help my 383
did a compression test on my 383. engine at 200deg. all plugs out. when i turn the key the gauge is jumpy and moves really guick. i can see it goes up to 160 ish but its to fast to deterimine a real number. needle goes up rapidly then down. it doesnt build pressure or slowy move and stay at a reading. its like this on all cylinders. any comments?? doing a leak down tomorrow.