Good morning all,

I was curious what the total timing (or "all in" timing) should be on my '66 Toronado's V8 but I can't seem to find this spec in the manual anywhere. Am I just missing it? The best I can find is in the distributor test specs which says it should be 8-10 degrees mechanical advance at 2100 RPM. That's not really telling me what the total timing should be on this engine though so I'm not sure what it should be. Stock, original engine, no modifications.

Thanks!

 

Including vacuum advance?

 

With the vac adv disconnected, use a dialback timing light, measure the idle speed timing (initial) and then measure at what rpm and the timing advance amount stops (total), note that timing. Subtract the initial from the total and it will give you how much mechanical advance is built into your distributor.

 

Yeah, okay I get that but what are you measuring against? How would I know if what I measure is within spec? I mean, this car is bone stock and never messed with so it shouldn't be out of wack but I'm just trying to learn more about the engine.

 

You disconnect the vacuum advance when checking this correct? So I guess no? Vacuum advance goes away at high RPM right?

 

SOP is to disconnect and plug vacuum advance for consistency, but people do measure it connected -- usually comes in ~ 50° altogether. Disconnected, with only static + mechanical, a good range is 32-36° depending on variables like cylinder pressure and gas quality. Most people like to get max advance in around 3K or just before.

 

You will likely get 100 different answers. I found the following to work well for most mid-60s - mid-70s stock or lightly warmed-up Olds engines

The distributor includes vacuum and mechanical advance...read on...Short answer 36-38°

The long:
Before doing anything obtain a vacuum gauge and set back timing light.
Verify the ignition & fuel systems are in good shape, and dwell is 30°.
Verify zero vacuum leaks present.
Put in the gas you will normally drive with.

Hook up the vacuum gauge to an intake vacuum source, (not a ported source).
Adjust the carb to achieve the highest possible vac reading.
Next, rotate the distributor to obtain the same high(est) vacuum signal.
Go back and forth between these two to get that "highest" vacuum reading.

Tighten the distributor and road test. You could be satisfied without going any further.

Basic rule is to give the engine as much timing advance as possible without detonation( spark knock).
You may need to back off on real hot humid days if it starts to detonate. Put some octane booster in at every fill unless you can source pump gas 92-94 Octane non-ethanol gas.
__________________________________________________ __________________________________________________ ______________________________________________
Granular details for today's gas and a little extra performance:

-Start with 12-14° base timing with vac canister plugged off, warm curb idle at 650-750rpm.
-Plug the vacuum canister into a direct manifold vacuum source. You want it to advance another 8-10° at curb idle (adjustable travel (not rate) canisters are recommended and readily available).
The centrifugal advance should bring the rest or total timing before 2800-3000rpm at ~36-38°.

Verify the centrifugal weights and springs are clean and lightly lubricated.
Base ~13+9° = ~22° at idle. Centrifugal total is ~14-16° = grand total of ~36-38°

Centrifugal should hand off the vacuum canister timing smoothly as the engine vacuum drops and the throttle plate opens. Beginning at ~800-1000-1200rpm.
The best way to achieve this optimal curve is to have someone put the distributor on a SUN dist machine and tune it for you.
But if you pay attention to the details using a vac gauge and set back timing light you can get real close.
You can change up the weights, springs, and stops. You can use two different weights of springs. They do not necessarily need to be a matched set to achieve the goal.

 

Dang! Where else are you gonna get such nicely presented answers to such questions? Thanks fellers, you guys are awesome!

 

I thought you understood the distributor numbers in the manual with my response. Getting back to this, what the manual is telling you is that at 4200 Rpm you should have 16-20* of mechanical advance at the crank built into the distributor. The numbers referred to in the manual are in distributor degrees, the distributor turns 1/2 the speed of the crank. Your ignition timing settings are in crank degrees, so add whatever the initial timing you set at idle to the total and you have the total timing for the engine. For example if you set your initial timing at 12* btdc, without vthe 16ac advance at 4200 Rpm you would add 12 + the 16 to 20 of mechanical advance for a total of 28 to 32 degrees.

 

So the initial spec on mine is 7.5 deg BTDC. So it would be 7.5 + 16 to 20 of mechanical for a total of ~ 24 deg to 28 deg stock? I don't really want to rev this thing to 4200 RPM in the driveway though, it should be all in way before that correct?

 

It should be all in around 4200. At light throttle you also have the vacuum advance which will contribute another 15-20*.

