Hi all,

I felt my /6 is due for new plugs. I purchased some NGK BP4EY, however it's currently running BP5ES.

Just checking if the newer plugs, which run hotter (the '4') is much of an issue. I was advised against fancy iridium components.

Thanks!

For the drool tube head, go with the NGK ZFR5N unless you have a lot of compression. It's an extended electrode plug which will be subject to detonation in a high compression application.
For 10.5:1 up to mid 11's or so look at the ZFR6FIX-11 It's Iridium, and works just fine. I run them in my 10.7:1 static compression, and ran them at 11:1 with good results.

For colder applications, the ZFR7F-11 is out there. I don't know anybody that has tested these. I'll be getting a set to play with. Might be a good choice for mild boost/N2O applications. Don't know yet.

2¢

CJ

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Part of Tyrde-Browne Racing

I would not run NGK #4 plugs. Too hot; they'll tend to lower the ping threshold, so you'll have to reduce the spark advance which will eat into your driveability, performance, and economy. I like ZFR5N or ZFR6FIX-11 as Ceej says, though I am currently running the latter and my engine has stock compression. Remember, modern fuels burn much cleaner than the fuels that were available when the slant-6 was still a current-production engine (and its plug specs were being written); you can as a result often get away with a colder plug without getting a fouling problem.

Can't imagine why someone would advise you against Irridium plugs; they're costly but quite good and durable.

Whatever plugs you pick, remember to remove their metal ring washers before installing them.

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

Thanks for the replies people. I'll query their recommendation.

do you have a normal number for the NGK??
ZFR6FIX-11

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1965 Plymouth A/FX 512ci (under construction)
1968 Dodge Dart SL6 14.25 @ 91.5 1.91 60'
1973 Dodge Dart SL6 Stock
Killer Bee's Member Since 09'
http://www.forabodiesonly.com/mopar/sho ... p?t=128702
http://www.youtube.com/user/805moparkid

6441

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Part of Tyrde-Browne Racing

Whatever plugs you pick, remember to remove their metal ring washers before installing them.


Not applicable for 62 and earlier, something different about those. I don't know why

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Dave

1977 d-200 crew cab ex-army pickup wants it's /6 back
1962 Valiant 2 door, 170, three on the tree
1972 d-100 parts truck
80 volare wagon now a parts car

thanks... im running 10:1 do you think since its so hot here i can get away with the slightly colder plug?

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1965 Plymouth A/FX 512ci (under construction)
1968 Dodge Dart SL6 14.25 @ 91.5 1.91 60'
1973 Dodge Dart SL6 Stock
Killer Bee's Member Since 09'
http://www.forabodiesonly.com/mopar/sho ... p?t=128702
http://www.youtube.com/user/805moparkid

Plug temperature has practically nothing to do with ambient air temperature, but all to do with combustion chamber environment; CR, fuel grade, timing, AF mixture, etc., and how the engine is used: drag racing; pulling trailer; heavy vehicle; light vehicle; putting around town; open road; circle track etc.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

But ambient temperature will affect the A/F mixture if he hasn't made a jet change for it...which then makes it a function of the above causes...

-D.Idiot

Certainly. I always felt that the 5 heat range was a bit hot even in a stocker with the fuels we have today. It's not like it's going to foul burning reformulated gasoline. With the high freeway speeds of today, EGT's are going to run pretty warm. Perhaps running just above idle during the winters in the mid-west, a five would be appropriate.

2¢

CJ

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Part of Tyrde-Browne Racing

CJ,
What is the DCR of your engine? I'm not sure if you have looked at my long rod rebuild thread, but using what i know about my engine and a couple of reasonable estimates, Doc has calculated a DCR of 8.11 for it. I did have the hotter zfr5n plugs in there and Im pretty sure they had a hand in the piston damage that occurred. I swapped those out during the rebuild for some 5 series stock length plugs, but am now considering a 6 plug. This is in a daily driver for my little sister, and she does tend to cruise around 70 on the freeway (especially since the firm feel suspension overhaul). What im now wondering is if maybe the 7 woukd allow a bit more advance. Id like to be able to run as much at cruise as possible. Anyway, thanks in advance for any advice!

Josh

i was thinking more on the lines of since its so hot out side (105-115) my engine usually runs @ 200 on the road... so it making the engine run hotter...

im running autolite 65's in it right now, the same plug they used in the street hemi's

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1965 Plymouth A/FX 512ci (under construction)
1968 Dodge Dart SL6 14.25 @ 91.5 1.91 60'
1973 Dodge Dart SL6 Stock
Killer Bee's Member Since 09'
http://www.forabodiesonly.com/mopar/sho ... p?t=128702
http://www.youtube.com/user/805moparkid

I was just looking around for those plugs and apparently the new design NGK ZFR series is referred to as NGK BKR, (i.e BKR7EIX -- 2667.......or BKR5N vice ZFR5N).
What have you guys heard about that? Supposedly the zfr series is on the way out and being superceded by Bkr series....sure hope they're not made in Chiner!

Your removing the crush washer from the plug right? If the plug runs hot, you may see problems localized to the spark plug. Burning holes in pistons is an indicator of too hot a plug. There are other culprits but that's the common one. The reason you need to cut the crush washer off is the plug will operate too hot if it's left on. It also doesn't allow the plug to seal well with a spark plug tube. The aluminum tube gets all beat up.

Try the 7. With the fuel we have today, I don't think you'll have fouling issues. It should work well with early ignitions, but I haven't run points in a while. If her car has points and stock coil, I can't answer the question.

I've run 5's with no piston damage, but don't high power cruise for protracted periods ever. Fifty miles at 60 even with my short gears doesn't qualify. If all else fails, BP7ES or BP8ES plugs will drop your heat range for high throttle setting cruise. You can work your way out to a 10 heat range without too much difficulty finding them. Just remove the crush washers.

Since you had a problem, try BP8ES. If it fouls, go to the BP7ES. I still don't think it will. B8EV will likely solve any fouling issues. Bit more pricey though.

CJ

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