Which 911 motors/distributors run off vacuum advance?

[tommott]

About to start the process of tuning up my 914 with a 6 swap and upon initial inspection noticed that my distributor has a provision for a vacuum line, but does not have one fitted. Also looking around I don't see a disconnected hose nearby and/or a provision on the manifold for a line to originate.

The motor in my car I believe was originally built up from a 2.4 liter case, but could have an array of mismatched parts. Can't say with 100% certainty which dizzy is in my car though as access to the distributor is close to nil with the landscape of a 6 cylinder 914. With this being the case another issue that I know I'm going to be running into is how to see a timing light down in there.....if anybody has some tricks on this please chime in as well.

I figured a search around the board would answer my question, but the info I found has me confused, as it appears that all 911 distributors have a provision for a vacuum line.....Though it also seems that some don't use vacuum advance as well.

[Flat6pac]

The 2.4/2.7 vacuum unit is a retard. The timing is set with the vacuum line connected. For example, I was doing a 76 S and the spec calls for 5 degrees ATDC with the vacuum connected 950 RPM. Disconnect the vacuum and the dist jumps to 10 to 15 degrees BTDC.
The true 914/6 timing is done off the flywheel. The 2 liter flywheel has markings and can be seen down through the notch of the bell housing from the top.
Bruce

[tommott]

Since originally posting this thread I have gleaned that the motor in my car was built off a 911/51 case. According to Bruce Anderson's book this was the 72/73 mechanical injection E motor.

Still trying to ascertain if I should have some vacuum line hooked up to my distributor. One is not connected at the present time, nor do I see a lines coming from the intake manifolds of the now equipped Weber carbs. I'm hoping that perhaps the original mechanical injection and distributor combination utilized a vacuum run distributor, and it was abandoned when the motor was rebuilt and the Webers were swapped on?

[Joe Bob]

Hook up a timing light.....rev the motor and see if you have advance.

[stlrj]

There were no provisions for vacuum lines in either MFI or Webers.

[Bob Kontak]

I also saw a post recently where Early S man said NO vacuum advance on distributors before the SC.

[BURN-BROS]

You can see the brass vac port on the throttle body. They are located on #1 and #4 cylinders on 1972/73 MFI cars. .

Earlier MFI systems had no vac provisions.

The Carburerated cars had vac retard around 1971 and it may have been California only.

[moneymanager]

But, again, it retards, not advances, timing, at least before 74.

[BURN-BROS]

The only distributors that have vac advance are 1980+ SC's and 930's ,everything else is retard.