20 replies to this topic

[maccers]

I have 3 sets of plugs. NGK B7ES BPR6ES BPR7ES

What’s the differences in practical use?

[unburntfuelinthemorning]

B (shell) = 14mm thread x ¹³/₁₆" hex   1.25mm pitch

P/R (construction) = projected insulator/resistor

6/7 (heat range) =  low number hot, high number cold plug

E (reach) = 19mm/³/₄"

S (firing end construction) = standard 2.5mm copper core centre electrode

 

David Vizard suggests heat range 6 for standard use and up to 50% power increase; 7 for high output engines and 8 for race engines. 

 

NGK plugs have a wide heat range but at the extremes:  if the plugs are too hot for the engine the electrodes get too hot and can cause pre-ignition; if too cold they can foul and misfire. 

 

The resistor plugs suppress electrical interference which can otherwise affect electronics such as audio systems and engine management.

[1968andyf]

The 7s are a colder plug than the 6s so would suit a more modified motor. The R denotes its a resistor plug

[maccers]

Ok cheers for that. So am running custom fuel injection s/c 1293 so will use the 7 R then..!

[nicklouse]

Ok cheers for that. So am running custom fuel injection s/c 1293 so will use the 7 R then..!

Fit the 6s go for a drive chop the plugs and see how they look.

7s will most likely be to cold.

[maccers]

Will give it a go, cheers!

[maccers]

The 7’s look a bit sooty after a short power run. Needs some RR diagnosis anyway. Running though.

[Cooperman]

My Cooper 'S' has a 286 cam, 11.1:1 CR, twin H4 carbs, etc.

I always run BP6ES plugs and they are fine.

[maccers]

Do people bother to set the gaps on them these days?

[cal844]

I just check for damage and fire them on

[unburntfuelinthemorning]

Do people bother to set the gaps on them these days?

Some will some won't.  I would.  They're supposed to be a certain gap and it's easy enough to check.

[RooBoonix]

Do people bother to set the gaps on them these days?

As said above for the time it takes, it's worth checking. Some engines/ignition systems are more sensitive to it than others

[maccers]

What drives the gap measurement? I have a Haynes book but the engine in my car is quite modified from what the manual would have.

[unburntfuelinthemorning]

Depends on the compression ratio and type of ignition system.  You won't go wrong with the basic 0.025" gap.  This could be opened up with a more powerful system. 

[guywilko]

Running 40” on CSI electronic small bore high compression