Tackling timing

[alini]

This might come across as stupid, but hell I've been here a few years and come up with some doozies.  So I want to work this timing stuff and the high RPM drop.   I want to set the timing, but the service manual calls for 500 rpm at idle in gear.   So at what idle speed should I set NOT IN GEAR to adjust the timing.  I know what degrees it should be but what RPM?  Since I have the base rpm so high right now Im thinking I need to turn it down, just not sure how far.

[Seafoam65]

                  Set the idle in park down to 675 rpm to set the timing. 

[alini]

I got down to about that, pulled the vac line and timing is about 5*, I know the book calls for 2.5 but ive also heard and done in the past more advance.    Ive got idle in 550 in drive and idle in park will be between 800 and 950.  I think its the dashpot on the throttle that's inconsistent holding the throttle open a touch.  No vacuum leaks to speak of, I checked intake, carb base and vacuum line connections

[Jim Cannon]

Your distributor has 2 different parts that advance the timing for you when you drive.  They add together to give you the actual Total Advance when you drive.

 

The first is the centrifugal advance.  Using 2 weights and springs, it automatically advances the timing as the engine RPM goes up, until it hits a maximum centrifugal advance point.

 

The second part is the vacuum advance.  When the engine is running, it uses the manifold vacuum on a diaphragm to further advance the timing.  But when you step on the gas hard, to accelerate, the manifold vacuum falls and the vacuum advance drops some (or a lot).  This is better for power, to not "ping", and then as soon as you let back up on the gas, the vacuum advance returns.

 

TOTAL ADVANCE = Initial Timing  +  Centrifugal Advance  +  Vacuum Advance

 

There are graphs of this in the shop manual.

 

You should use the shop manual's Initial Advance number, 2.5 degrees for your car, if your centrifugal and vacuum advances are working properly.

 

The book calls for a low RPM and the vacuum advance hose disconnected and plugged when setting the initial timing because they want to make sure that the centrifugal advance is not spinning fast enough to give you any advance.  They want the initial 2.5 degrees to be without centrifugal or vacuum advance adding in.

 

The vacuum advance hose should be removed and plugged.  You should notice a significant idle RPM drop when you do that, if that part of the system is working correctly.

 

Then put it in Drive (with parking brake set and a safety chock in front of the tire) and confirm that RPM is at least 500 or less.  If it's not, temporarily lower it to that or lower, just to set the timing.  The centrifugal advance is not active.  No vacuum, no centrifugal.

 

AFTER confirming that the point gap (dwell is correct -- adjust it BEFORE setting timing), set initial timing to 2.5 degrees. (This is NOT the 1963 spec, only '64 and '65).

 

Now put it into Park and watch the timing mark with your timing light as you run the RPM up.  This is just your centrifugal advance.  I use a tachometer to see what the advance is at a few different RPMs.  As RPM goes up, you should see timing advance smoothly until the maximum point.  Check that against the range shown in the shop manual for Initial+Centrifugal only.

 

Now take it back to idle.  I use a hand held vacuum pump on the vacuum advance port and I use the timing light to watch the timing advance as I draw more and more vacuum on the vacuum advance diaphragm.  It will go to a maximum vacuum advance number.  Compare that to the number in the shop manual.  Also, hold the vacuum (stop pumping) and confirm that the diaphragm is holding vacuum (not split).  They fail with time and heat.  If it will not hold a vacuum, replace it.

 

Take a vacuum reading on the vacuum hose that goes to the distributor.  You should have manifold vacuum on the '64 and '65 models (but not on the '63).  So confirm that you have somewhere about 15-17 in. Hg on that hose.

 

Now hook up the vacuum hose from the carburetor to the vacuum advance on the distributor.  The RPM should go up because the timing advances.   Set the idle RPM and mixture in Park or in Drive, whatever the book says to do.  The engine must be at normal operating temperature to do this.  After that, check "cold idle" RPM by moving the fast idle cam to the index mark (a V) and set per book.

