396 distributor / vacuum advance

[Bill W.]

A few months ago there was discussion about 396 vacuum advance numbers . At that time the only dist. I had at home was from serial number 16120 and it had dist 093 with vacuum advance # 355 . Today I removed the dist. from #17346 and it has dist. # 093 with a 355-15 vacuum advance . The fifth edition judging manual says it should be a 6201 . Has this been changed in the new almost done 6th edition ?

[Page C.]

Re: 396 distributor / vacuum advance

Hi Bill,
Old Delco distributor & vacuum units book list the list the vac for the 1111093 distributor as a 1115355

[Wayne M.]

Re: 396 distributor / vacuum advance

I have 3 of the old Delco test spec books DR-324S-2 (1964-66; 1964-'68 and 1964-'76). I agree with Page on the '355', and it does not change over the period 1965 thru 1976 [service, I assume].

P.S. I wonder if the 6th ed. of the '65 TIM&JG will show the 1116238 rather than the 1116236 for the base engine ?

Hi Bill,
Old Delco distributor & vacuum units book list the list the vac for the 1111093 distributor as a 1115355

[Wayne M.]

Re: 396 distributor / vacuum advance

P.S. Gets a little more complicated: Colvin's '65-69 Chev book calls for 1116236, then ...6201, then ...5355, then ...5360. Says he took these from original Delco blueprints.

It gets worse: checking my P&A30 parts catalog, (sheet revised 1st May '65), 1111093 distr. takes 1116163, for both 396 Sp. H/Per. w/T.Ign. for '65 Passenger and Corvette. This vac advance does not appear in the 3 Delco spec booklets I refered to in my previous post (nor does the 1116168), so they may have been service only.

[Duke W.]

Re: 396 distributor / vacuum advance

The tune-up specs published in Corvette News back when the L-78 was announced don't give the VAC part number, but the specs jibe with the 201 15 that was used from in '62 and '63 and some later engines like L-71, but it was not available in service for very long. The ..163 became the GM replacement for the ...201, and it's a boat anchor - won't even meet the Two-Inch Rule for a base engine.

A lot of GM parts consolidations were done without much engineering analysis. Fan belts are another where often a longer belt became the service replacement, and they cause no end of problems. The aftermarket keys off what GM does, so ALL the parts books end up with an ill-functioning or ill-fitting part.

Whatever the true story the best thing to do is install a VAC that meets the Two-Inch Rule (the ...201 didn't on L-78), which would be the 12" B20 or B26, which is very close to the ...355. At least L-78 has full time vacuum advance.

The VAC is worth three points - two for originality and one for condition, so in chapter judging I might deduct one point if it's not the correct OE number, assuming you can actually see a number on the VAC mounting bracket. Sometimes it's partially or completely covered by the dist. cap. If I can't see the number then no deductions as long as the plating is in good shape with no serious pitting or visible rust spots.

Duke

[Peter L.]

Re: 396 distributor / vacuum advance

Bill - The part number of the Distributor Vacuum Control in the Chevrolet Parts & Accessories(P&A) Catalog changed almost as fast as the 396. If original vacuum advances were the 1115355 my 1966 P&A, Revised November 1, 1965 lists the following:

65-PASS., CORVETTE (Sp. H/Per, w/T. Ign.) (396) -- 1116163

and it also lists the following for the 65 PASS:

65-PASS. (396) (exc. Sp. H/Per.) --------------------- 1116238
and
65- PASS. w/Sp. H/Per (396) (exc. T. Ing.) --------- 1115355

It's interesting that within a relatively short time there was this change. It certainly shows me that while the P&As might a good resource you need to do more research to verify & information original Production parts.

Who says working on old cars isn't FUN

Pete

[Wayne M.]

Re: 396 distributor / vacuum advance

Pete -- just came across this TSB; may not relate directly to base engine Corvette but shows the solution. First mention of the "163" can, refers to use as 'service'. Pity the team trying to update to 6th ed. of the '65 TIM&JG. (excuse the small image)

[Peter L.]

Re: 396 distributor / vacuum advance

Wayne - The image read fine. I wonder if there is something like that for the 396 engines. I'll look thru the TSBs I have. I hope so because that would like answer some questions & inquiring mind want to know. Pete

[Jeff P.]

Re: 396 distributor / vacuum advance

I also have a 1111093 but with a B26 vacuum advance on it. What would be the equivalant GM part number?

[Duke W.]

Re: 396 distributor / vacuum advance

Read post #5 - CAREFULLY!

Duke

[Bill W.]

Re: 396 distributor / vacuum advance

Pete my 65 BB was built in May .

[Jeff P.]

Re: 396 distributor / vacuum advance

Duke, The B26 pulls about 12"? This vac would work good on a L-79. I'm trying the figure out what you mean about the Two Inch Rule. Any past threads on the calculations to achive this Two Inch Rule?

[Mike Z.]

Re: 396 distributor / vacuum advance

I have worked on dozens of #093 distributors and have found all early units (65 396CI) had a #355 vac, which agrees with my copies of original design blueprints (best source for OEM P/Ns & data in my opinion), and Delco Specs. I have found later (66 427CI) original units all had #360. The design blueprint date for the #360 vac is 5-11-65, which is prior to the end of the 65 run; however, in my experience, I have not seen a #360 installed in a #093 earlier than late August. Although the normal delay; design date to seeing a design change on the line is usually about a month, in this case I have not experienced this change earlier than late August. So, this delay could be due to the use of what was in inventory (#355), or to coincide with the model/engine change; or, simply my lack of sufficient sampling in the 50+ units I have worked on (have 5 in inventory). The design blueprints do not indicate anything re: #163, therefore, I suspect it to be a service replacement, as indicated in the Service Bulletin Wayne posted. #201 could also be indicated as a Service Replacement, as it was used on HiPo BB motors from 67-71. The B26 is an aftermarket Echlin piece.
Michael Z

[William C.]

Re: 396 distributor / vacuum advance

Forget the GM parts books for distributor info, use the "Delco Remy Test Specifications" books for reference on Distributor advance and vacuum modules. The 1111093 used a 1115355 (stamped 355) at least per the 1964-1977 Edition. That is also confirmed in other period references.

[Duke W.]

Re: 396 distributor / vacuum advance

Duke, The B26 pulls about 12"? This vac would work good on a L-79. I'm trying the figure out what you mean about the Two Inch Rule. Any past threads on the calculations to achive this Two Inch Rule?

Do a search and download and study the following pdf. The Two-Inch Rule is a simple, but important concept to understand if you want a proper spark advance map.

http://www.metroli.org/pdf/2012%20Nationals%20tuningseminar.pdf

Duke