Timing Issues Relived (Corellian Corvette you there??)

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I've been reading. A LOT of reading lately on timing, advance curves, total timing, All in timing, Initial timing, Static timing, and so on. I read all the posts here that had to do with Timing. If you did a search in MSN on Ignition Timing Curves you would find over 2100 articles alone. This all got started for me with Corellion's post on Stovebolt and his problem. I soon found out that there was several problems (and in some cases non problems) that were do to definitions. I'm no expert at this, my main issues were with the effect or causes of overheating do to the timing, cooling system and carburetion changes I had made. I'm working backwards on this since I made all these changes, including several others, and ended up with a motor running 50% cooler and wanted to figure out why. So to this end I looked hard at the timing and distributor as a possible reason. While reading these articles I reread several major posts and wanted to clarify some issues and hopefully get conformation as well as input to help others that are as easily confused as I am.

DEFENISIONS:
INITIAL TIMING / STATIC TIMING (same thing)
The starting point that is specified in the manual for the timing. This is based on a stock motor in good condition with no modifications. It has been determined that 12° to 14° is a good starting point for a "modified" engine and we will use 14° as an example. Disconnect the vacuum line from the carb and cap off the carb port. Another MAJOR factor here is the RPM's during this test. The motor MUST be idling below (as low as possible) 800 RPM or there's a chance that the Mechanical (Centrifugal) Advance has kicked in and your numbers would be off from the get go. Take a reading and set the timing to 14°.

MECHANICAL / CENTRIFICAL TIMING (same thing)
The advance function of the distributor utilizing springs and weights to advance the timing in relationship to the RPM's. The higher the RPM's the more advanced the timing. To a point, there is a stop (can be adjusted or modified) were you can increase the RPM's but the timing advance stops. Also may be related to the phrase "hitting the wall". :D This is also the starting point to get the Total Advance numbers. With the timing light still connected and the vacuum line still disconnected, pen and paper handy we start to increase the RPM's by 500 and note the advance points on a dial back timing light. Note: I've read a lot about degreeing the balancer and adding tape and marking off additional degrees and determined there's to many variables I could screw this up so buy a good dial back. So before you increase the RPM's set the timing mark from the reading of 14° to 0° on the dial. As you increase the timing note the advance numbers at each 500 RPM increments up to 3000 RPM's or until you have 2 points that no increase is noted. I then decrease the RPM's until I see a decrease in the advance and know where the maximum advance and RPM's occurs. Note this also, typically this should be around 2800 RPM's at 24° on the dial back. 24° is your Mechanical advance.


TOTAL ADVANCE
Initial Timing + Mechanical Timing = TOTAL TIMING
Now this is where the fun begins. Some will say the Total should include the vacuum advance connected as well but think about it, the vacuum advance is only at idle or light loads to increase gas mileage in most cases. It's a variable and is vacuum only dependent. If this were the case why wouldn't we add (subtract) any retarding devices to this equation? The Total Advance tells us what the advance is under WOT, something performance nuts all want to excel at and lower the ET's. Were this occurs is adjustable by springs, weights and stop points modified in the distributor. The curve (according to what I've read) should be smooth from 1000 RPM to 2800 RPM. (Your engine may very) For this example the Total Advance is 14° + 24° = 38°. Several have referred to 38° as the correct number for Total Advance. If anything we should set a standard one way or the other for this definition so as to not confuse this complicated issue.

VACUMN ADVANCE
An advance state created when suction is applied to the distributor vacuum diaphragm causing the distributor to advance when at idle or under light loading such as cruising in high transmission gears at lower RPM's. A number of people have suggested disconnecting the Vacuum for better performance and I've read this as well. So if your basically going to start your car, point it in a straight line, floor it for 14 or so seconds, and then stop, I would also. If you’re driving it around town and paying over $2.00 a gallon hook it up.
Now we're still at idle (as low as it will still run), the vacuum line is still plugged, and we're reading 14° on the Timing light. Dial back to 0° and hook the vacuum line up. Check the reading on the timing light; it's probably around 15°. This is adjustable when an adjustable vacuum advance canister is installed on the distributor; normally ID'd when the canister has what looks like a large hex head at the vacuum nipple. By inserting a 3/16" allen wrench into the nipple you can increase or decrease the amount of advance. 15° seems to be the max you want under typical conditions.

