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66Mutt · 08-03-2010, 07:57 PM

Does anyone have a listing of the distributor advance cannister numbers used on the points distributors for the GTO's. I have a 400 engine that was built with an 041 clone cam. I bought a distributor from autozone years ago, but have often wondered if the vacuum cannister was the correct model for the engine. I think it was stamped 504. I have tried a B33 can and I think a B27 can that I had around.

If the vacuum cannisters changed much through the years what would be correct for a late 60's 400 GTO? I am not looking for numbers matching stuff but rather I am trying to get a vacuum cannister that functions better for my combination.
Thank you,
Doug

Kenth · 08-04-2010, 03:24 AM

The Standard brand part #VC24A, stamped B1, replaces most vacuum advance units for Pontiac V8´s.
Starts @ 8-11in/hg max 16° @ 16-18 in/hg.

Juliano · 08-04-2010, 07:54 AM

Would that be crank or distributor degrees ?

Kenth · 08-04-2010, 10:38 AM

Degrees @ crank.

66Mutt · 08-07-2010, 08:10 PM

With my low vacuum, I figured I needed a cannister that operated at lower vac. I had tried the The VC 1810 can is stamped B-28. I measured it as starting at 3.8" and ending at 7.5". The problem I had was that under part throttle acceleration, it pinged. When I hooked up a vac gauge and test drove, I could see that at part throttle acceleration, the vac often did not drop below 5", so the vac advance was not kicking out.

I also had an Accel adjustable can stamped B-33. It started at 4" and finished at 8.5". The adjustable can did not hold its setting and I returned two of them under warranty.

I ended up putting the Cardone one back on, stamped 502-14. It starts at 5 or 6" and finishes at 11. My idle vac in gear is about 12 to 13, so this one is working a bit better and does not have any ping after my most recent timing. Cruising the engine pulls about 15".
Doug

Kenth · 08-08-2010, 12:36 AM

Pontiac never used full manifold vacuum for the vacuum advance at idle with the 041.
I have found chasing a "correct" vacuum advance for a hot camshaft can be a tiresome task and mostly not at all rewarding.
Using a ported source, or a TCS system, for the vacuum advance and adjust the idle circuit in carb to deliver a combustible A/F mixture with some idle bypass air will cure the situation.

66Mutt · 08-09-2010, 12:22 AM

Thanks I'll give it a try.
Doug

Aus Goat · 08-09-2010, 03:32 AM

any tips on finding someone that has the correct part for my 1968 GTO.
Vacuum Advance module number ?

77 TRASHCAN · 08-09-2010, 11:55 AM

The VC24A vacuum advance can that Kenth mentioned, if I remember, has one of the smaller amounts of advance, in a advance can, that I have seen. I've only dealt w/ aftermarket parts, though, no knowledge of O.E. parts or part numbers. Several years ago I was looking for vac cans w/ the most amount of advance, seemed like the VC24A the one of, or maybe the least amount of advance of the replacement cans.

I would think this vac canwould work good in a high compression engine w/ 041 cam, a combo that probably can't stand too much vac advance...
Jeff

Lloyd-TX · 08-09-2010, 01:51 PM

This document has some great timing and vacuum advance information, including a chart of the most popular vacuum advance units.

Credit to a Corvette forum for this information . . .

EDIT: Remember that the RH column under the vacuum advance specs shows DISTRIBUTOR degrees. Double that number for crankshaft degrees.

By the way, I'm running the B28 can on my Formula, limited to 12* at the crankshaft and hooked up to a manifold vacuum source.

66Mutt · 08-10-2010, 01:33 PM

I've had that article for several years myself. It is a good reference but it is only cites the Chevy applications. That article led me to ask if there was a similar reference for all of the Pontiac engine / vacuum cannister applications.
The B1 cannister will not work all that well on my engine combo since I get about 14 to 16" of vac while cruising on level ground. My low vacuum puts me in the operating range of many vacuum cans resulting in inconsistent timing.
Doug

Lloyd-TX · 08-10-2010, 02:29 PM

Quote:

Originally Posted by 66Mutt

I've had that article for several years myself. It is a good reference but it is only cites the Chevy applications. That article led me to ask if there was a similar reference for all of the Pontiac engine / vacuum cannister applications.
The B1 cannister will not work all that well on my engine combo since I get about 14 to 16" of vac while cruising on level ground. My low vacuum puts me in the operating range of many vacuum cans resulting in inconsistent timing.
Doug

A list of the Pontiac applications could certainly be put together, as Pontiac vac advance part numbers are listed in the distributor charts in the MPC. Most, if not all, of the OE GM part numbers can be cross-referenced to the aftermarket PN's.

Would take some time, but certainly do-able.

Murf'sDad · 08-10-2010, 02:31 PM

When I set up my distributor I dug up a bunch of centre plates and weights and put together what I hope will be a good curve; 12 - 14 initial with 22 in the distributor in by about 3200 and a 1973525 can with 14 degrees of vacuum advance (in by 12" of vacuum) that I have limited to about 12 degrees with a bushing. The 525 can had the least amount of advance of any can I had. My stock can for the '76 put in about 25 degrees IIRC. If I want a little more vac advance I have a can that puts in 18 degrees and I can limit it to 16.

FWIW, Stewart

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