Early 1969 911 help needed (distributor related)

[Jerry L]

CFI = Bruce is a great guy and would be at the top of my list if you need to have repairs!!

Regards

The stock distributor has a dual advance mechanism - it purposely has a flat spot. The advance has two sets of weights to make the stepped curve.
Attachment 474243

If you have a stuck weight or broken spring or the shaft is binding, any of those things can cause the symptom you're describing,

Your best bet is to remove the distributor, disassemble, clean, and carefully reassemble. Be sure to get new points, cap, and rotor. Re-install and test.

There are great videos on YouTube of the disassembly process. Check this website for a wealth of early Bosch distributor info:http://www.sparkingplugs.com/9.html

hope it helps!

[Vintage Racer]

Many Thanks for your help,
I'd like to keep this car with the old original ignition system. It's a street car with an exemption to emissions testing. It gets around 15 Mpg on a normal active day.

I found the YouTube videos (thanks). This car has no notable distributor play as I see it. I don't own a vacuum testing device. My old way of testing this is to rev the engine slowly while watching the timing light to see were and when the advance kicks in.

It's my opinion that this car already has a modified advance curve that kicks in before the factory specs.

As I said, the car pulls hard from idle to ~ +/- 6500 Rpm which is below the recommended Rpm of 7300 Rpm.

[daniel911T]

Vintage Racer,
Aside from testing with the timing light, what steps have you taken so far?

Let me restate your problem to make sure I understand you. Your car starts and runs fine. When accelerating, the engine runs strong and normal up to 6500RPM, then loses power up to 7300. Under a timing light the timing signal (position of the timing mark) is unstable. Is that through the entire RPM range, or only some places? Is this an accurate restatement of your issue?

It would still be helpful to have the distributor number. I'm almost positive that the one pictured is not original to a 1969 engine.

We will figure this out!

[edmayo]

Is this the car Doc Jewell had?

[Frank Beck]

Is this the car Doc Jewell had?

Had?

.....

[Vintage Racer]

Aside from testing with the timing light, what steps have you taken so far?

The distributor cap and points where replaced. I adjusted the valves and checked the plug wires (they looked new). It was running rich so I did switch around the jets with the help of some nice guys in Texas (one was Ed).

Let me restate your problem to make sure I understand you. Your car starts and runs fine. When accelerating, the engine runs strong and normal up to 6500RPM, then loses power up to 7300. Under a timing light the timing signal (position of the timing mark) is unstable. Is that through the entire RPM range, or only some places?

It would still be helpful to have the distributor number. I'm almost positive that the one pictured is not original to a 1969 engine.

Not exactly. I try not to rev the engine over 6500 just to be on the safe side. I am sure that it would run well to the 7300 Rpm limit, and I don't see a rev cut-off in the distributor (I think it should be there?).

The problem is a stumble at around 2500-3000 under part throttle. It may stumble and pop under deceleration in that area. It's annoying.

I'll get you the distributor number. I keep the car at a local storage place.
Doc Jewell
retired former vintage racer (improved cash flow immediately )

[Vintage Racer]

...It would still be helpful to have the distributor number. I'm almost positive that the one pictured is not original to a 1969 engine.

On my best days I am a shade-tree mechanic so I know to go to the experts.

First, I could not find the Bosch model number. There was no plate. There were Bosch part numbers. I was hoping that these pictures would help (BTW, it stumbles under load and works fine in neutral).

[edmayo]

My best guess is that you have a mismatch of advance curve, cam shaft and jetting. Try removing the vacuum line and plugging it, see if it makes any difference. I think that vacuum retard distributor was from a 68 air pump engine. What do you have for exhaust?

[NZVW]

Doc, Is the rotor location slot all "munted" or is it just my eyes,, ie, is there 'play' left and right when the rotor is in place ???

Hope you get this fixed under the tree soon

Regards

[Vintage Racer]

My best guess is that you have a mismatch of advance curve, cam shaft and jetting. Try removing the vacuum line and plugging it, see if it makes any difference. I think that vacuum retard distributor was from a 68 air pump engine. What do you have for exhaust?

Ed,
Thanks,
I'll try plugging it. I have a good road to test it. I think that will block timing advance at the lower RPM?

The exhaust is headers with a megaphone so not much not resistance of exhaust gasses. It's rather loud but no problem (see the picture below).

I agree the pictures show a lot of stuff that should be cleaned out of the distributor. No doubt.