Ignition opinions
April 19th, 2018, 07:31 AM
#1
Registered User
Thread Starter
Join Date: Jan 2010
Location: central Indiana
Posts: 5,233
Ignition opinions
Anyone in readerland care to share their preferred spark plugs, gap, heat range, other relevant info? Just curious if anyone has some real world testing with results. Thanks
April 19th, 2018, 11:11 AM
#2
Registered User
Join Date: Jun 2010
Location: Rogues Island, USA
Posts: 3,613
Sure, I'm full of my own opinions.
1) I've never used a gap more than .035 on anything, but I have used .032 anticipating it will grow to .035 eventually. This is for a standard tip plug. If it's platinum, iridium or whatever then leave it at .035. Once you start opening them past that point any ignition component that shows any problems from defects, wear, etc will quickly show it's head. Fine tips work well but that's a function of decreased resistance to arcing or producing a spark. The pointier or sharper the jumping off point the less spark energy is needed to jump or cross the gap. Unfortunately it also erodes faster because there is less surface area. There is less erosion in iridium, platinum, etc. tips due to their hardness in relation to a standard steel tip plug.
A standard tip plug will always arc from the outside edges of the center electrode for the simple reason that the resistance is lower at that point to the arc over of the spark. This is easily noticeable on the center electrode as a rounded nose on a well used plug. In extreme cases the ground strap will also be worn. As the plug wears resistance goes up more and more and the secondary ignition starts taking more of a beating due to electrical resistance farther up the path. The secondary circuit is made of the secondary ignition coil windings, distributor cap, distributor rotor, spark plug cable, and spark plug.
2) Ignitions are a Catch-22 in most every aspect. A typical ignition probably needs no more than 10k volts (or less) to cause an arc over at the plug tip at idle. Those fancy counter gadgets that show a nice blue spark that get's louder and maybe bluer or even white as you crank up the speed and increase the gap aren't real world. Add in RPM, the hellish nature inside the combustion chamber, the increased resistance along the whole path as RPM increases and it's pretty impressive they work as well as they do. At higher RPM's the voltage required at the plug tip may be double of what it was at idle. If your ignition isn't up to the task you'll find out fast.
3) Unless you've changed certain things in a engine, heat range shouldn't be a big deal. Back in the day you had enough heat ranges to choke a horse and cover any situation. Now most plugs are 'copper' core or some other thing that extends the operating temperature of the plug over a greater range. Manufacturers went for simplicity and less part numbers. Probably for a bigger bottom line rather than making it easier for you. The KISS rule does work well.
If you're using aluminum heads, more compression and a larger engine overall then heat range is going to be a concern. The idea is to have the heat contained in the combustion chamber where it can do the most work. More heat generally means more power but that only works to a point and everything has to work in harmony.
My heat range guidelines are simple. I look at the plug tip and follow the myriad of spark plug reading charts out there.
There are two main things I look at, where is the heat ring on the ground strap and what does the porcelain look like. I like the porcelains off white to light tan and the heat ring on the ground strap to be about halfway back on the horizontal part of the strap. For me it's that simple. Hopefully they jive with each other and all is good.
1) I've never used a gap more than .035 on anything, but I have used .032 anticipating it will grow to .035 eventually. This is for a standard tip plug. If it's platinum, iridium or whatever then leave it at .035. Once you start opening them past that point any ignition component that shows any problems from defects, wear, etc will quickly show it's head. Fine tips work well but that's a function of decreased resistance to arcing or producing a spark. The pointier or sharper the jumping off point the less spark energy is needed to jump or cross the gap. Unfortunately it also erodes faster because there is less surface area. There is less erosion in iridium, platinum, etc. tips due to their hardness in relation to a standard steel tip plug.
A standard tip plug will always arc from the outside edges of the center electrode for the simple reason that the resistance is lower at that point to the arc over of the spark. This is easily noticeable on the center electrode as a rounded nose on a well used plug. In extreme cases the ground strap will also be worn. As the plug wears resistance goes up more and more and the secondary ignition starts taking more of a beating due to electrical resistance farther up the path. The secondary circuit is made of the secondary ignition coil windings, distributor cap, distributor rotor, spark plug cable, and spark plug.
