Plug gaps

[simmit]

Planning to replace the plugs just before the MOT ( first time I have done it on this engine ). I think the plugs are BCPR7ES but cannot find the info in the Haynes manual nor can I find any info re the gap which I assume is either 25 or 30 thou - can someone please confirm.

Peter. Like you I'm confused. Removed plugs, looked OK but decided to check to confirm right ones so went to NGK partfinder site and I find:-

Granada 2.9efi
V6 EFi / Gasket Seat Plugs 87 –> 91 BCPR6E Gap 0.7mm
V6 EFi / Taper Seat Plugs 89 –> 95 BPR6EF Gap 1.0mm

FORD 2.9 SCORPIO SPARK PLUGS
12V 01/95 –> BPR6EF
24v SEFI (COSWORTH) 01/95 –> 06/98 PFR6B-11

Now, MB50 came to me with with BPR6EF plugs and looking into the plug holes they do seem to have tapered seats at the ends of the threads (albeit very narrow lands) so all OK, I think.
But, can anyone here say why there is such a big difference in the recommended plug gap setting between taper seat and gasket seat. If(?) plugs are identical in every other way but in their sealing method then it doesn't make sense, does it?
In passing, I note plugs for Scorpio (12V) are same as later Granada so that at least is consistent.

[scimjim]

I doubt it's anything to do with the seat but more to do with the plug itself?

[Elizabeth's dad]

Fit Bosch Super 4s (FR78 as far as I know, but I don't have a 2.9 so check) and forget the gaps!

[Oldconn]

But, can anyone here say why there is such a big difference in the recommended plug gap setting between taper seat and gasket seat. If(?) plugs are identical in every other way but in their sealing method then it doesn't make sense, does it?
In passing, I note plugs for Scorpio (12V) are same as later Granada so that at least is consistent.

Actually they are not quite the same specification.BPR6E and BCPR6EI think there is a copper element in one of them which probably means different conductivity.

[scimjim]

For NGK plugs

The letter combination (1-4) before the heat rating indicates the thread diameter, hexagon spanner width and the design.
The 5th position (number) stands for the heat rating.
The 6th letter identifies the thread length.
The 7th letter contains data about special spark plug construction features.
The 8th position, another number, codifies special electrode distances.

https://www.ngk.de/fileadmin/Dokumente/ ... ode_en.pdf

[Roger Pennington]

Yes, as per Jim's link, I use the plugs starting with "BC" in the designation in my GTEs as the smaller hexagon makes it a little easier to get the plug spanner onto them when removing/replacing. John Wade originally recommended them. It does mean you need the smaller size plug spanner of course.

[simmit]

For NGK plugs

The letter combination (1-4) before the heat rating indicates the thread diameter, hexagon spanner width and the design.
The 5th position (number) stands for the heat rating.
The 6th letter identifies the thread length.
The 7th letter contains data about special spark plug construction features.
The 8th position, another number, codifies special electrode distances.

https://www.ngk.de/fileadmin/Dokumente/ ... ode_en.pdf

Thanks Jim for the link.

From the symbols/ code it appears the only difference between the two plugs is (1) plug spanner size and (2) one has taper seal and other has gasket seal. Both have same reach, heat rating and platinum electrodes, neither have any specified special features. So, I see no indication as to why plug gaps should be so very different.

Am considering Elizabeth's Dad's suggestion of Bosh Super 4 and to hell with gapping. Comments gratefully received.

