What is a B1 vacuum advance?

[Patrick B.]

I ordered VC1765BC vacuum advances from NAPA expecting to get B20 or B26 vacuum advances but they were marked B1. Are they correct for a 67 427/435 with advance all in at 12"?


Also I found a 236-16 in my boxes of stuff. Is this the same as the B28 recommended for my 70 LT-1?

[William C.]

Re: What is a B1 vacuum advance?

Well, a couple of questions hers, I'll try to give a semi-complete answer, The original unit for your '67-427-435 was 1115360, the original would have carried the "360" stamp on the flange. The '70 LT-1 distributor used a 1116163 with the 1111491 distributor and this unit would have been stamped 163 on the flange. The specs for the '163 are essentially 12 degrees (crank) advance at 6 inches of vacuum, and the specs for the 360 were 7 1/2 degrees advance at 12 inches of vacuum. Those were essentially the units used on most of the SHP solid lifter cam equipped chevy engines of the era. YOu will have to compare these specs with the specs for the B1-B20-B26 units and verify how close they are to the factory specs. I don't have a clue as to what those numbers relate to other than some generic manufacturers part number.

[Donald L.]

Re: What is a B1 vacuum advance?

VACs stamped B-1 @ 16"-18" Hg provide 16* -18* advance. Your 427-435Hp engine will be happier with the B-20 or B26 VAC.

Have your NAPA dealer try the following P/Ns for B-20.

Standard Auto Products-V181
Borg Warner -V375
Niehoff- D320
NAPA-VC1765

[Michael J.]

Re: What is a B1 vacuum advance?

I have the NAPA VC1765, but it used to be the VC1810, just can't find those anymore. That number should be stamped on the box from NAPA. Never heard of a B1.

[Duke W.]

Re: What is a B1 vacuum advance?

I ordered VC1765BC vacuum advances from NAPA expecting to get B20 or B26 vacuum advances but they were marked B1. Are they correct for a 67 427/435 with advance all in at 12"?


Also I found a 236-16 in my boxes of stuff. Is this the same as the B28 recommended for my 70 LT-1?

I don't know what a VC1765BC is. A VC1765 should contain a B20 or B26 VAC, which is 15 @ 12" - the one I recommend when converting a L-71 to full time vacuum advance.

They either sent you the wrong part number or the box didn't contain the correct part. The B1 is a boat anchor - useless on even a base engine.

The B28 is the current replacement for the 236-16. I recommend the B28 for the LT-1 when converting from ported to full time advance. Install some light springs in the centrifugal to get all 26 degrees in by about 2500 and set the total above the point of max centrifugal with the VAC disconnected at 38. If you get any significant detonation, slow the centrifugal as necessary until the detonation goes away.

Set the idle speed at 900 or you can go lower if you think the idle quality is acceptable at a lower speed.

Duke

[Joe L.]

Re: What is a B1 vacuum advance?

I ordered VC1765BC vacuum advances from NAPA expecting to get B20 or B26 vacuum advances but they were marked B1. Are they correct for a 67 427/435 with advance all in at 12"?


Also I found a 236-16 in my boxes of stuff. Is this the same as the B28 recommended for my 70 LT-1?

Patrick-----


"B1" is the Standard Automotive Parts nomenclature for a vacuum control that has specifications nearly identical to the GM #1116163. A 1967 Corvette with L-71 originally used vacuum control GM #1116201. The GM #1116201 was replaced more than 40 years ago by the 1116163 (which, itself, is now discontinued). So, NAPA has supplied you with the equivalent of the GM-specified vacuum control for your application. Whether that is the best one to use from a performance perspective is another question entirely.

[John H.]

Re: What is a B1 vacuum advance?

I have the NAPA VC1765, but it used to be the VC1810, just can't find those anymore. That number should be stamped on the box from NAPA. Never heard of a B1.

Michael -

The VC-1810 is the "B28" can, which is AC-Delco #D1312C or GM #88924985, and they're still available from GM; Rock Auto and GMPartsDirect.com have them too. I buy them regularly.

[John D.]

Re: What is a B1 vacuum advance?

Joe, Actually we have found that one of the worst vacuum advances is in fact the B1. I made a major goof years ago and bought what I thought was going to be the '163's. I don't know how many I bought but at least 50 of them. Toward the end of the real parts books from Chevy they listed the 163's as the Vac Adv for a 63. More false information.
REal deal 63 201 vacuum advances are extremely rare. You may find a service replacement 201 on Ebay, etc but it's not the same appearance wise as the original 201's. Correct real deal 201's have a two piece front on them. The vacuum tube is soldered on to the cone shaped cone. The SR's are not made like this.,

The spring in the B1 is too strong for our applications. POC is another description. My son has been selling B1's at the fleas for peanuts since he was a little boy. Selling them very cheap and telling guys the truth. I think I may have one more of those things left.
A rumor is that some companies have used the B1's for parts when they make a repro 201 but I don't know if this is true or not. JD
l

[Joe L.]

Re: What is a B1 vacuum advance?

Joe, Actually we have found that one of the worst vacuum advances is in fact the B1. I made a major goof years ago and bought what I thought was going to be the '163's. I don't know how many I bought but at least 50 of them. Toward the end of the real parts books from Chevy they listed the 163's as the Vac Adv for a 63. More false information.
REal deal 63 201 vacuum advances are extremely rare. You may find a service replacement 201 on Ebay, etc but it's not the same appearance wise as the original 201's. Correct real deal 201's have a two piece front on them. The vacuum tube is soldered on to the cone shaped cone. The SR's are not made like this.,

The spring in the B1 is too strong for our applications. POC is another description. My son has been selling B1's at the fleas for peanuts since he was a little boy. Selling them very cheap and telling guys the truth. I think I may have one more of those things left.
A rumor is that some companies have used the B1's for parts when they make a repro 201 but I don't know if this is true or not. JD
l

John-----


The GM #1116163 replaced the GM #1116201 for SERVICE in 1965. There may be a slight difference in specs between the two but, since 1965, the 1116163 was the only one available from GM to SERVICE all applications originally using the 1116201. Inasmuch as the 1116201 was discontinued from SERVICE 47 years ago, I'm not surprised that NOS examples are hard to come by.

