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Some 'person's who I will not further describe for fear of being banned due to bad language... have used a set of long thread 21mm plugs in a set of bbc heads designed for 16mm plugs. In doing so, they have jammed some like the pic below, so I cant get a socket on them!
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How they get them in there? Id soak them for a long time (week) and it looks like the spark plug hex protrudes slightly above. Maybe get a new quality socket and press down really hard and turn.
A machine shop could probably mill a plug socket so it could protrude into the openings. Kind of like a tap extractor would. Not an automotive shop but a one of, manual shop. If you were near here I think I could mill one like that or make one from bar stock, harden it and temper it to do the same thing.
Put a bolt extractor on the remaining plug and cross your fingers, sacrifices the plug but may get it out. If it doesn't and it tears it apart the hex should be intact and you should still be able to utilize the other options which have been discussed.
After soaking it for a few days try using a long narrow chisel and hammer to loosen the spark plugs enough that a socket will fit on the hex of the plug.
Did the plug thread itself onto the metal body of the plug????? If so, you have got some pretty well boogered threads in those heads. This was done by Bubba's stoopid cousin, Doofus....
What seems to be confusing to most who read this posting is the metric 16 and 21. What the original poster should have stated is that he / someone threaded a 13/16" hex spark plug into a head that was only made to use a 5/8" hex plug. Thus the took up all the space around the hex so the socket would not turn it in and now won't unthread either. I would think that the threads didn't bottom out to lock it in so maybe using a small chisel to tap it around to get it loose enough to get a socket back on. worth a try. It also looks like it has been in there for awhile by looking at the rust so maybe little PB Blaster might help some.
How would one 'thread' a 16mm spark plug into a 21mm hole and have it stay in place? Surely, this is in gest.
I wish it was! Lol
Here are the ones I've got out vs the delco r45ts that is correct spec for the head..
You can see that they've used long thread/reach plugs to compensate for the fact that they dont actually fit in the hole!
I've now put some acetone/atf mix down the remaining plugs and ordered a thin wall plug socket on Amazon.. once it arrives, I'll cut it down far enough to remove the socket lip and see how I get on.
That can't be in there too tight. All sockets have a taper away from the flats.
grind the bottom of a plug socket until the flats are at the bottom of the socket. Maybe grind the outside dia down a bit. It may be enough to get it
Last edited by derekderek; Oct 30, 2019 at 09:05 AM.
That can't be in there too tight. All sockets have a taper away from the flats.
grind the bottom of a plug socket until the flats are at the bottom of the socket. Maybe grind the outside dia down a bit. It may be enough to get it
That would be my plan to see if a grip could be had on the plug.
Here are the ones I've got out vs the delco r45ts that is correct spec for the head..
You can see that they've used long thread/reach plugs to compensate for the fact that they dont actually fit in the hole!
I've now put some acetone/atf mix down the remaining plugs and ordered a thin wall plug socket on Amazon.. once it arrives, I'll cut it down far enough to remove the socket lip and see how I get on.
I worked at a Pontiac dealer part time after school in the late 60's. They had a 69 or 70 GTO Ram Air III in the shop .The owner did the same thing when changing plugs. From what I recall it was towed in because every piston kissed every spark plug.
Add some ATF to the acetone and soak the plug in it. Acetone alone will evaporate too quickly and it alone will not act as penetrating fluid. I like the idea of grinding off the face of a deep thin walled socket. Good luck. Some people should not be left alone with tools. If this guy worked on the brakes, I would be worried. Jerry
Plug stuck - help!!
