parrothead

5, 6, & 7 report over 70% leakage on a leakdown test. The culprit is from the intake valves. Based on what I've read this is either due to bent valves or deposits on the valves. Any other thoughts? Whats the best way to begin diagnosis?
Thanks
- Eric

Jim bailey - 928 International

It is probably bent valves . The Euro CIS car uses a centrifugal cutout ignition rotor to prevent overrevs the more common USA rotor has no such feature so the Euro CIS will rev until there is no tomorrow when fitted with the USA rotor . That may well have bent some valves . The opening and closing under spring pressure makes build up of deposits to the point that it holds open a valve and leaks very unlikely . The 911 guys did believe that carbon build up on a spark plug might fall down on to an open valve and get caught thus messing up a leakdown test .

parrothead

Jim, Thanks. Thats what I am suspecting as well. I should know in the next few days. Its odd (to me at least) that its three cylinders in a row.
- Eric

Jim bailey - 928 International

Typically one cam is advanced or retarded a bit just by the spacing of the teeth on the timing belt . You should check the camshaft timing before pulling off the belt .