Is a Spark Plug...a Spark Plug??

[Ronno6]

In my engine build, I need 14mm reach plugs.
For my aluminum heads,the machine shop recommends NGK R5671A-7 or 8.
I understand that the -7 or 8 signifies heat ranges, with 8 being colder than 7,
In order to give better clearance around the headers, I would benefit from the use of shorty plugs.
Closest I can find are Accel 0414S, which has a hear range of 4 in Accelspeak.
I have run across 1 chart which equates the Accel heat range of 4 to NGK's 7
However, the Accel has a projected insulator, whereas the NKG has a non-projected insulator.
Is that critical?? The projected insulator generally slows heat dissipation, but if the heat ranges
are equivalent. does that matter??
Accel does not offer a colder shorty plug.
Are there other shorty plug manufacturers?
Are there other critical differences which require comparisons??
As always, I get caught up in specifications, and I chase a lot of dead ends on the web.....

Of course, I am also looking into other means of boot/wire heat protection.

 

[bucket]

I like to run the Accell 576S, it works well for all the stuff I've built, one being similar to yours. I can't say anything about the heat range stuff, but if they offer an equivalent with the extended reach threads, that should work.

 

[CoggedBelt75]

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Sbc would use ngk 7516, heat range 5. Not sure why you were recommended to run 8’s. That’s a pretty cold plug. Because of the blower, I have to run 1-2 ranges colder than stock so I run ngk ur6 7773. Tried 7’s but they didn’t burn as clean. I’m also running Hookers and have no clearance issues, but I do run boot protectors for good measures. Of course, this is only my 2 pennies worth of thought on this

 

[Ronno6]

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Sbc would use ngk 7516, heat range 5. Not sure why you were recommended to run 8’s. That’s a pretty cold plug. Because of the blower, I have to run 1-2 ranges colder than stock so I run ngk ur6 7773. Tried 7’s but they didn’t burn as clean. I’m also running Hookers and have no clearance issues, but I do run boot protectors for good measures. Of course, this is only my 2 pennies worth of thought on this

The 7516 is apparently for use with cast iron heads (.46 reach)......I have aluminum (.75 reach)...... Maybe the cold range is to dissipate heat to the aluminum heads faster??
I have Hedman headers. They were about the only ones I could find which were designed for use with mechanical clutch linkage. The offset plugs make things a bit tight, especially on the #5 cylinder. I am exploring wire boot options to find something that will fit.
Looks like protector sleeves may be in my future.

 

[Ronno6]

What is the difference from a performance standpoint of projected vs non projected tip when running aluminum heads?

 

[CoggedBelt75]

I’ll throw another penny in the pot. That topic is still being debated with no set answers. Performance wise, a projected tip burns cleaner and exposes more spark because it is “projected” just past the last thread in the plug hole. But because it is further into the combustion chamber, it can also act as a glow plug and contribute to detonation. Also, if the piston has a lot of dome to raise compression, they could slap the ground strap. Some people swear by them, others don’t. Also from a performance perspective, I don’t think the difference would be felt whichever you use. You never said who’s heads you are using, but IMO, I would give the maker a call and tell them your setup. I always go to the source since they have a better handle on things.
Thought I’d go ahead and raise it to a nickel. Just an old shade tree guy that’s picked up tidbits through the years from old car guys.

 

[Ronno6]

I am using flat top pistons; I don't think I'll be in danger of then hitting the plugs regardless.The heads, I have been told, are Brodix clones, and the machine shop from which I purchased recommended the NGK R5671-8 which is the same as the NGK 4554 recommended by Brodix. That is a non-projected tip. Brodix also specs the NGK 7405 which is a projected tip. They are both termed as "Racing" plugs by NGK. I have been considering using the Accel shorty plugs, #0414S for header clearance, but they are projected tip and also resistor plugs.They are also a tad hotter than the NGK by 1 number, but the same as the R5671-7 which was also recommended my the machine shop.
Detonation may be a concern as I will be seeing 10.1:1 compression, but a nice .043" quench. I may wind up burning premium fuel. Don't know as of yet.
I may consider getting into the art of shortening plug insulators..............
But, til I receive the plug wires (Accel ceramic boots) I am not sure that clearance problems actually exist. I may also consider sleeves.

