#3 cylinder fowling plugs

[hemmah]

Really helpful folks on this forum have helped me to get my 69 911T running well. My car sat for 5 years in a drive way with a cover in poor weather. My 911 engine was rebuilt 10000 miles ago by a Pro Mechanic from Germany. So the engine was right and ran right at that time.

I have worked to get it back to running well but not perfect - #3 cylinder has low compression and low airflow.

______History____________

I took my 911 back to the Pro Mechanic after the 5 year setting to get it started and tell me whats wrong and right. When first started my 911 only had 2 cylinders at 150 psi and 2 were 100 psi and 2 were 90-80 psi. The Pro Mechanic said it was stuck rings and tried 30W oil setting for 2 weeks to free-up the rings. That freed the 2 100 psi cylinders. So #3 and #6 cylinders were at 80-90 psi and the rest of the cylinders at 150 psi.

I could drive the car (that ran poorly) home to continue the work myself. I have enough experience to take from there.

_____________Now_____________

Fast forward to now I have freed #6 cylinder with either MMO or Enginerelease fluid or just running it. I also rebuild the carbs and re-conditioned my gas tank. Now my 911T is running well. The #3 cylinder is still low compression.

I've asked how to get rings unstuck in this forum before with good suggestions. Now I'm asking more complicated questions of this forum.

My questions are could the #3 cylinder problem be something else??

• Is the #3 cylinder problem stuck rings
• Is the #3 cylinder problem problem valve seals
• Is the #3 cylinder problem something else

I am working under the assumption that the #3 cylinder problem is stuck rings because:[LIST][*]Other cylinders had stuck rings and are now freed[*]The Pro Mechanic said that stuck rings are the problem


What I see on cylinder #3 now is:

• Low compression
• Really low airflow going through the carbs
• Fowling plugs with oil deposit
• Popping noise in the exhaust when I idle or drive at low RPMs

Please help,
Steve

[faverymi]

Im not a pro.

I would start re-torquing the heads. It's free.

If it doesn't work I would start with the expensive stuff.

[gshase]

I would say rings. If it is rings you should have excess blow by in the crank case.

[porsche930dude]

have you checked the valve lash and made sure #3 isnt sticking anywhere in the cycle

[E Sully]

Perform a leak down test and see where the air is escaping.

[Deadeye]

Ed is right on here.

Set the cylinder at top dead center on the compression stroke. Pump compressed air into the cylinder with a leak down detector or some other way and you will hear the air escaping. If you hear it through the oil tank fill hole it's the rings, or it could be the exhaust valve or intake and you will hear it out the tail pipe or the carb.

[hemmah]

The compressed air test is a good idea. I'll think about how to do it.

Am added clue is after my oil change the oil turns black quickly. Not sure if this is just cleaning out the engine or the ring blow by.


Thanks
Steve