Hood clearance and electronic ignitions

[pgtr]

First Vettehead Mikey wrote:

Sorry, Mr. Know It All, you're just as much an a-hole on this subject as you are the glass fuel filter discussion. You're not fishing me in.

Then he followed it up with:

I'll be darned if I set myself up for an attack like John got on the fuel filter topic. I don't need cr*p like that.

Not sure what the purpose of labels like "Know It All":ugh and "a-hole" or what fuel filters has to do with ignition...?:confused

But at any rate, how different triggering mechanism affect coil voltages is usually well discussed in most introductory auto mechanic texts that cover engine theory. One of my favorites is _Small Engines_ by R. Bruce Radcliff ISBN 0-8269-0008-9.

The technical/political history behind why all automakers (yes, even GM) dropped breaker points and went to electronic ignition in the mid 70s as standard equipment is abundantly documented everywhere - try google.com for starters.

Let's not confuse 'attacks' with facts shall we?:W

 

[Craig -1965]

Regarding the spark is a spark is a spark, one thing I'd like the add, is with the pertronix system is the balast resistor is bypassed. Therefore removing resistance is an inginition system can only increase the quality of the spark. To date I have had no problems with my pertronix...... Now with that said, tomorrow nights cruze is cursed.......................

 

[Jack]

With all due respect Jack, a spark is a spark is a spark. If it lights the fire, a hotter spark won't make any difference during combustion of the fuel and air. The stock system does an excellent job of lighting the fire.

The non HEI systems you named still rely on the stock coil to provide the energy, so there is no 'hotter' spark to be had.

The big drawback with the pertronix POS is it's habit of failing without warning.

Respectfully, I both disagree and agree. I'm not an EE but know enough to wade through the hype. The newer systems have more spark energy and can jump a wider gap without being blown out ... and can burn the intake charge more completely. I can't think of any ignition that does not rely entirely on a coil to step up the 12v to fire the plugs ... heck, I think they all do ... even the newest LS7 w/ecm uses coils. There ain't a thing wrong with points ... they do a great job and that's what fired most cars for some 70 years ... but better systems have evolved. Both the Breakerless SE & Crane XR-1 are more like an HEI than not. HEI's more-efficient burn helped GM achieve compliance with emissions standards. And just as GM's stock points do a great job ... so does GM's stock HEI ... only better. I have an old H-D pan-shovel 86" stroker that has a points distributor ... I learned a long time ago how to set the timing with only a few hand tools and a cellophane cigarette pack wrapper ... and the points gap with a matchbook. While new twincam bikes have ecm's (H-D now in smog-nazi crosshairs too), I'll probably keep my old bike's points ... but the vette's a different matter ... personal choice. None of the circle track cars around here run points ... most run an HEI w/ a DUI Dyna module ... and in classes that permit, an MSD box. The Late Model I co-owned last two years runs a gutted HEI (trigger only) coupled to MSD 6TN and external coil. But NO, I don't recommend MSD box for most street cars. For a street car, I want a reliable ignition that I can get parts for anywhere ... HEI stuff is universally available ... not always the case with points anymore ... any aftermarket electronic such as MSD, Pertronix, Breakerless, Crane etc definately not so available. No cat-calls here, just friendly discourse.
JACK:gap

 

[Vettehead Mikey]

All good points Jack, but the original statement I made is still true - "... a spark is a spark is a spark. If it lights the fire, a hotter spark won't make any difference during combustion of the fuel and air. The stock system does an excellent job of lighting the fire."

The key point that is being overlooked is the part " If it lights the fire, a hotter spark won't make any difference during combustion of the fuel and air. " In this particular context, we are talking about a C3 Corvette with a standard (or possibly lightly modified) production engine and not a top fuel drag engine. The stock ignition system is more than capable of lighting the fire under these conditions.

Other engines that through design considerations or performance expectations cannot achieve reliable ignition of the intake charge may require a system that features higher output, but as suggested before a 'hotter' spark than required does not equate to higher engine performance.

My company designs and builds engines that are required to start first time, every time, after being cold soaked at -40 degrees or lower. In-field testing determined that the standard 3 joule ignition system did the job just fine, and the proposed 5 joule system just burned out plugs faster.

Unless I have been completely BS'd consistantly over the last decade by various senior GM employees, their decision to convert to HEI in '75 was not driven by a need to achieve good pollution numbers, but as a means to MAINTAIN good pollution numbers over a prolonged period. No one can argue that a standard points system does not need occasional maintenance (remember twice annual tune-ups?) and it is true that an engine that is out of tune can produce serious pollution. The HEI system was primarily introduced to keep the ignition 'permanently' in tune.

Let's agree to not mention the p_rtr_nix POS, it will just ruin my lunch (again).:L

 

[pgtr]

statement I made is still true - "... a spark is a spark is a spark.

What was false yesterday is still false today if mere repetition is all that's being added to the discussion. Then again one wonders how an engine might run w/ a pair of sneakers and a wool rug since a spark is just a spark. . Hey is lightning just another spark too?

The stock system does an excellent job of lighting the fire.

By decades old standards applied to a vintage limited use collector vehicle, sure it 'minimally' 'gets the job done' with a number of potential deficiencies. A FAR cry from any reasonable understanding of "excellent job".

The key point that is being overlooked is the part " If it lights the fire, a hotter spark won't make any difference during combustion of the fuel and air. " In this particular context, we are talking about a C3 Corvette with a standard (or possibly lightly modified) production engine and not a top fuel drag engine. The stock ignition system is more than capable of lighting the fire under these conditions.

