911 t 1971
 

I just bought this car the engine is popping back through the carbs. They are zenith carbs. Some one has put electronic ignition on the car. The car sat for several years inside. I was going to change rotor and dist. Cap, checked the plugs they all look new.
Could this be timing, carbs gummed up or the worst worn cams. I am no expert so I am looking for someone to tell me the best route to discovery as to what the issue might be. 90,000 on odom.

By the way I am also looking for a pair of original seats for this 1971 911 t should anyone know where to find some

With all due respect, I think your best course would be to take it to someone who is an expert. If you are not familiar with diagnosing automotive problems it's very easy to make things worse and that can be disheartening and expensive.

regards,
Phil

I sent you a pm.

I agree I am not an expert, but I did decide to go on and and pull the valve covers and check the valve adjustment. Set the number one at TDC and found the top rocker okay but the bottom tight. It is my understanding they they are both to be the same .1mm.
Tell me if I am correct here with a foreign order of 162435 I should start with 1 set both at .1 mm role the crank over till 6comes to top, adjust top and bottom then role over the crank till 2 is at the top, set and so on. If this is correct when I rolled it over to 6 the bottom rocker was tight. It appears clear to me that the valves need to be adjusted and that being the case if they were out of wak enough that could explain the air popping back through the carb, would you agree?

Popping back through carb should not be caused by tight exhaust valves....intakes yes.
Setting the valves is a good thing...and by your post...it looks like you are doing it correctly.
Just make sure you are at the correct place on the rotation...because both valves on one cylinder can be closed at 2 points in the rotation.
Bob

Actually, in each cylinder, both valves will only be closed at TDC only once in two revs of the crankshaft.

Observe the distributor rotor. If it points to the spark plug wire leading to the cylinder to adjust, both valves should be closed and ready to adjust to the specified valve clearance.

Sherwood

Thanks sounds like I got a couple people who know what they are talking about. With that do you have any other suggestion on what the cause may be for the popping back out the carbs. I know it is one thing at a time I am just looking for suggestions as to what the things are

What is a pm
Clearly I am new to this but I need to learn I am going to have this car a while

PM means Private Message. You should receive an email notification to pick it up on your Pelican page. Enjoy.

Take the carbs apart and clean every orifice and jet.

If the car (and carbs) sat for a while. Don't do anything else until you pull them apart and clean them. Jets are smaller diameter than other makes and clog easily if not kept clean with good filtration. However, dried gas will clog jets easily.

I would do a full fuel system clean and flush. Including the tank, lines, change filters, clean pump, etc. Start fresh. You will be rewarded.

btw, popping through the intake usually means its lean. Don't drive the car too much as you risk burning a valve.

Now we are getting somewhere. I resurfaced the valve covers and got new gaskets, adjusted the valves and put it back together. No oil leaks and it runs a little better. Can I get a diagram of these carbs on line and I assume I need to get a rebuild kit and take one apart at a time. Can you direct me in reducing the lean running, making richer. It may sound dumb but a little sea foam and adjusting and making richer might do the trick, no?

Zenith carbs
 

I would second the suggestion to rebuild the carbs. Today's fuel does not store very well, and does turn to jelly if left standing too long. The Sea Foam will help, but rebuilding the carbs will give you the most improvement.