Ignition requirements
 

Ignition requirements

We've been discussing the building of our Flathead engines from stock to blown. And the tuning requirements of these many different engines are different and confusing. I think an explication of what necessary and why, would make it easier for those wanting to get the best bang for the buck. I have received many Emails and PM's lately asking me for advice. One such person asked, Why should he spend 75 dollars on a new set of $625 heads just to take .020" off of them? Good question.
OK, First, there is only one commercially available distributor on the market that meets ALL the requirements of our daily driver and a trip to Bville, that's the 49-53 MSD unit. I know that may create an argument in some circles. Why?? Well it's the only distributor where you can adjust the mechanical and Vacuum advance to any desired curve. Name another? There isn't one. Lucky we have the SBC distributor which the MSD unit copied down to the last detail. Several of the members here on the barn will rebuild these to any configuration you desire. You can't get that with any other distributor at any price. And they do fit 48 and earlier engines, but don't look right, unfortunately, if you want the best system for your engine this is it. now for the purest the 11A works very well and come close to meeting your needs.
Now just what does the engine need? Well the combustion chamber determines that. The combustion chamber determines the Compression ratio, which determines the volume of the chamber, and the volume determines the area. By milling the heads for a TIGHT fit between the piston and head we in effect shorten the flame front and increase turbulence at a time just before the spark plug fires.
WE also have a carburetor in this equation to deal with. It provides the power to run the engine under heavy load and economy driving down de road. It does this by having the main jets adjusted for a lean mixture and a power valve for those times we need all the power the engine can produce. Some carbs do this better than others.
Now how does the distributor do all this? Well depending on the engines needs it offers a controlled mechanical l advance based on engine RPM. And the Vacuum advance determine the amount of advance under load.
Now if your AF (air fuel) is correct for these conditions, you have an inexpensive engine management system, 6 or 12 volts. well lets see what happens now. Happy New Year..

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Ya know Ron, you should write a book....;)

Re: Ignition requirements
 

[QUOTE=Ol' Ron;1221360]Ignition requirements


OK, First, there is only one commercially available distributor on the market that meets ALL the requirements of our daily driver and a trip to Bville, that's the 49-53 MSD unit. I know that may create an argument in some circles. Why?? Well it's the only distributor where you can adjust the mechanical and Vacuum advance to any desired curve. Name another? There isn't one.


Ron ,

I think you got up on the wrong side of the bed this morning.:)
Our chevy conversion has always had the same adjustments the MSD units have (including the one i did for you), the chevy distributor limits the advance with a bushing ( just like the MSD ) and has since the very first one.

The rate of advance is determined by the springs and are very interchangable ( just like the MSD) and always have been since 1955.

The vacuum advance on most distributors are adjustable with a allen wrench today and even the earliest GM units was adjustable ( required changing the vac advance).

Our units even use a adjustment that even MSD dont have and thats rate adjustment with a allen wrench, ( copied from your friend Richard). I service the MSD ( did three last week) and personally would take a early delco in all cases as i had to bead blast each of the units to remove the rust from the parts that are mostly off shore pieces at best....

I think you may have mis-spoke a little bit here...:confused:

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I guess you didn't read my post very well. I said the MSD copied the SBC dist, and we are lucky to have several people on the barn that make them. That includes YOU!!

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From Two of the best!Thank you both.

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Ron , I kinda knew what you meant to say but the first sentence made me wonder .

First, there is only one commercially available distributor on the market that meets ALL the requirements of our daily driver and a trip to Bville, that's the 49-53 MSD unit.

See what i mean , i thought you might have been hanging out with Richard again...:D:D

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No, Richard had nothing to do with it. I get allot of emails and PM's about this stuff, and thought an explination would help. What supprises me is the fact that a simple electronic advance hasn't been put on the market. It's been around since the early 80's. hat would put everybody out of business. I can't believe they still sell distributors without Vacuum advances, it's more important, because the mach adv has no idea of the load.

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Ron,

Some thoughts on electronic advance :

From RC universe:

If set up for electronic advance, the electronics module gets a signal from the crank position sensor [Hall sensor] long after the time when the spark should have been generated. Therefore on that particular rotation it is too late and the only thing it can do is fire the plug immediately, so you get at least one cycle when the timing is off. The ignition module has to remember that the engine is accelerating, remember the rpm, and try to anticipate at what point the spark should be fired for the next rotation. As you can see things can change pretty rapidly, a full rotation could see the engine no longer accelerating.