 

Most tuners will tell you that for best performance the centrifugal advance in the distributor should be fully deployed by three grand as noted in @droldsmorland 's post.

 

No bump it up to 12-14° base timing. Then the other two specs will be additive from that.

If you want to run nicely with pep ignore the factory lame timing spec. At least the base.
Not once in almost 50 years of tunning have I ever run any IC engine at a factory timing spec...not even a lawn mower.

Today's gas must be addressed with specific carb tuning (float level and enrichment, AVS adj etc) and timing revisions.
Think about it... who does a 7.5 timing spec. 1/2 a degree meh.
That spec is 50-55 years old. The gas and other technology was totally different back then.

Do this:
Before doing anything obtain a vacuum gauge and set back timing light.
Verify the ignition & fuel systems are in good shape, and dwell is 30°.
Verify zero vacuum leaks present.
Put in the gas you will normally drive with.

Hook up the vacuum gauge to an intake vacuum source, (not a ported source).
Adjust the carb to achieve the highest possible vac reading.
Next, rotate the distributor to obtain the same high(est) vacuum signal.
Go back and forth between these two to get that "highest" vacuum reading.

Tighten the distributor and road test. You could be satisfied without going any further.
Then put a timing light on it and see where it likes to live. I guarantee base is above 7.5°

Steve

 

That's really awesome information everyone. I'm super scared to bump the timing up on this thing though. I'll take these tips into consideration and definitely make sure I have no vacuum leaks before I try this. Right now I have my timing at 9 deg initial (i've got a vac gauge and a dial back timing light here as well with a built in tach).

 

Ahhh, I remember now why I was confused about this as I tried doing this before and immediately was thrown off so I didn't continue.

I'm in my garage here now fiddling around with the timing, etc and what I found was that when I advance the timing the vacuum goes higher and higher and higher along with the RPM.

I started with the engine completely warm, hooked up the gauge and I got 18 in-hg and the engine idling around 700 rpm. I fiddled with the mixture screws until I got about 18.5" and it seemed happy so then, following the advice here, I loosened the distributor and advanced it a touch.....instant RPM rise and the vacuum bumped up to 19. Advanced it a bit more......20" and the RPM rose again. Advanced it a touch more.......21" and RPM rise once again. It's idling a bit too high now so I tried backing off the idle screw to bring it back down but it wasn't long before I had the screw completely backed off and the RPM's stay high.

Before I started doing all this, the engine was running fine......and it still is but my results are what you would call, confusing? I did run some propane around the carb and the vacuum lines to make sure there wasn't any vacuum leaks and I didn't see anything crazy that's for sure. And yes, vac advance disconnected.

Edit.....at the current settings the initial is at 21 degrees LOL

 

When you advance the timing the RPM and vacuum will increase. Just remember what ever advance you add at idle it will also add to the total, it's directly proportionate. The best way to do this is to see what your total is at 4200+ (where the mechanical timing stops) and then add or subtract the initial to get that total to 34/36* BTDC. In addition, increasing the advance may induce pinging at higher RPMs, and once you hook up the Vac Adv it may be worse. So that may have to be limited to 10.

 

Ahh, I see ok. I think I misunderstood earlier thinking I was supposed to increase the timing until I got max vacuum readings. Maybe I'll just stick with 10 degrees and see where the total is.

 

You will know when it has too much timing and you wont hurt anything short term. In fact try twisting the distributor too far you will hear and feel the over advance. Same for the other direction. The engine will be very sluggish when to far retarded. Get a feel for it. You wont hurt it.

Back it down to 12-14 adjust the rpm and take it for a ride. I guarantee it will be a different car.

At 21° in park with no load it might be fine. But once in drive with a load it will spark knock like you dumped marbles down the carb.
You should here it popping out the exhaust at 21° base?

I will leave the distributor just loose enough to adjust during the road test. Again you wont hurt anything.
If it knocks under load back it down until the spark knock goes away. You're there.

Careful...the right front tire will likely roast when you nail it.

 

Please remember your engine is high compression and will want the most octane available in current pump gas. Best of luck!

 

Yeah about the best I can do around here is 91 octane and I add some decent quality octane booster. There's really nothing else I can do unfortunately.

 

I'll start with 10 deg.....I tell you what, I'll make a quick video of the process and show ya how it is.

 

... but not loose enough that it could slip out of position.