ALL IN TIMING (I think this is what it's suppose to be called)
All in Timing is with everything added up and again from what I've seen and read is a total of everything, your initial, mechanical, and the vacuum advances. This number seems to be just a " Total Not to Exceed number which I'm not really sure is obtainable under normal driving conditions.

At idle you don't have Mechanical advance
At WOT you don't have Vacuum advance
At Partial you have a combo of the 2. I guess if you were at WOT, min. RPM's and going up hill like a bat outa hell?? I'm open to suggestions.

From what I've seen 55° is the top number.

Well there is a lot of good advice out there on tuning the Dizzy as well as conflicting advice. My thought here again was if I was confused then maybe someone else was also. Hopefully this will be added upon as well as any errors or omissions corrected to further clear the subject up. ALL responses are welcome.

Steve
 
Good summary -

I've been pouring through all of the timing/advance threads recently to get a good understanding of my 40 year old peice of technology sitting under my hood.

I just swapped my points/condenser for a Petronix II and added a new Flamethrower II coil. The engine fired right up, but my timing (Static) was ~ 35* (I had to use ye ole' calibrated eye ball). My initial timing was around 12-14* with the points/condenser. I dialed it back to 14*. I think I've entered a huge iteration now between timing, idle, and idle mix settings.

The car is actually worse now than with the points. I know going to the Petronix should have smoothed out the rpm's, but...not so much. I have 12 V (actually a little more) at the coil => no ballast resistors to worry about. When the rpm's increase, the voltage at the coil goes down to around 8 V. To me this makes sense.

Now that I seem to be in a never ending do loop... What is a good method to "tune" an engine? Start with the plugs, play with the distributor, play with the carb and then play with the distributor agian?

Also... I plan on taking some data on my mechanical advance and vacuum advance curves to get a better understanding of what is really going on inside the dizzy...

At idle (~ 800 rpm), there is no vacuum at the carburetor port and about 17" of vacuum at the manifold (just below the base of the carb). When I increase the rpm's, the vacuum at the carb port jumps up pretty quick to 20" and the vacuum at the manifold drops off fast. My dizzy will get about 10* of advance going from 5" of vacuum to 10" of vacuum.

Should I have advance come or go as I raise the rpm's? (speaking vacuum only - I understand that the mechanical will pickup after about 900 or so) The real question... Should the dizzy be connected to the carb or the manifold? Or is this all part of the art of tuning and fiddle around until whatever works best presents itself? - true trial and error.
 
Ski,
You say it's running worse but how/what is running worse??

Is that the original carb? They came in 2 configurations high or low vacuum. You probably had the sparkomatic to begin with. The early distributors required low vacuum (under 4 hg I think). Your new one requires High Vacuum.
The 1100 and 1940 (Motorcraft) carb came in both versions - high and low vacuum, but the 1904s Holley were all low vacuum. There are three different ways they did the distributor vacuum on the 1940. If it has a spark valve (small screw-in diaphragm) near the vacuum fitting it will be a low vacuum carb. Those were sold under Motorcraft as a replacement carb for the '63-67 engines ('63-65 in CA).

If it doesn't have a spark valve it could be one of two versions. You need to look on the carb body for a small metal plug. If it has the plug it's the "universal" replacement carb, sold by both Motorcraft and Holley. Those came set up for low vacuum, but driving the plug in switches internal passages and changes it to a high vacuum. Once it's driven in, it doesn't come back out again. Those don't have a spark valve, the hole where it would have gone is blank and unthreaded.

