I would like to use some of these plugs:

NGK ZFR5N or an autolite 985


But I have the later head - It appears that there is not any extended plugs with the tapered seat, so what is the next best Choice?


BTW, I have to run colder plugs in this motor.

So I currently use Autolite 23's, and I was thinking of switching to NGK UR-5's

Any reccommendations?


Thanks Greg

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http://www.youtube.com/hyperpack

Gregg,

I did some catalog look up a while back, the mythical plug for our head would have been "coded" ZTR-4,5, or 6

Sadly, the catalog has no plug, the closest we can get is a TR-4, or TR-5 these have a longer reach(.7 vs. .460) for the tapered seat plug (mainly listed for the Chevy 400), but they have no extended electrode (thus no "Z" at the beginning of the code).

I have yet to try these out in my car, so you'll be the guinea pig I guess, before me. I use a hotter plug so my choice'd be the TR-4's...

I ran UR-5's for a while and they are pretty cold, if going colder you still can get UR-6's...

good luck and let us know how the "TR" models work,

-D.Idiot

Thanks D/I I will wive those a try - I believe I will use the 5's 6's might be too cold.


Greg

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http://www.youtube.com/hyperpack

Damn Peanut heads!

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No name calling please.

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Excuse me, does this smell like chloroform to you?

For longer reach, are you talking about the threaded portion????

I wouldn't think you'd want any threaded portion in the chamber. Don't know what happens when the engine is running, but I'd think the threaded portion would carbon up and make removing the plug very difficult.

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

.46 threaded portion spark plugs ain't correct for slant six heads... the tip sits way to far away from the sweet spot in the combustion chamber plus in some cases it kind of "half buried" inside he threaded part of the plug's hole.

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

For the 1975+ "BL" plug head(peanut plug) we use the same spark plugs as the Chevy 250/350 and the correct usage for those motors and the 1975+ slant six is the NGK UR-4,5,6
Which has: 14mm thread diameter, 5/8" hex, .460 reach, "tapered seat" and projected insulator tip...

"Drool Tube" headed slants use the "old style" the GR-4,5,6
14mm thread, 3/4" reach, 13/16" socket, Resistor, "Gasket Seat"

The improved plug Dan has is: ZFR-5N
14mm thread, 5/8" hex, 22.5mm/ 3/4" reach, projected insulator, extended electrode,"Gasket Seat"

(if you wanted the 13/16" hex, then try to find a ZGR-5N)


The next best bet for the "BL" head guys is the TR-4:
14mm thread," tapered seat", Projected tip, 5/8" hex, .708" reach (these are also listed for Chevy racing guys)

If you mythically "make a plug" from NGK's own "coding" system then we would want a "Chevy" equivalent to Dan's plug which would be something like"

ZTR5N-10A
Extended Gap, Tapered Seat, 14mm, 5/8" hex, 17.5mm reach, Middle heat range, .040 Gap, Special Construction with no Gasket



FYI,

-D.Idiot

H'mmm. Wonder how well NGK support racers. Wonder what it'd take to get 'em to make a run of those plugs. Probably not feasible, but it can't hurt to ask...

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

Man, I keep forgetting about the non-tube heads.... we never got that down here.! Anyways you covered that pretty good.

May I ask why you use that head and not the drool tubes one? seems as I read that there's no benefit at all in investing big bucks or big time doin that kind of heads if you can't (as you can't with other tapered seat plugs heads, we have some brazilian 318 heads that takes tapered plugs, 18mm thread) suit it with the proper heat range plugs....

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

One reason for me was it was the stock head on my Feather Duster (also it had no smog pump port), also I have several stuffed away as they are easy to get on Aspen/Volare's...Drool Tube heads are getting much harder to find in junkyards as old iron is now being crushed upon delivery...and I'm not willing to pay Wildcat Auto Wrecking's price for a drool tube head. I have yet to see BL plug head below 54 cc for combustion chamber size on average, yet out of 3 drool tube heads I've gotten anything from 68cc to 52 cc...

half of one, and 50% of the other...

-D.Idiot

I've gone over another section of the site,

Your choices now are:

LZTR5AGP for $2.68 each

PZTR5A-15 (stock number 7862) for $9 each

LZTR4AIX-11 $8 each

PLZTR4A-13 (stock number 4997) @ $11.71 each


sheesh, don't make a lot of these I guess...

-D.Idiot

Those are expensive because they are the platinum/iridium versions.

Looking on NGK's site, I also found P/N LZTR5A-13 which looks to be the same as the ones you referenced, but in a "normal" flavor. Now that I've got an engine with a peanuthead, I'm also looking for an equivelant to the ZFR5N that'll work in my head. The center electrode portion doesn't protrude from the threaded portion as far as the ZFR5N, but given the length of the threaded portion, it looks like it'll still put the spark in the right area of the combustion chamber. Now my question is, will having that long of a threaded portion be a detriment to its ability to ignite the fuel in the case of our engines?

Here's NGK's info page on the LZTR5A13: http://www.ngk.com/more_info.asp?AAIA=1424607&pid=15855

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'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG

Know how they always build a better idiot? That's me

Thanks for tht treatise DI. Would you mind taking the time to define the different terms you have used there. What is Reach for instance? It this the distance from the seat to the electrode tip, or the length of the threads. Of course some of them are pretty obvious, but you know the old addage about "ASSUME", and what it does to you and me.

I was trying to picture the difference between these different model plugs, and wasn't sure what the different terms meant. I had no idea there was so much to know about spark plugs. I think all things considered the industry guys are doing a pretty good job of trying to maximize the design for each application.
Sam

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