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Discussion Starter · #1 ·
I am in the process of changing to K&N air filter and lid and HEI upgrade.
In looking over information on sites I came across an article on wags site regarding coils. It stated that putting in a higher voltage coil and increasing spark plug gap would increase horsepower. Has anyone put in a higher volt coil and increased sparkplug gap, and if so did it make any noticable differance.

Thanks for any input.
Bill
 

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Bill,

Wag & I both put high voltage units in ours, kind of a hard item to segregate as to how much it helped. But in the whole scheme of things, with the adjustable vacuum pod, the upgraded coils and timinng it made a large improvement overall.

Tim
 

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Discussion Starter · #3 ·
Tim

Thanks for the response.
I confused myself by asking if anyone had widened the point gap instead of saying sparkplug gap on the other site :oops: Now I am only half confused. Did you do anything with the sparkplug gap and what was the coil output .

Bill
 

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Bill,

We used Accel Super coils.......they are 48,000 volt. I did not change the gap from recommended......This spring I am going to index my plugs and go to a plug better suites for the NOS.

Tim
 

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Bill,
I tried posting this twice on the Yahoo site, but it didn't post for some reason. I bought the Hi Perf coil from Summit. It's Summit's brand, 50,000 volt, 46,000 volts spark energy. I don't know what the difference is between voltage and spark energy voltage, but that's how they list it. I set my Plugs at .047. Works well for me. No Mis-fire at high RPM. As Tim said, I can't tell if it made any difference by itself, as I also put in the advance kit, and adjusted timing.
Here's a portion of the HEI article that is in the "Files" section of the Yahoo site. You should read the whole article if you haven't already. It's pretty good.........Don


Let's start with the coil. Its located on top of the distributor between the plug wire towers under a plastic cover. It's the "engine" that makes the sparks. Stock its capable of about 35,000 volts and so-so total spark energy. Its fine for a naturally aspirated street motor that rarely sees the high side of 5000 RPMs. It will provide the energy to jump a plug gap of .040-.045 with no problem in these applications. You can upgrade the coil with an Accell or MSD replacement coil that will jump the voltage up to about 42,000 volts and total spark energy will also jump about 10-15%. There are even hotter coils than this from Accell, MSD and others that will give you the same 42,000 volts but a LOT more total spark energy (like 50% more). Either one of these "super high output" coils is a worthwhile upgrade for a hot street motor- you'll get better response and HP especially at higher RPMs where the stock one hits a kind of "wall". A new coil is also a lot cheaper than a complete MSD ignition amplifier setup and at least 95% as effective at making HP in most naturally aspirated applications (the MSD will still give you slightly better mileage & emissions due to it's multi-strike spark capability below 3000 RPMs). With either hotter coil you can open the gap up to .045-.050 for just a smidge more HP. There are 2 different versions of the HEI coil and you need to make sure you get the right one. The only external difference is that one has red and white power leads, the other has red and yellow power leads. You will need to know which one of these you have stock to order the appropriate aftermarket upgraded coil.
 

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Discussion Starter · #6 ·
Tim
thanks for the info.

Don

Your post went through on the other site. Thanks to you also.
Just about got all the parts together for the first minny tune up oil change and shine. How can I not plop another coil in at the same time. BTW A BIGGG Moosejaw " THANKS " to everyone on this site for their tech posts.


Bill :shock: :D
 

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Coil

Coil Q;

If I go to the MSD 8502 upgrade kit, will I still need a higher output coil?

I messed around for an hour with this Krappy internet connection, and found out the 8502 upgrade includes an 8220 Extreme output HEI coil, but darned if I can find out what the voltage output is.

I also didn't find the MSD site terribly easy to navigate around in.

Thanks.

Ride Safe!

HAWK88
Jack Phillips
 

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Discussion Starter · #8 ·
Jack

On the other site Joe Ramiri (sorry for the spelling joe) feels having a higher output coil (example 48000 ) with rpm below about 6000 may be redundant if the spark plug ignites at(example 15000). So now I am thinking that it is the fuel mixture and compression that makes the differance. Does how hot the match burns make a differance on how quick the explosion happens, as long as the match is hot enough to ignite the combustable gasses. I am still at the point of what the hell just throw it in just in case.

Bill
 

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Bill...I threw it in just in case also but what I'm saying is that the needed voltage potential to fire the mixture at a given compression ratio and air/fuel mixture is what is needed and not a volt more. A stock motor that needs 15,000 volts to fire with a 0.40 spark plug gap will not benefit from a coil that can produce 50,000 volts because the plug will fire at 15,000 volts potential...PERIOD! The 50,000 volt coil will fire with much more dense compressed mixture which may require 20-30,000 volts as in a stroker or other high compression engine but if anyone believes that upgrading a coil to much higher voltage than is needed will do anything...they are wrong and don't understand the physics of what is going on. The coil doesn't "force" or "drive" a spark through the center electrode to the side or vice versa but only creates a potential difference between the two and sparks when the difference is overcome by that potential difference. I am saying that no spark is "hotter" than another between electrodes that are the same distance apart. If you want to increase the gap..sure you will need a stronger coil to produce the energy to jump the bigger gap, The electrons will jump the gap as soon as the potential difference is reached even if you have a 200,000 volt coil.
Morris Magneto used to have demos at bike shows that showed it could throw a spark across a 1" gap and you could light a cigarette in the spark. I don't have a 1" gap in my plugs so what would that setup do for me...nothing...Joe
 

