Bill Schooler wrote:
>
> James W. Dunn wrote:
> >
> > Hello,
> >
> > I have a problem wtih my 52 MGTD with the spark plugs
> > "fouling out". I can't seem to get more than 80 miles on a new
> > set of plugs. When i remove the plugs they are coated with a fluffy
> > black coating, so I put in a new set and the car runs great for
> > another 80 miles or so and then they have to be changed again,
> > The engine was overhauled about a year and a half ago with
> > many new parts. The car has just been tuned including points,
> > condenser, rotor and dist cap, also the valves were adjusted, the
> > timeing set and the carbs adjusted. I checked the compression
> > and all the cylinders were within normal limits for this engine. The
> > engine doesn't seem to use much oil and I haven't noticed any black
> > smoke coming for the exhasut pipe. I use champion L82C spark
> > plugs set at .025 and even tried .035 with same results.
> > Any help greatly appreciated as I'm tired of changing sparks plugs.
> >
> > Thanks,
> > Jim Dunn
> > 52 MGTD
> > Birmingham, Alabama
>
> Jim,
>
> Although you said the carbs were tuned, I would expect you are dealing
> with an overly rich mixture, or incomplete combustion. Regarding the
> rich mixture question: in the rebuild/tuneup process, were the carb
> jets and needles replaced? I am going to defer to the TD operators
> about the heat range of your spark plug.
>
> As far as incomplete combustion goes, are you using the correct "reach"
> plug for your head? 3/4 inch or 1/2? And is it correct for your
> particular head? There were two different designs of cylinder heads
> used in the TD, and the casting change caused a change in spark plug
> reach. I'm going to cite Chip Old on this matter: "The simplest way
> (to tell which one you've got), although I'm not sure it is foolproof,
> is to look for the number which is cast into the top surface of the
> cylinder head at the front right corner. All XPAG heads I have seen or
> heard about which bear the number 22592 are early heads, which
> ...require 1/2 in reach plugs. The later heads bear several different
> numbers, but as far as I have been able to determine any head showing
> any number other than 22592 requires 3/4 in reach plugs." The
> "foolproof" way to tell requires the head be removed. Again citing
> Olds, "Check the water holes on the head which conduct coolant from the
> engine block to the head. If they are oblong (banana-shaped), then you
> have an early head. If round, the head is a late one."
>
> Here's why I went through this dialogue. Chip Olds explains, "If a 1/2
> in plug is used in a head designed for 3/4 in plugs, the engine will run
> but the electrodes of the plug will be shrouded by the unfilled part of
> the spark plug hole and will foul rapidly". Hoo boy - does this match
> your symptoms, or what! Chip goes on to explain the often dire
> consequences of using the longer reach plug in the older head. You
> don't want to do that.
>
> Sorry about the length, and I hope this is of some help.
>
> --
> *Bill Schooler *Check the MGCC Wash DC Centre Web Page
> *Woodbridge, VA *http://members.aol.com/mgccwdcc/
> *schooler@erols.com *Editor of The Spark
> *69 B/GT, 53 TD *Web Page Coordinator
I don't think you need to go to that extent. Simply remove a plug, bend
a stiff wire and inset in the plug hole and measure the distance.
Steve
52 TD
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