Plugs and Gaps

[WGB]

I decided to replace the plugs in my Euro 6.9 while having a weekend fiddle and arrived home with the usual set of NGK's to find that NGK no longer manufacture their plugs with screw off mounting terminals.

It had been fitted with Bosch WR 9DCX and were gapped at 1.1mm+. Starting was OK but not inbstant like my 450 and the car ran fine.

On a drive around I scored some old stock NGK BPR6ES with screw off terminals but also found a set of Bosch WR 9DCX+ which are apparently the same as what I had but have Yttrium electrodes (I am sure with an element sounding like that they must be special in some way).

Again they are supposed to be gapped at 1.1 mm but I set them for the recommended 0.8mm - the car started instantly and I am about to take it for a drive and see what I've done.

Any comments from the experts gladly received.

Bill

 

[Mercules]

I don't know what it is about 0.8mm, but just about every car I have worked on got 0.8mm in the plug gaps. The engineer who I was apprenticed to swore by 0.8mm and every tuner I have worked with since reckons 0.8mm is the best (especially for Japanese turbos)

My Snap-On gapping tool is worn down on the 0.8mm loop and is unmarked on all the other loops!!

You must have dug deep to find NGKs with screw off terminals... they stopped making them years ago!

 

[Styria]

Hi Mercules, unless I am mistaken, I bought some NGK's with screw fittings only a few weeks ago. I'll just have to double check.

Bill, the heat range that you're using, in my view, is one range too hot. Normally, workshops employ that range with 6.3's that run a higher compression and are inclined to foul up especially if the fuel system is not spot on.

With my Gleaming Beauty which has the higher compression engine as you have in your car, I've always run '8s for suburban driving, and '7's for extended high speed (higher nowadays) driving without any detrimental effects.

Incidentally, I have been using Platinums for years now - it is remarkable how clean they run when compared to conventional plugs. Regards Styria

 

[WGB]

Thanks for the comments.

My car has the 8.8:1 motor and never gave any trouble on the previous plugs it was just that I had them out to check the chain stretch and it seemed like a good idea to change them.

From a previous comment of yours Styria - yes the 6.9 plugs are very easy to change.

Bill