 

This is a lot of steps and a lot of detail, but it's the thorough way to do it and confirm that everything is working properly.

 

Good luck with it.

 

Edited August 10, 2016 by Jim Cannon (see edit history)

[60FlatTop]

Wow, here I have just been making sure mine idled smooth and didn't stumble when I push the pedal. I don't have a tach in the Riviera but I notice it in my modern cars and once in a while they will nudge 3,000 RPM taking off from a light.

Well, I still use a beam torque wrench, too.

Bernie

[1965rivgs]

The vacuum hose is removed when setting initial timing to eliminate the contribution of  vacuum advance which will negate your ability to check initial timing.

Initial timing must be set at a specifically low RPM to keep the centrifugal advance from adding to the timing.

No vacuum = no vacuum advance

Low RPM = no centrifugal advance (provided your springs are not weak or non-stock)

  Tom

[rodneybeauchamp]

Thanks Jim, that's a great step by step.

 

Apart from the timing setting and increased idle for A/C cars, anything that changes or differs with 63?

 

tnx Rodney

[Jim Cannon]

2 hours ago, rodneybeauchamp said:

 

Apart from the timing setting and increased idle for A/C cars, anything that changes or differs with 63?

 

 

Not that I can think of.

 

 

[alini]

Thanks guys, I cranked down the idle for the timing test and its better but still see a bit of a drop in RPM.  I do have the idle in park at about 800 now.  I do have a mild cam and the car isnt quite broken in yet.  I have 78 miles on her as of this moment.  I notice it idles better and better as we go, so the rings are setting in and Im completely confident my car is running the best it should right now.

Its been a long time since I drove a carb car, let alone one with a cam in it....so knocking the cob webs out of my head and learning how an old car drives.  Its not a 2016 Camaro in more way than one

[60FlatTop]

11 hours ago, alini said:

  Its not a 2016 Camaro in more way than one

 

"Men" understand that.

 

[RivNut]

If you're into videos as apparently Bernie is, then perhaps you'll like this one as well.  You have to consider three different elements when you watch it.  1) A lot of it is from a 1973 Buick ad. 2) The still pictures are of cars owned by the Dutch, and 3) the song is about a '63 Riviera.  At the 1:15 mark in the video the words relate to "V8 .... made in '63."  "Turbine Drive", "Riviera.....smokin' in it's tracks."    If your wife, like mine, is a fond of heavy bass, then turn up the volume. - NOT.

 

Ed

 

 

[60FlatTop]

I'm just interested in subtle comments, especially sexist ones. Rivieras aren't for girls, not old ones. They paid that woman to drive the white one. Well, they paid the man too, but he wanted to take his home.... and the girl....and the white car, too.

Bernie

[alini]

So I guess mine handles well too. I laughed at how much steering wheel they used and watching the car wiggle over the humps in the road.    Always nice to compare mine to someone else's cause I never drove it til after it was rebuilt.  So I have no marker of how well it rides now

[60FlatTop]

I like videos, but I usually watch period ones. That obligatory rock music and flashing stills is just too prevalent. As soon as the fist couple of bass notes come on it's "Oh, God, not another one of these wanna be rock stars..

 

On the car, a 50 year old car taken out of context and compared with five decades of technology, well, you wonder what the expectation was.

You have one with a recirculating ball steering box, joints and rods with a parallelogram arrangement, and heavy unsprung weight compared with rack and pinion, light weigh brakes, and McPherson struts. In a visual example, here's the 1964 system:

 

 

And here is rack and pinion:

 

It is all in the linkage.

Look no hard rock or flashing stills!

Bernie

[XframeFX]

While searching for a Nailhead Distributor O-Ring, I found this old post which seems to be a good place to elaborate on the Vacuum Advance Pot I've wondered about.

 

My question is: What is the correct Vacuum Advance for our Nailheads?

