeks ago

    hahaha a troll... NO WAY.. IMPOSSIBLE TO HAVE ABSOLUTE 0 COMPRESSION ON ALL 8 CYLINDERS.. But...

    There is a slight possibility that the TIMING CHAIN PIN was not installed and even though the engine is turning over the TIMING CHAIN is not turning the Cam Shaft which open and closes the valves. IF the valves are not OPENING AND CLOSING as the Piston moves up and down nothing will happen.

    • Quentin4 weeks agoReport

      I suggest worn out inlet valves, all of them.

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  • Anonymous
    4 weeks ago

    Have all the plugs out and put your thumb over one spark plug hole and try to block the hole.  Now have a buddy crank over the engine.  If air goes past your finger with a squeak - that cylinder has compression.  Check all 8 holes.  If they all squeak, then you got a bad compression tester gauge for your thumb does not lie.   That is where I would start. Then would guess they did not install the valves at all, or the pistons at all.  I mean 180 out will still give you compression, but at the wrong time. So firing would be spotty at best with much exhaust coming out the carb as flaming backfires.>it is "Cool" as it singes your eyebrows.

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  • 4 weeks ago

    To all of you that answered my question I greatly appreciate it especially the ones not being a smartass. Now I will tell you what I found and I fixed the problem. I took the front cover off and got looking at the timing again. Come to find out I had it right but the crank sprocket was stamped wrong. I got ahold of Cloyes and sent them a picture of it and they apologized and they're going to make it right with me even though I went to the local parts store and got another one and installed it. Motor runs fine. Never had this problem in my life and it had me so aggravated that I was second guessing myself. Lesson learned to always check new parts. Thanks again to everyone! 

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    • Loren4 weeks agoReport

      It was a three key sprocket and I can't remember how much it was off but I think it was around 4 or 5 teeth. It really had me aggravated. I've rebuilt many motors and never ran into a problem with a new part especially something like this. Lesson learned but the hard way as usual. 

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  • 4 weeks ago

    Out of time - very possibly 180 degress out (fairly common mistake).

    After rebuild a simple attempt at turning the engine over by hand should've let you (or whoever rebuilt it) know whether or not it was getting compression.

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  • JetDoc
    Lv 7
    4 weeks ago

    Your valves MUST be closed when the piston comes up on a compression stroke, and no compression in ALL cylinders means that's not happening. Either your cam is not timed correctly or lifters are not adjusted properly.

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  • 4 weeks ago

    It's not timed right.

    Source(s): Mitsubishi Master Tech
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  • Anonymous
    4 weeks ago

    Cam timing chain installed wrong, crank and cam marks must line up at TDC on cyl #1.

    ETA, nice that you figured it out. It always helps to have the old parts to compare with.

    The gear you have will work if you scribe the proper timing mark from the old cam gear. Lay those 2 cam gears down on cardboard and transfer the proper cam timing mark.

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