What's your plug gap?

[SLR No.77]

What's the consensus on spark plug gaps?

My SLR (VHPD with RBTBs) is fitted with NGK BCPR7ES plugs, which when fitting new I open up to 0.9mm. In truth they don't appear to foul at 0.8mm but I'm also aware that some people run with them as wide as 1mm. 

But what difference does it make? What are the gains from running smaller or bigger gaps?  These  plugs are around 0.8mm out of the box and I'm sure in most applications a general garage mechanic wouldn't bother checking!

Note: in old money 0.8mm is 31.5 thou, 0.9mm is 35.4 thou.

Stu.

 

[Colin Cooper]

Not much help, but I have always used a hacksaw blade on all the cars i have had since 1965!

Col

[StevehS3]

I run my standard 1.6K at 0.9mm. I am sure I'm in the minority but I don't like the NGK plugs and prefer the original platinum type supplied with the engine that last a lot longer too. 

[David_Long]

Modern coils are pretty good and will generate a spark at almost any gap. But at the end of the day, the energy stored in the coil is dissipated by creating a voltage high enough to discharge a current through a spark. A bigger gap requires higher voltage and therefore less current will flow (p=IV), so the spark will be cooler, or at least thinner. If the gap gets too big, the spark may become less reliable at ignition (misfires), too small and it may just be physically too small to ignite rich fuel (poor starting). So it best not to deviate too much from recommendations as that is just throwing away performance, particularly starting and WOT performance. 

[HendrixsWhiteStratReturns]

On the recommendation of James Whiting I run NGK BPR6EIX's on my Xflow Supersprint. They're pre-gapped and superb, don't get the fouling issues that used to get with B8ECs

[Tom H]

Hi folks,

I have a replacement set of NGK B8ECS for my 1989 Supersprint - Ford Kent OHV2265EV Crossflow.  I am trying to determine what is the torque requirement for installation and secondly if I should be applying copper slip anti seize when I do so. Any help?

I should add the assembly manual for this engine configuration calls out a 0.025" spark plug gap.

[7 wonders of the world]

Engine spec, cam choice / timing and compression ratio all have a bearing on the gap.

[John Vine]

Re #6:

General torque chart here.

Re the use of a lubricant or anti-seize compound,  NGK say don't.

JV

[HendrixsWhiteStratReturns]

Have never used slip/anti-seize on plugs, not necessary.

[alan7]

VHPD with DHTBs  fitted with NGK BCPR7ES plugs running at 0.9mm

[SLR No.77]

Similar spec Alan, mine's 1900 but basically the same. I've been playing around with the gaps and reducing to 0.8mm gives a less harsh tickover, I'm going to leave it there for a while and see whether the starting remains reliable and everything is stable, I'll also check what the gap is on a new set of plugs, NGKs are pre-gapped but I'm not sure to what, another set ordered.

Stu.

[Alastair B]

Just checked some NGK BCPR7E new plugs I have; out of the box and they are gapped at 0.030" or ~0.8mm

[TomB]

What’s the best price/ place for the NGK plugs these days? Wary of buying dodgy from eBay. 

[Wrightpayne]

I got mine from Opie.

 

I tend to put a smear of coppa slip, now alu slip on the threads, knowing the implications on torque settings.

I've never had a plug seize in on the seven but have encountered many other 'solid' fixings on other cars, where a steel bolt is used in ally, to the extent the fixing snaps.

[Paul Richards]

Tom

Car and Garage at Haslingden. If they don't have them on the shelf they can usually obtain in a couple of hours. 

[pete_h]

Need to check my gaps, but have a kinda related question. Is it possible to clean flouled plugs? I have tried carb cleaner and a brass brush but still have a miss fire at tick over (k series R400 - ngk BCPR7EiX plugs from redline so should be genuine)