hmmm...wet head stud.

[adavis]

I haven't driven my '31 since November and a couple weeks ago I noticed the center head stud between cylinder 3 spark plug and cylinder 4 spark plug was wet on top. No water/moisture anywhere else, just on top the stud in the gap between the nut and the stud. I looked up and my garage roof isn't leaking so I'm not sure what's going on. The oil looks fine and the coolant is good. I turned the engine over with the hand crank and it seems fine. I assume its seeping up the stud from the water jacket but anyone have the same experience? Its a fully rebuilt (about 3000 miles) model B motor with a 7:1 Winfield head. Ran great when I parked it after the last drive. Should I be worried or is this something that can be easily remedied?

[Joe K]

That is just about the place where the head fails when the block freezes. (yeah, ain't I a joy to behold.)

Don't know your status of coolant. Anti-freeze? This will seek out ANY small leak point including following bolts/studs.

HIGH compression head I see. Have you checked your head bolt torque since the first 50 miles?

You may be fine. Start by confirming torque. After that it might be time to get out the permatex no. 2.

Joe K

[adavis]

I'm sure that my coolant is good....I replaced the head gasket mid-summer and put new coolant in then. The strange thing is the wetness is only on top the stud, in the little valley between the nut and the top of the stud....no where else. Its like its wicking up through the threads or something?? I torqued the studs 3 times (run to temp....cool completely.....torque....repeat) before I even drove it but its been a while since I checked them. That's easy though. I'll do that right now........
Thanks.

[tbirdtbird]

there is controversy on this forum about this but I have always re-torqued HOT, that is when they are expanded. That is how every mechanic I ever met did it, and also a buddy of mine who races and builds racing motors.

I also seldom work on a Model A that couldn't use a re-torque. There have been several threads about this just in the past yr, you might wanna search. Several people who had re-torqued 3 times or so were surprised to learn they could re-torque again after a yr or more.

[James Rogers]

If it continues to leak, drain the coolant, remove the nut, wrap the threads on the stud with a few wraps of dental floss and replace the nut. Put the coolant back in and drive it. You want to drain the coolant so it won't drain into the #3 or 4 cylinder while you work on the stud.

[Dick Deegan]

Sponsored Links (Register now to hide all advertisements)

I had the same situation. I decided to just wipe the coolant up with a cloth and drive it. The leak eventually stopped. Another solution is to add some Barrs to the coolant, although I don't like doing it, but have done in the past.

Dick

[160B]

Originally Posted by adavis

.......... center head stud between cylinder 3 spark plug and cylinder 4 spark plug was wet on top. No water/moisture anywhere else, just on top the stud in the gap between the nut and the stud..........................

This is head stud #8, and if the last rebuild left this stud with the correct height for the clamp on the ignition cable and you are not using a clamp then the nut is bottoming out on the stud threads and you are not getting proper compression on the head gasket in the area of this stud.

[hardtimes]

Hey adavis,
Yeah, 'capillary' action is what (can) brings the water/coolant to the top of stud. I'm interested in your problem and have used an 'unusual' fix that has worked for me...for future and/or longer term. As it (not stock stuff) is not liked here, PM me if interested to discuss. Maybe able to help. Do you have any picture of situation for us to see ? Good luck.

BTW..there is such a disparity/variety of opinions on the torqueing of head nuts on this forum (and others also) that it would be beneficial for engineer types to add their professional knowledge of how it (proper clamping force ) is supposed to be applied technicially.
For instance, there used to be a great source (IMO) of information who actually build A/B heads and had a specific method of torqueing that made sense and as usual , his method was belittled , as was he...until he withdrew form this forum. Anyway, just two days ago, I was getting some information/instruction , about torqueing my B, from this OLDER engine builder. He happened to describe the EXACT same method as Larry used to teach here, to correctly torque head nuts/studs. Go figure !

Engineer Q: What effect does putting lube on nut/stud have on torque;
What effect does putting lube/sealant on bottom of stud in block have thread function...pos/neg ;
Does torqueing MANY times have any neg impacts and WHY is that necessary at all as gasket should compact/compress after first few ? Just examples of Qs.

[Joe K]

BTW..there is such a disparity/variety of opinions on the torqueing of head nuts on this forum (and others also) that it would be beneficial for engineer types to add their professional knowledge of how it (proper clamping force ) is supposed to be applied technicially.

