Hello,

I own a Range Rover 322 4.4 tdv8.

I measured the compression of the cylinders (dry, 10 sec) and got a result of 330-350 psi with a warm engine .

Does anyone know how much this should be or have you measured it on your vehicle?

On an older car that’s done a few miles I’d be more concerned that they were all similar rather than comparing them to the factory original specs.

I think there’s a factory workshop manual in the Wiki on here, you’ll likely find the specs in there.

David. 2002 4.6 Vogue SE - Alveston Red with Lightstone Leather
2007 Range Rover Supercharged in Java Black with Ivory Leather
2012 Range Rover 5.0 SC Autobiography in Indus Silver with Jet/Ivory Interior
2012 Range Rover 4.4 TDV8 Autobiography in Baltic Blue with Sand Interior

What matters with compression is that they're all within tolerance of each other, not what specification said 100,000 miles ago. 2015 Range Rover Autobiography 4.4 SDV8

To a point, yes - there needs to be a baseline for things to 'work' but the high to low isn't bad. What matters is the relative compression and cylinder contribution. It's also not good to have the highest contributor next to the lowest contributor in the firing order. ~300psi is pretty much the low end of diesel compression limits at 16.1:1 and 60psi is generally the acceptable maximum high to low range variance.

So what is the problem that led to the question?

The problem lies in the crankcase ventilation and pressure.

The engine has been overhauled, but as is known, original parts for the lower part of the engine are not sold.

New pistons with rings have been installed, there is a question about whether they are tight enough.

In that case a cylinder leakage test would be most appropriate, the compression figures are not a good way to determine the rate of leakage as they rely upon movement.