Help understanding GM vacuum advance codes
 

I am looking for an original GM advance unit. 1970 Buick GS350. A search finds a lot of them . Most have an M or an MS at the top. Then a three digit number that looks like it could be the last three numbers of the part number? Then a 2 digit number that could be the degrees of advance it gives? Thanks for the help...

What is your distributor number?

As far as your assumptions go, I'd say you are correct. I can look up your distributor in an old (1981) Delco Remy breakdown book and give you the number it lists for the distributor. Only caveat is, some of the sheets have replacement numbers instead of actual O.E. numbers. That's always a possible problem, part numbers superseded by GM.

The 2 numbers are the max advance built into the can.

More than you want to know about this is here:

https://www.crankshaftcoalition.com/...ance_Specs.pdf

The only other thing I will add is always obey the rule and the rule is always use non-ported vacuum.

Engine code SP Dist. number 1112006

Great info !

My Delco book shows your distributor, number 1112006, uses a vacuum advance number 1116210. The sheet is dated 1978 and has about 25 different distributor numbers on it. I have no way of knowing what was changed on which of those distributors that caused that page to be updated. The short Delco number would be D1336. The 1116210 advance unit is stamped MS 210 16. I don't have any Buick parts catalogues from that time, but maybe you can find someone else that does.

Thank you Sir...

Laws are made the be broken. Use what works best. On my car that is ported.

Ported was around since way before anyone ever thought about emissions. Don't believe all the garbage that gets regurgitated on the 'net about ported being for emissions only.

Help understanding GM vacuum advance codes
 

I have a May 1971 Delco TBA Parts Manual showing vacuum advance unit Delco part D 1328 for 70 Buick Special/ Skylark 350 v-8 Hi-compression as distributor # 1112006. It correlates to GM part #1116163. I hope this helps. Don.

Thanks to all . I found one for $ 299.00 . Then I found one for $ 68.00 . Then the winner at $ 29.00 Evilbay search .