My factory manual says the cylinder compression for this engine is only 119 psi. Is this correct? Seems rather low for a 8.9:1 compression ratio....

perfect at sea level would be only 131pai. 119 is not that bad considering how inefficiently the engine breathes at cranking rpms and how poor the ring seal is at those speeds...

My Factory Manual (page 11-55) says Service Specification compression pressure, in other words the 'perfect at sea level' pressure, for this engine (3.0 L 6G72) is 840 kPa, 119 psi. I also have a Haynes manual that says 119 psi at 250 rpm for the 3.0 L engine

Hence my question.

This seems too low. 130 psi sounds more reasonable. But, the manuals says 119 psi.

Are the manuals wrong? If so, what is the correct specification for the cylinder compression.

Maybe I wasn't clear. If everything was perfect, the best you could get is 14.7psi atmo pressure at sea level x 8.9:1 compression ratio, which equals about 131psi. The piston rings have a gap, so air leaks past the rings. The slow rotation speed means there is a longer time for the leak to leak, so it's relatively bigger. Thus, at the low cranking speed of 250rpms, you won't see 131psi of compression. Replace the cast iron piston rings with the gap with rubber orings and you might see 130ish, but once the engine fires, it gets a little toasty for rubber orings. Volumetric efficiency is not great at cranking speeds, either, and the throttle may be partially closed, so the engine is pulling against less that 14.7psi in the manifold. There are places in the rpm range where the measured pressure would be above 131, because the ram effect built into the intake (the long runners) sets up a helmholtz resonance which has a pressure wave hitting the back of the intake valve just as it opensm and the measured intake mani pressure will be much higher, say 18psi.

So, are all those issues why the shop manuals specify only 119 psi for the best expected expected cylinder pressure in a compression test at 250 rpm at sea level?

Presumably the specifications assume standard atmospheric pressure at sea level. 119 psi is 90.8 percent of the theoretical maximum (131 psi) an 8.9:1 compression ratio would provide at sea level.

yes

My motor full rebuild was 121-119psi

Note you should test the Compression with the Throttle all the way down.