Well. . . here we go again.

First of all, I was attempting to try to test different style plugs to determine if I noticed any results. I tried NGK TR-55's, NGK TR-6's, Bosch Platnum, AC Delco Platnum, and the AC Delco Rapidfire. -What I found out? -That my supercharger was leaking oil into the intake and fouling the plugs, regardless of what I was running! DOH! Besides the fact that it would idle smoother, rev faster, and put out more power for about 50 miles after changing the plugs, due to the fouling, I noticed no measureable difference. 1/4 mile times were within +/- .2 sec regardless of the plug. I generally get that much error in runs anyway. I'd like to retest AFTER having the blower fixed. I do have historic data on The NGK's though. . . For about 2 years I ran NGK TR6's (This was before my blower leak) and I had to replace them every 4 months due to extreme fouling. I than switched to the NGK TR-55 and had little trouble with fouling, a smoother idle and a drop of .25 sec ave. on the 1/4 mile. After a year I switched back to the AC Delco Platnum and noticed no difference to the NGK TR-55. Therefore, my conclusion on this limited trial is that the TR-6's smaller gap or colder temp were causing incomplete burn. As noted above when I decided to do some honest testing my blower started leaking. . . .

So. . . 1st topic of debate: Platnum VS Non-Platnum:

In the earily days of platnum plugs, the concensius was that platnum plugs were bad to run with a blower due to the possibility of the platnum tip burning/falling off and causing the gap to open up. -Vortech kinda broke the mold when they announces that thier kits could and should be run with factory platnum plugs at the factory gap. It would seem that with advancements in plug design and manufatoring, there is no reason to not to use a platnum plus, but likewise, the only reason TOO use a platnum plug is so you don't have to change plugs as often.

-Any other points/counterpoints?

2nd topic: Plug Gap; Factory .50 VS .35:

Here, the idea historically has been to run a smaller plug gap, I.E. .35" in order to facilitate positive ignition. In other words, there were concerns that with a wider gap, such as the factory .5, that the spark would be to weak and would not ignite the fuel in a forced induction system. Again, Vortech kinda shook things up when they stated that you could run factory gapped plugs with thier systems. The concern with running smaller gaps is that you will have incomplete burn of the fuel in the combustion chamber. Generally this could be offset by running a high temp plug.

-Other points/Counterpoints?

3rd topic: Plug heat range; Stock Vs. -1 VS -2.

Again, it is generally accepted that a colder plug will help reduce the chances of predetination on a forced induction motor, however the concern is that a colder than stock plug will not burn as completely as a stock heat range plug.

-Other Points/Counterpoints?

4th topic: Single vs. Multiple contacts. (I.E. Bosch +2 and +4).

I guess the idea is that with multiple contacts the plug will either be more reliable, less likely to foul, or deliver a more consistant burn. Now, with a basic understanding of electricity and knowing that it always takes the path of least resistance, we can conclude that the plug will only spark from one contact at a time anyway, whichever offers the least resistance due to distance or lack of fouling. However, Bosch would have you believe that all the contacts will produce a spark at once. In reality? I have tested the +2 plug and seen only a single spark. Is this always the case or has someone seen otherwise? I have tested this plug in a non forced induction application and found no diffrence between the +2 and a factory AC Delco Platnum in terms of fuel consumtion or engine output. The largest cons are the difficulty in setting the gap, and the price.

-Other Points/Counterpoints?

In conclusion, I would say that the best plug to use would be: Factory heat temp, .5 gap, platnum, single contact. (In particular, I'm going to stay with the the AC Delco Platnum). This plug would be less likely to foul than one with a smaller gap or heat temp, last longer, and be the best value in terms of cost VS suitibility. I have experienced no predetination from using stock temp plugs, and had no problems with regards too complete burn of the fuel with a .5 gap.

If you are having problems with predetination, than switching to -1 may help, however I would still use a .5 gap.

Any other topics I missed? -Please chime in with your thoughts or any corrections (as I'm up in the middle of the night typing this because I can't sleep and probably messed something up).

I guess one other topic could be: Why the heck am I up in the middle of the night worrying about spark plugs????

-Justin

 

It all depends on peoples setup. Boost,compression and cam can all change. My best results were -2 heat ranges with about a .42 gap. And I just use the autolites they are cheap for when it comes time to replace.

 

Might list your commpression ratio ,boost level, type of blower, ect.
FWIW I called Ngk and they recommended TR7ix plugs for about 10psi on a 350ci with about 9:1 compression, which looks like two ranges colder than stock by their numbers. If I ever get it together I'll let you know.

 

im running autolite 104s at .35 with stock compression and a powerdyne making 5-6psi what would be a better plug? i drive alot too BTW

 

You get the same spark energy out of a cold plug as a hot plug, it's just that the cold plug may not run at a hot enough temperature to be in the self cleaning range, thus it will foul at some point. Multiple electrodes pretty much get in the way of the fuel mixture and kind of block the flame, so you don't want those - that +4 design, for instance, dates back to the '30s, so it's nothing new & exciting. If you look at a formula one plug, for instance, it has no welded on ground electrode at all - it is just a surface gap which has been ground flat and sharp at the same level as the center electrode. Platinum plugs are mostly for mileage and have hot tips and might cause detonation, but some FI guys like the iridiums & NGK is pushing those real hard. I use a single ground electrode, extended tip, plain jane resistor plug which I cut the electrode back a little and gap at .040 and I go one to 2 heat ranges colder than stock. the extended tip plugs have a wider heat range than the recessed tip (for NOS) plugs do so they give you a little more leeway. The best electrode is a sharp edge - that's what the spark likes to see which is why you are seeing fine wire electrodes and v cuts, etc, but a sharp edge is what the spark needs to jump off. If you look at a high mileage plug, the electrodes are rounded off and the gap is larger, so these stress the secondary wires, coil, opti distributor, etc.

 

I picked .35" and -2. But an even colder plug may be needed for high-po setups. Don't forget, it's detonation that kills FI motors.

Rich

 

Well, I just took out all my plugs and re gapped em to .40 from .50 and I got an extra lb of boost. By the way, they're ac delco 906 plugs. Really have no complaints. They all still looked brand new with about 2000 miles on em.

 

I would say increased boost from an ignition change would mean you've lost power. Boost is just a measure of the engine's INABILITY to accept the provided intake charge.

If you do some pulley/induction change that increases boost, that's because you've increase the supply. But anything you've done after that which increases boost would seem to me to be a reduction in the engine's ability to USE that air.

 

Well, I dunno a bout the laws of boost, but I hadn't been able to get over 5 psi, and after I regapped em smaller, I got up to 6 and almost 7 psi. I think by regapping em, it's not blowing out the spark at high rpms, unlike before. Seems like it has better response too.