Well, you asked...

Torqueing of bolts is all about STRETCH. Or more properly the translation of rotary motion of the nut into stretch of the bolt.

Turbines used in central station power generating station actually have central holes drilled nearly the length of the studs, this both to heat the stud prior to tensioning AND to calculate and confirm the amount of stretch resulting.

Heating the bolts allows turbines to be put together by "flat of the nut" method where the nut is brought up tight by hand, and then turned a flat (or number of flats) to verify full face/face contact of the nut. As the stud cools off the stud stretches and compresses the joint making a seal. This stretch can be compared to the previous cold-un-stretched position to compute the amount of clamping force the stud now presents.

For head bolts, the torqueing of the nuts stretches the studs. The translation of rotational torque into stretch is what everyone is arguing about.

IIRC, fasteners are recommended to be torqued "lubricated." This to achieve uniformity of torque and maximize translation of torque into bolt stretch. Also to minimize a tendency to combine linear and rotational shear force at the outer diameter of the fastener and effectively "twist off" the fastener. The object for gasket sealing is unit of linear force achieved through bolt stretch.

As to hot or cold, this actually has more to do with the elastomer sealing the facing surfaces of the gasket and their ability to "mold" to irregularities in the surface. Hot gaskets mold easier to irregularities, of course.

That said, given an equal thermal increase in temperature for cast iron and steel, a given bolt stretch will be relaxed relatively about 21 percent overall due to thermal expansion of the iron relative to the steel. (thermal expansion units 6.0 for cast iron and 7.3 for steel for equal temperature change.) As a joint is heated, the steel expands faster than the cast iron and relaxes the stretch.

Thus, it probably pays to do your stretch/bolt loading to a specific rating while hot. As the assembly cools, it will stretch the bolts further - but if the bolts don't go into yield (failure) and as the heat is regained, the stretch will not fall below what was previously achieved with torque.

This thermal cycling/increase in compression going cold MAY further deform your gasket yielding the thought that one might want to go back afterwards and "touch up" that torque/stretch. As the assembly heats and compression relieves, the gasket may not recover fully yielding a further decrease in fastener tension/surface compression.

So with all this in mind...
1. Lubricate studs with high pressure lubricants. I like STP.
2. Do your final torqueing HOT.
3. Fail not in doing it again HOT after thermal cycling.
4. Don't be afraid to touch it up afterwards for whatever reason, preferably HOT (did I say that?)

An additional benefit from continued torqueing during service life is that generally, fasteners are most likely to fail during the process of torqueing - not in service. Think to that combined tension/torque situation during the tensioning. The initial tensioning is likely the WORST possible loading that a fastener will see during it's lifetime. Everything after that is bread and butter.

You also "proof check" your fasteners when you torque them. A fastener that spins, either through lack of torque or outright breakage, is a fastener that is failed.

Hope this helps. Likely there will be difference of opinion.

Well, this is a FORUM.

Joe K

[hardtimes]

Hey Joe K,
I learned a lot from that which you shared...I think ! Thanks much. I've several follow up Qs, but will wait for more input.
I was beginning to think that this 'torque' thing was looking more like oil discussion...every time that I read a differing method/opinion.

[tbirdtbird]

totally agree with Joe.
As he mentions the quality/design of the head gasket plays a role as well. There is only just so much Felpro is gonna do with a Model A gasket.
Very modern head gaskets do not require re-torquing because of the design/composition/etc of the gasket. Plus, Henry didn't exactly have an excess of head studs per cylinder. Low compression, yes, but even one more stud per cyl. would have been a big help.

I just put a nice racing set of Felpros on a 350 Chevy I am working on and it is one time torque and you are done. But that is with everything all in today's advanced technology.

[1930artdeco]

Joe, I just want to make sure I understand the logic here. You are saying that steel will expand more than the cast iron head. So that when you torque cold and then heat up the engine the head will expand but the stud will expand further thus weakening the sealing power.

Then when the head is torqued hot, you keep the correct sealing power (stretch in this case) and when the head cools it shrinks but the stud shrink at either the same rate or more.

I know this is a simple way of looking at it but I am not an engineer and I am a visual thinker. But do I have the gyst of it?

Mike

[Joe K]

I know this is a simple way of looking at it but I am not an engineer and I am a visual thinker. But do I have the gyst of it?

You are right on.