The whole operation is some guesswork and a lot of computation to get it right. In an environment with rapidly changing RPM values some error may occur. The calculations are much simpler and error is much less with an auto-retard system. Auto-advance works, but it's not quite as precise in all conditions.

With auto-retard the module can calculate the firing angle over just a few degrees of crank angle in the current firing cycle. Auto- advance systems inherently must calculate over the last full 360 degrees of crank rotation and then average that with several previous cycles. This is because when auto advance senses in the current firing cycle that it should have fired, it is already 20 odd degrees too late to do so.

Auto-retard provides extreme accuracy and allows to actually anticipate rapid increases in RPM and compensate the timing for better engine response. This is achieved because the calculation time required is so minuscule as compared to the ignition firing rate.

Auto-retard requires an extremely accurate calculation be done extremely fast because it occurs within the current firing cycle. Auto-advance requires only remembering past cycle(s) and guessing what the next cycle should be. Both methods can be accomplished with discrete components. Newer auto-advance systems use micro-processors to reduce part count and increase accuracy.

Some more study for ya....

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I know nothing about Electronic ignition devices except the Pertronix triggers that I use in both my cars. I do know about the advantages of vacuum advance and wish I could incorporate it in my 11-A distributor on the Flathead in my 32.

However, when we ran my engine on the Dyno (twice), we were able to check the timing under load at 1000 rpm intervals to see if varying the timing made a difference in power output. With all 28 degrees of timing in @ 2000 rpm, there was little to NO difference by advancing or retarding the timing a couple of degrees. (this was time consuming exercise, as no one is allowed in the dyno cell when the engine is under load)

Had there been a great difference a t the various rpms, I would have attempted to modify the advance weights using my friend Larry's Sun distributor machine. Fortunately that wasn't necessary.

So, other than the vacuum advance, or lack of it in my case, I see no advantage to an electronic advance/retard module. Plus, to me , an early Flathead engine looks weird with a top mounted distributor. I like symmetry (sp?)

Just my thoughts
Jim

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I'm not sure how they do this,but most cars today have computer controlled ignition timing and fuel delivery systems. Todays systems are very complicated and expensive. However GM started this back in the mid 80's with their first EMS using a simple throttle body. This system can be modified to run on any engine. Now, if a guy like me that likes to puts around can take the distributor (8BA) and trigger this system, he can run the ignition requirements of any engine quit accurately and the MAP sensor makes great mileage. I'm working on that. However I don't think that's necessary for getting the most from our flatheads. Just one of Bubba's distributors properly tuned for the application will do the trick.
Now the thing that confuses me is how you can get a flathead to run WOT at 28 degrees adv. MY engines would destroy them selves in just a few seconds. I must be missing something. I use 26-28 degs to burn the lean mixture in cruise. Ont the 294, I have 20* @ 2k any more and the thing hammers like hell. However in cruise 26 works just fine. Don't have any results on the 280 yet. You can also use an Ardeno(SP??) it has allot of memory and only costs 35 bucks.

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OK, what does that mean?

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Not to worry Richard, I have it covered. No harm, no foul. Just a little miss understanding,

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That chevy distributor started in 1957 not 1955. The first two years were a different style.

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Well I'm disapointed in this thread. I was hoping for more of a discussion on tuning and combustion chambers than a few ruffeled feathers. For those wanting to get the best ignition system for your engine. The MSD and the Converted Delco unit properly set up is the ONLY way to go. Just remember the carburetor is part of the system and you'll get plenty of power as well as great mileage. Also running a rich mixture affects ring ware.
On to another project: The Loudon engine.

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I haven't been thinking about ignition lately( as I have one of Bubba's Chevy conversions), but I have been thinking hard on carburetion.
I started out running my 52 Merc, 265 CI motor last year with an edelbrock triple setup. Three Chandler Groves carbs, only thing is I used two of Uncle Max's cheater plates to block off the end carbs. It ran great all summer, so I'm thinking of opening up the other two carbs, but I don't want to spend the entire next summer putzing around with them.
I really like the way it runs now, but I'm sure there's more power to be had, I've been mulling this over for awhile and still haven't decided if I'm going to do it or not.
Our summers are so short here you can't afford to waste even one weekend.

