Ah-ha!! I found it! No wait, this isn't good is it?

[speedo]

I figured out why this 2.4 was running on 5 cylinders and I wish it had been a piece of carbon keeping the exhaust valve from closing fully. Pulled the right top valve cover off and rotated the engine to make sure the rockers and valves were making contact. So far so good....noticed the gasket looked brand new. Went below to the lower cover, and as this cover came loose and the washers dropped of....something else dropped...the end of the #6 rocker. It appears to have broken off just before the adjustment screw. Couple questions remain...this would mean that the #6 exhaust valve wasn't opening when I did the compression check. But #5 was the cylinder with virtually no compression...could this piece have lodged somewhere and kept the exhaust valve on #5 open...not probable. When I did the compression check on #6 I remember a "popping" sound which I thought was from #5 plug hole...but now I'm wondering if it was actually the compression in #6 cylinder forcing the exhaust valve on the same cylinder open as the rocker which normally would have held it shut was non-existent. Is this a result of missing a shift and forcing the valve back up into the rocker? Do these break due to fatigue or abuse?Can I replace the rocker without pulling the head? I have loosened the rocker-shaft retaining bolt, but it seems the shaft only wants to exit out the end of the head that I can't get to it. Can it be removed either direction? Now I can't get that song outta my head..."one thing..leads to another "!

[john walker's workshop]

mmmmmm, i'd say the valve(s) hit the piston and the weak link broke. tensioner failure, even momentarily, or over-rev. the rockers don't always break. the dead hole in #5 is probably a bent valve. in that case, #5 exhaust rocker would have excessive clearance. like quite a bit. yes, the rocker can be swapped without teardown, and the shaft will come out the easy side, using a crowfoot prybar and a screwdriver behind it to get it moving inward, but i don't think that will fix anything. the damage is already done.

[speedo]

why if the rocker broke on cylinder #6 did it affect the compression readings on #5....there seems to be a lot of free room inside the rocker cover for the loose piece to move around....is a mis-shift the likely way this happened. Really I guess I'm asking....sucks to be me....piston on #6 is probably toast then. But why the problems on #5??

[john walker's workshop]

read my post again. maybe #5 has a bent valve. the pistons usually survive this. did you check #5 rockers for excessive clearance? rockers generally break because the valve hit the piston. the valve can bend as well in the process, and the rocker may or may not break.

[Oldporsche]

This had been my experience:
The exhaust valve gets wacked. The stem takes a hit. The face is bent at an angle and the bent stem portion under the head can break the nose of the valve guide. I know that this doesn't sound good but remember; the broken pieces can be unbolted from the motor.

JW said the magic words: "the pistons usually survive"

Good luck,
David Duffield

[speedo]

Thanks much guys...I'll check the #5 for excessive clearance and/or any movement. When the valve stem bends...does it tend to jam in the sleeve? Or does only the face take the hit. And John ...just out of curiosity, based on your experience, when a shift is missed and a valve takes the hit....which valves end up being the chosen ones more regularly, or is it truly arbitrary?

[john walker's workshop]

a light hit can bend the valve head a bit where it joins the stem, and not affect the guide or cylinder head. a harder hit can bend the valve stem badly which can break the guide boss in the head, or worse yet, the head of the valve can come off and kill the whole engine. exhaust valves usually hit first on engines with the CIS/carrera piston crown.

[Joe Bob]

Sounds like engine pull time....

[A Quiet Boom]

Just a few corrections to the original post since the questions have already been answered. Rockers don't hold the valves shut, the springs do that. Also excessive pressure will not force a valve open, it will hold it even more tightly closed. It's is possible on most engines to remove the rockers and replace the valve springs by filling the cylinder with compressed air through the spark plug hole, the pressure holds the valves in place while the springs and retainers are changed. BTW you'll never get anywhere near combustion pressure with a compression test.

[Wayne 962]

We sell a spring compressor tool that allows you to remove the springs with the engine in the car. It bolts onto the camshaft towers (very useful).

However, #5 sounds shot. My best recommendation would be to do a leak down test. You will be able to hear exactly where the combustion chamber is leaking, and you will then know instantly...

-Wayne

[speedo]

Dropped the motor today. I'll borrow the leakdown materials and check #5 and #6. Since I gotta get in there anyways..I'm tempted to just pull the heads off and see what I've got and what I don't. Exchangers are trash anyways...so they go regardless. Since you guys have been so helpful up to this point...any suggestions for identifying modifications from previous owner as I go in? I mean "good" modifications, not the version that I now need to fix!

[john walker's workshop]

good idea to check cam timing before teardown. both sides, and record it. hard to tell what cams and what specs were used if they're not stock.

[A Quiet Boom]

Originally posted by Wayne at Pelican Parts
We sell a spring compressor tool that allows you to remove the springs with the engine in the car. It bolts onto the camshaft towers (very useful).

However, #5 sounds shot. My best recommendation would be to do a leak down test. You will be able to hear exactly where the combustion chamber is leaking, and you will then know instantly...

-Wayne

Wayne, does this tool allow you to remove the springs without compressed air? or the old rope through the sparkplug hole trick?