compression checked my engine...
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Tuned
Joined: Nov 2004
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compression checked my engine...
stock 400 in '77 f-250, came up w/ 105-115 lbs on 7 cylinders, 50lbs on 1. going to check the low one w/ a leak-down tester. my question is are the other #s low, should they be higher than 110-ish? i have no idea no the mileage or history of this engine, i dont think its the original. i am planning on eventually rebuilding it either way , was just curious what kind of #'s a fresh engine would have to gauge the condition of mine
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From: Delaware
Atmospheric Pressure is approximately 14.7 PSI at Sea Level. The intake valve on a '77 400 motor closes at 53 degrees ABDC. The Dynamic Compression Ratio based on that IVC is approximately 7.16:1. 14.7 x 7.16 = 105.25 PSI compression.
I would say that your readings on 7 cilinders are OK. The best way to tell is by the uniformity of the readings. If they measured 110 PSI and varied by +/- 5 pounds, that is a good result.
I would say that your readings on 7 cilinders are OK. The best way to tell is by the uniformity of the readings. If they measured 110 PSI and varied by +/- 5 pounds, that is a good result.
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