Why do people assume that all spark plugs are pre-gapped? Do you know how many engines that one plug could fit? Every single one has a different gap, and yes, that will affect how your engine runs.
Two out of every three customers that rolls into my store to buy plugs, asks if they are pre-gapped. I don't know if it was some lazy person who said "yeah, sure they are" to get someone off their back or what, but I'm tired of it dammit.
/rant.
Yeah, could be. But there's bigger things to get riled up about. I usually check the gap on new plugs and adjust accordingly (assuming they're not irridium), but I've never noticed any real difference attributable to off-spec plug gaps. Assuming all the rest of the ignition components are good, most vehicles will tolerate a pretty big range in plug gaps just fine. If there are other ingnition system problems, properly gapped plugs won't fix it.
Hahah!!!! I have this argument with my buddies everytime they change spark plugs.
Bench Racer (BowtieBandit) wrote: Why do people assume that all spark plugs are pre-gapped?
Because the gap is right there in the part number? XXXX-1.0 = 1mm gap. XXXX-1.2 = 1.2mm gap.
I check it, but it's always dead nuts on, at least on the NGK Coppers that I tend to use.
Every spark plug I have ever purchased has been pre-gapped. That doesn't mean they are gapped correctly, but none have been completely closed. 
That said, I can only remember one or two that was not set correctly.
I have yet to gap the plugs on my TDi ;)
(I don't have a TDi, but I am a smarmy VW owner and I have a pen from the a Holiday Inn Express)
bludroptop wrote: Every spark plug I have ever purchased has been pre-gapped. That doesn't mean they are gapped correctly, but none have been completely closed.
Touche.
DILYSI Dave wrote:Bench Racer (BowtieBandit) wrote: Why do people assume that all spark plugs are pre-gapped?Because the gap is right there in the part number? XXXX-1.0 = 1mm gap. XXXX-1.2 = 1.2mm gap. I check it, but it's always dead nuts on, at least on the NGK Coppers that I tend to use.
Same here.
Except for rare circumstances, plug gap is not critical, or even important.
DILYSI Dave wrote:Bench Racer (BowtieBandit) wrote: Why do people assume that all spark plugs are pre-gapped?Because the gap is right there in the part number? XXXX-1.0 = 1mm gap. XXXX-1.2 = 1.2mm gap. I check it, but it's always dead nuts on, at least on the NGK Coppers that I tend to use.
Exactly. I check all of them, but they've always been pretty much right on.
DILYSI Dave wrote:Bench Racer (BowtieBandit) wrote: Why do people assume that all spark plugs are pre-gapped?Because the gap is right there in the part number? XXXX-1.0 = 1mm gap. XXXX-1.2 = 1.2mm gap. I check it, but it's always dead nuts on, at least on the NGK Coppers that I tend to use.
Lost me there.
ZFR7F-11...
What should the gap be at?
92CelicaHalfTrac wrote:DILYSI Dave wrote:Lost me there. ZFR7F-11... What should the gap be at?Bench Racer (BowtieBandit) wrote: Why do people assume that all spark plugs are pre-gapped?Because the gap is right there in the part number? XXXX-1.0 = 1mm gap. XXXX-1.2 = 1.2mm gap. I check it, but it's always dead nuts on, at least on the NGK Coppers that I tend to use.
I don't think he necessarily meant that every spark plug manufacturer puts the gap verbatim in the part number, although his did. I think he means that the gap is specific to the part number.
edit: nevermind, there it is, 1.1mm = 0.043" - got it right there at the end.
racinginc215 wrote: I've never gapped the plugs on my RX7.
You never gap yours? 
So what's a nice gapper to use? In highschool auto shop we had some nice gappers but ever since I've been without. And something tells me I'm going to have to go back and start reading plugs again in the near future...
I stopped checking the gap on new plugs when I realized I didn't have to. 3 or 4 years of checking only to have them spot on every time made me not care enough to look anymore.
I close mine down to about 35 anyways. I can't remember if they all come to me at 43, though. It's close, for sure.
RX plugs are not gapable.
Take a box of plugs and drop it on the end. Then check the gap. It will be off. I always gap my plugs and they usually need adjustment.
NGKs have a cardboard sleeve to protect the tip, they usually come out of the box at the intended gap.
If you've got a turbo car, plug gap might be more important than you think to prevent misfires. And the bigger your gap, the more power you make. So it's certainly worth doing right - but as Dave pointed out, if you need the gap that's written on the box, you're probably safe dropping them in.
I must not be the norm because every time I replace plugs I'm surprised at how close they are to what I need and I'm also surprised at how far off the ones are that aren't correct.
I've never had a complete set be right.
I'd much rather check it than have to go to the trouble to try to figure out why my car isn't running right and then find the time to pull all of them out and check them all. It just makes sense to check them BEFORE I install them.
My rule is "always check everything that goes into one of my cars." Most of the time the gaps are correct, but every once in a while one is off. It just takes a minute to check and fix.
Bench Racer (BowtieBandit) wrote:bludroptop wrote: Every spark plug I have ever purchased has been pre-gapped. That doesn't mean they are gapped correctly, but none have been completely closed.Touche.
Spend more time selling parts at Dangerzone and Additivvanced auto and you will see them come in with zero gap for sure!
The plugs are pre gapped! They may or may not be to the spec your motor calls for... DOH just finshed reading the rest of the post...
Add me to the "always check, always dead on" group. I can think of one that I've gotten in the last 5 years that was off, and it had obviously been dropped or something as the gap was zero.
This thread got me as I just replaced the plugs on my turbo Volvo 850. All 5 plugs were gapped wrong according to the measurement on the box. Turns out the box marking was incorrect and I gapped the plugs wrong. Huh. Car's running great. Factory calls for .028" and I gapped to .035". Should I re-gap or leave it at the higher gap?
Brett_Murphy wrote: My rule is "always check everything that goes into one of my cars." Most of the time the gaps are correct, but every once in a while one is off. It just takes a minute to check and fix.
IF YOU DO IT BEFORE YOU INSTALL IT!
It takes a lot more time to diagnose the problem and go back through and pull all 4-6-8-10 plugs.
That's one of those words of wisdom you learn when you live a long and fruitful life.
You'll need to log in to post.
