Stuck #7 spark plug

Hi,

I have a 1940 Pontiac Torpedo with the original straight 8 which has the heater hose routed over the top of the motor and the heater valve mounted between the 4th & 5th plug. When I purchased the car from the previous owner he pointed out that he replaced the heater valve recently. Which I would think that the shop that did the replacement work let the excessive coolant/water burn off from the heat of the block.

I went to change the plugs starting with the #1 and worked my way back #8. However when I got to the #3 I saw surface rust developing on the metal area just below the white porcelain before the threads. As I proceeded to #6 the rust got progressively worse. When tried to remove the #7 plug it wouldn't budge. However the #8 did come out without a problem. FYI: The condition of the tips plugs were in very good condition.

I sprayed a fair amount of WD40 in the #7 spark plug galley and left it overnight and nothing changed except the WD40 was gone probably into the cylinder. I did the same thing again and nothing. Then I warmed up the engine first and tried to remove it and nothing.

I have asked around to some mechanic friends and they all say to leave it alone. One even told if you break the plug loose you stand a chance of the plug taking out the threads from the block. Then there's the obvious possibility of breaking the actual spark which then has to be drilled out and a heli-coil installed. Hope I don't have to go down that road.

Any suggestions ???

Have patience.

I would continue to soak it (try PB Blaster or Marvel Mystery oil).

The fact that the WD40 appeared to have gone through the rust into the cylinder is a good sign.

Also, try 2 things.

While spraying the plug threads with PB or Marvel or ??? try lightly tapping the metal base of the plug using the handle of a large screwdriver or something else other than a hammer or metal. If the penetrant goes through keep doing this several times and then try to gently break the threads free. If they free up only back the plug out a little bit, spray more penetrant, then screw the plug back into the head and then back it out a little bit, spray again, screw back into the head, etc....This way you should be able to unscrew the plug a little more each time - but don't force it.

One other solution might be to heat the plug base with a butane torch and before it cools down all the way give it a squirt of the penetrant. By heating the metal it will expand it and the spray will get into the threads. Then try the out/in method as described above if it breaks free.

Don't be in a hurry.

Joe

The best penetrating fluid is a mix of acetone and ATF. Give it a try.

Thanks for the tips. I am going to try the PB Blaster first including a good dose of patience mixed in. I have come to find that WD40 is not a very strong penetrant in the first place. I'll post the results too.

BTW: what's the mixture of ATF and acetone ??

Thanks for the tips.

BTW: what's the mixture of ATF and acetone ??

It's a 50/50 mix of acetone and tranny fluid. Google in "homemade penetrating oil" . Great results.

I finally was able to make a concerted effort over a week's time and removed that stubborn plug!!  I used PB Blaster at first and it showed some results.  When I tried to loosen the plug it didn't feel smooth. I then tried the acetone/tranny fluid mixture and I have to believe that gave me the result I was hoping for; smooth feeling when I turned the plug.  I slowly worked the plug until it loosened and came out.  I cleaned the spark plug galley, used a thread chaser and installed the new plug and the engine runs like a top!!! 

A lot people were surprised and questioned the tranny fluid acetone mixture; the tranny fluid was fine but the acetone raised quite a few eyebrows.  I must say the acetone was probably the ingredient that ultimately did the trick. 

Thanks to all that contributed to my thread.

When you make the 50-50 mix, you have to shake the container each time you use it to get both parts on the rusty part.

It helps to use a wire brush or something around the base of the plug or other part to remove obstacles from the path  of the penetrant to.