MENU Subscribe to a Magazine
  • Sign in
  • Join

Subscribe to Print or Digital! Save up to 83%

Magazine Muscle Mustangs & Fast Fords
Magazine Mustang Monthly
Magazine 5.0 Mustang & Super Fords
Magazine Modified Mustangs & Fords
  • Print Subscriptions
  • Digital Subscriptions
  • Gift Subscriptions
  • Subscriber Services
  • Back Issues
  • Personalized Cover
  • Subscribe to a Magazine
Item Posts    Sort Order

Spark plug for 67 200ci fouling/engine misfires?

New User
Posts: 6
Joined: 10/13
Posted: 11/22/13 07:51 PM

Having a problem with my 1967 mustang. The engine is running rough and misfiring, causing a rumbling. When I took out the spark plugs, they were wasted and covered in oil. I changed them with some Autolite copper plugs, but they still get fouled and oil leaks onto them.

What kind of plugs are recommended? A mechanic friend of mine recommended I use a stronger plug, maybe Autolite Platinums? Also wondering if anyone has heard of/had experience with this problem.  

Post Reply
Posts: 105
Joined: 10/13
Posted: 11/23/13 12:25 AM

a few things...

check valve cover thru oil filler hole after a drive as fast as you can hop out and open hood and look down into the filler hole to make sure that the engine oil that is pumping up thru the lifters is actually draining back into the pan... not filling the area around the valve springs and flooding the under side of the umbrella type valve seals used on that engine..

think of standing in water up to your knees .. with mid calf rubber boots on and an umbrella keeping your head and body dry..  the water in your boots is sliding down the valve guides and having fun with your spark plugs..

compression test...

if you have a solid 4 bladed fan... pull the distributor cap.. so you can see the rotor... rock the fan and crank back and forth to see how much play there is in the timing chain...

the replacement timing chain and gears are fairly cheep...  it will cost you more for oil, filter and coolant than it will for timing chain, the cam and crank sprockets and the timing cover gasket set..  slack timing chain will retard the cam timing.. not the ignition.. but will greatly effect how the engine runs...  won't have a lot of power with a lot of slack..

change the valve stem seals...  if the compression test checks out and its actually draining..
please use a length of cotton rope with a big knot tied in one end .. pushed thru the spark plug hole to hold the valves up as you bring the piston up after inserting the rope.. this prevents the valve dropping as you remove the valve springs and keepers to replace any cracked seals..  you can see them thru the valve spring windings..

next.... ignition improvements..  so you get more spark for the plugs..

duraspark distributors from late 70s fairmonts 200's can be installed easily installed..  you can also go with the cap adaptor. the big electronic rotor and the big cap that takes 8MM wires.. even the later coil.. you have several options for modules.. the blue grommet ford duraspark module..

there is an article in the archives about using a GM HEI module with the 3 wire duraspark distributor.. let me tell you either works just fine..

you can also drop in one of the point replacement electronic ignition conversion kits..

why increase the ignition.. so you can light the spark plugs...

you might want to check the spark output.. position the coil wire removed from the center of the cap.. about 3/8 of an inch from the block.. and have somebody crank the engine.. do you get a nice bright blue spark.. or a none or a dim yellow spark..  

as for going to exotic spark plugs..    autolites.. or motorcraft conventional plugs are all that are needed...

Motorcraft Copper/Spark Plug
1967 Ford Mustang 3.3L 1BL 6cyl
Part Number: SP-431   Alternate Part Number: 631

Autolite Copper/Spark Plug Part Number: 46

lastly.. and this is something i have run into .. is the valve cover gasket leaking oil onto the outside of the spark plugs??? causing external electrical shorts that steal the spark before it can get inside and light your combustion..

oh... and if you have only one or two spark plugs fouling out..

Help/18 mm. gasket seat spark plug non-foulers
Part Number: 42009
these go on the spark plugs and move them away from the oil.. but still have a hole that the air and fuel can get thru so they will light the mixture..  

Post Reply
New User
Posts: 24
Joined: 11/13
Posted: 11/30/13 07:28 AM

do the suggested compressiin test.

then put 3 squirts of engine oil in one cyl at a time and do test again.

post results.

the oil foulers never worked for me.

your engine has bad valve guides and/or bad rings. it needs major repair, nothing else will help if the tips of the plugs are oil fouled.  

Post Reply
New User
Posts: 13
Joined: 11/13
Posted: 12/24/13 10:43 PM

could be time for a rebuild. try this first... one step hotter spark plugs, and an MSD multi spark ignition triggered by the oem points.  

Post Reply