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MG TD TF 1500 - What is correct plug for 22952 head?

After researching the archives for this I came out none the wiser than when I went in.
The question of which plug to use is addressed but wanders into engine numbers, shapes of water passages, and other stuff about long reaches and short reaches and spark plug brands.
My cylinder head number is 22952. This is NOT the engine number, it's the cylinder head number.
Which is the correct NGK plug for it?
Thanks.

BobbyG
Bobby Galvez

Bobby - You should be using 1/2" reach plugs in that head. Is that what you're asking?

Gene

P.S. - Great putting a face to a name this past week in Salado! Hope you're about to get the TD running smoothly again!
Gene Gillam

B6HS or BR6HS. see info here: https://www.ngksparkplugs.com/about-ngk/faqs/spark-plug-faqs/when-should-i-use-a-resistor-spark-plug
George Butz

Hey Gene! You and Sherwood are on my agenda for notes today.
Great meeting you both in Salado and fabulous to see each of you take first places in class and your Show Favorite as well.
Yes, that's my question. I currently have NGK BP6HS plugs in there. That is a 1/2 inch reach plug, so it's correct.
All four are very sooty, as if they've been held over a candle flame.
What puzzles me is that some soot runs all the way up the threads. They are black. Photo attached.
I can understand soot on the parts that are in the combustion chamber, but why the threads?
Best,

BobbyG


Bobby Galvez

George, thank you.
Is there any reason why a resistor plug would be used in such a basic car with no advanced electronics in it?

BobbyG
Bobby Galvez

Correction - currently have B6HS.
Bobby Galvez

Bobby,

If no radio and you do not use a cell phone or GPS there is little reason to use resistor plugs. Can anyone think of an other reason beyond RFI, Radio Frequency Interference?

Regards,

Jim Haskins 1953 TD
J M Haskins

Bobby...

No need for resister plugs or wires since you're running points.

Not sure why the threads would be black unless the plugs weren't tight.

And not sure the plugs are the problem - with today's gas the only real way to tell by the color of the electrode is by getting the car up to temperature and then drive it full out for a 1/2 mile or so, then cut the ignition and coast to the side of the road and pull them. You'll probably find that they're the brown/tan you want...if not then you'll know they're potentially part of the problem...your mixture could be too rich or weak spark or plugs are too cold for your engine.

Gene
Gene Gillam

Jim, thanks for the input. No radio and rarely use GPS in the car. Definitely no cell phone use.

Gene, I'm hoping it's a weak spark issue. I got new plugs and will also replace the ignition wires. Am also going to see if a different condenser makes a difference. I've bought several new "suspects" as condensers.

Can't think of much else to do other than to swap things out one at a time to see where the fault lies.

The issue originally was that the cup where the coil lead comes in to the distributor broke clean off about 1/4 inch from the top. The engine had been misfiring and finally just quit when the part broke clean apparently it had been cracked for a whole and wasn't detected.

A new distributor cap made no difference, neither did a new ignition coil. New condenser neither - but it was one newer condenser for another, it could be a swap of one bad part for another. I understand that there have been known failures of new condensers out of the box.

First I'll put in the new plugs, then the condenser and lastly new ignition wires.

And once the issue seems resolved, the dizzy will go off to Jeff Schlemmer.

Thanks all for the help.

BobbyG
Bobby Galvez

One reason to use resistor plugs is if you are using one of those induction timing lights that have a pick up you clip around the spark plug lead.

Can lead to all sorts of issues trying to set the timing ( ask me how I know...)

Dave
D Moore

Bobby,
I reread the thread, and your last comment confused me,, Are you actually having a plug/firing issue?????? Or are you just concerned about the color???

Steve
Steve Wincze

Thanks, Steve - having a plug/firing issue. We have been looking for a cause.
Pulled plugs and had spark at all four plugs, but weak. Photo shows what the plugs looked like coming out of the engine. We were at a GoF in a town with no auto shops and no access to fresh plugs, so no way to see if weak spark was simply from dirty plugs.
Plug color has me curious on two aspects.
.- Excess rich or weak spark can cause that sootiness
.- why the soot was up into the threads.
New plugs will be going in as soon as I have time to take a look at how it behaves with them in.
If the misfiring is gone it was the plugs, and I will re-check carb mixture settings.
If the misfiring remains there's more to be done to track the cause.
In effect what I'm doing is tracking the issue from the combustion chamber and back up the system.
Dave, thanks for the heads-up on using the induction timing lights with non-resistor plugs. Good to know.
I started the thread just wanting to be sure about what reach the head calls for. I wanted to eliminate the possibility that there was a short reach plug in a long reach head.

BobbyG
Bobby Galvez

Do you have a red or black/brown rotor?
George Butz

George, black is currently in it and will become a red as soon as I can secure it.
I have heat resistant paint for it ...
;-)
No - seriously, it was one of the things that was put into the range of possibilities by the committee under the bonnet.
Thanks!

BobbyG
Bobby Galvez

I would change the rotor to one of the Advanced Distributor manufactured red ones (Moss and everyone has them now)before you do anything else. Saw a new black one fail at GOF South a couple weeks ago, they are garbage! Search archives for this topic if you are not familiar with it, or I can fill you in. George
George Butz

Don't use resistor plugs with resistor wires or you will get a weaker spark. Use one or the other if less interference required. I prefer neither, and use copper core wire and non resistor plugs, and have no trouble with timing light, but can see how that is possible. With that head you want 14mm 1/2" reach plugs. Champion L86C is somewhere between NGK 6 and 5. L82C is about NGK 6.

When using a resistor plug, the numbering system is thrown off a bit, and a resistor L86 is closer to a standard L84. NGK is backwards, with a 5 hotter than a 6. NGK jumps in larger (heat range) increments than most others. Another element is projected tip. A projected tip champion L86YC is hotter than a standard tip L86C.

Heat range of a plug only effects the plug, and not the engine operating temp. Too hot a plug can cause problems, and that is why people try and get the coolest plug in there that will not foul itself. Around town driving requires a hotter plug (to keep from fouling) than highway driving, so a compromise must be struck. In racing engines with very high RPM, very cool plugs are needed.
D mckellar

George, I just ordered a couple of the red rotors and should have them in a few days.
D McKellar, I've found Champion L86C plugs at the local Auto Zone.

BobbyG
Bobby Galvez

This thread was discussed between 09/05/2016 and 10/05/2016

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