I have a xflow 1660 with piper 285 cam and twin weber 40's and uprated stage 2 head ( 42mm in/34ex). in 2011 it was rebored and fitted with 1300 HC +60thou pistons and new rings the compression test showed
Cylinder pressure test – Hot 03/09/11
1 2 3 4 173psi 168psi 173psi 170psi
The engine has only done 5,000 miles since then . I had the head refurbished with new guides, recut valves /seats and skimed a few months ago. but it has been idling very rough so redid the compression test.
Cylinder pressure test – Hot 02/01/18
1 2 3 4 120psi 112psi 115psi 118psi
I have set the valve clearances as per piper spec and warmed the engine up and using the same compression tester in both tests.
I was expecting 160/170 psi but these values are really low. Any ideas of what has gone so wrong?
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