can someone tell how to tell the difference between trailing and leading spark plug by looking at them

 

BURQ7 and BURQ9 written on ze side

 

slight difference in those numbers.
BUR7EQ and BUR9EQ or if platinum BUR7EQP and BUR9EQP.
the 9's have a blue stripe on the ceramic part.the 7's don't.

 

they are also labeled with a T or an L

 

What he said.
The plugs, assuming your using the NGK's (stay NGK) are labeled T and L I always have trouble with auto parts stores saying they don't have a full set of plugs failing to realize the car uses two different types.

 

which is leading and which is trailing

 

 

Trailing (top) are 9's.
Leading (lower) are 7's.

 

but how do you tell them apart

 

More importantly, what size socket do they require?

 

Thank you for the correction... I was going off of memory and with something "close enough" I felt safe to say it in this case.

You guys use a socket? I just use my teeth.

 

lol

 

I think one is named Sparky.

 

Socket is 13/16 or 21mm both same size

 

I don't think we've reached a consensus on that.
The debate rages on.

 

The leading ones taste a bit like cabbage. The trailing ones smell like asparagus. It's very easy to distinguish.

 

On the chance that you are dealing with old or non-NGK plugs that are not clearly marked or you really want to know what is different besides the numbers / letters / blue rings...

The ceramic insulator surrounding the center electrode is more deeply recessed on the trailing plug compared to the leading plugs. Another way to say the same thing...the exposed center electrode is longer on the trailing plugs.

 

To clokker & AGreen: It was a tough day. Thanks for the good laugh!

Seriously now...do I need a left-handed or right-handed 13/16 socket? And who's gonna turn the motor while I hold the ratchet?

 

Well those are the sizes, maybe some should check with their own sockets but i have changed then numerous times.

 

To get the joke, see this thread spark-plug-socket-size

 

Yes, I see, thank you for chiming in.
Many believe as you do, others do not.
Let's not dismiss the world view of others by becoming inured to differing views.

Also, let's be a bit more expansive in our considerations.
We shall, to be generous, assume you've changed an even one hundred plugs.
During that time frame, NGK sold millions, if not billions, of spark plugs and you want us to assume that they are all the same exact size?
Have you accounted for differences in foreign markets?

What socket size for the UK, where everything is measured in "spanners" (and involves oxen, somehow*)?


*Citation needed.

 

Here is a break down of what the spark plug part numbers actually mean incase anybody is interested...

Specification part number breakdown: NGK BUR7EQ
B= 14mm Thread Diameter
U= Surface or Semi Surface Discharge Type R= Resistor Type Plug
7= Heat Rating
E= 19mm Thread reach
Q= 4-Ground Electrodes (Firing End Construction)

The higher the number on the heat rating, the colder the plug.
If the plugs are platinum, they would simply read a (P) after the (Q)

 

Well as being never left the U.S. i figured the rest of the world used milimeters. But stil should not be that complitcated to figure out with a conversion calculator when you have a starting point.

And yes there are many spark plug sizes but i have only ever seen those 2 in a rotary.

 

Ah, gotcha.
When "being" does leave, he'll be surprised.

 

Im sure i will no doubt about that but from what i do know just trying to help.