has anyone got a head off a car and can measure the depth of the spark plug thread hole...

 

(i.e. to work out how long the thread should be so that the plug fully clears the thread hole).

 

this is just to prove a point....

 

cheers.

One thing are do know is zed ngk iridium plugs are about 2.5mm shorter than standard zed plugs.

Yeah, cheers...

 

want to convince someone that the iridiums are not suitable for the Zd for a number of reasons.... and the length of the thread and therefor position of the ignition/spark is very important.

I've just taken iridiums out after 200 miles and put platinum in, seems better.

There is an old thread which has pictures showing the different lengths of different plugs, will search if i get bored lol

smithy

 

This is the pic I posted awhile back, standard on the left,iridium on the right

With the iridiums in I had a bottom end misfire which disappeared as soon as I fitted standard plugs.Im convinced the tip and therefore the spark was shrouded.

when you say standard I assume you mean the NGK PFR6B-11C...

 

because there are PFR6B (Platinums) that are too short as well...

 

thanks guys but I still need the actual depth of the bore/plug hole thread... :)

when you say standard I assume you mean the NGK PFR6B-11C...

 

because there are PFR6B (Platinums) that are too short as well...

 

 

By that your referring to the 11's only? as they are N/A plugs

 

Theres PFR68 11 AND PFR6B 11C + B being Different lengths!

 

smithy

yeah... but not sure if all of them are available....

 

as far as I can see the only ones you can easily get now are the 11c's

 

 

 

 

 

 

just in case the actual point of the thread gets lost..

 

And can anyone please measure the depth of the spark plug thread hole in the head...

 

cheers.

iirc the stock ngk plugs were not not only found to be the best but they were designed for the zed specifically.

LOL.. thanks guys, really appreciate all the info, and by the way I already know it...

 

never the less it is valid and helps to explain to other on here about the correct plugs for the car.

 

 

However I really need the depth of the spark plug bore.... it's to settle an argument..

 

cheers.

18.90mm is the lenght of the thread and the bore that the plug sits in is 43.87,measured from the face the washer sits on to the top,measured on a spare head I have got :)

Edited July 11, 201214 yr by Rebel Scum

18.90mm is the length of the thread and the bore that the plug sits in is 43.87,measured from the face the washer sits on to the top,measured on a spare head I have got :)

 

Top Man.!! :thumbup1: .. the part I'm interested in is the thread depth...

 

need to show that the shorter threaded plugs don't position the spark head correctly in the cylinder/head cavity.

 

i assume that here isn't any other tapered section or hollow the spark end of the plug sits in.

Ah... just found this.... shows exactly what I'm after (other than the measurement of the depth) an I correct in assuming your head is a TT one?

 

http://www.twinturbo.net/nissan/300zx/forums/technical/view/1078188/Those-plugs-in-your-pics-are-too-short-for-a-TT-application.html

Yeah, it is a tt

thanks.... :)