Where to Start

[Jaykel]

Just purchased my 1st Porsche! It is a 1974 911 Sportomatic Coupe with 54K original miles. Being a bare foot pilgrim I had no idea about the 2.7 engine and or Sportomatic transmission woes. I bought the car in a non-running state for what I thought was a good deal. I did not research anything until the car was in my garage (VERY BAD – DO NOT ATTEMPT).
Appearance wise I would rate the car as an 8 (I am harsh, I know). There is no visible rust and the car had a single repaint (same color) that I suspect involved a frontal impact (hood original color is red as seen by scratches by the hinges).
It is a 2 owner car and it came with service records indicating the following work was done less than 100 miles ago.
Check Starting Problem. Fuel Press off – replace regulator & cold start valve. R & R engine, remove heads for machining – reassemble and adjust. Replace 2 CV boots.
Parts List:
Cold start valve
Hose
Warm up Regulator
CV Boots
Manifold Gaskets
6 exhaust valves
12 valve guides
1 hose
Gasket set
6 piston rings
I heat tube.

Ok ready for the punch line? The receipt is dated 10-01-2001!
All of the work was done 13 years ago after which the car was driven around 100 miles since.
Work performed to date:
Rebuilt pedal box using Bronze kit (removed Mouse nest)
Drained gasoline and replaced fuel filter
Changed Oil and filter
Replaced battery
I can get the car to start but it is backfiring badly. After it warms up it smooth’s out a bit but is blowing white smoke from the tail pipe. The car is 100% stock and appears to have all original CIS components.

Any suggestions what is causing the cold start problems and backfiring when at operational temp?

[E Sully]

Welcome to the forum and 911 ownership. The old gas could have gummed up quite a bit sitting that long, so getting the tank and all the lines cleaned is first order. Besides the fuel filter in the engine bay, there is a filter screen in the bottom of the fuel tank that can get clogged. CIS is dependant on getting a set of fuel pressure gages and setting it correctly, along with making sure there are no vacuum leaks. Yours is an early one, so it has a few less components to check than later ones.
For your reading pleasure:
911 CIS Primer - Index
CIS Troubleshooting for Dummies

[yel911]

Welcome!!! Whatever you do, do not take things apart and toss them, thinking you'll just buy new!!!! Trust me..... Bag and tag. Make sure the calipers aren't frozen. Drain the gas. (there is a plug in the center of the tank) Keep us posted!!! Good luck!!

[Targalid]

Who changed the oil and filter? You? If so do you know how to tell if the oil is too full? White smoke could be oil overfill. This is a common mistake. Make sure brakes work then drive it. Your car looks really nice and it sounds like the previous owner spent a lot of money on the motor. Also, do you know the correct starting procedure for a 74 with a cold engine? This may be part of your rough running on start up. Backfiring? From the intake? This could be because you are not using the cold start hand lever.

[steely]

Welcome and congratulations!

[NeedAJoker]

Congrats...I just bought my first last month, and it sits at the Mechanic as we speak. I think we are in for a world of expense, greatly outweighed by shear happiness every time the garage door opens.

[Jaykel]

I suspect the white smoke is caused by an overfill. I purchased the 101 projects book and see that I should not have added any oil until the car was at operating temperature. Rookie mistake of checking oil level prior to the 1st start. I ran the car for 10 minutes or so after adding oil. I am confused because I have since change the oil using the book to ensure it was right. Where does the overflow go? Should it be gone after draining? Did I Damage the engine? FYI the backfiring has subsided and the engine is running very smooth at idle but it is still billowing white smoke, how long will that last?

[Newfie911s]

Check for vacuum leaks, CIS is very picky with vacuum leaks.

[yel911]

Congrats...I just bought my first last month, and it sits at the Mechanic as we speak.

If you can spin a wrench, this forum is priceless.

[JeremyD]

congrats = 1974 is a great year for these cars.

[Targalid]

Most people agree that after an oil overfill, the car must be driven for at least a half hour to get the engine hot. Best done at night so as not to alarm the neighbors. The oil will burn off the heat exchangers, cylinders and other hot parts of the engine. Don't feel bad. I did the same thing when I first started my "new" 911. I think everyone has at one time or another. Have fun with your new ride! Have you studied up on your cold start lever? If it runs a little rough, try some injector cleaner such as Techron before you fiddle with the CIS.

[74-911]

As far as problems with the 2.7L engines, the main problem with '74 2.7s was valve guides and the top-end rebuild done on your engine in 2001 should have fixed that problem. You should have the 11 blade fan and with no thermal reactors, the '74 2.7s ran much cooler than the '75-77s (as a general rule anyway).

If your leak down numbers and compression are OK, you should have no problems with your 2.7. If your '74 does not have an external oil cooler in the passenger side front fender, this is one area you might want to address, particularly if you live in one of the warmer climate areas of the country.

The suggestion to put a bottle of Techron in your fuel tank as a starting point for any fuel injection issues is highly recommended.

And by the way, with the exception of the fog lights, that could be my '74 sitting on the trailer in your pictures... great looking car I might add