[simmit]

To those who may be interested, today I have had long conversation with very helpful NGK Technical Dept. man, Mik Peirce. Based on Granada 2.9efi engine of 1990 era he says:-
(1) Recommended plugs for gasket seat heads are: BCPR6ES (basic spec), BCPR6E (improved 'V' groove spec) and BCPR6EIX (further improved iridium spec). Plug gaps will have been determined by Ford at 0.7mm but will be supplied from NGK at 0.8mm.
(2) Recommended plugs for taper seal heads are: BPR6EFS (basic spec), BPR6EF (improved 'V' groove spec) and BPR6EFIX-10 (further improved iridium spec). Plug gaps specified by Ford at 1.0mm but will be supplied by NGK at 0.9mm.
The reason ford specified lager gap for taper seat plugs is that those engines, being later development, were to meet improved fuel emission and probably had adjustment to ECU and electrical ignition system (coil) etc to suit.
In Mik's opinion, for either the gasket or taper plug types there would be no noticeable difference if plug were used with out-the-box factory gap settings. Iridium plugs give much longer life and are more tolerant of gap settings to boot.
He could not offer advice as to determining which specific engines might have taper or gasket seat plugs and I have contacted Ford to see if there is truth in the here-say there is a letter cast on the exhaust manifold that identifies (not holding breath for response). My engine has taper plug but possible previous owner simply forced them to seat, just can't be sure by looking down the plug holes.

Good news is that Mik promised to include Middlebridge into next update of NGK plug guide for Classic Cars, so we get a bit more recognition for the marque there.

Finally, can anyone say for certain how we might determine which engines have gasket plug seat and which have taper?

Apologies for long winded ramble but it might be useful info to some of us.

[peter freeman]

I used a small screwdriver to determine if I needed taped or "square" plugs - you can feel the edge. That of course was before I bought a endoscope which confirmed my requirement.

[simmit]

I used a small screwdriver to determine if I needed taped or "square" plugs - you can feel the edge. That of course was before I bought a endoscope which confirmed my requirement.

Peter.
What did your examination reveal, tapered or gasket seal? Also, cast onto the exhaust manifold above the nearside bank front exhaust is a letter, can you say what it is for your engine (I'm trying to establish if there really is a connection between that letter and the type of plug seal).

[peter freeman]

Tapered plugs were fitted when I bought the car but found that "square" plugs should have been fitted. I think that some mechanic had assumed that tapered plugs were required without checking. I will have a look to see what letter is on the car tomorrow afternoon when I get back home - out in the morning.

[efi_sprintgte]

The reg of my XR4x4 2.9 was F800 PPE which sometimes makes it easier to find parts at motorfactors.

[simmit]

Tapered plugs were fitted when I bought the car but found that "square" plugs should have been fitted. I think that some mechanic had assumed that tapered plugs were required without checking. I will have a look to see what letter is on the car tomorrow afternoon when I get back home - out in the morning.

Hi Peter.
Much appreciate your input as I suspect same thing might have happened to MB50 (taper plugs fitted in error). I've looked best I can in the plug holes and whilst there does seem to be a taper seat at end of the threads it is quite small and possibly could have been formed by overtightened taper seat plugs. How can I tell?

[peter freeman]

First of all the letter stamped on my engine is a K. It is also not the original engine as it was fitted when the car had done around 200,000 miles - quite when that was I don't know - its now over 300,000 miles. Took a plug out and used the endoscope ( first time I have used it on this engine ) and it looks like a tapered plug hole however this may be a optical illusion. What I can say is the landing where the plug body comes to rest is quite wide so I think you can fit either tapered or square plugs without effect - I have square plugs fitted and they have been in for 3 years. Quite how you can determine if the hole is square or tapered I don't know as its not easy to get a good look and getting some sort of measuring instrument down the hole ??? no tool I have will do it.

[RonH]

I have square plugs fitted and they have been in for 3 years.

I’ve been wanting to change the Bosch plugs on 404 for some considerable time. I don’t remember seeing corrosion on the outer surface of plugs before and that’s the main reason I wanted to replace them - bling factor However that was nothing compared to what I found at the other end. What’s going on here? What can of worms have I opened Engine not hot just kicked up to check it was running ok before I pulled each plug out to replace with NGK Iridium one by one. Fuel shell v power with Millers additive. Cologne with unleaded heads. Car has always started and run without problems. The plugs will have been in approximately 5 years. Weber 38 DGAS.
The iridium plugs certainly make it seem smoother and I can’t hear the engines normal tappety noise. However, traveling just one mile isn’t a true test. Anyone offering any suggestions greatly appreciated.

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