C2 Small Block Vacuum Advance Can

[William G.]

Greetings,

I almost hate to ask this question as the topic has been discussed at great length before.....and I have read all the earlier posts I could find. Hopefully someone knows the answer to this off the top of their head.

I've just purchased a rebuilt distributor for my manual transmission, 300 hp 327 and I'm unsure as to the suitability of the VAC which is on the dist. as delivered from the seller (who advertised in Driveline). I've read Lars' and Duke's article in which many VACs are listed by number. However.......the VAC supplied on this distributor is a B-10 and that number doesn't appear on the list. Does anyone know the suitability of a B-10 unit on my engine? My local auto parts stores have no listing for a B-10......so they cannot help. They can get me a VC-171 but for around $30 and I'd rather not spend the money and then throw away a brand new B-10 which might meet my needs. The auto parts stores believe the B-10 to be an old listing which no longer appears in their computer and not available.....but they are kind of guessing, it would seem.

Thanks.

Bill

[Duke W.]

Re: C2 Small Block Vacuum Advance Can

The information I have on the B10 is that it is equivalent to the OE 1115360 that was used on L-72: 0 @ 7", 12 @ 12", and the NAPA part number was V1765SP, but it's no longer available.

It will work okay on a 300 HP/manual, but the B22 (NAPA VC1802) 0@8", 16" @ 15" is better suited, and the should only cost about 10 bucks.

(All the above advance listings are cranshaft deg.)

As a minimum, I would test the B10 with a Mighty Vac to see if the start and stop points are in spec, but it's tough to check total advance unless the distributor is mounted to a Sun machine or on the engine.

VC-171 sounds like a SMP part number and it should be a B22 - same as NAPA VC1802 according to my information. As you should be aware, all these "B-number" VACs are made by SMP, but each "brand" has its own part number.

I think your retailer is charging way too much. Try someone else.

Duke

[William G.]

Re: C2 Small Block Vacuum Advance Can

Thanks Duke.

I had hoped you could kick in with the info I needed.

Much appreciated.

Bill

[Wayne M.]

Re: C2 Small Block Vacuum Advance Can

Check out this eBay auction; the guy has two 1115360 cans for sale (at least according to the Delco boxes). One is stamped B10 and the other is re-stamped 360 over a 373 (and, IMO, looks like a '2' stamped over the 2nd digit of the max. vacuum ).

Call out the judges; check the broach marks . eBay link below

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=330552957879&ssPageName=STRK:MEWAX:IT

[Timothy B.]

Re: C2 Small Block Vacuum Advance Can

William,

I think the correct V/A for your engine is a 1115355 which is the 15*@ 12" vacuum control. Like Duke say's, the replacement B22 is better suited for the 300hp manual engine because the idle vacuum is approx 18" so it's fully pulled at idle but retards quickly.

[Randy S.]

Re: C2 Small Block Vacuum Advance Can

Bill,

I have the same motor and have been using the Napa VC 1802 (B22) based on Duke's recommendation.

On a related matter what did your distributor rebuilder provide for centrifugal advance? The Service manual specs for 1111153 say 26* @ 4100 rpm. Other references show 30* at 5100 rpm.

Randy

[Duke W.]

Re: C2 Small Block Vacuum Advance Can

William,

I think the correct V/A for your engine is a 1115355 which is the 15*@ 12" vacuum control. Like Duke say's, the replacement B22 is better suited for the 300hp manual engine because the idle vacuum is approx 18" so it's fully pulled at idle but retards quickly.

327/300 distributors changed nearly every year of production. The ...355 VAC was used in '66 and '67 because it worked with both Powerglide and manuals. Automatics don't pull as much vacuum idling in Drive as a manual in Neutral, so autos with the same engine may require a more aggressive VAC to meet the Two-Inch Rule.

I recommend the B20 or B26 12" VAC for Powerglides and the B22 15" for manuals.

Given that the entire VAC is worth three judging points - two for originality and one for condition, the one point deduction for a B-number isn't worth the hassle and price of a NOS VAC, and some OE VACs aren't even well matched to some engines, which I've discussed before.

The specs I have from Corvette News show the same specs for '66 and '67 300 HP distributors (30 @ 5000, 15 @ 12") except AIR with Powerglide, which is a real oddball, and I believe the dist. number is 1111117, which conflicts with my NCRS spec guide that lists 1111153, which I think is the oddball Powerglide distributor that has 40 degrees of centrifugal with an initial timing spec of 4 ATDC. This oddball was only used on California bound 300 HP engines with Powerglide.

Duke

[William G.]

Re: C2 Small Block Vacuum Advance Can

Randy,

Unfortunately, I cannot at this time answer your question as to centrifugal advance. Presently I have a few other things which I intend to do before I install this distributor--when I get those items completed I will install the distributor and get an approximation on advance. If needed I will then try and locate someone with a Sun machine who can properly set this unit up. As Duke says even in the pre emission days Chevrolet tended to change advance specs from year-to-year. So........at the risk of criticism from some, I may not get too excited if this distributor is not "perfect" for a '66 300 Hp. As long as I can get 36 degrees total advance and 15 or 16 degrees of vacuum I don't think I'm going to sweat it--not for now anyway. I can post my "approximation" when I get this unit installed in a week or two--or I can e-mail you direct. (Our spring weather so far has been really crappy, so I'm not yet too excited about not being able to drive it.)

Not to get too involved in my situation, but I just bought a dist. w/o the through hole for the tach drive thrust button. When I bought my car nine months ago it had (has) a later (early 70s) tach drive dist. in it. The dist. seller told me it was rebuilt and set up for 300 hp 327. But whoever rebuilt it did not know or understand the issue of installing the drive gear with the dimple facing the rotor tip and installed the gear wrong way. So.........how well is it rebuilt? And, of course the VAC is not correct as it is a B10. So.......we'll see what transpires. (IF I wanted to point fingers I'd also mention that the seller of this '66 Bowtie car had this early '70s distributor installed one tooth off and it sure ran crappy when the transporter delivered it. Cold engine it hardly ran at all--warmed up: some better.. Some people will tell you they won't run at all one tooth off........but this one did--it just wasn't happy about it.)
Bill