What the compression should be on 3.5L or 3.9L?

[Eugene]

Hello. I got recently "parts 1991 Rover" Runs, but no muffler and plates, so I can't drive it on the road. It has a 3.9L motor. Would you know what the compression on 3.5L ( that's what I have now) and 3.9L should be in case I need to swap engines in the future? Thank you for input.

[Savannah Buzz]

Old rovers are covered in the free download of shop manuals called the RAVE - see link below. In workshop manual will have procedure and values for compression check, etc.

[Eugene]

I had no luck finding it there, maybe I am doing something wrong. In search box, it will only list compression ratio.
The engines have over 100K on them. I was hoping someone with this same dilemma would chime in for more "hands on experience".
Eugene

[Savannah Buzz]

From the RAVE shop manual for the 4.0, should be close (older engines are usually off quite a bit in one or more cylinders):

CYLINDER COMPRESSION - TEST
Equipment:
Compression pressure gauge
Test
1.

Start and run engine until normal engine
operating temperature is achieved (thermostat
open).

2.

Remove all spark plugs.

3.

Disconnect both coil negative (WB) leads

4.

Insert compression gauge, crank engine until
reading stabilises.

5.

Expected readings, throttle fully open, battery
fully charged:
8.31:1 = 10.2-10.9 bar, 150-160lbf/in2

9.35:1 = 11.5-12.2 bar, 170-180lbf/in2