No Compression #1 Cylinder

For those keeping up with my winter project. Got the engine back in yesterday. Fired right up, but was running rough. Went thru basic troubleshooting. Turns out I've got no compression on #1. Had compression before. Only thing I did to that cylinder is adjust the valves. Did a leak down and air is coming out both the intake and muffler. I'm in a minor panic and hoping that I just screwed up the valve adjustment and the valves aren't closing. Rest of the cylinders are fine. Am I guessing right? Thanks for the help!

That's what I'd check first. See if the valves are hanging open. If there was any crud between the valve and seat when you adjusted them, the crud would blow off and possibly leave the valve open.

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'83 SC

Anyone else have any suggestions?

Kurt V
72 911E

do what superman says.

I had the same thing happen to me on a solid lifter cam chev and it turned out that I had the valves adjusted to tight and it got worse as it warmed up.I just readjusted them and they were fine.

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Grant 75 911 targa

Kurt,

I seem to recall that this was your first valve adjustment, so there is a very good possibility that luck turned against you on that #1 cylinder! Some, but not all, and not even a majority, swivel-foot adjusters have a tendency to tighten up ... that is, close the gap completely when you tighten the jam nut. I have seen some that want to close up by as much as a quarter-turn, and since the thread pitch is 1.00 mm, if you start with a 0.1 mm clearance, and it moves 1/4 turn ... that leaves you with a valve that is 0.15 mm off the seat! A definite compression leak, and if it happened on both valves, then you have leaks out the intake and exhaust pipe when compressed air is applied! I suspect that when you pop those left side valve covers off ... you will find 'negative' clearance on both valves! Good luck!

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Warren Hall
1973 911S Targa