Timing Changed without twisting distributor

[1969911T]

1969 911T original engine with Bosch distributor. Had this car for 49 years.

Engine just stopped in the drive way. After checking all the usual actors(new distributor cap, rotor, new plug wires, have spark to plugs, relatively new NGK plugs), still wouldnÂ’t start, but acted like it was barely trying. 12.7 volts everywhere and 50 amp battery charger did not help. Checked static timing with a VOM and found it is about 20 degrees BTC. It is supposed to be 0. I never touched the distributor after it stopped running, so it did not twist by itself as it is tight. The distributor is centrifugal and is mechanical, not vacuum and advances like I think it should when you turn the rotor by hand.
I can twist the distributor to 0 degrees static and try to start it, but before it starts and maybe destroys something——has anyone had this happen? My guess is something twisted inside the distributor.

Suggestions?

I do have the old Marelli and it worked when I took it out, so that is another thing to try

[911pcars]

1969 911T original engine with Bosch distributor. Had this car for 49 years.

Engine just stopped in the drive way. After checking all the usual actors(new distributor cap, rotor, new plug wires, have spark to plugs, relatively new NGK plugs), still wouldnÂ’t start, but acted like it was barely trying. 12.7 volts everywhere and 50 amp battery charger did not help. Checked static timing with a VOM and found it is about 20 degrees BTC. It is supposed to be 0. I never touched the distributor after it stopped running, so it did not twist by itself as it is tight. The distributor is centrifugal and is mechanical, not vacuum and advances like I think it should when you turn the rotor by hand.
I can twist the distributor to 0 degrees static and try to start it, but before it starts and maybe destroys something——has anyone had this happen? My guess is something twisted inside the distributor.

Suggestions?

I do have the old Marelli and it worked when I took it out, so that is another thing to try

Unless the distributor housing moved by itself (loose hold down?), it sounds like the centrifugal weights are stuck in an advanced timing position. Maybe lack of lube. Quick check. Remove the cap, then attempt to rotate the rotor in the CW direction. It should freely rotate and return slightly under spring tension. If not, remove the ignition point mounting plate and inspect. Wait. The weights on the Marelli are in plain view above the points. Take a look.

An advanced timing at start results in early combustion that fights the piston as it tries to rotate over TDC.

Sherwood

[edmayo]

Have you checked for spark by removing the coil wire from the distributor, lay the end next to a ground, and rotate engine by hand to see if you have a spark.

[1969911T]

Don't know why, but two posts started at the same time and the other one explains that the static timing was about 20 degrees ATDC.(not 20 degrees BTDC like I said originally) I had the distributor off by one tooth. Now its fine.

Did find a new Beru rotor for the Bosch distributor would make the car run rough and stall, then not start. Put the old Bosch rotor back in, runs fine. The resistor in the Beru is 1K Ohms, while in the Bosch is 5K ohms. Would this difference cause spark problems? I have an MSD ignition if that makes any difference

[edmayo]

I don't know about MSD because I never use them, but realize the purpose of resistance built into the system is to make the coil increase the voltage to overcome the initial resistance which will then increase the voltage at the spark plug. So if you lower the rotor resistance you could be lowering the voltage seen at the spark plug. The 5K ohm number was normal for Bosch rotors.