Ignition requirements

[JSeery]

Originally Posted by steves29

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?

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.

[flatjack9]

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.

[flatjack9]

Originally Posted by shoe box Jack

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

Why?

[BUBBAS IGNITION]

Originally Posted by steves29

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?

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...

[flatjack9]

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

[Richard in Florida]

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Originally Posted by flatjack9

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.

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.

[keith oh]

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

[Ol' Ron]

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.

[40 Deluxe]

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)!

[Richard in Florida]

I drove this car and was impressed with its performance and drivability.

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

[Sid the Maineiac]

Great looking setup !!

[hotrodcbx]

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.

[Ol' Ron]

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.

[40 Deluxe]

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.

[flatheadmurre]

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.

[CA Victoria]

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?

[Ol' Ron]

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.

[Richard in Florida]

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.

Here it is.

[JSeery]

Originally Posted by CA Victoria

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?

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.

[tubman]

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.