If it doesn't have the plug it's a high vacuum only, sold by Motorcraft, as a replacement carb for '68-69 engines ('66-69 in CA). Again a blank hole were the spark valve would have gone.

The Autolite 1100 the spark valve will tell you which you have. If it has the valve it will be low vacuum. No valve should be high vacuum.

Verify the carb
Depending on when the last tune-up was done you need to start with that. Be sure your spark wires are good as well as all connections also set the timing (vac disconnected) to 14°, idle as low as possible.

Steve
 
Total timing = initial + mechanical + vacuum. Most of our dual advance distributors will have between 20-28 degrees of mechanical and 5-8 degrees of vacuum advance. Total timing is usually no more than 40-44 degrees. Keep in mind that you only get the vacuum advance at low load, high vacuum.

The vacuum port will not have any vacuum until the throttle blade opens past the vacuum port slot. It is designed to do that so that the engine runs only on initial timing during startup and idle. The vacuum on your distributor port increases whenever your throttle blade crosses that slot. That's normal operation.

The proper procedure is to disconnect and plug the vacuum line and set initial timing. Ignore the carb for now, unless you also have mechanical advance and the engine is revving too high. Turn the speed down to something near a normal idle if that's the case.

Once that's done, reconnect the vacuum. First set idle speed, then mixture, then idle speed again if necessary. Idle mixture is usually correct when you get best vacuum at the desired idle speed.
 
Jack,
I highly respect and found your information extremely helpful in the past but I'll disagree on the "Total" including the Vac. I’m going to hold of until later. I’d like to see other opinions on this. I held off getting to deep with Ski because I think he’s got the wrong carb on. I could be wrong but he just put a new dizzy on a 64 ½. I didn’t want to go any further until he checked it.

Please take a look at the following for discussion.

http://www.automotiveu.com/SolvingOverheating.aspx

http://www.centuryperformance.com/timing.asp

http://www.fordmuscle.com/archives/2000 ... ndex.shtml

Look forward to some good info on this,

Steve
 
Steve - I have an Autolite 1100 without the spark control valve => the high vacuum carb/distributor combo. I replaced the distributor back in '96 with a '71 coded distributor (vac/mech andvance type; or dual advance type)

Manifold or carb? That is the question.

ski
 
I'm with Jack on this one. 30 years ago when I started being a motorhead, total advance meant everything added together. It still does.

Total: involving all aspects, elements,participants, resources, etc. (Websters Encyclopedic Unabridged Dictionary)


What part of "Total" do you not understand?

Joe
 
Steve, I think you provided a good explanation of the various components that contribute to the total ignition advance. But I would not get hung up on specific terminology as long as you explain what you consider the term to mean. The SAE has a publication Standard J139 that covers nomenclature and terms regarding the ignition system. Maybe it is in there, but free copies are not readily available. The cost is about $60 if you want to order. It is likely to be a more authoritative source than something just posted on the websites you referenced.
Anyway, I, like Jack, Dan & Joe, have always thought of total timing as just that, the sum total of initial, centrifugal and vacuum at a particular condition.

I have used and read "all in" to imply that a certain component of the total timing was at its maximum at a certain condition. e.g. The centrifugal advance is at its maximum or "all in" at a certain rpm such as 3000 rpm. Or the vacuum advance is at its maximum stop or all in at a certain vacuum reading such as 10 inches. Under driving conditions, neither of these maximum conditions will coexist at the same time. The vacuum and centrifugal vary with engine speed and load, therefore, the total timing varies and is the sum of the three components at a specific rpm or vacuum level. That is what a digital spark advance Map does. In a simplified form at specific combinations of engine speed and rpm, there is a specific total advance for those conditions. When you see mention of total timing in the range of 36 to 38 degrees at WOT, it is implied that the centrifugal timing is "all in" or at its maximum. In addition, under WOT, the vacuum advance component of the total timing is zero. At idle, using the manifold vacuum source, the vacuum advance is "all in" at its maximum and the centrifugal advance is at its minimum which may or may not be zero depending on the tuning of the distributor.
Just my two cents
 
Dan,
Am I miss reading something in that link??