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Don...The voltage of the coil is that which the coil is capable of producing if needed. The spark energy voltage is the voltage at which the plug fires which has to be the same or less than the than the coil voltage. If I have a 50,000 volt coil and have a 0.40 gap in the plugs with a normal motor, the coil voltage is 50,000 whereas the spark energy voltage is 15,000 volts. The spark energy voltage is nothing more than the energy the coil must generate to produce the spark although the coil is CAPABLE of producing more if needed..Joe
 

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Don....a couple of vodkas get my physics lessons going but what I'm saying is the truth. If what I'm saying was not the case then all of us should just keep putting stronger coils on the puppies and we'd keep getting better and better performance. I know you get it...Joe
 

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Jack..I believe the MSD upgrade you are talking about has a 48,000 volt coil. Look in Jegs or Summit catalogs. It's the one I have on my stroker..joe
 

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Coil

Joe;

Thanks, just wanted to be sure when I can scrape up the nickles and do the ignition upgrade, I am not doing it half arsed (Brit Ass!).

Each project on this is rather a first for me, and I want to learn it correctly and do it well.

I can rig and flight trim most helo turbines for you as a Maint test pilot, or track and balance your prop or rotor blades, but thats all past now, and this is my new game. Thanks to all for being so patient and informative.

Ride Safe.

PS: I was 1/3 of the Boss's @ the First Turn tonight. Hard to read there sign thru bifocals in the rain. Thats OK, got to visit with the Mountain Boss Hoss gang, met some other neat folks, and learned a lot.

HAWK88
Jack Phillips
 

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Joe,
I guess you could say a Hi Perf coil ( depending on how you ride) is a bit of overkill, kinda like the rest of this bike. But at least for the price, "it couldn't hoit!"
Quote of the week............To coil, or not to coil........THAT is the question!
PS.......save some of that Vodka for me! :wink:
 

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Joe,

I'm gonna have to change my drink of choice...vodka gets you going on physics.....rum gets me started on pussies......something is wrong here :lol: Here is an interesting piece from a high performance site dealing with 'hot' coils. As I mentioned on the other site, they really are only advantageous above 5000 rpm..........

The HEI coil is the device that actually generates the high voltage needed to fire the sparkplugs.. In some cases it can generate up to 40,000 volts. Usually only about 12,000 volts is needed but having the extra voltage means that the ignition will be reliable under all circumstances. And it makes the sensation of being shocked much more intense. Be careful with these high voltage systems as they can be hazardous to your health.. And unnecessarily stimulating.

The coil is one area that needs upgrading in a performance application. The stock system only generates full voltage under about 4150 rpm due to the time necessary to charge the magnetic field in the coil being about 3.6 to 4 milliseconds. With the voltage dropping rapidly above 4200rpm by the time the motor reaches 5500 rpm the HEI ignition is no longer reliable. This is not a problem in stock motors and normal driving but is inadequate for racing.

The charging time of the coil is directly related to the charging current. One of the reasons for the slow charge time specified during the initial design of the HEI was that the early transistors used in the control module were limited in the amount of current they could handle. Times have changed in the last 30 years and modern control modules are much more capable. The performance coils (using matching control modules) charge in about 2.5 milliseconds which means that they can develop full voltage up to 6000 rpm and useable voltage up to 7200 rpm.

To be able to charge this quickly the performance coils are constructed differently with smaller cores and fewer primary windings. The smaller cores can cause a serious problem if the longer screws used to mount the stock coils are reused for a performance coil. Since they would be too long they may crack the distributor cap and cause problems later. You can see the stock coil on the left with the performance coil on the right. Note the thinner core of the performance coil.

Wow, this guy must have been drinking scotch :wink: :lol: But an interesting and plain English disertation on the HEI coil issue. So if you're not going to run above 4500 to 5000 rpm relatively often, I guess you don't need 'em. But for about $50 they are a cheap investment. I now Wag & I run up into the 6200 to 6500 range often and never have ignition issues....they pull hard all they way up.

Tim
 

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Tim...You are absolutely correct and high output coils are needed for performance applications and you, obviously, know much more about this than I do.. I was just trying to say that using a high output coil in a stock motor that is run under 6000 rpm will not improve performance. Great to have if you want to do some mods on the engine but for the stocker in normal use they mean nothing...Joe
 

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Tim..fortunately, in my profession, I need no alcohol to get started on pussies since that's what I do for a living. I never tried Rum before office hours and don't think it would be a good idea!...Joe
 
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