Spark Plugs?

[TexasT]

I used to do the autolite and ac but the ngk are just as cheap with a solid track record for me. I've been getting them off eBay eight at a time. I'm going to look onto the rockauto again, last time the shipping put them over the eBay ones. If the ones in getting are fakes/copies I can't tell a difference. Must be good copies.

[good2win22]

NGK for the win

[Grumpy]

NGKs here to 

[larrym]

Ok let’s see where this leads UR5 or YR5 NKG


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[Steve Wood]

and why 5 instead of the colder 6?

[larrym]

Another good question why would a cooler plug be needed.
“Conversely, a cold spark plug has a shorter insulator nose and absorbs more combustion chamber heat. ... A colder heat range is necessary when the engine is modified for performance, subjected to heavy loads, or is run at high rpms for a significant period of time.”

How effective would they be on a 3.8?




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[Grumpy]

iron heads UR5s worked for us.

[Steve Wood]

Another good question why would a cooler plug be needed.
“Conversely, a cold spark plug has a shorter insulator nose and absorbs more combustion chamber heat. ... A colder heat range is necessary when the engine is modified for performance, subjected to heavy loads, or is run at high rpms for a significant period of time.”

How effective would they be on a 3.8?




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From the beginning, we have been told that we need colder plugs to prevent detonation so we went one or two steps colder than the factory.  We were also told that the CR42, which is the commercial plug with heavier electrodes, is less likely to cause detonation,

First, detonation is auto-combustion of the end gases away from the flame front.  Therefore, the plug is not the cause of detonation.  If anything, it might be the hot spot that causes preignition which is entirely different and far more destructive.  Preignition does not normally occur on our engines due to the shorter timing.  It might be a bigger fear on E85 if we run enough timing.  Preignition is more of a fear on methanol fueled race cars that run too much timing.  Does this carry over to ethanol fueled cars?  I have no idea.

I often wonder if spark plug induced detonation is really a common or significant problem on our cars.  Coincidentally, I wonder if the use of cold plugs increases the need for tighter plugs gaps as we go to very rich fuel mixtures in the quest for higher boosts and more power.

Is a minor change in spark plug heat ratings more a myth when it comes to safety in performance?

[TexasT]

I went ur5. I think I did a .027 gap, been in there a few months. Tighter seemed to work better. I think I had em at .032 or .035. Tightened it up and it seemed to run better. Gotta get that powerlogger hooked up one of these days.

[Scoobum]

Yes - but I order 40 or more at a time. They are cheap and don't go bad sitting in a box on the shelf. As long as you don't forget you have them!


Brad put some 42s in that thing and put the screws to it!

Tried a set of 42's a few years back and it idled like crap...prolly to cold to fire. I've tested the 43's to 28 PSI and the plug has looked fine. The AC's...from the dealer...have worked fine for me.

[Steve Wood]

Yes - but I order 40 or more at a time. They are cheap and don't go bad sitting in a box on the shelf. As long as you don't forget you have them!


Brad put some 42s in that thing and put the screws to it!

Tried a set of 42's a few years back and it idled like crap...prolly to cold to fire. I've tested the 43's to 28 PSI and the plug has looked fine. The AC's...from the dealer...have worked fine for me.

I wonder what would happen if you closed the gap down to 0.027"?  I have never had to go tighter than 0.032" to get a turbobuick to run at high boost.  I am obviously not running the cylinder pressures that a nine second car is running but I have run tens on 35 thousandths.  I wonder when I read that people have to run such tight gaps.  Could it be excessively rich A/F's?  Could it be too cold a heat range?  Could it be an ignition system that is defective or dying?  Probably all of the above...

[Scoobum]

I've got 'em cranked down to a tight .030. My logic...and it's prolly flawed...is that it takes less energy to jump the gap...and less chance of a misfire. Having said that...maybe a wider gap would produce a longer(bigger) spark and ignite the fuel/air mixture better. That's about as far as my IQ goes...carry on gents.

[nocooler]

Your worried about how it idles? I thought you’d be more worried about what it does at wot.

I’ve been told/read that each heat range pulls 100 degrees of heat out of the cylinder. Looking at the how far the heat penetrates the plug I’d have to agree.

Steve, ethanol is very sensitive to pre-ignition but very resistant to detonation.

Light bulb! My car probably liked the colder pull due to all the methanol I was spraying. The with a 43 it sounded like it was making popcorn but wouldn’t register knock, stuck a 42 in it and it would run its ass off.

Ls cars come with tr55, everyone puts a tr6 in them. Br7ef for 100-150shot/boost, and br7e8 for more spray/boost.

I dyno’d my Firebird and raced it n/a with br8ef and it didn’t care.

I always laugh when I here someone ask the parts guy for a hotter plug for their modified sbc

[Steve Wood]

 

[Steve Wood]

Alcohol is hard to ignite. As long as you keep it on the rich side it's not too sensitive to pre ignition. Otherwise, af is not critical