Carrera 3.0 engine problems.
 

Hi.

Here’s something for you engine gurus.

We are working on a 1976 3.0 911 Carrera engine that has several problems. Here’s the 3 main ones:

1.
Very hard to start unless timing is set to 5 degrees BTDC, thats 10 degrees away from the 5 degrees ATDC it is supposed to be timed at.

2.
Excessive smoke on startup, both cold and warm, it’s burnt oil.

3.
Spark plugs on 1-3 looks like they have been running for 60.000 miles but the ones on 4-6 looks absolutely like new right out of the box.

It is verified that both 1-3 and 4-5 gets sparks and that the fuel distributor works as it should, sending same amount of fuel to all injectors.

The engine has had a top end rebuild, could it be that one or both cams are out of sync?

This engine has breaker point style distributor and 3 point style CDI.


Any thoughts ?


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one possibility that you are missing the guide pin on the crankshaft? This way the pulley is on the wrong place.....Also did you try moving distributor one tooth over?
Ivan

Double check the following........
 

Check cam, ignition, and valve timing to confirm they are within specification.

Tony

Thanks will do :)


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Carrera 3.0 engine problems.
 

Thanks will do :)

Here’s the to do list for the next couple of days:

Cam timing check
Valve adjustment check
Leak-down test
Compression test
Individual and joint ignition components test
Fuel delivery test, once more


:)


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did the 911 drive in ....your shop, or is it some kind of barn find........

Are you setting the idle timing w/ the vac connected?

Yes Sir :)


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Carrera 3.0 engine problems.
 

Helping a friend with his car. 4 mechanics has tried to time this engine before me and I found quite a few strange "things" done to it that I had to fix.
The next steps now I think has to be to check / perform:

All electric and vacuum components and contact points on the engine.
Vacuum hoses
Cam timing
Valve-rocker adjustment
Compression test
Leak-down
Fuel distributor
Rubber hoses between plenum and runners
Injectors

In "short" find whats what and adjust / repair according to factory spec. / baseline.


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aj aj jaj..4 mechanics;-) you`ll be fine... start with the basics..the list is good..
ivan

btw..do you see if the upper end was apart recently..that would lead to cam timing as Tony suggested

Have you checked the distributor adv curve mechanism, missing soft or soft springs etc

max advance @ 4500+/-

dist installed correctly?, it would be easy to be off a tooth

why is the CDI the later inductive style? but still w/ points, speaking of points, clean and gapped correctly?

The only issue I ever had w/ mine was the cold start valve which needed a bump

Carrera 3.0 engine problems.
 

Have not checked the curve mechanism other than it responds to vacuum. Must check further when we are able to get the engine running.
Dizzie installed correctly.
Was under the impression that the three point CDI is correct for the 3.0 Carrera and it’s breaker point dizzie?
Breaker correctly set to factory spec at 0.35mm.
When we get the engine started we will also be checking dwell angle and adjust if needed.


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Takes 2 mins to put a timing light on it. Failing that, sounds like one cam is off.

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I'd have to go look I still have the one I removed when I started down the 3.6 road, but it probably is 3 wire, just from reading your op I was under the impression that the CDI had been changed to the newer pointless version

I also had issues w/ the wiring at one point and replaced the oe shielded wires w/ braided ss cores and the ends

it seemed to be relatively indifferent to dwell though I always set it on the low end(wide gap if my memory is still good about that relationship)

Thanks a lot Bill :)


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Carrera 3.0 engine problems.
 

Here’s today’s findings.

Cyl. no. 4 valves fully closed when cyl. no. 1 is at TDC compression stroke = no overlap on #4. Both cylinders opens intake at the same time = right camshaft is 180 degrees off.

So it is obvious that somethings is not quite right.
Also found other not so good "doings", so the engine is comming out for a complete check.


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Cam Timing Inspection........
 

While it could be done in situ, having the motor on an engine stand would make your work less strenuous and easy on your back. Work wisely and use a degree wheel. I have done hundreds of trials measuring cam timing over the years using the conventional visual method (crankcase seams) successfully but after using a degree wheel, you will find that the degree wheel method is more consistent, easy, and less stressful than the conventional procedure.

You won’t realize this advantage until you try both methods. Good luck.

Tony

I would check the cam timing...I suspect that you have one or both timed incorrectly.
regards,
al

Thank’s Tony :)


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Thank’s al :)

I found that # 1 is timed correct but #4 is not, the right camshaft is 180 degrees off.


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