1975 2.7l SC engine problems.

[classicsdubai]

Hi Guys,

Firstly I would like to say I am not an expert on porsches and might find it difficult to explain the issue with my car. Kindly please bare with me.

So i have a porsche 911SC 1975, i have been working on with the help of few mechanics from time to time. Over an year ago I bought the car and slowly worked on it to get it started, faced many issues along the way as the engine was dead when I bought it. I replaced the rocker arms as they were broken along with the intake valves and exhaust valves as they were bent. Replaced head gasket and when it came to putting the timing chain back on I realised it was nearly impossible. I contacted a mechanic at the porsche service centre in dubai who was kind enough to help me out and put the timing chain on with the help of some special tools. I then faced the problem of the fuel plunger system and replaced the gaskets in it, so the fuel injectors were working fine. The car started finally. This all happened during the course of months. The car was fine on idle, didn't shut off infact it would start up as soon as i turn the ignition switch only consisted the problem of the engine missing and backfiring when the throttle was pushed in.

It finally came down to driving the car a few weeks back and the ignition easily cut off while reversing. When putting The car in 1st gear the engine would respond with jerks "missing" on 2nd gear it became worse. So decided to take it down to the local garage to see what could be the issue. They suggested that the sparks plugs needed to be changed as a few had turned black.. and replace the ignition distributor rotor. Did that as well.

Now i have started the engine and it dies off as soon as i let go of the accelerator pedal. Dont know what has gone wrong? however there is no backfire now. I bought a carburetor cleaner and did the spray test on the rubber hose on the manifold and no vacuum leaks spotted however when i sprayed on top of the cylinders connected to the engine there was leakage on all 6 cylinders ( i have not removed the engine cover).

What do you suggest I should do? Or look into something i have missed out on? Im thinking of cylinder compression test?! Help would be greatly appreciated!

[47silver]

You may have various concerns you need to start with one sysetm at a time:
1. did the shop know what they were doing when they put the timing chains on? did they know how to time the cams?

2. You mention injectors is the induction system continous injection (CIS)? mfi? Each require a different method of troubleshooting.
3. did the shop know what they were doing putting the timing chains on teh cams with the correct timing?
4. Did you adjust the valves when cold?
5. did you adjust the points and put the timing close?

[classicsdubai]

Hi silver,
Firstly thanks for your reply, secondly yes the cams were times properly with the installation of valves and rocker arms because as I mentioned earlier it was done by a senior mechanic at porsche service centre, the company which is the only authorise dealer of porsches in dubai. No one else could do it around here.
As for the ignition distributor timing, that is what i am thinking is at fault. What tests do you suggest?

[Walter_Middie]

classicsdubai,

Your problem could be very simple, and it could still be somewhat complicated. From your repairs so far, it looks like the engine had a cam timing issue - if you had to replace rocker arms and bent valves.

Do you know what caused these issues? Was the cam chain broken? Did the cam timing slip due to worn out chain tensioners? What happened?

If it were my engine, this is what I would do:

1.) Adjust the valves

2.) confirm cam timing. With a "Z" block and dial indicator, you can check the cam timing in about 30 minutes. Just measure the amount of #1 intake valve lift at Z1.

3.) Confirm that you have enough clearance between the valves and the pistons.

4.) Check the ignition timing at idle and at 6,000 RPM

If the above are all OK, and you have good spark plugs, wires, points, distributor cap, and rotor, then you will need to get a fuel pressure tester, and start troubleshooting the CIS system.

There could also still be vacuum leaks - especially the seals that hold the injectors to the intake runners. Mine were bad after all these years, and replacing them made a huge improvement.

[fred cook]

The first year for the SC is 1978. Also, all SC engines are 3.0 liter. Your problems may be caused by setting adjustments to the wrong specs.

[Walt Fricke]

Fred - Europe got the 3.0 engine before 1978. Leaving aside the racing RSRs, the 73-4 3.0 Carrera RS had mechanical fuel injection. The 76-7 Carrera 3.0 had CIS. Bruce Anderson's book doesn't list a 3.0 street motor for 1975, but his could be either.

[unclebilly]

This is a mess. Surely there must be a Porsche specialist in Dubai?

If it runs, you can't be far off but there is too much confusion posted here to be of much help.

You replaced a head gasket? Really?

[Bill Verburg]

Originally Posted by fred cook

The first year for the SC is 1978. Also, all SC engines are 3.0 liter. Your problems may be caused by setting adjustments to the wrong specs.

The timing decal in the engine compartment of the early '70s 2.7 had an SC internal code
here's an example


That is only an internal engine code and it has nothing to do w/ the model or engine type
in '75
the n/a models would have been
911
911S
911Carrera

engine types would have been, all these have CIS and 2.7L mg. block motors
911/41 for Row 911
911/42 for RoW 911S
911/43 for US 49 state 911S
911/44 for US/Ca 911S
911/46 for RoW 911 sportmatic
911/47 for RoW 911S sportmatic
911/48 for US 49 state 911S sportmatic
911/49 for US/Ca 911S sportmatic

the first 3.0 was the '74 Carrera 3.0RS only a few of these were ever made
the first RoW 3.0 that was generally available was the '76(and later '77) Carrera 3.0
the '74 Carrera 3.0RS used 911/77 based on the 911 RSR racing al. crankcase
the '76 77 Carrera 3.0 used 930/02 engines which were based on the 930 aluminum crankcase