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MG MGA - sparkplugs appropriate with HRG cylinder head

I have continuously firing problems when starting my recently bought MGA 1600 MkI, equipped with an HRG crossflow cylinder head. I have very basic mechanical knowledge but I wouldn't be surprised that, beyond a deficient coil which I have now replaced, the sparkplugs have also some responsibility. Actually, when I replaced them for the first time, I found three different types of them, notably Champion RN5C, RN19YCC and RN19YC! Using 95% octane petrol, could anybody advise me what the most appropriate sparkplug type is for normal/fast road use? I couldn't find the info nowhere on the web.

With my best thanks in advance, and sorry for the bad english.

Alain
Alain Demoulin

Alain,

In the MGA Workshop Manual (General Data 10)the Champion N5 plug is recommended.

Wim.
Wim Betzel

Alain, the factory manual suggests N5 for the normal engine but does not have reference to the HRG head.
I always use NGK BP6ES in all engines unless there is a special reason to not. These would be absolutely fine for your engine unless you have very high CR in which case a BP7ES might be a better choice. The 7 is a cooler plug and would cause cold starting to become more difficult so one should have a good reason for using it.
Bob (robert)

Alain,
Firing problems can also be caused by a worn distributor, cracked cap, damaged rotor, bad condensor, or bad wires.
Several people have written lately about poor replacement rotors. I would check this first, as well as the cap and wires. Another potential problem area is the wire in the distributor going to the points. Insure that the wire insulation is good here. I have a friend who bought a car for $25.US because the points were shorting out in the distributor. Assuming that the distributor is in good repair, I would suspect the cap or wires. You can easily check this by wetting the wires and cap down with water while running when dark. Spray a water mist over the distributor side of the engine while running. If the engine stalls, you have a definite problem which should be easily found. If you get misfire, check the wires and cap for arcing (hence the need for darkness). If this seems ok, check the distributor shaft for excessive wear by removing the cap and attempting to move the rotor shaft side to side in the distributor. If you have noticeable movement, the distributor bushings may be worn. Note that the rotor will turn a little while you attempt to move the shaft. This is normal.
This should get you started.
Good luck.
mike parker

Alain- Awhile back Bill Sporn was kind enough to post the installation instructions for a HRG head and at the time they recommended K.L.G. plugs FE 75 or 80 for normal use and FE 100 or 220 for competition use.Maybe someone knows of a cross reference to a modern plug. Gary
gary starr

My cross reference chart shows:

KLG FE 75
Bosch W7CC
Champion N6
NGK B6ES

KLG FE 80
Bosch W5CC
Champion N4
NGK B7ES

KLG FE 100
Bosch W4CC
Champion N3
NGK B8ES

No FE 220 shown.


Mick
Mick Anderson

The KLGs mentioned in the installation instructions aren't readily available (thanks to Mick for posting equivalents).

I would use NGK BP6ES.
Bill Spohn

Many thanks to all for the infos, and especially to Mike for the additional advice.

Alain
Alain Demoulin

For what it's worth, I'm using NGK BCPR7ES plugs for my HRG Derrington equipped car...

Alex, near Ghent
Alexander M

Most MGA owners, both normal pushrod, HRG, and Twin Cam, seem to use NGK spark plugs.
But what do all the symbols quoted above mean?
B8ES
BP6ES
BCPR7ES

See website:

http://www.angelfire.com/amiga/mga/index.html


Mick
Mick Anderson

I am terribly sorry when in my original post I simply quoted BP6ES. I was under the impression that most enthusiasts understood that if they wanted a resistor plug they simply added an R. It is a long time since I have seen anyone use the B6ES which of course is the forunner of BP6ES and so does not have the extended "nose". The main thing with NGK plugs is of course the heat rating, ie the number. 6 is ideal for most applications and others must only be used for specific installations. These may be 7 for a high compression engine or perhaps 5 for an engine that is burning a lot of oil and fouling plugs. I have not seen many BCs used as I dont see the benefit and it would probably be an expensive alternative that is not readily available of the shelf.
Bob (robert)

In NGK nomenclature 1st space B is 14mm thread size 2nd space is construction (none or more letters) c is 5/8 hex size P is projected insulator type R is resistor type 3rd space is a number between 2 and 11 with smaller being hotter 4th space is thread reach E=19mm or 3/4 in. with gasket 5th space is firing end construction S is standard 2.5 mm center electrode( there are over 20 choices in this area) in the last position a "-" then a number(8-20) shows a wide gap plug .8mm (.032) through 2.0 mm (.080) no number at end means .7mm or .028in as standard. all NGK plugs come pre gapped and parralel so dont touch. there are many more letters and designations (see page 2 of catalog) but these cover our applications. BPR6ES is usually what to use. ps champions are poor quality in my opinion and shouldnt be used.
R J Brown

To all you people using Japanese plugs, you might as well drive a Miata - I prefer to experence British motoring as God and Abington intended it to be, with Champion N5's,points & condencers,SU fuel pumps, and Lucas the Prince of Darkness.-----Just Kidding!
gary starr

This thread was discussed between 15/06/2005 and 22/06/2005

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