What is a B1 vacuum advance?

[Timothy B.]

Re: What is a B1 vacuum advance?

So if a solid lifter big block with high overlap camshaft used ported advance and approx. 12* inital timing in 1966 what was GM looking to solve.

I don't think that's any where near enough timing at idle but the benefits of vacuum advance by that time were well known.

[Duke W.]

Re: What is a B1 vacuum advance?

AIR with ported vacuum advance was required for California L-72s and L-71s in '67 to meet tailpipe emission standards. GM decided to use the same carb for 49-state verisons even though ported vacuum advance is not ideal for non-emission controlled engines.

Because these were low volume engines, it might have just been a cost issue - use the same carb rather than re-engineering it for full time vacuum advance and having another part number to inventory.

Duke

[John D.]

Re: What is a B1 vacuum advance?

According to a Delco Remy specification manual a 163 and a 201 vacuum advance are close but not the same.

'163 specs in laymans terms. : Starts at 8 to 10. All in at 16.25 to 18. Moves 8* which is 16* crank.

'201 specs ---------------------: Starts at 7 to 9. All in at 15-16. Moves 8* which is 16 crank

'236-16 specs------------------: Starts at 3 to 5. All in at 5.75-8.25. Moves 8.2*

Error factor in all of the above is 1 degree plus or minus.

Credit for the above information goes to Don Baker.
If I were you I would print it and save it.
JD

FOR: Dennis Kurmai