Ngk plug gap

Shoebox

Shoebox

Well-known member
I'm using NGK B7ES-11 plugs in new Offy heads, ignition is a GM dist-points and a Bosch coil. I was curious about the -11 designation and looked it up on an NGK spec sheet, it relates to gap, calling for .044, seems excessive, my gaping tool doesn't go that wide. Wouldn't something like .025 work? Thanks
 
Are you sure you have the correct plugs? That does seem excessive. It appears NGK makes several varieties of the B7ES. Since the heads are new, they must have the paperwork; what does Offenhauser say?
 
The B6ES-11 is a wide gap specific plug. I believe you need the B6ES. These are are STD.NON-RESISTOR Plugs per the NGK catalog.
 
tubman said:
Are you sure you have the correct plugs? That does seem excessive. It appears NGK makes several varieties of the B7ES. Since the heads are new, they must have the paperwork; what does Offenhauser say?
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Offenhauser had nothing to say, no paperwork other that Speedways invoice.
 
the proper plug gap for the OP's head unknown to me, but i was curious as to the difference between a b7es and a b7es-11 plug so i did some research and was not surprised to find that there are (from what i found anyway) no differences between them other than the preset gap.

curiously, 11 is probably a millimeter designation sans decimal point. so the accurate designation for the b7es-11 should, if i'm correct, read b7es-1.1. as 1.1 mm is equivalent to about 0.043 inches. i suspect the decimal point was omitted due to clarity, economy and/or manufacturing issues.

personally, i set the gaps on all plugs before installation. not sure when it became common to trust plug gaps straight out of the box... but i don't. even the slightest impact on the electrode will alter a plug gap. it takes about ten seconds per plug to check and set IME. :)

if true, the b7es-11 plugs can be re-gaped to whatever gap is required.
 
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In my opinion the correct plug gap for MOST sparkplugs is driven by the ignition system components, not the plug itself. Most of our older ignitions tend to have plug gaps of around .020 to .025. I set all my flathead (points ignitions) to about .020 to .022. I also set my plug gap at .020 for my Vertex Mags (on flatheads).

On many racing magnetos (like a MSD ProMag), the plug gaps are really small - about .014 to 0.18 or so. This is because at starting RPMs, the ProMag doesn't put out a lot of energy to "jump the gap", but once the spark starts to jump it has a lot more duration than a typical points ignition. The amount of amps a ProMag puts out is amazing - even in the lower 20 amp versions. The top-fuel boys fun dual 44 amp ProMags.

Another tip --> do not run resistor plugs or wires on our early ignitions . . . too much resistance is put into the secondary and all sorts of erratic spark events can occur.
 
Shoebox said:
I have a set of B6ES plugs coming from NAPA.
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SPOKE TOO SOON,...got message from NAPA, "availability problem, call store Monday".


Went to Summit Racing, "not in stock, unavailable to special order"


At this point I think I'll gap my B7ES plugs at .025 and see how that works unless a better idea comes along. I'd also mention that whether working on a motorcycle, airplane or car, I've never expected plugs to come out of the box properly gaped, I always check and gap as needed. Thanks guys for all the responses.
 
Shoebox said:
SPOKE TOO SOON,...got message from NAPA, "availability problem, call store Monday".


Went to Summit Racing, "not in stock, unavailable to special order"


At this point I think I'll gap my B7ES plugs at .025 and see how that works unless a better idea comes along. I'd also mention that whether working on a motorcycle, airplane or car, I've never expected plugs to come out of the box properly gaped, I always check and gap as needed. Thanks guys for all the responses.
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my apologies if my post appeared to be critical. if so, it was unintentional... as i didn't assume, one way or another, whether the OP did or didn't gap their plugs by hand. it's just that i found it remarkable (literally) that a sparkplug manufacturer would include the gap (easily and most often changed intentionally or by use) in the model number of a plug. and attributed it to some of the comments i've read on the various internet forums in which i participate that mention trusting pregapped plugs to be a convenience or utilitarian for one's particular use.
 
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Shoebox said:
SPOKE TOO SOON,...got message from NAPA, "availability problem, call store Monday".


Went to Summit Racing, "not in stock, unavailable to special order"


At this point I think I'll gap my B7ES plugs at .025 and see how that works unless a better idea comes along. I'd also mention that whether working on a motorcycle, airplane or car, I've never expected plugs to come out of the box properly gaped, I always check and gap as needed. Thanks guys for all the responses.
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Try Rock Auto. I get all my NGK plugs from them. Just put in the plug part # you want.
 
Bored&Stroked said:
In my opinion the correct plug gap for MOST sparkplugs is driven by the ignition system components, not the plug itself. Most of our older ignitions tend to have plug gaps of around .020 to .025. I set all my flathead (points ignitions) to about .020 to .022. I also set my plug gap at .020 for my Vertex Mags (on flatheads).

On many racing magnetos (like a MSD ProMag), the plug gaps are really small - about .014 to 0.18 or so. This is because at starting RPMs, the ProMag doesn't put out a lot of energy to "jump the gap", but once the spark starts to jump it has a lot more duration than a typical points ignition. The amount of amps a ProMag puts out is amazing - even in the lower 20 amp versions. The top-fuel boys fun dual 44 amp ProMags.

Another tip --> do not run resistor plugs or wires on our early ignitions . . . too much resistance is put into the secondary and all sorts of erratic spark events can occur.
Click to expand...

Totally agree with everything Dale stated here. This “low voltage ignition “ for lack of a better term works very well with all the correct components in working condition.
 
Ziggster said:
What head exactly are you using from Offy, and what plug do they recommend?
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#1069 Offy with 400 valve relief. As I mentioned to Tubman, no documents came with the heads. I'm going to run this by Speedways tech guys tomorrow but not expecting much, we'll see.
 
Ziggster said:
From this link, they (Offy) suggest Autolite 216 for their 1069 head.

https://offydirect.com/product/offenhauser-1069-400-cylinder-heads/

Autolite 216 has a 8 mm (0.315”) reach and a recommended gap of 0.8 mm according to this link.

https://www.autolite.com/spark-plug-216.html

Seems this is a bigger issue based on the link provided by Tubman.
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Those heads (at least the new set I have) need a plug with a reach of around 3/4" (.750") Those 216's would utilize less than 50% of the threads in the head and would be seriously shrouded. What is Offenhauser thinking?

Yeah, it is obviously a bigger issue. I am a stickler for having the plugs fit the threaded hole in the head exactly. Some don't think it's that important, but you can't start cutting corners anywhere. Here's a Champion L82YC in one of my Edmunds heads for example. These plugs have a 1/2" reach.
 

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Bored&Stroked said:
In my opinion the correct plug gap for MOST sparkplugs is driven by the ignition system components, not the plug itself. Most of our older ignitions tend to have plug gaps of around .020 to .025. .
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Well said. All the components must play nice together. My system is a late '90s GM (brain and coil). I run it at .040
 

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