Mysterious Designations - Centrifugal and Vacuum Advance Specifications

[Henry J.]

At the back of the 68 Chassis Service Manual, in the Specifications section, there is a table of specifications for distributors. In that table, there are columns for centrifugal advance and vacuum advance for all distributors. Above each set of centrifugal and vacuum advance specifications for every distributor, there is a mysterious alpha-numeric designation, having the form C-xxx. For example, C-4626 and C-3955 are the designations for distributor #1111293.

What do these designations mean?

[Joe L.]

Re: Mysterious Designations - Centrifugal and Vacuum Advance Specifications

At the back of the 68 Chassis Service Manual, in the Specifications section, there is a table of specifications for distributors. In that table, there are columns for centrifugal advance and vacuum advance for all distributors. Above each set of centrifugal and vacuum advance specifications for every distributor, there is a mysterious alpha-numeric designation, having the form C-xxx. For example, C-4626 and C-3955 are the designations for distributor #1111293.

What do these designations mean?

Henry------


I believe those series of numbers are Delco-Remy codes for particular and specific centrifugal advance curves and particular and specific vacuum advance curves. I've never understood what relevance they have in a factory service manual, though. However, it might be that they are of use with distributor machines.

[Henry J.]

Re: Mysterious Designations - Centrifugal and Vacuum Advance Specifications

Thanks, Joe. Your explanation makes sense to me, as I had speculated similarly.

[Wayne M.]

Re: Mysterious Designations - Centrifugal and Vacuum Advance Specifications

Henry -- it's much as Joe L. mentions. I looked in a 1964-1968 Delco Remy Test Specifications DR 324S-2 (Supplement to DR-324S and DR-324S-1), under your distr. # 1111293 and there's a # 4626 in a column headed Spec. No. I see that this distr. takes the 1115360 vac. advance, so I turned a few pages to the data on Vacuum Units, and there's # 3952 on that line, under the column labelled Spec. No.

The details of those spec #'s must be in another book.

[Henry J.]

Re: Mysterious Designations - Centrifugal and Vacuum Advance Specifications

Wayne:

Thanks for taking the time to look this up.

Do I understand correctly, then, that C-4626 would be the Delco Remy reference number for the centrifugal advance data presented in the Chassis Service Manual? Stated another way, do the centrifugal advance numbers found in the CSM represent Delco Remy specification C-4626?

[Joe L.]

Re: Mysterious Designations - Centrifugal and Vacuum Advance Specifications

Wayne:

Thanks for taking the time to look this up.

Do I understand correctly, then, that C-4626 would be the Delco Remy reference number for the centrifugal advance data presented in the Chassis Service Manual? Stated another way, do the centrifugal advance numbers found in the CSM represent Delco Remy specification C-4626?

Henry------


I would say the answer is definitely yes. However, the full specifications under the "C-number" might be more comprehensive than those published in the FSM.

[Wayne M.]

Re: Mysterious Designations - Centrifugal and Vacuum Advance Specifications

Henry & Joe L. --- OK; digging into the Delco Test spec book referred to previously, under distr 1111293, reading horizontally [there's about 60 distrib's per page, 8_1/2 pages (by Jan '68). You should see the '64-'76 version .

"Service Bulletin = 1D-151; Rotation viewing D.E = CC; Point opening; Cam Angle 27-31 (note b); Spec No. 4626 (no "C"); Centrifugal Advance: Start, 500 Distrib RPM = 0-2.7 degrees; Intermediate, 600 rpm = 2.5-5; (2nd) Intermediate, 1000 rpm = 7.5-9.5; Maximum 2500 rpm = 15-17; Vacuum model 1115360.

(note b) satisfactory range. When adjusting, set to 29 degrees (gives .016 point opening).

There are about 3 other distrib's listed with spec 4626; they all have the same as above (except 1111169, which uses a 1116201 vac can).

Now, turning pages to the Vacuum Units section: Vacuum model 1115360, Spec No. 3955 (no "C"); Inches Hg to start advance 6-8, Inches Hg for max advance 11.3-12.5, Max distr advance (degrees) 6.4 (+/- 1 degree).

So there may be something additional in the C-spec #'s as Joe mentions.

Do these numbers match the '68 Chassis Service Manual ?

[Henry J.]

Re: Mysterious Designations - Centrifugal and Vacuum Advance Specifications

Wayne and Joe:

Yes, this matches up quite nicely and provides more information as well, as Joe suggested.

The data in the 68 CSM is reported in crankshaft RPM and degrees, so it appears as twice that you have presented, as follows:

Centrifugal advance: 0 @ 900 RPM, 8 @ 1250 RPM, 17 @ 2000 RPM, 32 @ 5000 RPM.
Vacuum advance: 0 @ 7" Hg, 12 @ 12" Hg

I can't thank you both enough for taking the time to look through your reference material. For now, this has satisfied my curiosity but, no doubt, I will have more inane questions in the future. Stay tuned!