From the FordMuscle artical:
Total Advance: So far we have looked at initial advance and mechanical advance. Both of these combined gives total advance. Say for example initial was found to be 6 degrees, and we visually verified that the reluctor arm was on the 15L side. Total timing, theoretically, is then the initial + mechanical. In this case 6 + (15 x 2) = 36 degrees. If we shined a timing light on the marks (with vacuum hose disconnected and plugged), at idle we'd see 6 degrees, then as we increased the engine speed, we'd see more and more advance, until at some point the total centrifugal advance would be reached, and we would see 36 degrees. When exactly the total advance occurs is of great importance when it comes to performance, and we discuss this in the section below on "curving."

Under Total it only included the Initial and Mechanical. My point was to try and get everyone on the same page and hope to clearify the 55° All In that several have come up with but didn't believe was possible. What if you don't have a vacuum or the vacuum hooked up? Is the total then a non calcuable #?
Fastback at any given point there never is a total of the 3 at there max occuring. 1 stays constant, Initial. The other 2 are eather at their respective "ALL IN" or ramping up and down respectivly. The question then is how can you total all 3 if at no time all 3 are at their "All In" condition?

I really appreciate this discussion guys and would be more than happy to fall in line but I'm not sure I'm out of step here. :?

Steve
 
At part throttle cruise it is possible for the centrifugal advance to be at maximum and still have enough vacuum to pull in some additional advance from that source, thus producing an instantaneous "total" advance that exceeds the initial+mechanical. Also at that speed if using manifold vacuum the total will go to the limit if the throttle is suddenly closed (not that it really matters at that time). But the part throttle cruise condition is EXACTLY what the vacuum advance was developed for. That condition doesn't exist much on the race track, so isn't considered important by some.
Joe
 
Steve,
You correctly paraphrased what I said. The total timing varies constantly if conditions are changing. The total timing must be defined at a point or combination of operating parameters. Depending on how your vac advance equipped distributor is set up, you will see total timing that gets up into the 40's and 50's when cruising under light throttle because the engine is developing some decent vacuum readings. Looking at the specs for my 61 Vette, depending on the model, they provide 10 to 17 degrees of distributor degrees advance. This translates into 20 to 34 degrees of crankshaft advance. So if you have your car set up at a total timing of 36 degrees at WOT (no vac advance), under light cruising you will generate sufficient vacuum to get some portion of that 20 to 34 degrees of advance added into the total timing which will easily put you into the 40's or 50's for total timing. If you simply add the maximum values, the total timing would range from 56 to 70 degrees. But as stated, the maximum "all in" does not simultaneously occur all three components when driving. In your driveway, you can't simulate the light load cruising advance. So you need to test drive. If you get pinging, then you have the choice to alter one of the 3 components. You should adjust the one component that has the most influence under that condition or pick the one that may be out of balance compared to the others.
 
Total timing is the calculation of the combined initial and mechanical advance timing settings (max). This "can" also include your vacuum advance though, I like to describe it as "total timing plus vacuum advance".
Click to expand...

What if you don't have a vacuum or the vacuum hooked up? Is the total then a non calcuable #?
Fastback at any given point there never is a total of the 3 at there max occuring. 1 stays constant, Initial. The other 2 are eather at their respective "ALL IN" or ramping up and down respectivly.
Click to expand...

They have their definition. I got my definition from what I was taught out of the instruction booklet of the Sun distributor machine in the machine shop where I used to work. It doesn't matter as long as you account for all of it.

You may not have all of your advance all the time, but it can happen. Give you an example. Say you're in second gear, engine is turning 3500 or so, and you are not accelerating, just scooting along at high rpm. In that situation, you will have all of your advance elements in full. As you tip into the throttle, the vacuum portion drops out and you revert to the other two portions.

If you don't have a vacuum advance, that portion is simply zero.

