Need compression advice - 69 911E sitting for 35 years

[911heaven]

Dear Porsche friends, I am not a new guy, yet not a regular forum guy. I mean, I live in Japan, so most of the time when I have time to get on the forum due to time zones they are off line doing maintenence. Moreover, I am pretty busy most of the time working, or if not, working on this 911E in a remote area in the mountains far from my home, about 1.5 hours, so I get up there on weekends and time goes too quick before I have to come home for the work week, so please bear with me.

I did a compression check today with a snap on tool. There is low compression in 3 cylinders. Let me give you the numbers as read off of the snap on compression guage:

cylinder number

1: 140/950
2: 130/900
3: 63/400
4: 140/960
5: 108/740
6: 95/660

Looking at the spark plugs after running for a bit, they look like this when I pull them:

Cylinder number

1: great shape
2: carboned up/black
3: plug always clean, but wet looking
4: plug black but cleaｎ
5: plug black and a little carbon/oily maybe
6: plug a little black but pretty clean


I realize there could be so many variables here with etc. etc. so just let me give some back drop to the scenario on the motor. I have had the car for 1.5 years, but only started to work on it in March of this year. From service records the last time it was on the road was 1975, so sitting for several decades without running. I spent about 5-6 weeks this past summer with it, lots of cleaning up everywhere. Here is a synopsis:

1. repaired floor pan front of the gas tank
2. spent 10 days on original gas tank, finallay gave up and used later tank I had in storage, derusted it, sealed it.
3. flushed out the fuel lines, rust remover, alkaine, plus flushed out with fuel.
4. had the electric fuel pump overhauled via Fuel Injection Corp.
5. changed out the return tubes, collapsable from Pelican
6. new gaskets in sump area.
7. new valve cover gaskets
8. new fuses, and lots of cleaning on terminals with contact spray etc.
9. Lots of sand blasting rusted parts or cleaning etc. etc.


3 weeks ago the motor fired up. It idles fine but at about 500 rpm. working on different oil leaks and have most solved. There is some back firing, but not that bad.

I am thinking that the low compression cyliders are the culprit so far and think that it is due to the long 3-4 decade sit with some cylinders valves open in a moist country. I am thinking that those valve or valve seats have some rust which is not allowing them to close enough to get compression. Moreover, I thought that just running the motor for a long time might bring up the compression on those cylinders.


I sure appreciate you all and the advice you experts can give. So far anything I have searched on Pelican has been rewarding and you guys are experts and enviable. I have never been a motor rebuilder or tuner. As many 911s as I have had I never got into doing it myself. I want to do it myself for a change and with your help I may do that. I have been buying plenty of parts from Pelican these days.

Much obliged,


Bernard

[Porboynz]

If the oil pressure is OK and you have no sticking valves I would drive it for a hundred kilometres, swap out the oil and drive it some more only harder. Follow this up with another compression test and plug inspection, then use a leak down tester to discover the cause of any remaining low compression numbers. A tear down may be on the cards but just maybe you will get lucky. An engine that idles OK is a good sign, but that #3 is real low.

[Porboynz]

How about a photo of the 911 and didn't the Blossoms do well at the Rugby World Cup? I have seen some very interesting 911's come out of Japan to NZ, old race cars, all sorts. What's Japanese for Barn Find?