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I have tried two chev. dis. for my 49 one with a vac. advance and one from Bubba with out. The dis from Bubba is the best for my engine . Jack

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Is there any advantage to running a converted distributor with vacuum advance on a stock engine VS the stock Load- a' matic? Assuming both being points.

Scott

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The mechanical and vacuum combination is better than the vacuum only on the original. And the mech/vac distributors are adjustable so they can be tuned for your application.

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Hi fellas. Visiting here from over on the HAMB. I am running a sbc points distributor on my 53 239 , 3 94s on an edelbrock. I currently have the vac adv. capped. Is there much advantage to running man. vac to it?

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Here is a quick shot of my setup.Attachment 253908

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Depends on what your interested in. The vacuum advance/retard allows the distributer to adjust to engine loads in cruse. It mostly benefits fuel economy. If you are more interested in straight ahead acceleration performance I don't think it makes much difference.

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Why wouldn't you want the vacuum advance? The engine will be more efficient, you will get better mileage and the engine may even run a little cooler. Win, win, win in my book.

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Why?

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Vacuum advance is used to balance out the mechanical advance ( also cleans up emissions etc) When vac is high ( no load ) vac advvance is in and when rpm ( load) is high the mechanical is in .
Together when one is down the other is up and vice versa....
I have found that vacuum advance is very hard to tune with the flathead engine and takes some time with the timing light and adjustments...

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Actually load is independent of rpm. Load refers to the strain being put of the engine. High vacuum - low load, low vacuum - high load.

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I agree. '53 Victoria - 3300 lb, 276 ci, 8.5:1 compression, L-100 cam, Edelbrock 500 cfm 4-barrel, my own SBC distributor electronic conversion with both mechanical and vacuum advance triggering a simple 4-pin HEI module, T5 with .72 5th gear, 4.10 rear end, 205/75R15 radial tires --- about 22 mpg over a measured 50-mile course that was 2/3 local driving and 1/3 high-speed interstate driving.

Easy steady cruise = 28°. Accelerating = 20°. No ping.

The use of adjustable vacuum advance with either a converted '60s points distributor or a later larger diameter Chevy HEI distributor couldn't be simpler.

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Mr Fords original duel point distributor has served me very well for many years and don't have to worry about all that mumbo jumbo that goes right over this old 85 year olds head.My only complaint is the location down at almost the worst place to get too he could find, the older I get the worse location it gets to be. I have seen that old dist. do its thing in the worst condition all over the world from Alaska, to S. America jungle, to Korean winters to West Texas dust storms. Oh well, just an old Ford guys experienced opinions. Keith Oh

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I drove this car and was impressed with it performance and drivability. Watching the AF meter, as it wandered around 15.5- 16:1 in cruise. I like the Edelbrock carb because it's power valve is the rod system. In his quest for better economy actually made some of his own rods. Unfortunately, they didn't work much better than the ones supplied in the kit. I don't expect you to do this kind of experimenting, I know you'd rather drive your car than tune it. However, some of us actually like doing this and the results of our research is given FREE for you to use as you see fit.

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I may be stating the obvious here, but in discussing ignition systems the need for a strong spark can't be overlooked. Especially when trying to fire leaner mixtures like Ron mentioned, larger spark plug gaps are needed to prevent a lean misfire. Larger gaps require higher voltage which requires a stronger coil that draws more current. More current (higher amps) burns points and shortens their life. My '40's owners manual calls for .025" plug gap and the entire ignition system lives a long and happy life at this setting. If I were to let the plugs wear to (or set them to) .030-.035"+ gap, the coil is unhappy and can't fire reliably or it just goes belly up. Add a stronger coil or bypass the resistor and the points die. Plus the higher voltage can eat holes in the rotor. And the original wires will leak. Chances of cross fire go way up, too.
So the whole system has to considered to get reliable ignition.
In the mid-70's the factories had to meet emissions standards so went to leaner mixtures which called for large plug gaps (.045" to .060"-Olds even had .080" for awhile) to light these mixtures without misfire. In turn this required 8mm plug wires (or better insulation on 7mm wires), large diameter caps, epoxy or laminated coils to handle the heat, and solid state electronics to replace the old points and condenser setup. Instead of 10-15,000 volt coil output, we got 40,000 plus. All-in-all, a win-win situation! The more of this stuff we can adapt to Henry's finest the better they will perform (both power and economy)!

