There's something I don't understand about the proper procedure in torqueing head bolts. The answer to my question is no doubt in the forum someplace, but even with using several different "key word" combinations, I can't find an answer. My question is this:
Some very knowledgable "T" guys have stressed the point that head bolt threads should NOT be oiled prior to torqueing. My question is, "WHY NOT"? I have always applied a small amount of oil to the threads, and also a bit of oil on the bottom side of the bolt head (or the bottom of the nut in the case of studs), but I guess this is wrong. WHY?
This is how it seems to me; if you torque to a value of say, 55 ft/lbs, it stands to reason that part of that torque will be expended in just overcoming friction, and the rest will exert actual downward force. It also seems to me that because this downward force is basically what we want, why not use a bit of oil and have a larger percentage of that 55 lbs actually exert downward force instead of overcoming friction?
In other words, 55 lbs is 55 lbs, whether half of that torque is just overcoming friction and the other half is exerting downward force. What does it hurt if we oil the threads and only one fourth of the 55 lbs (hypothetical of course) is applied to overcoming friction, and three fourths of the 55 lbs is actually applying downward force. Isn't maximum downward force what we want?
Because I am definately not an engineer, there's probably a good reason, but right now, I just don't "get it"!
The bolts should be free to turn in the threads. If you have so much friction that the bolt won't turn, such as bottomed out. You will get a false reading. I personally see no problem with oiling, however I don't oil them, I just make sure the threads are clean and don't bind and that the bolts don't bottom out before the head is all the way down.
Harold - I'm Bachelor in Mechanical Engineering and maybe that's the difference between being bachelor and master that a master may know why. ;-)
I have also always applied a little oil.
I could think of two reasons to not apply oil:
1) If excessive oil applied it may fill the room in the bottom of the hole and then the torque is used to compress that oil
2) The lesser friction makes it possible for the bolt to unscrew.
Of these 1) is a real issue, but can be controlled while 2) to me is rubbish. I have never experienced top bolts being loose.
I oil them too - actually, I use anti-seize on head bolts. The model T was built with no torque specifications whatsoever so claiming a head bolt torque AND saying don't oil the threads is absolutely ridiculous, in my opinion.
Greasing, oiling, or adding anti-seize to the threads prevents corrosion. On something 80 plus years old, that should be plenty good reason to do it.
Unless otherwise stated, all torque chart values are for "DRY" torque. That is, clean and no lubricants on the bolt and in the hole. There are separate torque value charts for "WET" torque. Google "Wet Torque" and you will find many charts for wet torque values.
I seem to remember a specific paste type product for torqueing bolts used by engine assemblers. I canít seem to find and information on it. It's another one of those memory vs. age issues.
Your torque may vary ...
Regardless of your engineering degree level, the reason that torque specs are given in terms of dry versus oiled are that you can snap a head bolt if you use a dry torque spec on an oiled bolt.
There is no official Ford torque spec for any part of a Model T. Ford and any other manufacturer of the era did not have torque specs, they used appropriate sized tools so that an average man would tighten the specific fastener to an appropriate amount.
One should be aware that Model T blocks cast before about 1916 have very poor metallurgy, it is common to strip out one or more head bolt holes if you go beyond 45 pounds dry torque. Another greeat reason to make sure the threads are clean and dry.
Just as easy to use a 3/8" socket wrench on head bolts, these normally have a 7" long handle, and then tighten with one hand, the old Armstrong pull. The leverage using a short handle won't cause harm to head bolts, unless you can pull like Gov. Arnold
Back in the days, there weren't torque wrenches anyway, I have a pointer style torque wrench, but that long handle scares me, and who claibrated that Chinese tool anyway?
Your just getting the head on tight enough to squish the gasket fully and keep the water ports and cylinders sealed. Use a bit of Anti-seize on the new bolts, have the holes cleaned well and tested with a bottom tap. Fit the gasket correctly, then tighten down in sequence
and...if it seeps somewhere after warming up the engine, wrench the bolts a bit more
The one hand method was explained to me almost fifty years ago by a then elderly gentleman. He said the true indicator is when the hair on your arm stands up!
Lightly lubricated threads provide more uniform torque from bolt to bolt. I have probably overhauled 40 different makes of engines in my time, and most, if not all, service manuals call for either motor oil or a thread sealant such as International Compound on all head bolts or studs. I have never seen a service manual that called for head bolts to be installed dry.
I've torqued a hell of alot of headbolts, T and mostly otherwise. While modern vehicle specs may state oiled or not there is no spec for a T. I oil the threads. At a relatively low torque of 50 pounds friction can skew your readings pretty good. Also don't be to sneaky to get up to torque, I go snug, 35# then 50#. Use a good torque wrench and be sure to retorque after warm up.