low compression

[Saphire]

I went to the mechanic and replaced the head gasket (head resurfaced), changed rings, main bearing, sealings... before rebuild I had excessive oil consumption, and this compression:
1 cyl 7.5bar
2cyl 3cyl and 4cyl. 10.5bar
Now after 1100km I want to check compression and I disappoint
1 - 9.0 bar
2 - 8.0 bar
3 - 9.2 bar
4 - 10.1 bar
All measuring are done on cold engine.
btw engine is m10 1.8
Engine is working fine in general only when is cold running little bit a rough. Spark plugs are clean, engine is not smoking, oil consumption is about 0.3-0.5l.
So should I consider about compression, is the mechanic do something wrong....? Should I do more km and the rings will sit in place. I do first 1000km in very low rpm and low speed.

[Jeroen]

A decent compression test is done with a little temp in the engine and at full throttle. Would be weird if compression has gone down after an overhaul so I'd first suspect tester or test method. Rough running could just be ignition and carb adjustment.

[Saphire]

I have did test again with little temp, of course and full throttle, and compression increase by 1 bar of all cylinder. But then again the second is 8.9 and fourth is 10.7.I must say that to get 8.9 on second cyl. I must turn a key for about 8sec and for fourth one it goes on to 10.7bar for 3-4sec.
I use same tester like I use before overhaul.
My mechanic says that I must wait 3000km and more to get everything in place. Is that have any sense!?

[A.P.V.]

did you have done a hone on the cylinders? Whit new piston rings you need to hone otherwise they new rings will not get the right brake in. It will go without but to make them real fit is wil take a few 1000 miles before you get results.
And when you are going to put more acceleration stress on the pistonrings they will brake in faster.

[stefankj]

Did your mechanic gap the rings manually? could be some difference there, and maybe if the gap on the rings line up straight on all three rings(not 120° apart from the other) you could get results like this.

[Saphire]

He had sad that he wil hone a litlle, but I don't know for sure is he done that. Can he hone to much.?
I left standard sizes, mechanic says that the cylinders are in perfect condition.
I think he do it manually. I know that can be the reason, and another reason which I scary about, that he maybe put ring in oposite direction...
I will wait one more 1000 km and check, what else I can do?.

[Jeroen]

Perhaps I am asking about something very obvious, but the valves, where they kept in the same order, inspected for damages and freshly grinded onto their own seats?

[Saphire]

I didn't grid valve seats they look fine. Before the overhul compression was excellnt on three cyl. and One cyl has broken ring. I will try wet compression to see is there valve problems.

[Jeroen]

Were they removed, freeplay on guides checked, seals replaced? And clearances checked after a few 100 kms?

[Saphire]

Everything checked exepct last one. I will check clearance.

[Peter V.]

Do not read this comment wrong please but It seems to me that the engine overhaul was not a full one. I hear things that had to be checked and done to get everything complete.

[Jeroen]

And if the valves were removed and put back (hopefully in their original locations) without grinding that may be a cause for your lack of compression.

[Saphire]

Many thanks Jeroen, the problem was in valve clearance. Valve clearance was terrible, on some place I can't put 0.05mm.
After I finish, I only measure compression on 2 cyl. (cold engine) It was 10.5bar.!
My mechanic didn't warn me that i must do valve clearance after few 100 km. even I had told him that compression is not good.

[Jeroen]

Phew, good news mate!

[Peter V.]

Good news that it was a simple thing.