It may be a moot point because like so many old car parts, most everything has been discontinued except for maybe 1 flavour. Sort of a one-size-fits-all.

 

My '63 has the 1110993 Distributor. The Shop Manual indicates a vacuum of 8-10" Hg to start with a max. advance between 18-22°

Echlin P/N VC680 appears to be the closest match. It starts between 8-10" but max. advance is only 16-18°. This Unit has the Dana #B1 stamped on it. Correct?

 

 

 

[Riviera63]

8 hours ago, XframeFX said:

While searching for a Nailhead Distributor O-Ring, I found this old post which seems to be a good place to elaborate on the Vacuum Advance Pot I've wondered about.

 

My question is: What is the correct Vacuum Advance for our Nailheads?

It may be a moot point because like so many old car parts, most everything has been discontinued except for maybe 1 flavour. Sort of a one-size-fits-all.

 

My '63 has the 1110993 Distributor. The Shop Manual indicates a vacuum of 8-10" Hg to start with a max. advance between 18-22°

Echlin P/N VC680 appears to be the closest match. It starts between 8-10" but max. advance is only 16-18°. This Unit has the Dana #B1 stamped on it. Correct?

 

 

 

 

I found a couple of these on e-bay a while back for my 1963. I don't know if you will find any of these but, maybe these numbers will help with a cross reference to another. I would also ask Tom Telesco about this. He rebuilds distributors and he would know where or what to buy for a replacement.

 

Bill

 

 

[Riviera63]

Here is a shot of the vacuum advance on my rebuilt distributor. Also, I have attached the notes Tom sent along as far as specs for the distributor.

 

Bill

 

 

 

 

[Jim Cannon]

PLEASE NOTE:

The specs given by Tom Telesco, and posted here by Bill, are for 1963 Rivieras only.  Not for '64 or '65.

 

There is a timing curve provided by Buick engineers in the shop manual for our cars. It indicates a range of acceptable advance for various engine RPM, with and without the vacuum advance added.

 

Keep in mind that distributor degrees are half of the crankshaft degrees you will see. For example, 18 degrees at the distributor will equate to 36 degrees at the crankshaft.  I use a timing light and a tachometer to roughly reproduce the centrifugal advance portion of the curve in the shop manual with no vacuum advance.  Then I use a hand vacuum pump to apply full vacuum to the vacuum advance unit and repeat the measurements.  If curves fall within the bands provided by Buick, you are good.

 

It is possible to purchase performance vacuum advance units that allow you to adjust the spring tension (requires more or less vacuum to get a certain amount of advance) and allows you to set an advance stop, to limit the maximum advance. This can help you dial in the vacuum advance portion of the timing curve to be exactly what you want.

 

 

[gungeey]

 

 

 

MIGHT COME IN HANDY FOR DIYers

 

 

 

 

 

Edited March 9, 2023 by gungeey
spelling (see edit history)

[telriv]

The specs posted are for ALL NailHead engines.

That's what re-curving a distributor is all about.

I mostly limit the vacuum advance to a MAX of 10*-12* using a custom home made limiter plate. NOT the one that can be bought through Crane. Works differently than the Crane OR an adjustable vacuum advance.

In MANY instances increases bottom end & INCREASES cruising MPG's.

After many years doing this stuff you do LEARN some things.

 

Tom T.

 

[XframeFX]

39 minutes ago, gungeey said:

MIGHT COME IN HANDY FOR DIYers

Yes, I've encountered that PDF. Very handy indeed - TX.

 

"MS210   16" on the rebuilt unit does not show in the table. The NOS Box says 1116163 which is for premium fuel (4BBL) Nailheads.

 

Keep in mind, the available selection has slowly diminished to only the B1. Even vacuum advance pots for the HEI distributor are disappearing.

Prefer to shy away from adjustable units. Can only adjust start setting and need a pump to test for initial setting. 

