Changing the plugs tomorrow. What should they be torqued down to? Did a search and came up with a wide range of values. Whats correct? 14ft/lbs seems to be the number.

 

You are correct with 14 ft.lbs. Be sure to use a quality antiseize lubricant on the threads only.

 

i used 24ft.lbs on my 03, but it has the PI heads with updated thread count..

not sure if you truck does or not given its age..

p.s. i installed the plugs dry

 

He has the heads with the short threads. I would not go over 20ft/lb max. Shoot for 14ft-lb and check the torque often. I think that many problems with plugs are that they back out and strip what little threads are left. Blow all the dirt out and put some penetrating oil in the plug hole before trying to loosen the plug. Crack them loose and let them sit a little while so the penetrating oil can soften any rust/carbon on the threads. Use antiseize on the lower part of the plug only and work it into the threads.

Perry

 

Aluminum heads with the short threads. I do not think I will use anti-seize; the use of it seems to be controversial. Thanks for the info.

 

I would not install them without it.

 

Antiseize protects the threads from friction and the abrasive effects of taking the plugs in and out. It also keeps the threads on the plug from bonding to the threads in the head which leads to broken plugs and stripped threads. Leaving the upper portion dry that seats against the head and provides friction to keep the plug from unscrewing is a good thing. Since the torque on the plugs is small, it is a good idea to check them periodically, like maybe once a year or every 10k miles. Remember that the breaking strength of a 14mm bolt is probably upwards of 100 ft-lbs and if there were twice as many threads you should be able to break a steel bolt without ruining the threads. Since there are about half the optimum number of threads in the early heads, I would say that they will probably strip at about 50 ft-lbs. If anybody has a junk head I would see what it actual torque it takes to strip 4 threads worth of engagement. I would quess you could do a similar test on a piece of aluminum as well if you don't have a junk head. Why does a plug unscrew in the first place. Well the aluminum head expands and contracts alot more than the steel plug. This tends to work the plug loose over time. For this reason I like the old crush washer type of plug because I think it helped keep even tension on the plug. Every jap engine that I have worked on has the crush washer. They have been building aluminum heads alot longer than we have so they probably know what they are doing. I have worked on motorcycles for a long time and stripped plug holes is not real common and it is usually caused by cross threading. It was common for the old 2-strokes to have shallow threads as well as law mowers. There are enough threads on the early V10's but there is no room for screw ups.

Perry

 

I never thought of doing that, but I have a bad engine sitting around.
I'll see what the threads breaking point is and post back in the next couple days.

 

yea do that bill..

i must admit to being curious what teh shallow thread heads will stand up to before ruining teh head...

 

Try it with and without lube as well. Make sure you test an undamaged hole to get a true reading. On another note you need to make sure your torque wrench is actually giving you a reasonable reading. It is not rocket science to check one. The torque on the bolt is the force in lbs applied to the wrench handle times its length in feet. So if you get an old fish scale that you have faith in or have some weights to check it with you can use that to check the calibration on your torque wrench. So now all you do is set the torque on your wrench and apply force 90 degrees to the handle at a given distance and see if what you get with the fish scale is the same you get from the wrench. I think the wrenches that click are the ones that have to be calibrated most often. I have one of the old type that uses a calibrated bar and a pointer. It is low tech but it works and it always reads the same.

If you have the deflecting beam type wrench you have to put the scale at the center of the handle where the pivot pin is. I would expect you need to be pretty close to the center of the handle on the click type wrench as well.

Perry

 

I always use the clicker type, but for this I am going to dig out the old beam style torque wrench.
I'll go ahead and do it with antiseeze and without. The threads are all undamged.
It won't be until sunday, I'm tied up all day today.

 

Thanks Bill that will be good info to know. The 14ft-lb torque spec may have more to do with being able to get them out after 100k miles than it does to do with stripping threads.

Perry

 

Did the plug change this afternoon. Piece of cake. Two of them were a little difficult to get to, but I have alot of patience. Everything came out as easliy as they went in. It has 78,000 miles they looked pretty darn good.

 

I got 190k out of the ones in my Ranger and they did not look so good. Platinum plugs will get you 100k no problems. Glad your plug change went well.

Perry

 

Tested for the breaking point on the early 4 spark plug thread heads - Ford Truck Enthusiasts Forums