1970 350/300 Vacuum Advance Control -Correct Codes?

[Clark E.]

20 years ago (before any interest in restoration) I had the distributor converted to breakerless during an engine overhaul. Fast forward to 2014 and concluding a 4 year total restoration during engine start-up, one of the vanes hit the module and broke it. Closer inspection revealed the VAC had also been replaced. Fortunately, I kept what I believe to be the original VAC but couldn't find the section of the AIM that details the part. The markings on the bracket that holds the VAC to the distributor are "MS" followed by "357" (the last 3 digits of the GM part #??) and "20". Are the markings on the VAC correct for this engine? Thanks...Clark

[Mike E.]

Re: 1970 350/300 Vacuum Advance Control -Correct Codes?

The JG spells that out for you on page 64. 357 16 is what that indicates.

[Clark E.]

Re: 1970 350/300 Vacuum Advance Control -Correct Codes?

Thanks Mike for pointing out the JG information. Not sure how I missed it. I've owned this car since 1972 and have to believe this VAC is original to the car. The "357" appears to be an extension of GM part # 1115357 (got this GM # from an earlier Joe Lucia posting) but not sure of the following # 16 as the JG reports vs. the # 20 on the bracket I have. Any thoughts?

[Mike E.]

Re: 1970 350/300 Vacuum Advance Control -Correct Codes?

My 30k-mile 71 LT-1 had the correct number but the vacuum rating stamping was one off from the JG. That's the extent of my C3 knowledge.

[Henry J.]

Re: 1970 350/300 Vacuum Advance Control -Correct Codes?

Clark:

The inventory I have (which I got from Bill Clupper) indicates a VAC flange stamping of 357 20, for both the 1111490 and 1112020 distributors used for 1970 350CID 300HP.

[David L.]

Re: 1970 350/300 Vacuum Advance Control -Correct Codes?

In most all cases the 3-digit stamping represents the last 3 digits of the GM part number ("357" = GM # 1115357). The 2-digit number represents the degrees of advance. I do not know the meaning of the "MS" stamping.

However, there is at least one exception to the 3-digit abbreviated part number. The distributor vacuum control in 1970 Chevrolet, Camaro SS350, and Nova models w/300 H.P. engine & M.T. is stamped "MS", "400", and "15". The GM part number is 1968861. I do not have an explanation. I have 3 original 1111996 distributors from these 1970 models and all have the "400" vacuum advance. The GM part number listed in my 1970 Chevrolet Parts Catalogs (9/69, 11/69, 1/70, and 10/70) is 1968861 in Gr. 2.410. I also have a NOS 1968861 vacuum advance in a once "sealed string box" with the 1968861 GM part number. I had to open the string box to verify my conclusion.

My 1969 Corvette Parts Catalog (10/69) lists GM # 1115357 for the 1969 Corvette (350)(exc. H/Per.) and my 1972 Corvette Parts Catalog (9/71) lists GM # 1115357 for the 1969-1970 Corvette (350)(exc. H/Per., Sp. H/Per.).

Dave

[Clark E.]

Re: 1970 350/300 Vacuum Advance Control -Correct Codes?

Many thanks guys. The Forum is a great place to get an education. My distributor is a 1112020 with "Delco Remy" and an 0 B 5 date code on the band (red side is in) which is approximately 6 weeks prior to the car's build date. Appears 357 20 is correct for this application.

[Wayne M.]

Re: 1970 350/300 Vacuum Advance Control -Correct Codes?

The Delco Test Specifications manual confirms the 20 (crank) degrees. It gives maximum distributor advance degrees = 10.3. (or 20.6 degrees crankshaft).

I have a "357" from a 111109_5G7; 1966 BB passenger, points distrib., and it has a MS 357__20 unit.