Help with the #8 plug

Power · 05-23-2001, 12:52 AM

Anybody ever had any trouble with any of their plugs reversing themselves? My #8 plug refuses to stay tight no matter what I do. Every 6-8 weeks I have to retighten it. It comes far enough out that it won't fire correctly. None of my other plugs are doing it. Only #8. Any ideas beside Loktite??? I know this was an issue to the previous owner as I broke the plug trying to take it out when I first bought the car. It was in really tight and I think had some sort of sticking agent on it.

Any ideas are always appreciated.

Rev · 05-23-2001, 01:10 AM

I think I would clean the threads (head) with brake cleaner. Then torque in a new plug with a torque wrench to about 50 lb/ft, no more. I would be suprised if it loosened by itself after that.

Rev

------------------
'66 Coupe, 306, 300 HP, C-4, 13.97 e.t., 100.3 mph
1/4 mi.

Power · 05-23-2001, 01:47 AM

Thanks man.......I'll give it a try. Gives me a good excuse for the wife on why I'm buying a torqe wrench.

Remember the old school torque wrenchs with nothing but an engraved scale and a tension rod?

Good ol' days with my pops.

Rev · 05-23-2001, 01:53 AM

Hee, hee, that's only kind I have.

Rev

------------------
'66 Coupe, 306, 300 HP, C-4, 13.97 e.t., 100.3 mph
1/4 mi.

PNYXPS66 · 05-23-2001, 12:53 PM

Actually, I had the #4 plug on my '66 289 do the same thing. If the suggestion with the brake cleeaner and 50ft/lb torque (geez!) doesn't work, I'd suggest a more radical, yet permanent, approach -- remove the head and have a machine shop drill out the old threads that are stretched and insert a heli-coil threaded replacement insert. It's permanently installed and won't give you another problem. My concern with the torqued approach is that if the threads are already stressed out, they may not take 50ft/lb torque and the plug will strip in the head. Then the only thing torqued at that point will be you because you may or may not be able to remove the plug. I usually tighten plugs snug then an additional 1/4 turn. The heat of the engine will make the plug get tighter as the metal expands and contracts. Good luck.

------------------
Pony Express 66
God Speed and keep it between the lines!

Rev · 05-23-2001, 05:58 PM

Just thought of this. Don't put that much torque if you have aluminum heads. That would probably strip the threads for sure.

Rev

------------------
'66 Coupe, 306, 300 HP, C-4, 13.97 e.t., 100.3 mph
1/4 mi.

Power · 05-23-2001, 06:51 PM

yeah.......right. I wish I had aluminum heads. Too much $$ for me right now.

Speaking of aluminum, has anybody ever swapped out their driveline for an aluminum one? Does that work very good?

[This message has been edited by Power (edited 05-23-2001).]

PNYXPS66 · 05-24-2001, 10:36 AM

Aluminum driveshafts are a good thing especially if you are racing. the tend to keep their balance better, and are of course lighter. They are not less suceptible to warpage, or twisting as some steel shafts can be, and they can be cost effective. Example of this goes to the newer mustangs '79+; The steel driveshaft new from Ford costs $400+ and is in great limited supply. The Motorsport shaft is better and lighter and costs $225. I just had to replace the shaft on my 88 because the slip yoke had worn a groove where the extension housing seal had worn over the years. The only way to replace the slip yoke is salvage yard (great! get someone elses worn part!) or Ford/Motorsport driveshaft. I don't know of a slip yoke sold separately. That's another issue for another forum though. Bottom line, Aluminum is better.

------------------
Pony Express 66
God Speed and keep it between the lines!

Gearhead999 · 05-27-2001, 04:06 PM

When you clean the threads take a good look at them and see if they are damaged. You can also run a cleaner tap down in the plug hole too. If thread have carbon on them it will be impossible to keep the plug tight.

I would tend to think that the threads are damaged and plug has alot of movement. Will have to be heli-coiled to repair. Not a real big deal.

05-23-2001, 12:52 AM	#1
Power Registered Member Join Date: Feb 2001 Location: Oregon Posts: 420	Help with the #8 plug Anybody ever had any trouble with any of their plugs reversing themselves? My #8 plug refuses to stay tight no matter what I do. Every 6-8 weeks I have to retighten it. It comes far enough out that it won't fire correctly. None of my other plugs are doing it. Only #8. Any ideas beside Loktite??? I know this was an issue to the previous owner as I broke the plug trying to take it out when I first bought the car. It was in really tight and I think had some sort of sticking agent on it. Any ideas are always appreciated.