As the fastener assembly cools, tension on the stud will increase. If this were allowed to go to extreme, then the stud might be stretched to yield, which is a non-returning condition.

Once tensioned past yield in cooling, the hot stud tension will be irretrievably reduced - at least until the stud is re-tensioned while hot, when the stretch cycle will begin again.

But, the presence of the gasket is the safety valve for the Model A head. On cooling, the gasket simply deforms more - and this additional deformation is undone as temperatures approach the hot end of the range.

Today these things are examined for possibility and the sizing of the bolt is made such that yield will not be exceeded.

Or...

Certain bolts system are designed so that yield on the bolt IS exceeded during torqueing. This their way to assure optimal and maximum tension. The downside for this is it makes bolts "one use" since in tightening to yield the bolt IS deformed and can't be re-tightened again to the same degree. This also their way to assure proper compression to the gasket when hot - but not more. And torque to yield is also done "cold."

My TDI VW is EXACTLY like that on many of the bolts holding the head and even the motor in place in the supports. One of these requires 475ft-lbs to achieve designated tightness, which is a torque that I cannot achieve with my 275 ft-lb beam wrench. So I did what I could for that -and so far have not had an issue.

Hope this clarifies.

Joe K

[adavis]

That's great info about head bolt torque, but I'm thinking my issue is something else. I checked all my bolts and they are right at 50 lbs.

160B....that's a good point but when I rebuilt the engine I used all new studs and am not running the stock ignition cable.

I remember an old guy at the local machine shop told me once to put a dab of sealant on the threads of each head stud on a flathead V8 I was working on and I'm wondering if this is why. At this point I've drained the coolant until I can figure out what's going on. Does anyone see a problem with pulling of the nut, wrapping a little Teflon tape around the threads, and re-torque it down? Or should I try to remove the stud completely and put some sealant on the block end and re-install?

[gpits68]

The dental floss trick worked for me .

[Joe K]

Originally Posted by adavis

Or should I try to remove the stud completely and put some sealant on the block end and re-install?

Permatex No. 2 to the rescue? Maybe pipe dope if you do the female threads in the block.

I generally don't like Teflon tape on joint interfaces where continued threading might occur. On the Model A head the nut threads are fine threads and SHOULD take most of the turn when doing torque, it is possible to reduce the coefficient of friction of the coarse threads enough to turn the studs into the block, possibly breaking the block - or at least burying the stud.

Better to choose a sealant that "solidifies" much as pipe dope does under influence of temperature.

You might even accomplish this by use of Loctite Blue - then take a few turns of dental floss to fill in any gap on the top turns just below the shoulder of and as you "seat" the stud - although I haven't tried that.

Don't use Loctite Red.

Joe K

[tbirdtbird]

I use Permatex No. 2 on these babies.....

[modelAtony]

50 # seems light for a 7.1 head . Thought it would be around 60-65.

[tbirdtbird]

Originally Posted by modelAtony

50 # seems light for a 7.1 head . Thought it would be around 60-65.

Agree.

[hardtimes]

Originally Posted by adavis

That's great info about head bolt torque, but I'm thinking my issue is something else. I checked all my bolts and they are right at 50 lbs.

160B....that's a good point but when I rebuilt the engine I used all new studs and am not running the stock ignition cable.

I remember an old guy at the local machine shop told me once to put a dab of sealant on the threads of each head stud on a flathead V8 I was working on and I'm wondering if this is why. At this point I've drained the coolant until I can figure out what's going on. Does anyone see a problem with pulling of the nut, wrapping a little Teflon tape around the threads, and re-torque it down? Or should I try to remove the stud completely and put some sealant on the block end and re-install?

Yeah, I'd REMOVE the stud and apply sealant (as we discussed off line). IMO 'dental floss' at top of head, under nut, is not only ..band aid fix..but poor fix at best. What I mean, is that if you allow the weep/seep to continue up to that point, just think of what IS going on down between block/stud/gasket/head...NOT GOOD ! And when/if you ever want to remove head/stud down the road, you will regret what you find therein ! I just went thru exact same same, and moisture , with time, will cause rusted block and head surfaces....and eventually blown gasket in that area...due to thin distances BETWEEN cylinders. That's also why I experimented with the method that I told you of. Seeping/weeping means that most likely the stud has poked thru into water jacket. Sealing is just smart logical and to do this..remove stud. Good luck.