Help with "Valve Job" on 2.0

TC911e · 05-13-2009, 04:52 PM

I've just restarted my recently purchased 69 911e after it had been sitting for 15+ years. Unfortunately it's only running on 5 cylinders and #6 reads zero compression (and #2 is down 40% from the rest). I need some help picking the next step. Is there anything I could, or should, do before dropping the engine and working towards pulling the heads?

In Wayne's engine book it made reference to the possibility of carbon deposits flaking off and getting stuck under the exhaust valve on engines that have been sitting for awhile. That seems plausible, but though I've pulled heads and done full rebuilds on other engines I've not been inside a 911 engine and I'm a bit concerned about heading down the slippery slope to a full rebuild I'm not sure is warranted.

It's a one owner car with 85000 miles so other that sitting for years, and whatever's going on with #2 and #6, I wouldn't think it needs a full rebuild. I got plenty of other things to work on on it.

Any recommendations on the path forward?
Thanks,
Tim

Flat6pac · 05-13-2009, 05:29 PM

Run it through a few heat cycles, check for broken springs on the bad cylinders. The heat cycles will possibly loosen the rings imbeded in the pistons.
Take a deep 13mm socket and the pointed air chisel and impact the rockers in case there is anything under the valves.
Keep running the heat cycles several times.
This doesnt cost anything and may help
Bruce

ajwans · 05-13-2009, 06:02 PM

Have you checked your drain plug. If you've got broken rings parts of them
should be stuck onto the magnetic sump plug.

andy

TC911e · 05-13-2009, 06:24 PM

There was nothing on the drain plug when I drained and changed the oil, but that was before the start attempts.

The air chisel to the rockers idea is probably worth a try. If I understand right the idea is just to slip a deep socket over the adjuster nut on the rocker and then bounce it around a bit with the chisel and see if it shakes anything loose. Is that right?
Tim

304065 · 05-14-2009, 05:42 AM

Do NOT take an air hammer anywhere near the engine.

Use a plastic mallet and GENTLY tap, tap, tap on the valve adjuster. If you hit it too hard you will bugger the screwdriver slot or bend the jam nut, so be careful. All you are trying to do is dislodge any carbon that's holding the exhaust valve open, preventing the cylinder from sealing.

Does this engine run? Get it running somewhere outside, rev it to 3000 rpm and pour 1/4 cup of seafoam or water down the #6 stack, slowly enough that you don't choke off the engine. This will be accompanied by a smoke screen from the exhaust sufficient to cover the invasion of St. Lo, so do this procedure in a location where you will not cause a nuisance.

Next, borrow or buy a leakdown tester to localize the source of the problem. This will tell you exactly where the issue is, if you hear leakage from the tailpipe you could have a stuck valve, but it's more likely that you have either a bent valve or seriously broken rings.

The test results don't lie-- see this thread on my 2,0 teardown.

Leakdown Results 1966 911 Normal

Good luck!

TC911e · 05-14-2009, 06:27 PM

Thanks John, I'm proceeding cautiously and looking for ideas on how to proceed. I may give the Sea-Foam a try, but it's still inside and up on the stands right now and I haven't yet tried to make it move under it's own power. I did do the Sea-Foam trick on my son's Accord a few years back and it did produce a heck of a cloud (and then lost a cylinder a few months later).

I haven't tried a real leak down test, but I did make up a psuedo leak tester that would allow me to run air into the cylinder. It's not good enough to get leakage percentages (I never could figure out what orfice size should go between the gauges), but it works ok find where it's leaking. Best I can tell it is leaking out the exhaust (no noticeable flow through the intake or the case breather), but it's not exactly conclusive even with the air line running full open.
Tim