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05-23-2001, 01:10 AM	#2
Rev Registered Member Join Date: Nov 1998 Location: Houston, Tx. Posts: 3,887	I think I would clean the threads (head) with brake cleaner. Then torque in a new plug with a torque wrench to about 50 lb/ft, no more. I would be suprised if it loosened by itself after that. Rev ------------------ '66 Coupe, 306, 300 HP, C-4, 13.97 e.t., 100.3 mph 1/4 mi.

05-23-2001, 01:47 AM	#3
Power Registered Member Join Date: Feb 2001 Location: Oregon Posts: 420	Thanks man.......I'll give it a try. Gives me a good excuse for the wife on why I'm buying a torqe wrench. Remember the old school torque wrenchs with nothing but an engraved scale and a tension rod? Good ol' days with my pops.

05-23-2001, 01:53 AM	#4
Rev Registered Member Join Date: Nov 1998 Location: Houston, Tx. Posts: 3,887	Hee, hee, that's only kind I have. Rev ------------------ '66 Coupe, 306, 300 HP, C-4, 13.97 e.t., 100.3 mph 1/4 mi.

05-23-2001, 12:53 PM	#5
PNYXPS66 Registered Member Join Date: Feb 2001 Location: Beaufort,SC,USA Posts: 72	Actually, I had the #4 plug on my '66 289 do the same thing. If the suggestion with the brake cleeaner and 50ft/lb torque (geez!) doesn't work, I'd suggest a more radical, yet permanent, approach -- remove the head and have a machine shop drill out the old threads that are stretched and insert a heli-coil threaded replacement insert. It's permanently installed and won't give you another problem. My concern with the torqued approach is that if the threads are already stressed out, they may not take 50ft/lb torque and the plug will strip in the head. Then the only thing torqued at that point will be you because you may or may not be able to remove the plug. I usually tighten plugs snug then an additional 1/4 turn. The heat of the engine will make the plug get tighter as the metal expands and contracts. Good luck. ------------------ Pony Express 66 God Speed and keep it between the lines!

05-23-2001, 05:58 PM	#6
Rev Registered Member Join Date: Nov 1998 Location: Houston, Tx. Posts: 3,887	Just thought of this. Don't put that much torque if you have aluminum heads. That would probably strip the threads for sure. Rev ------------------ '66 Coupe, 306, 300 HP, C-4, 13.97 e.t., 100.3 mph 1/4 mi.

05-23-2001, 06:51 PM	#7
Power Registered Member Join Date: Feb 2001 Location: Oregon Posts: 420	yeah.......right. I wish I had aluminum heads. Too much $$ for me right now. Speaking of aluminum, has anybody ever swapped out their driveline for an aluminum one? Does that work very good? [This message has been edited by Power (edited 05-23-2001).]

05-24-2001, 10:36 AM	#8
PNYXPS66 Registered Member Join Date: Feb 2001 Location: Beaufort,SC,USA Posts: 72	Aluminum driveshafts are a good thing especially if you are racing. the tend to keep their balance better, and are of course lighter. They are not less suceptible to warpage, or twisting as some steel shafts can be, and they can be cost effective. Example of this goes to the newer mustangs '79+; The steel driveshaft new from Ford costs $400+ and is in great limited supply. The Motorsport shaft is better and lighter and costs $225. I just had to replace the shaft on my 88 because the slip yoke had worn a groove where the extension housing seal had worn over the years. The only way to replace the slip yoke is salvage yard (great! get someone elses worn part!) or Ford/Motorsport driveshaft. I don't know of a slip yoke sold separately. That's another issue for another forum though. Bottom line, Aluminum is better. ------------------ Pony Express 66 God Speed and keep it between the lines!

05-27-2001, 04:06 PM	#9
Gearhead999 Registered Member Join Date: Sep 1998 Location: Oviedo, FL Posts: 992	When you clean the threads take a good look at them and see if they are damaged. You can also run a cleaner tap down in the plug hole too. If thread have carbon on them it will be impossible to keep the plug tight. I would tend to think that the threads are damaged and plug has alot of movement. Will have to be heli-coiled to repair. Not a real big deal.