what spark plugs helpp

i absolutely cannot find the right spark plugs for my 69 135 with 3 cyl, not sure what reach, i called a couple mf dealers they are no help i wanna put a little hotter plug in it then is in it now. its got autolite 216 in it when i bought it but i think they are wrong. all iv been able to find is 3/8 or 3/4 and a 216 is 7/16

For some interesting conversation on this put " Autolite 437's longer than AL216." in the search function at the top of the page..

According to my MF service manual the long reach plug was used after engine serial number 152 UA 15061A. The spark plug in the manual is a Champion UN-12Y (14mm, 3/4" reach). Even with the engine serial number I would recommend looking into the spark plug hole to see how deep the threads are in the head (someone could have swapped cylinder head unless you know if its the original cylinder head).

is there anyway if i count thread number on head and get plugs with same number of threads would this work?

BC,
I see what you mean about the confusion for spark plugs for this tractor
MF 1969 model 135 with 3 cylinder Perkins AG3.152 engine

A-834236M1
Spark Plug (Long Neck)

A&I - Spark Plug (Long Neck) (w/Perkins engine). PART NO: A-834236M1

per my research this is the proper sparkplug for your tractor
they have them on ebay,

the MF tractor information I found only gives the proper spark plug data for the MF 135 with 4 cylinder continental engine

This is really odd.
but check it out on ebay and see what you can find,

note: these plugs are long reach and must be what you need, as you suspected.

good luck and let us know what you find.
(odd the MF dealer would not have this info)

I also found this information which only further Muddy's the water.

The AG3-152 used three different length or reach plugs, the engine serial was used to figure which reach plug was used in the engine. so you need to identify you serial number

the information I found did not reference any difference in serial numbers, but there may be a difference in proper plugs used per serial numbers.

The right reach plugs does make a difference in how the engine performs.

what was MF thinking when they made these different plug requirements for the same engine?????????


Those engine are very touchy to tune up the plugs point settings & timing make a big difference in how that engine runs and performs.

So I just got home and took a plug out, the
wierd thing to me is that the hole extends
at least 3/4 to a inch past the threads
toward inside of motor. I put the autolite
347 in it since it was 7/16 reach after
talking to my dad he said since it's running
fine with the 7/16 reach already. But for
some reason after putting the new plugs in
it seems to be blowing a little grayish
black smoke, when I turn the idle screw on
carb one way or another a substantial amount
it does a steady stream so I think it's a
air fuel mixture issue. One thing after
another lol

A similar difficulty occurs with Ferguson TEA20 and TED20 tractors . The TED is designed to run on a kerosene petrol mix and has longer reach, hotter plugs to compensate for this .
Many times the shorter TEA plugs are used and this leaves threads uncovered in the head plug hole , combustion gases and carbon deposits ruin these over time . When you then attempt to install the correct plugs they can bind , cross thread or simply refuse to seat properly . The fix really requires the head to come off . I would persevere with the search for the correct ones to avoid an annoying if not costly mistake .

Ideally the electrode on the spark plug should just stick out in the combustion chamber. I'd put a long reach plug in, and turn the engine over by hand a few revolutions. If it doesn't feel like anything hit, or stop the engine from turning pull the plug out, and see if the plug gap didn't change. Another thing you can do is look through the plug hole while turning the engine over, and see if you see any of the valves through the plug hole. If you don't see any valves moving past the plug hole you can then put the piston on top dead center, insert a round rod through the plug hole, and see how far down the rod goes until it stop against the piston.

bcliburn
Let's start from the beginning. Why do you think you need a hotter plug ?

I pulled a plug out and it's a long ways
past the threads before it opens up, I also
noticed that it makes no diff for me because
it has had to short of plugs in it for so
long that it has the last few threads which
the 3/4 in reach would probly hit are carbon
covered/ rusted to the point I don't think I
could safely screw a long reach plug in
without stripping or not seating the plug
all the way into the hole

I do not know if I would run a spark plug tap down those threads or not, others will know better than me.

It may be that you would have to pull the heads to have those threads cleaned out,

You do not trash filings etc dropping down into the cylinder

I'd run it with short plugs, if you ever have to pull the head for some reason then run a tap in the plug holes.

Here's my view on hotter plug use. IMHO, for whatever reason, spark plugs tend to foul faster with today's modern 88 octane ethanol, no-lead gasoline. So to reduce "fouling", you change to a hotter spark plug of the same reach. The colour of the exhaust, black versus gray to clear indicates a couple of things, as you say the air fuel mixture is to rich. Either their is a restriction in the air supply, the carburetor is set to rich or their is an excess amount of oil being added to the mix because of internal engine problems which need to be resolved or lived with. The other problem with hotter plugs is the increase temperature rise to the engine which is not good for engine longevity when operated hard for long periods of time, although tractors with light use may benefit from hotter plugs to reach optimum operating temperature. If your original plugs are not fouling then their is no need to change. If one plug is fouling you might try a hotter plug in that cylinder, you can confirm the effects by taking a before and after temperature reading with an infrared thermometer of the exhaust manifold compared to the other cylinders. Again this is just my opinion, take it or leave it. :wink: :wink:

Autolite 295 is what it should have.