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MG TD TF 1500 - Spark Plug Reach

I’m sure this has been addressed in detail many times but my search skills are inadequate and I’m hoping for a definitive answer. My car is a 1953 TD (TD25009) with engine (or at least the block) XPAG/TD2/25404. I strongly suspect that the PO replaced the head with a head from an earlier engine. The casting number on my head is 22952 and I think the water passages are banana shaped (see image attached). The post that follows will address the spark plugs.

J. K. Chapin

Thanks for continuing to read this thread.

Using Tom’s bent wire method and believing that my head (casting 22952) is older and not original to the car or the block, I believe that I should be using ½ inch reach spark plugs. The image attached is of one of my current spark plugs (NKG B6HS) which I believe is ¾ inch reach. It certainly appears to me that the last ¼ inch of the threads have been in the combustion chamber. So, my questions are:
Does a 22952 head call for ½ inch reach plugs?
Are the NKG B6HS ¾ inch reach?
If the answer to the first question is “Yes,” what current NKG or Champion or other bran plug is recommended?
Thanks.
Jud


J. K. Chapin

Just another view of the spark plug.

J. K. Chapin

A 22952 head does indeed use 1/2" reach plugs. I use Champion L86C or KLG B6HS plugs.

Tom Lange
MGT Repair
t lange

Tom, I hesitate to question this part of your answer:
"I use Champion L86C or KLG B6HS plugs."

The plugs I'm using are B6HS but I think they are NKG. I should have liked more carefully or taken better notes. At any rate, the ones I'm using appear to be too long. Can you confirm that KLG B6HS are 1/2 inch reach? Thanks. Jud
J. K. Chapin

Take your old plug with you
To the parts store and tell them you
Want the same hear range but half inch reach. Measure yours from the base to the tip of the electrode and yours should be 3/4". Banana heads take 1/2". If your threads are sooty the 1/4 " you have the wrong plug. I just dealt with this when I went from my Laystall 3/4" to my original iron head 1/2".

Bill Chasser jr
TD4834
W. A. Chasser Jr

Yes, the head wishes to use 1/2" reach plugs. Yes, the NGK B6Hs plugs are 1/2" reach. The 3/4" reach plugs are B6ES. I don't know of KLG on NKG. I think you mean NGK. Bud
Bud Krueger

Bill, yes, your thread was what prompted me to start this inquiry.

Bud, now I'm going to go back over to the shop and pull the plug again to measure it and confirm what it is. I know it's B6HS from the photo but I only think it's NKG. I'll also measure from the base to the tip 'cause I think it's longer that 1/2 inch. More in a bit. Thanks to all. Jud
J. K. Chapin

Jud, I've never seen an engineering drawing that shows where the thread reach is actually measured. I know that there is always carbon on the bottom couple of threads of my plugs. Bud
Bud Krueger

Well drat!! I thought that maybe I'd stumbled onto the cure for all that ails me but it is not to be. As usual, y'all are correct. Here's an image of the plug on a ruler. It's pretty danged exactly 1/2 inch from the base to the end of the plug. Closer inspection reveals that only the unthreaded last little bit of the plug is sooty/blackish. I think by the time you account for the gasket it is just about exactly 1/2 inch. Not only that, I now know that it's NGK, not NKG. The electrodes look pretty good for a plug with 1,000 - 1,500 miles on it. Greyish but not oily or sooty.

Thanks for the definitive answer of the correct reach for a 22952 head. Jud

J. K. Chapin

Jud, Bud,

There is a lot of information on the net on spark plug specs. for example:

https://www.sparkplugs.com/glossary/8/spark-plug/R


John

J Scragg

Sorry, I was suffering a senior moment, and wrote KLG above when I did indeed mean NGK. I had been reading an eBay ad where the seller had an NOS KLG 2-piece original plug for a T-series, and my mind drifted when I wrote the note. My apologies!

Tom Lange
t lange

I put a set of these in my truck and replaced them at 70,000 miles. I really didn't have to replace them as even though they were discolored, they looked almost like new. Iridium plugs. They were pretty expensive, but I couldn't believe the durability. I still have them on the shelf and when the plugs in the truck go bad, the Iridium plugs will go back in. PJ





Paul161

John, an interesting and informative page. Thanks. Jud
J. K. Chapin

This thread was discussed between 23/08/2015 and 24/08/2015

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