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Engine Rebuilt & Low Compression on all Cylinders, Cause?

Hi, I own a chevrolet optra 2007 with 200.000 KM,
I did an engine rebuild & yesterday did a compression test to check the work done & found out it was low on compression on all cylinders.

- Cyl #1 135
- Cyl #2 75
- Cyl #3 135
- Cyl #4 65

We did a wet & dry test, after adding the oil I got:

- Cyl #2 100
- Cyl #4 90

What I bought:
- New Pistons & Rings
- 10 new valves (they were broken because timing belt went off). 5 intake valves & 5 exhaust valves. The other 6 were ok and were used again.
- 8 Guides for exhaust valves, mech told me only 4 exhaust guide valves were bad, but decided to change all of them instead because I got the set of 8 guides.
- Head Gasket
- Valve Seals
- Oil Pump
- Water Pump
- Timing Belt

The valves job were done by a professional, and I still I got these results.

Mech thinks theres a problem with the cam / valves, but from what I read it seems more likely the piston rings are at fault because of the results I got after the wet test.

Mech wants to take down the cam and have it checked again & mount it again to re-check the compression.

Mech says that it if were pistong rigs, the wet test results would be WAY higher.

I don´t really want to buy a new head gasket & valve seals & have the valves job done again....for nothing :/

If it doesn´t work, mech would have to take it all down again to check the piston rings & I would have to buy the head gasket & valve seals again....meaning more money....

With these wet and test results, what do you guys think? What would you ask the mech to do?

Any help will be really appreciated!!!

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Well done area for discussion.
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in future

buy non-interference type engines. Does this use hydraulic lifters, or mechanical? Did you change camshaft with higher lobes? Did you use a thin metal head gasket, or a composite type?

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