Suddenly introducing a lot of qualifications as well as comments like "In this particular context" bring a thought that back-pedalling is in full motion: Suddenly the simplistic proclamation that "A spark is a spark" isn't so simple anymore. It's starting to get awfully thick w/ qualifications.:W

A standard conventional points based ignition produces a spark that is both colder and skinnier. And NO, that is not 'good enough' for many an engine - especially many of the lean burning early C3s.

Other engines that through design considerations or performance expectations cannot achieve reliable ignition of the intake charge may require a system that features higher output, but as suggested before a 'hotter' spark than required does not equate to higher engine performance.

"May require a [electronic] system"? Why did C2 Corvettes of the 60s have optional electronic ignition? A: They needed more energy. And when leaner mixtures were encountered by the time of the early C3 which spotlighted ignition deficiencies in the same standard ignition what was the solution? A: Mercy me if it wasn't the same ol' answer: electronic ignition! And what of the marketplace demands and government encouragement for cars that lasted longer w/ less maintenace overhead...? A: HEI.

My company designs and builds engines that are required to start first time, every time, after being cold soaked at -40 degrees or lower. In-field testing determined that the standard 3 joule ignition system did the job just fine, and the proposed 5 joule system just burned out plugs faster.

I'm not sure what the above story has to do with anything here. Is he attempting to imply that electronic ignition burns out plugs quickly? But since Vettehead Mikey brings up longevity of plugs let's explore some facts shall we?

FACT: plugs run in an electronic ignition system last anywhere from 50K to 80K miles. (rough ballpark)
FACT: plugs run in a points system last anywhere from 6-12K miles. (rough ballpark)
FACT: points begin mechanically wearing the instant they are installed/set.
...which leads to...
FACT: optional electronic ignition is what GM offered on performance engines of the C2 era with good reason.
FACT: points based systems of the early C3 era struggled w/ the lean mixtures.
FACT: GM resolved this by re-introducing electronic ignition which was ultimately standardized across all divisions/platforms by '75.

Unless I have been completely BS'd consistantly over the last decade by various senior GM employees, their decision to convert to HEI in '75 was not driven by a need to achieve good pollution numbers, but as a means to MAINTAIN good pollution numbers over a prolonged period.

They BS'd Vettehead Mikey by omission. As performance engines went away - they were replaced by very (overly?) lean engines, heads, carb settings etc... A standard ignition struggles to dependably light every ignition cycle of every cylinder every time under lean conditions - voila, HEI to the rescue. HEI was needed to achieve better emissions and mileage up front given the lean mixture approach Detroit was taking at the time and (yes Vettehead Mike) certainly this needed to be sustained over a period of time longer than a few thousand miles.

No one can argue that a standard points system does not need occasional maintenance (remember twice annual tune-ups?) and it is true that an engine that is out of tune can produce serious pollution.

Arguably you can set electronic ignition and leave it set for years at a time on a daily driven car. A far cry from twice annual.

The HEI system was primarily introduced to keep the ignition 'permanently' in tune.

Yes that is one of the many reasons but "primary"? Is there any evidence to back that up and be so dismissive of resolved issues such as lean misfire, spark energy, mileage and emissions?

Let's agree to not mention the p_rtr_nix POS, it will just ruin my lunch (again).

I'm sure most folks would be glad to agree that electronic ignitions systems such as the "p_rtr_nix" are just a "POS". Of course Vettehead Mikey needs to share some statistically valid facts rather than antecdote and opinion first...

In summary this fascination w/ the old points based ignition in early C3s is quaint but deficient in facts or logical engineering practices. Yes any of us can pine for the 'good ol days' of tubed tires, wooden spokes, tube radios and dependable hand crank starters. To appreciate the functionality of the Kettering ignition system is one thing (and I VERY much appreciate it). To call it "excellent" or even 'good enough' by the time of the early C3 era is a denial of reality. But if Vettehead Mikey wants to take his 'good enough' argument to the next step - let's just shortcut to the end and agree with him that if we all still lived in caves as hunter-gatherers - that it would be 'good enough' and end this discussion.

 

[WayneLBurnham]

Guy I only have experience with the aftermarket L88 hood

and several after market carbs and cleaners, typically with the <3" element and typically with a 1" phenolic spacer.

With all that height, the three ignitions which have been on mine - including the original HEI, an aftermarket HEI, yet another aftermarket HEI and now the....wait....FOUR ignitions...the origi.... ..... and now the seemingly taller and canted inward MSD ProBillet thing, the ignition sat well below the top of the carb.

Now this is the highest stock-like hood made ("stock-like" - that's a phrase *I* just coined! You can use it, but send me a dollar every time you do! :L ) so I don't know how well this transits to your situation, but I thought SOMEONE should chime in about hood clearance and ignitions sooner or later....

I don't think the HEI ignition cap, if I remember your start of the thread, is really any higher than the previous stock GM points distributor.

So, if you want to get rid of the hassle of setting points (can I even find a dwell meter out in the heap now?) and them getting wet or pitted and corroded and breaking down, and the joy of bumping the thing over and over again to get it stopped right on top of a lobe....ugh....and go with a nice modern HEI, reliable Pertronix or Pertronix II (with the rev lmtr I understand) or something else, I would THINK it would fit if a regular, ancient, hateful, unreliable points thing did. (Gawd, I remember setting DUAL points at one time.....never...again....)

Did I fail to annoy any of the combatants? ad

 

[Vettehead Mikey]

Did I fail to annoy any of the combatants? ad

!

 

[Chiller]

Yes you did. Most the Iraqis do not have vettes !

Did I fail to annoy any of the combatants? ad[/QUOTE]

 

[WayneLBurnham]

If they did, I'd bet they'd have points!

:L

So how long you got before you can play with your car again?