So from what I understand, the NGK ZFR5N spark plugs can't be used in later style heads (ie 74 or 75+). Is there an equivalent to those plugs for the later heads, specifically a late-model head with hydraulic lifters? I'm not sure exactly what year the head is from.
Enlighten me, please, I'm lost.

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<i>D'Artagnan</i>
<img src="http://img.photobucket.com/albums/v432/stephaniexchaos/dart/th_IMG_0326_zpsumhhfxi0.jpg">

The tapered seat plugs for the 1975-1987 heads are limited in selection... you are stuck with the same type of plugs NGK UR-4, UR-5... AC/Delco RTS-45... etc...

I had found a plug that would work and was extended reach, but it is not for an automobile application and decided it wasn't worth the gamble, of burning a hole in a piston or two trying it out...


The good news though is the spark plug is so common, that if you get stuck in the 'outlands' every old Chivvy 250,307,350 uses this plug (as well as the Boss 429, the Boss 351...etc...), so supply isn't a problem...

Sorry,

-D.Idiot

Interesting...what plug, made by whom, and for what app?

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

DI-
Are there '75+ plugs that are generally preferred over others? I got Chris a new MSD coil and Magnacor wires, and wanted to upgrade the spark plugs a bit too while I was at it. I didn't realize at the time that the ZFR5Ns wouldn't fit, and I don't want to put junk in - at the same time, I know many claims of "spark plug performance" are BS. So I'm trying to figure out what will work well with that setup.

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<i>D'Artagnan</i>
<img src="http://img.photobucket.com/albums/v432/stephaniexchaos/dart/th_IMG_0326_zpsumhhfxi0.jpg">

NGK would be fine, you can also use AC Delco if needed... no Bosch, no Champion.


The plug in question was for something that didn't use the ground as it's primary mode of travel, and came out of a buddy's catalog for his hobby of custom machines... I no longer have the number or my notes....

-D.Idiot

It's very tough to go wrong buying the NGK spark plugs that fit your '75+ head. To DI's "no" list I would add Autolite, which are now Chinese-made junk.

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

Dan's right. I tried the Auotlites a while back and the NGK UR4's are a much better plug and make the engine run very nice. It will idle forever and never skip a beat or make any unusual sounds that some folks describe.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Thanks for the help guys, I appreciate it.
Sadly, the MSD coil I got (MSD Blaster 8207), which I thought was still being made in the States, had "MADE IN CHINA" stamped along the bottom.

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<i>D'Artagnan</i>
<img src="http://img.photobucket.com/albums/v432/stephaniexchaos/dart/th_IMG_0326_zpsumhhfxi0.jpg">

Yeah, a few months ago I took the MSD coil off the recommended list for that reason.

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