 

[CoggedBelt75]

Must be a mistype. Never heard of a gas engine producing that kind of compression. Even if they could, it wouldn’t be with flat top pistons and sure not on pump gas. Diesels do make those numbers, but that a total different animal.
Myself, I would go with either plug, run them a bit, and pull and read them. Still wondering on why such a cold plug for a mild engine. 2 ranges colder than my boosted engine to me just doesn’t add up. Maybe we’ll all learn something.

 

[4WDKC]

I am using flat top pistons; I don't think I'll be in danger of then hitting the plugs regardless.The heads, I have been told, are Brodix clones, and the machine shop from which I purchased recommended the NGK R5671-8 which is the same as the NGK 4554 recommended by Brodix. That is a non-projected tip. Brodix also specs the NGK 7405 which is a projected tip. They are both termed as "Racing" plugs by NGK. I have been considering using the Accel shorty plugs, #0414S for header clearance, but they are projected tip and also resistor plugs.They are also a tad hotter than the NGK by 1 number, but the same as the R5671-7 which was also recommended my the machine shop.
Detonation may be a concern as I will be seeing 19.0:1 compression, but a nice .043" quench. I may wind up burning premium fuel. Don't know as of yet.
I may consider getting into the art of shortening plug insulators..............
But, til I receive the plug wires (Accel ceramic boots) I am not sure that clearance problems actually exist. I may also consider sleeves.

Was that supposed to 10:1 or 10.9:1? either way look for the NGKs list of plugs and the break down of them.. each number represents something like thread size, amount of threads heat range length of plug outside of the engine etc.. once you find all the details of the recommended plug write them down or copy and paste to a notepad and save the file. Then try to find a plug that has the thread/length, heat range and exterior dimension you need to not hit the headers... Are these vortec chamber heads?

 

[SquareRoot]

19:1 compression is a diesel. You no need no sparky plugs.

 

[Ronno6]

19:1 compression is a diesel. You no need no sparky plugs.

OOPS...sorry Guys......10.1:1
The "0" and "9" keys too close together for my fat digits........

I did manage to find a short spark plug socket.
5/8 hex and short body that the plug protrudes thru, and hex on outside to turn with a wrench.
I had conjured that one up, but nobody locally carries them.
Did find them on ebay from 3 manufacturers......

 

[Ronno6]

Was that supposed to 10:1 or 10.9:1? either way look for the NGKs list of plugs and the break down of them.. each number represents something like thread size, amount of threads heat range length of plug outside of the engine etc.. once you find all the details of the recommended plug write them down or copy and paste to a notepad and save the file. Then try to find a plug that has the thread/length, heat range and exterior dimension you need to not hit the headers... Are these vortec chamber heads?

Yup 10.1:1.....
I have good suggestions on NGK plugs, but I want to use the Accel shorty plugs for header clearance. Those are limited to 2 choices with the needed reach and thread, and those are both projected tips and resistor.
The machine shop man said they should work fine, so I have them on the way from good ol' Amazon (best price...)

 

[donnieray]

The 7516 is apparently for use with cast iron heads (.46 reach)......I have aluminum (.75 reach)...... Maybe the cold range is to dissipate heat to the aluminum heads faster??
I have Hedman headers. They were about the only ones I could find which were designed for use with mechanical clutch linkage. The offset plugs make things a bit tight, especially on the #5 cylinder. I am exploring wire boot options to find something that will fit.
Looks like protector sleeves may be in my future.

Can you give me some info on the headers? I have an 84 K10 with mechanical clutch linkage.

 

[Ronno6]

Can you give me some info on the headers? I have an 84 K10 with mechanical clutch linkage.

Hedman #69092
5/8" long tube without the A.I.R. pump.......
#69093 with pump
Supposedly the A/C compressor bracket has to be modified...I haven't got that far yet.
Good luck!