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Ol' Ron did indeed drive Daisy Mae and here's proof!

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Great looking setup !!

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This is what works for me, and still working well at 25,000 miles. My steel 34 coupe with a 296" Mark Kirby built flathead has the following specs. The engine: 296", full port and relieve, .050 over piston, Offy 425 heads milled .060 over valves, potvin super 3/8, B&M 144 blower pushing 5psi @ 5000 rpm. This is what REALLY works after 10 years of dicking around with ignition and timing.

Dist... modified GM Mallory unilite.. 28d total centrifugal advance
MSD 6A with boost control retarded 2 degrees per lb of boost
Vacuum advance ( Manifold vacuum) 4 degrees total
This combo gives me 18 degrees at wide open throttle, cruise at 70 mph (about 2000 rpm with the t5) about 30 degrees ( incl vacuum advance)
This gives me great MPG and performance. Every engine is different an will require something different.

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40 Deluxe
I agree with you on every account except one. What we're working with is not a modern engine with hi compression etc. The averaged street rod has 8.5 at most, any more would require higher Octane gas. Yes we use .035 plug gap and some use electronic instead of points. I on the other hand yes a points dist and I doubt the voltage required to fire the plugs is much higher than stock. But, consider this, pretty soon the old points, condensers and other Old ignition components won't be available, or of inferior quality. Most of us will like to drive out cars and trucks, so having some of the modern stuff just might come in handy. Just trying to help.

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Hi Ron, I'm sure we're on the same page here. I guess what I was trying to get at but didn't say it was the need for sufficient ignition reserve to fire reliably under all conditions. As you know, a coil will only develop enough voltage to jump the plug gap. So a coil rated at say 40,000 volts seldom puts out anywhere near 40,000 volts unless the plug gap is huge, the compression is high, or the distributor rotor is worn to a nub. At idle and light throttle the voltage seen on a scope may be only 5,000 or so. Crack the throttle open and the voltage jumps to 20,000 plus briefly. If the coil can't put out that much, we have misfire. I was taught that you can have significant misfire before you can hear or feel it. Misfire raises emissions and lowers power. This was another reason for electronic ignition coming out.
Remember the old AC spark plug cleaners? You sandblasted the carbon off the plug and then tested it by threading it into a chamber, hooking up the coil and watching the electrodes in a mirror as you added shop air pressure. At some point the spark would blow out. If below a certain amount, which I don't recall, the plug was bad. You could save some by decreasing the gap. The spark voltage was deliberately low in these machines but it was interesting to see the spark actually stop, unable to jump the gap.

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No one have mentioned sparkplugs here so far.
A hotter working plug takes less to fire up.
Choosing an as hot plug as possible to avoid fouling and stumble, and that the hotter plug will light the flame faster at all RPM resulting in an increased burn rate. Good aproach if you dont mind cooling the plug with some extra fuel aiming for power and not maximum fuel economy.
Choosing an as cold plug as possible.
This gives you the advantage of being able to use increased timing and leaner mixture eliminating the plug being a preignition point.
Eliminating the heat of the plug gives you a more tuning sensitive setup.
The backside is low rpm handling.
One aproach to getting a higher spark energy at low rpm is to use a internally gapped sparkplug.

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Q: Do you use a portable air fuel ratio gauge of is it plumbed into your car(s)?
Any recommendations on which one to look at?

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I like the new one Richard Bought, can't remember the name. The one I have is an old one that only goes to 16. For those interested, I'm making a fixture that will allow you to install a power tip plug in a stock head. I feel this will help with the lean mixture. Now the flame front is what causes the "Knock or Ping". When the plug fires the flame fron runs across the chamber increasing the pressure. If the pressure builds to a point where the remaining un-burnt fuel is, it detonates like a Diesel. This is another reason to reduce the piston to head clearance.

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Here it is.

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To get accurate reading the sensor needs to be fairly close to the engine and plumbed into the exhaust line, something like an O2 sensor.

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I checked out the air/fuel meter on the Innovative Motorsports website. They have the complete manual for this unit available there which should answer any questions you should have.