Be careful using NGK FR5's in your alloy headed Windsor!

[hybrid]

I switched over to FR5's because they were a 0.750" reach plug, but I've had a misfire recently and thought I would check out the plugs.
I'm pretty sure as I was checking it all, my misfire issue was a lead that wasn't on properly because I could see flashing in the plug cap area.

Anyway I thought I would check the condition of the plugs as well.
I found this:


Three of the plugs had this mark on them, but one of them was only a very small mark.
I then put my old plugs and these ones side by side. If you look up the specs, they both show 0.750" reach, but one of them is lying.



If you aren't running flat top pistons you will probably be OK, although it may be a valve skimming it too.

[boofhead]

Wow - interesting find. I have not used the FR5s but many swear by them.

[nassi]

Struth that is a big difference

[hybrid]

Wow - interesting find. I have not used the FR5s but many swear by them.

Yep, that's why I went with them!
I suppose if you're not zero decked and not using flat tops, you might be OK - if it's the piston hitting and not the valve.
I'm actually thinking it's the valve hitting though because I'm not sure the piston would leave the kind of mark I'm seeing.

To be honest, it can't hurt to go back up to a colder plug with the supercharger anyway.
And the best part is... imagine that lower compression because there will be less room taken up in the combustion chamber with the shorter plug!
I'll be able to shove another pound of boost in there

[boofhead]

Well good thing your not running a domed piston and decided boost is the go instead.
Keep adding the boost Hybrid ... we need more build threads

[CobraJet]

this is the second issue I've heard about NGK issues. About 18 months ago a mate I worked with complained about NGK's when he swapped all his Land rover plugs to them. Like me we have both used them in the past and never had an issue. This time the Landie wouldn't start. Went through the lot, leads, distributor etc etc. Swapped back to old plugs and started right up.

At the time we mentioned maybe production had changed to a different location and QA had dropped off. Seems like they have gone done the gurgler.

[hybrid]

Yeah I can't really comment on the production quality, but I don't see how both of those plugs can be considered 0.750" reach.

[ants]

I think that the reach refers to the thread then after that NGK refer to the electrode as extended or something similar.
Looks like you have FR5-1 not FR5 (I could be wrong)
This is just from a quick look at the NGK website

https://www.ngk.com/product.aspx?zpid=9759

https://www.ngk.com/product.aspx?zpid=9760

[boofhead]

Looks like your spot on there Ants.

[hybrid]

Yeah I think you're right. The issue is that most of the time, the -1 would mean 1mm gap (which is what I assumed).
Obviously that's not the case with the FR5's.

It's kind of a stupid way to measure reach because the thread length doesn't normally matter. It's how far the electrode reaches that really matters.
I just bought BCPR6ES-11 and they are 1.1mm gap.

I also don't know why you would bother selling the same plug with different gaps when you can just set to what you want anyway.