I have a 78 280z that I believe is stock. What should teh cylinder compression levels be in LBS per SQ Inch? How much should they vary from one cylinder to another?

fsm states 164-178

best regards

John

There should be no more than a 20% difference between cylinders.

Be sure to do the compression test correctly or the results will be useless. Adjust the valves per the FSM. Warm up the car before performing the test. Remove all 6 spark plugs, remove the coil wire and hold the throttle wide open. Crank the car over through 4-5 compression strokes and then record the results. Repeat for each cylinder. You should have 150 psi or higher and all 6 should be within 10%, not 20% as stated above. If the numbers are all low, add a bit of oil to each cylinder and repeat the test. If the numbers go up significantly, the problem is with the rings. If not, the problem is valve related.