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Old 10-14-2012, 04:03 PM   #1
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Default Dropped a cylinder - Help

Begi S4, MS3, 99 head, 94 block, wiseco pistons, eagle rods, yada yada.. "Well built"

Was cruising along, and noticed a "clack" at mid-range load. Babied the car home. Idle sounded fine, minus a weird-ish sucking sound (sorta like.. "fwump"). With the car at idle, pulled the spark plug wires - cylinder 1 made no noticeable difference at idle. Discovered a vacuum port cap had also disintegrated closest to the 1st cylinder runner. Ran a compression test -

Dry: 100 150 155 165
Wet: 115 169 171 180

Fearful of a cylinder 1 lean condition causing that destroyed an exhaust valve, I pulled the head. To my surprise, the exhaust valves look "okay" to my untrained eye. Roughly 20k miles since I've gone turbo. I inspected the valve and seat as well as I could without pulling the valve, cleaned the carbon off the piston heads and inspected the walls - no lip at TDC, no major gouges in the cylinder wall - nothing I could catch my fingernail with anyway.

I filled the combustion chamber with some rubbing alcohol...

It started slowly leaking out of the intake port (hard to picture - but you can see the oil pool.. should've tried with some food dye..) I doublechecked the seat and valve as best I could without pulling them and still can't find damage.

So... Here's some more pictures of my combustion chambers. Can anyone provide me some feedback/thoughts for low compression? The combustion chambers are still a little oily from the wet test, sparkplugs looked to be OK - some brown specks on cylinder 1, but it looked more like soot than detonation.




Since the head is off and I'm probably gonna need work on it anyway, I'm considering ponying up for Supertech +1mm / exhaust valves.. just weighing the benefits vs cost..
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Old 10-15-2012, 01:29 AM   #2
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Took it over to my buddies tonight, and we figured some of it out:

1. Valve lash is all whacky. Can't fit a feeler gauge on some lobes. D0h.
2. Guides are feeling loose, a bit of slop present.
3. Uneven wear mark on one of the valve / valve seats. Probably from the slop.

Time for a rebuild.
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