As far as I can tell, the specs of the GM #1116163 and the SMP "B1" are the same.

[John D.]

Re: What is a B1 vacuum advance?

Thanks Joe. But if in fact that info is true than the 163 is nothing to brag about either.

Standard makes the SR vacuum advances for all. For GM, NAPA, etc.

I like Dukes answer on the B1 VA the best. Now I am being negative to you Joe. But when your buddy Duke calls the B1 a boat anchor he hit it right on the nose.
Don Baker has tested a ton of the SR vacuum advances.
He likes the B28 for 64-65 30-30, etc.
What is the B# for a 201?
Is it a B22 or is it a B20?? I hate it when I forget basic stuff. Thanks, John

[Joe L.]

Re: What is a B1 vacuum advance?

Thanks Joe. But if in fact that info is true than the 163 is nothing to brag about either.

Standard makes the SR vacuum advances for all. For GM, NAPA, etc.

I like Dukes answer on the B1 VA the best. Now I am being negative to you Joe. But when your buddy Duke calls the B1 a boat anchor he hit it right on the nose.
Don Baker has tested a ton of the SR vacuum advances.
He likes the B28 for 64-65 30-30, etc.
What is the B# for a 201?
Is it a B22 or is it a B20?? I hate it when I forget basic stuff. Thanks, John

John-----

I don't think there ever was a different SMP B number for a 1116201. As far as SMP is concerned, a GM #1116163 and a GM #1116201 are the same. Essentially, that's what GM says, too. I believe that manufacturing tolerances are probably greater than the actual specs between the 163 and 201.

What I'm saying is this: I don't know how one could like the performance of a 1116201 and not like the performance of a 1116163. I could understand why one might not like the performance of either in any particular application but I can't understand how one would perform better than the other.

[Richard M.]

Re: What is a B1 vacuum advance?

Last year I used the VC1765 from Napa for a rebuilt stock L71 using manifold vacuum. It is marked B26.

According to the Napa link below, one of the photos shows B26 marked on the flange. I did a search for VC1765BC and it does not exist. Strange.
http://www.napaonline.com/Catalog/Ca...765_0195970883

Some results of vac advance testing in post#30, and specs from Duke's info in post#32 in this thread....
https://www.forums.ncrs.org/showthre...433#post533433

Note the M201 15 repro I bought was way out of spec.

For the record, I stayed with manifold vacuum using the VC1765 and never went back to ported vacuum. Engine ran great after final carburetor and timing adjustments.

Rich

[Joe L.]

Re: What is a B1 vacuum advance?

Last year I used the VC1765 from Napa for a rebuilt stock L71 using manifold vacuum. It is marked B26.

According to the Napa link below, one of the photos shows B26 marked on the flange. I did a search for VC1765BC and it does not exist. Strange.
http://www.napaonline.com/Catalog/Ca...765_0195970883

Some results of vac advance testing in post#30, and specs from Duke's info in post#32 in this thread....
https://www.forums.ncrs.org/showthre...433#post533433

Note the M201 15 repro I bought was way out of spec.

For the record, I stayed with manifold vacuum using the VC1765 and never went back to ported vacuum. Engine ran great after final carburetor and timing adjustments.

Rich

Rich------


I have a different spec for the GM #1116201 than that shown in the previous thread. I show it as follows:

inches of vacuum to start plunger= 8 "

maximum advance= 15 degrees @ 16"

and for the 1116163....

inches of vacuum to start plunger= 8"

maximum advance= 16 degrees @ 16"

If these are the correct specs, relative to manufacturing tolerances, these two controls are essentially the same.

[Duke W.]

Re: What is a B1 vacuum advance?

The spec I have for the ...201 is 15.5* @ 15". The B22 is 16 @ 15", so I think it is the closest match to the ...201.

I recommend the B22 for all base cam small blocks (either OE full time vacuum advance or converted from ported) with manual transmissions ( 12" B20 or B26 for with automatic transmissions.)

Data I have on the ...163 indicates that it may not be fully deployed until up to 18". This violates the Two-Inch-Rule for even base cam engines with manual transmissions.

Some of these GM parts substitutions don't get a proper engineering evaluation. A case in point that had a big impact on me. The OE 3/8" alternator drive belt on the Cosworth Vega was substituted with a slightly longer 7/16" drive belt and the aftermarket followed suit. This substitute belt required the alternator to be pulled to nearly the limit of adjustment which caused the belt to impinge on the lower radiator hose, and it created a "wear divet". Fortunately I found the damage before the hose failed.

Since I still had the original belt I measured and found a Dayco 3/8" drive belt that was essentially identical, and wrote a tech bulletin that was published by the Cosworth Vega Owners Association to warn of this issue.

Thank-you GM! Next time you do a parts substitution do a REAL engineering evaluation before you screw your customers!

Duke

[Jim B.]

Re: What is a B1 vacuum advance?

John--do you happen to have a good photo of one of the two-piece "real deal" 201 soldered-on nozzle cans? I guess I've never come across one. Would like to see what the fabricated finish looks like. Thanks.

Jim