 

Further I did a quick wire brush to my spare distributor with the 1110993 Delco Remy band and if original, shows "B1" which is the only type still available today.

Again, just focusing just on vacuum advance pot replacement.

 

[65VerdeGS]

Are Jim's instructions applicable to the LX 425cu in. dual quad engine?

 

If there are differences in how to set the timing on this engine, can you let us know?

 

Thanks!

[RivNut]

From what I’ve read, the timing for the ‘63 and the Super Wildcat engines (KX, LX, MZ) are the same.

[Jim Cannon]

15 hours ago, 65VerdeGS said:

Are Jim's instructions applicable to the LX 425cu in. dual quad engine?

 

If there are differences in how to set the timing on this engine, can you let us know?

 

Thanks!

See the shop manual for the curves produced by Buick engineers for your engine. If you measure what you have using my approach and it falls within the bands they provide, you are good.

[Jim Cannon]

15 hours ago, RivNut said:

From what I’ve read, the timing for the ‘63 and the Super Wildcat engines (KX, LX, MZ) are the same.

You need to read the shop manuals carefully.  One '63 401 difference is the use of ported vacuum for the vacuum advance and a fairly large initial advance (compared to later years). IDK what Buick called for on the Super engines.  Having less initial advance on later years might imply more centrifugal advance built in; IDK. You need to compare the timing curves from the various years' shop manuals for the various engines to decide what you need to do.

[XframeFX]

6 hours ago, Jim Cannon said:

One '63 401 difference is the use of ported vacuum for the vacuum advance

Always wondered about vacuum source. Makes sense if "ported" with 12° initial adv for 1963.

I have many AFBs with a 1963 3503 showing a scallop in the butterfly at 11:00 position (left image below). Notice the plug for that port. This in my opinion still allows full manifold vacuum at idle because of the scallop. But, this is considered "Ported Vacuum", correct?

 

 

Image-2 is a 1964 AFB without the plug with the port at the carburetor flange. So, this would be direct manifold vacuum for sure.

 

Still would like to confirm if the available "B1" Vacuum Advance pot is correct for 1963.

 

[telriv]

Manifold vacuum is picked up BELOW the primary throttle blades.

 

Ported vacuum is picked up ABOVE the primary throttle blades.

 

Tom T.

[XframeFX]

6 hours ago, telriv said:

Ported vacuum is picked up ABOVE the primary throttle blades.

Yes, understood Tom. I would think that would be the case with the '63 AFB on the left. But, why the scallop at 11:00? Why not a solid throttle blade?

Edelbrock Performer appears to be more straight forward, has both.

[telriv]

The Edelbrock gives you an option.

It IS a universal carb.

Can't answer your question. Don't know the why OR the reason.

 

Tom T.

Edited March 11, 2023 by telriv (see edit history)

[Jim Cannon]

On 3/10/2023 at 4:12 PM, XframeFX said:

Always wondered about vacuum source. Makes sense if "ported" with 12° initial adv for 1963.

I have many AFBs with a 1963 3503 showing a scallop in the butterfly at 11:00 position (left image below). Notice the plug for that port. This in my opinion still allows full manifold vacuum at idle because of the scallop. But, this is considered "Ported Vacuum", correct?  NO. See below.

 

 

Image-2 is a 1964 AFB without the plug with the port at the carburetor flange. So, this would be direct manifold vacuum for sure.

 

 

 

 

You can see the scallop, but you can't see the small hole in the side of the throttle bore that is the vacuum port.  That's because it is above the throttle plate, where it is not seeing engine vacuum, hence "ported vacuum".  As that throttle plate opens, the scalloped area passes over to the other side of the port and exposes the port to engine vacuum. The scalloped area produces a thin edge on the throttle plate to pass smoothly and quickly to the other side of the vacuum port opening to provide a calibrated and predictable build of vacuum on the ported nipple.

 

Hope that helps.