spark plug type

waldo · Post by **waldo** » Sun Jun 03, 2012 11:30 pm

hi
please could someone tell me the right plug type for my 1938 37/26 TWINPORT.

rex.webb · Post by **rex.webb** » Sun Jun 03, 2012 11:43 pm

What length is you Plug threads ?
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Rob Harknett · Post by **Rob Harknett** » Mon Jun 04, 2012 12:03 am

http://archives.jampot.dk/Book/Workshop ... dition.pdf
For fast road work use Lodge H53 although H14 was standard fitting in 1938. KLG831 should also fit Ok. Earlier models had Lodge H1 or KLG KS5.
All you need now is 1938 fuel and away you go. There is a little green book published advising of suitable plugs to use with todays fuel. BUT, theres ifs & buts that can be argued. I assume you are having problems with plugs, maybe its how they are used thats the problem, are you using an old stock plug or something later. I guess you make sure your plugs are well cleaned?? If so thats probably the problem.
For years the central electrode insulation of the plug has not been glazed. If cleaned these plugs soon contaminate with tiny particals that cause the plugs to short out.
Edited by - Rob Harknett on 03 Jun 2012 11:05:44 PM

Rob Harknett · Post by **Rob Harknett** » Mon Jun 04, 2012 12:17 am

I just noticed you have stated 1938 then 37/26 ( 1937 )
It was 1938 that plugs fitted were changed. Don't ask me why, It was only these two years in the late 30's engines were almost indentical to look at. Both having the semi enclosed valve springs. Apart from the crank case being stamped 37 or 38 the most noticable difference is the timing covers, for 1938 the rounded profile type was introduced that went right through to 1954. At first they had a grease nipple, then the nipple hole blanked off with a flat, then this flat was smothed out. But the 38/22 E ???? part no. still cast on the inside. Castings had the first year of introduction and the smallest model they fitted, pt. no cast.Edited by - Rob Harknett on 03 Jun 2012 11:18:34 PM

waldo · Post by **waldo** » Mon Jun 04, 2012 1:54 pm

[quote]
What length is you Plug threads ?
I am running with a b6hs thread length is 12mm thanks.

waldo · Post by **waldo** » Mon Jun 04, 2012 2:11 pm

Thanks for the information,i am running with a NGK 6ES and the problem is exactly the way in which you explained it with my plugs
fouling on a long trip,where i have to pull over and replace with a
cleaned plug.The same happens when I have stopped and I have to clean/replace plug. Could there be other issues, not just with the plug? Thanks.

Rob Harknett · Post by **Rob Harknett** » Mon Jun 04, 2012 2:39 pm

Now youved said it " cleaned plug " which will soon contaminate and fail. plugs are now really throw away, unless you have very old original plugs with the glazed central electrude insulator. they can be cleaned.
Maybe you need new piston rings or rebore.