A little more clarification on how the Load-o-matic and the infamous spark control valve works. The Autolite 1100 has a ported vacuum that opens when the throttle blade moves past the port. This ported vacuum allows the distributor advance mechanism to see manifold vacuum. However, at wot and at high speed under loads, there is not enough manifold vacuum to provide enough advance for high speed operation. So when the manifold vacuum drops, the spark valve closes and the distributor picks up venturi vacuum. As the engine runs faster and inhales more air, the venturi vacuum increases and the distributor can advance to meet the new demand.

Hot rodders have been dealing wth this issue since 1948. This arrangement was far superior to the "vacuum brake" used on 32-48 Ford V8's and was continued on all its V8's until the 57 model year. You are dealing with the same thing that happens when you try to install a bunch of Strombergs on a flattie using the stock distributor!

You "can" install a later distributor with an 1100, but the venturi advance will add that vacuum advance at speed and it may be too much, since the later distributor was designed to use manifold vacuum only. Installing a newer carb with a Loadomatic distributor should be avoided since the carb without a venturi advance provision will not be able to provide enough advance at high speed/load.
 
Steve,

You are right, the link didn't support what I was saying. I read it a couple weeks back and then just re-read a brief section of it before I posted it. I thought the section I read supported me but I can't find it now, so whatever.

Ski,

I wish I knew what the axes were on your graph. It is pretty interesting though.

The way I figure what you really have is a 3-dimensional chart. Vacuum and RPM are independant of each other, so they have rwo separate axes. Advance is the third, dependant, axis. RPM might be high, causing a lot of mechanical advance, but vacuum might also be high, causing a lot of vacuum advance. When these two add up it could be more advance than the centrifugal advance ever achieves by itself. The point of maximum advance on the 3-d chart would be called total advance in my scheme.

If you did not have a vacuum advance on your engine then you would use a 0 for Vac in the Total=Vac+Initial+Mechanical equation.

-Dan in Atlanta
 
I'll take a stab at the graph. I think the left axis is inches of vacuum. The right axis is percent of full throttle position 0 to 100%, and the bottom axis is likely a time measurement in order to show the changes in throttle position etc from one position to the next.

Ski, as you stated, manifold vacuum will yield higher vacuum and advance at idle versus ported vacuum. Advantage is that you get a steadier idle and better cooling at idle using manifold source. The ported sources became more common as a way to raise exhaust temps burn the unburned hydrocarbons more thouroughly. I would use manifold vacuum. However, it depends on the distributor model and vacuum cannister. You might try the manifold port and see if you get any pinging. If you can't tune it out, then go with the ported source.
 
That's how I read the graph as well. I just replaced the plugs and gapped them to .045. The originals were @ .030. It seems to run smoother. I was able to get the idle with the c4 in drive down to 600. That's a first. I have not had the chance to test drive it yet. I'll test drive it with the port and then the manifold to see which is better.

There is still a miss though. I'm trying to hunt it down.

When I first started it up, one of the front lifters was tapping pretty consistently. After about 5 minutes, it stopped. The lifters were replaced about 10,000 miles ago (~ 8 years ago - I don't drive it much - had it in storage for awhile). Does that oil detergent work to solve sticky hydraulic lifters? (substitute in one quart of the detergent oil, run the engine for five minutes and change the oil again).

I played with the gap between the rotor magnet and the petronix mag pickup - tried to get it as far as I could - I had to file down the aluminum base of the petronix mag pickup to swing it far enough away from the rotor magnet to get the .030 spacing required. The aluminum base was hitting the vac advance arm.

I'll post this as another topic - keep it on track.

Ski
 
I freed up a stuck lifter on my car after it had sat for a long time. I used Marvel Mystery oil, and drained it after it freed up.
Doug
 
I don't recall if it was missing. But it the lifter was ticking awfully loud. I am not a fan of miracle fixes in a can, but I figured the Marvel Mystery Oil was worth a try and a better alternative to tearing apart the engine.
 
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