compression

Book says minimum at cranking speed should be 160. Having said that, I have the 361fe says the minimum is 180 and I am running 75% of that with no problems.
 
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If they are all similar, it may run on for years with less that 100. Look for big drop from one to the next, that's trouble.
 
As mentioned, depends on the engine:
Is it stock? Modified? Cam change?
All these items affect the compression test & readings
I have a very big cam in an engine and the compression
readings are in the 105# range.
Also, Carb butterflies should be wide open when cranking
 
Depending on the condition of the engine and stock/aftermarket parts variables...
anything above 110, as long as all readings are within 10% of each other.


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Ford somewhat embellished on their compression ratios. I have seen fresh 292's barely go over 140 put back to stock. Also factory head gasket was a shim.Most head gaskets today are just shy of .050 thick. Basically try to stay within about 10% on the lowest to the highest reading. As long as you are 110lbs. or more just drive it like you stole it.
 
And you have to check the calibration of the gauge---4 different gauges, 4 different readings,25lb spread on the last ones I checked,2 the same read different) the ones with the longest hoses read lowest, the flexible hose swelled with each compression stroke (the gauge I use has steel corded hose)

What I find more important that the highest reading you get is how even, and how much on the first --2nd pump, you have to remember the engine running only gets 1 compression cycle, if you don't make 75% of the total on the first or 2nd full pump there are compression losses that there shouldn't be, and if there is much of a difference between cylinders you can't have it as smooth as it could be
 
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