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I recently installed the vacuum advance back into a 070 distributor. It had been missing since the car was purchased and the breaker plate was secured to prevent movement. The problem I am running into is the vacuum can is either up against the plenum or against the coil bracket depending on which gear tooth is engaged on the cam to achieve approximate timing. Reading previous posts on the dimple subject and the way it was configured when I pulled the distributor, the dimple on the drive gear is oriented toward the tip of the rotor. Is this the standard orientation for the FI distributor dimple or was it a special case and configured 180 degrees opposite?
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Other factors
The dimple was originally aligned with the rotor tip on FI cars too. However, there are other factors in a used engine that may require you to turn it opposite the rotor tip in order to orient the distributor properly in the block.
I'm talking about slack in the timing chain or off-spec tolerances in a replacement timing set or aftermarket cam. You could even have a replacement distributor shaft or bottom gear that is a little different from the assembly line part.
I would turn the gear 180 degrees and reinstall the distributor. There isn't enough clearance between the plenum and coil mount to time your engine any other way. -
Re: 65 FI Distributor Dimple
Joe, I've run into this exact problem several times over the years and finally decided that indeed, the F.I. distributor gear is installed in the opposite position. In the early 70's when the service 070 distributor was still available at a reasonable price from GM, it was easier and cheaper to replace an old worn unit than it was to rebuild the original and I vividly remember having the exact problem that you describe. I knew that the rotor tip should point to the drill start, or between two teeth, on the drive gear on all non F.I. distributors but if an F.I. distributor was assembled that way, the timing could not be set properly. It seems like the service units that came out of Delco in the late 60's were all assembled in the normal clock position for non F.I. The original distributors had the odd reverse installation and the only way the timing could be set was to rotate the gear on the new replacement unit 180 deg.
I've run into this on some pretty low mileage cars so I really can't imagine there being something being that worn inside the engine to cause this and these cars ran too well after the new distributors were installed to have an internal problem.
I seem to remember having this problem mostly when installing an 070 replacement in a 63 but I can't think of any reason why it wouldn't be the same problem on 64 and 65.
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Re: 65 FI Distributor Dimple
The Delco drawings for the 063 and 070 distributors both have the same note on the installation of the drive gear - "Mark on gear in line with rotor segment"; same note that's on all the non-F.I. distributor drawings ("Mark" is the "dimple" on the cylindrical portion below the gear teeth).Comment
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Re: 65 FI Distributor Dimple
This thread got me curious. I checked all three fuelie distributors I have which are out of the car. A '62 unit with 50 miles on it, a '63 with maybe 20,000 on it and a '64 with unknown history. All have the rotor in-line with the dimple on the gear.Comment
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Re: Thanks
Thanks for the input guys.
JoeComment
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