2) Ignitions are a Catch-22 in most every aspect. A typical ignition probably needs no more than 10k volts (or less) to cause an arc over at the plug tip at idle. Those fancy counter gadgets that show a nice blue spark that get's louder and maybe bluer or even white as you crank up the speed and increase the gap aren't real world. Add in RPM, the hellish nature inside the combustion chamber, the increased resistance along the whole path as RPM increases and it's pretty impressive they work as well as they do. At higher RPM's the voltage required at the plug tip may be double of what it was at idle. If your ignition isn't up to the task you'll find out fast.
3) Unless you've changed certain things in a engine, heat range shouldn't be a big deal. Back in the day you had enough heat ranges to choke a horse and cover any situation. Now most plugs are 'copper' core or some other thing that extends the operating temperature of the plug over a greater range. Manufacturers went for simplicity and less part numbers. Probably for a bigger bottom line rather than making it easier for you. The KISS rule does work well.
If you're using aluminum heads, more compression and a larger engine overall then heat range is going to be a concern. The idea is to have the heat contained in the combustion chamber where it can do the most work. More heat generally means more power but that only works to a point and everything has to work in harmony.
My heat range guidelines are simple. I look at the plug tip and follow the myriad of spark plug reading charts out there.
There are two main things I look at, where is the heat ring on the ground strap and what does the porcelain look like. I like the porcelains off white to light tan and the heat ring on the ground strap to be about halfway back on the horizontal part of the strap. For me it's that simple. Hopefully they jive with each other and all is good.
April 19th, 2018, 12:32 PM
#3
Administrator
Join Date: Oct 2009
Location: Poteau, Ok
Posts: 40,524
For HEI ignitions I gap plugs at .045, I've found no reason to go bigger. For anything else .035. The factory HEI used .080 at first, but issued a SB to drop it to .060 due to component failures. I use the spark plug size recommended for the particular head I'm using. If your engine is stock use the stock recommended plug for your engine. For performance read the plugs and see what the engine likes.
April 21st, 2018, 02:55 AM
#7
'87 Delta 88 Royale
Join Date: Dec 2010
Location: Margate, England
Posts: 2,513
Modern ethanol laced fuels require a hotter spark than the old leaded fuels of yesteryear - all else being equal I must add, having said that you only need an ignition system powerful enough to provide a reliable spark. A top fuel or alcohol drag racing engine needs a massive spark to work properly, a low compression grocery getter won't need anything more than a old fashioned points system can supply.
For a factory spec motor what it left the factory with should be fine, spending money on a hotter spark won't make any difference. As has been said if you have a performance modified engine you will learn by trial and error what plugs your particular engine will like. As a general rule the more power you make the colder the plug you need. remember a gasoline engine is a heat engine, the more power it produces the more heat it makes.
Roger.
For a factory spec motor what it left the factory with should be fine, spending money on a hotter spark won't make any difference. As has been said if you have a performance modified engine you will learn by trial and error what plugs your particular engine will like. As a general rule the more power you make the colder the plug you need. remember a gasoline engine is a heat engine, the more power it produces the more heat it makes.
Roger.
April 21st, 2018, 06:55 AM
#8
Registered User
Join Date: Jul 2012
Location: Vancouver BC
Posts: 2,788
They were better than original AC plugs as well as the expensive plugs back in the 80's and 90's
You could see the difference in performance on the ET slip, it was marginal but it was still a gain in performance.
I have never tested a modern plug in a Oldsmobile engine. It would be interesting to see results Old V New designer plugs.
Last edited by Bernhard; April 22nd, 2018 at 08:54 AM.
April 21st, 2018, 07:43 PM
#9
Out of Line, Everytime😉
Join Date: Dec 2006
Location: Melville, Saskatchewan
Posts: 8,911
I found the same thing with the NGK plugs, they do make them in Iridium as well as the basic copper the Olds V8. I have tried regular Autolite, AC Delco regular, AC Delco rapid fire and Bosch Platinum plugs for the Olds V8.
April 22nd, 2018, 09:05 AM
#10
Registered User
Join Date: Jul 2012
Location: Vancouver BC
Posts: 2,788
He carried all the big dollar plugs for those that just had to have those yellow ceramic color plugs
they did look cool!
Thread
Thread Starter
Forum
Replies
Last Post
labrats804
Small Blocks
3
July 19th, 2007 07:16 AM
