Does anyone have a chart for the NGK ZFR5N WITH the heat ranges?
I've found plenty of in-line cross reference stuff, but nothing that says:


ZFR?N = one step colder
ZFR5N = ( heat range )
ZFR?N = one step hotter

Ive tried looking for ZFR2N and almost every other combo...what am I doing wrong?

I'm looking for a plug that is 2-3 steps colder than the NGK ZFR5N

OK so I found this for champion plugs, but I'm not running a lawnmower

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My '73 "Gold" Duster /6
http://www.cardomain.com/ride/2789359

There is no colder version of ZFR5N, unfortunately, in any brand. You can't get the long extended projected electrodes with a colder heat range. I've used ZFR6FIX-11, which is colder (higher number = colder plug in NGK), but its electrodes aren't as long as ZFR5N and it's a costly Irridium plug.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

ok... That would explain the odd search results.

I was able to find a cross reference for the Champion C-series plug 791 / C57YC ( projected tip, 14mm thread, 5/8 hex, .750 reach ) on the Autolite site of AR3910 that has an application of "CHEVROLET BIG BLOCK, CHRYSLER HEMI (Racing)" and a honda RC51 ( 1000cc ) engine and that cross references to NGK R5672A-9
It doesn't say what heat range the plug is, just "see racing section"
The standard Autolite 985 says heat range D11 but not sure where that is in the grand scheme of things...

OR, does that mean that I'm stuck going through the boxes at the store to figure out what plug is closest to the dimensions of the ZFR5 and then guessing at the number?

I just want to know if I'm headed in the right direction.

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My '73 "Gold" Duster /6
http://www.cardomain.com/ride/2789359

OK I might have answered my own question...
from NGk's plug number breakdown it looks like I need a
B - 14mm thread
P - projected tip
R - resistor type
6 - heat range ( maybe a 7 )
E - 3/4" thread reach
S - standard electrode 2.5mm

Does this look right?

SO..if all of this is correct

one step hotter would be BPR4ES
ZFR5N should = BPR5ES
one step colder should be BPR6ES

For the sake of the searchers NGK BPR5ES

...the funny thing is that some of the google results for BPR6ES reference lawnmower applications

even more research shows BR6ES does have the ( marine ) slant six as an application but it's not a projected tip plug like the BPR6ES

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My '73 "Gold" Duster /6
http://www.cardomain.com/ride/2789359

Good info here - thanks. Based on this I'm going to try and use the BPR6EY which is the V-Power plug for my /6 turbo setup, when it's done. I've used the V-powers a bunch in 4 cyl turbo applications are they are dynamite. I coudn't find the V-power in a 7-series heat range for the slant, which may be best... dunno until I try, right.

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Tony Bracamonte
'66 Dart GT
built /6 w/ garrett gt32
air-air intercooler
330 hp / 440 lbft @ 16.5 psi

For clarification, the BPR6ES is the same body style as the standard /6 plug and is NOT like the ZFR5N plug

I've been poking around all morning and it looks like the ZFR6A-11 ( 1041 )is a "longer" reach plug than stock, but not a long as the 5N

I bought most of a set of BPR7ES today at lunch but have to wait to install them as they only had 5 in stock

I'm going to try to install them tomorrow night, .030 gap to start and see how it behaves

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My '73 "Gold" Duster /6
http://www.cardomain.com/ride/2789359

-11 suffix means extra-wide gap (0.044", if I recall correctly); make sure your ignition system is up to the task.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Good point. The -## indicates the stock gap.
I plan on setting the gap closer anyway. I learned looooong ago not to trust plug gap out of the box

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My '73 "Gold" Duster /6
http://www.cardomain.com/ride/2789359

You have to watch using the translator in building dream plugs as NGK may not make that style of plug...in some cases one that is 'close' may not have a comparible heat range if the reach, electrode configuration and body is slightly different...Also each manufacturer has a different way to test their plugs so if you end up using a 'stocker' type plug (1975+ head guys are in this group for sure...), you may find that one brand might be slightly hotter or cooler than another. In my experience I could not get my 10:1 hyperpak mill happy with NGK-UR4 or NGK-UR5...no matter how much I played with timing and carb it was either sooty or lean...I switched to the AC Delco brand just to try it, and the R-45TS made perfect coloring during road tuning tests...

So if you end up splitting fine hairs you may want to try a different brand...that being said a move like this may not necessarily work
if you use a 'knock off' brand like Bosch/Recent Autolite/etc....

Just food for thought...

-D.Idiot