No compression in cylinder 1

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New Member
i bought a 91 ls400 1uz and i tested compression before i bought it. 1 cylinder was 200 and the rest were 210. I did a compression test now and theres no compression in cylinder 1 and the rest have compression. Can someone please explain what couldve happened?
Zero comp, sounds like a stuck valve. Any chance something went through the intake into No.1?
I've seen this happen on the rear cylinders when the head gaskets have been fitted to the wrong sides. Rear cylinders run hot, carbon builds up on the exhaust valves more so on modified engines and a valve can get stuck open.
Something might have fallen in im not sure. I did vacuum the hole to intake valves before putting it back together. Yesterday i checked for intake valve movement and it seems to go the full range. I opened the valve cover yesterday as well and the buckets for the exhaust valve were moving up and down with the camshaft.
Its not too hard to check for a stuck valve. Use a feeler gauge to measure the clearance between the shim and camshaft heal. From memory the intakes are 10 and exhausts are 14 thou clearance. If you you have one that has heaps of clearance, I'd be looking into that.