Hi again,

 

I’ve just taken a look at the state of the spark plugs that are currently in the HZ engine of my 1986 1.0L Polo. They’re looking pretty horrible as the engine runs too richly. I want to replace them ideally. For some reason the current plugs are triple pointed but I think single point plugs would be sufficient.

 

Is it possible to get VW spark plugs at all? If so does anyone know the part number?

 

Failing that what is the recommended type to get? I’ve heard either Bosch or NGK are good brands.

 

Can anyone explain what ‘BPR7ES’ is? I believe they’re a colder plug but I don’t know how this makes a difference?

 

Finally, what gap should they be set to in the engine and do they need to be inserted in a particular order?

 

Thank you

Spec is 0.8mm gap from August 1985 when VW switched to TCI-H electronic ignition.

 

Very rare to have to adjust a spark plug gap compared to the olden days of contact breakers and magnetos. Electronic ignition easily generates sufficient kiloVolts to jump 0.8mm even at high revs with low coil recovery time.

 

Single earth electrode is fine. Multi electrode tend to last longer, but cost more.

I think VW code was 191905450A.

 

BPR7ES-8 (or an NGK BUR6ET-8 or a 94024) would all work.

 

B is spark plug thread type (14mm x 13/16" in 1.25mm pitch)

P is Projected insulator.

R is resistor (suppresses AM radio interference, stops coil melting)

7 is the NGK heat range (less ceramic insulator nose means more heat is conducted into the cylinder head, smaller numbers are hotter for NGK, 6 is mid-range, 7 is a bit colder ... 8, 9, 9.5 are cold plugs)

E is the reach (19mm or 3/4")

S is the firing end (copper core)

-8 is the gap (0.8mm)

 

https://ngk.com/ngk-spark-plug-numbering-systems

 

You usually only need colder plugs if you have high compression or have done tuning mods and you expect to do high load running. Cold plugs take heat away, but can carbon foul at idle. Bosch -  whose heat numbers go the other way - have Super4 0242232504 that covers their heat ranges 7 and 8 which would also work.

 

Do one lead at a time so the leads don't get mixed up.

Pull the spark plug connector off, not the lead.

Clean the hole around the plug.

Be careful not to cross-thread when fitting.

 

Here's a list of alternatives for the Champion N7YCC that Haynes recommends.

(still sold by Green Spark Plug co and also listed on eBay) 

 

https://www.sparkplug-crossreference.com/convert/CHAMP_PN/N7YCC

I assume the plugs are black and sooty dry...

 

I have cleaned spark plugs of carbon using Mr.Muscle oven cleaner in a cup or plastic bag, then rinse with water, then dry. A mini cook's blowtorch blue flame will dry and also burn off the sooty carbon.

 

You'll need to fix the richness or the new/cleaned plugs will get fouled again which is either too much fuel or not enough air.

 

Edited 9 August, 20215 yr by dvderlm

Green Spark Plug co say NGK BP6ESZ for HZ engines with Grey coil.

 

So have you got contact breaker distributor?

Or is there a plug and 3-way cable coming off it. 

 

 

I use Bosch Super-4 (4 ground electrode) plugs in my 89 HZ, and have done for many years. I found them to give better responsiveness and smoother running.

 

Bosch Ref is WR78 and I’ve just put a new set in last week as part of a service. The old ones had covered 20k miles without problem.

 

W= M14x1.25 thread size

R= With Suppression Resistor

78= 7 to 8 Heat range, which is the just to the warmer side of mid range.

 

Bought from Powersparks on eBay:

https://www.ebay.co.uk/itm/153704601060

 

Edited 18 August, 20215 yr by mk2tastic