Series 3 Low compression after rebuild, advice?

Chaps, I bought a diesel series 3 a while back, it wouldn’t run due to low compression (circa 130 psi) we, well mostly a mate with me handing him spanners! Did rings, head gasket, honed bores and lapped valves, compression was upto 390 psi and it started well.
I drove it to a local mechanic and performance was poor, 2nd gear up a fairly steep hill, when I got there it was difficult to restart, he did a compression test and all cylinders were down to approx 230 psi.
Any thoughts on what would cause a loss of compression on all cylinders?
Thanks
G

Why did you need to take it to a garage? Was there another problem?
Are you sure the valve timing is right and the tappets are set?

It went to the garage to have the brakes checked over.
Nothing changed between recording 390 psi and 230 psi apart from a 5 mile drive.

I'd do another 'wet' compression test along with a leak down test.
If the pistons and rings were well oiled to help fitment, this could impact the initial compression test

I'd recheck the tappet clearances again, in case the rocker shaft etc is well worn

I reckon your original compression test was wrong, the second reading done by the mechanic is closer to what it would have been from the factory.

Col

Colthebrummie said:

I reckon your original compression test was wrong, the second reading done by the mechanic is closer to what it would have been from the factory.

Col

Click to expand...

It’s a diesel !

I thought compression should be just over 400, but I'm not a diseasel expert

Solstice said:

It’s a diesel !

Click to expand...

Oops, my mistake, I never noticed that in the original post. My teachers were right all those years ago, I must pay more attention.

Col

What head gasket did you fit?

Sounds like it didn’t like the trip much.

I would agree with @kermit_rr above and do another "wet" compression test and see if you get the higher figures again.