Just a quick one for you guys.

Does gap size have any effect on the temperature of a spark plug? ie. closing the gap makes a spark plug run hotter.

Thanks, Jon.

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62 Valiant, 225cid Slant 6/PB 904 with lots of good bits

http://www.moparmarket.com/readersrides ... user=SV162

No. The heat range (operating temperature) of the spark plug is a function of the length of its insulator, not of the plug gap.

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

Thanks Dan, I knew I could rely on a quick response from you.

I have another question that I'm sure you can answer Dan. I've just had some head work done so I'm wondering how much can come off the head before I start running into clearance problems with ZFR5N plugs. I was running these plugs before with out any problems but my engine builder tells me those plugs are not an option anymore. I haven't got the exact amount that the head was shaved on hand now, but I know it was at least 0.100".

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62 Valiant, 225cid Slant 6/PB 904 with lots of good bits

http://www.moparmarket.com/readersrides ... user=SV162

No watching and eating popcorn emoticon for times like this eh?

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74 Dodge Charger 225 factory A/C auto 1920 carb stock exhaust.

Mods;
HEI, MSD B3, Magnecor 8 mm, ZFR5N, .060 rotor, CH410X cap, new 3874814 dist, fuel mod, valves hot .010 & .020, all new hoses, JP chain, brake hoses and fluid.

Ok............

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

There might not be room for those plugs any more, but there might still be. What's your piston deck height? The easy way to find out is to remove all plugs, put a ZFR5N into one cylinder, and turn the engine over by hand through a TDC event. Remove the plug and examine it. If there's no apparent contact, then you're probably fine, but to be sure put a lump of modelling clay on the end of the plug, completely surrounding the tip with an outward-and-endward thickness of about 3mm. Install the spark plug and turn the engine by hand again through another TDC event. Remove the plug and examine the clay. If it's mashed through to the plug electrodes, or nearly so, you probably don't want to use those plugs. If the clay is untouched or just barely touched, you're fine.

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

As i understand it. You may have problems with heat buildup on the plug. Even to the extent of melting the plug down. Also note worthy is the difference between the standard tip and extended tip is 1/2 cc, I measured it when I cc my heads.
Frank

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Scrapple: Because a mind is a terrible thing to waste.
73 Duster - Race Car
66 Dart Wagon - DD
178" FED
82 D150
All Slant powered

If clearance is tight, indexing the plugs so that the ground electrode is at the top (away from piston) may give you the needed room.............

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Um…what? :shrug:

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

Thanks for the info Dan, I'll give it a try.

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62 Valiant, 225cid Slant 6/PB 904 with lots of good bits

http://www.moparmarket.com/readersrides ... user=SV162

In a race engine most of the guys I talk to say to run a shorter plug. The longer plug heats up and cannot dissapate the heat.
Frank

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Scrapple: Because a mind is a terrible thing to waste.
73 Duster - Race Car
66 Dart Wagon - DD
178" FED
82 D150
All Slant powered

Racers I've talked to have said to NOT use the extended tip plugs. They are apparently more detonation prone, and may have caused melted pistons, at least in one boosted application. I have spoken with others who said they had more pinging on the hwy (like climbing hills) with those plugs than with regular plugs.

This is to some extent heresay, but I don't see there will be enough potential benefit to try them. I have a set I may try, but haven't bothered yet. If you are looking for max mileage in a mild motor, they should work well. For high power output, I would stay away from them. In my experience, plug type and gap don't make a bit of difference on the dragstrip unless you are WAY off.

My guess is you will never remove enough head material to have a piston/plug interference problem with flattop pistons. Plugs are too far in up in the chamber and pistons are not at zero deck if you are removing a lot of head material (unless at 13:1+ comp ratio).

Lou

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Home of Slant6-powered fun machines since 1988

Let's be clear here, because we're obviously talking about two different (but related) things.

Thing #1: You have to use a spark plug of the right heat range (tip operating temperature) for the application, regardless of electrode configuration.

Thing #2: The ZFR5N has a heat range appropriate for stock and near-stock slant-6 applications, but is too hot for many high-compression, boosted, and/or race applications. If they made a ZFR6N or a ZFR7N (same plug design, one and two steps colder heat range), there'd likely be no issue arising from the extended electrode design — but they don't.

The key to understanding this is that a GR5 would be equally too hot, as would a UR5 or an anything-else-5 (in NGK's particular heat range numbering system).

The ZFR6F-11 is one heat range colder than the ZFR5N, and its electrodes are midway between regular and extended length. ZFR6FIX-11 is the Iridium version which is quite costly but very durable and well suited to high-compression/ping-prone applications (less-massive electrodes = less tendency to ping). ZFR7F-11 is one more heat range (total of two) colder than ZFR5N. No Iridium equivalent.

Remember not to use the metal ring washers, whatever plug you use, unless your head is a pre-'63 casting.

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

What are the Aussie Slant 6 heads classed as.........pre-'63?? I know we had Slants up till '69, but are ours all the same casting. I'm asking because it seems everyone "down under" leaves the ring washers on their plugs.

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62 Valiant, 225cid Slant 6/PB 904 with lots of good bits

http://www.moparmarket.com/readersrides ... user=SV162

good luck Sv162, I asked that very same question some time back,and silence on the board was the reply.
until someone tells me otherwise,I leave the washers on. no apparent ill effects. and I use ZFR5N plugs.
SS Dan,your comments would be appreciated on this. (please .... )

regards,Rod