I will be putting the head back on tonight or Friday night (depends on how long the copper coat takes to dry...)
I have read through a lot of threads and it seems everyone has an opinion on the best thing to do. Most say 50 ft-lbs, but then there are debates about if that is with threads lubed or dry... I was thinking a little never seize on each bolt, torque to 45ft-lbs, run engine and repeat.
That's about it. I'll add 2 things. First did you clean/blow out the head bolt holes? Actually it's a must. They might bottom out & strip on the crud in there. Second is after the first torque and run cycle let it cool completely (over night) before re torqueing and you're done. Some (not me) retorque again after 500 miles. 45 is OK.
Thanks for the tip. I read about the bolt holes, so all were cleaned with a pick, then I ran a tap through them, then I vacuumed them out, then I checked every bolt height.
I was under the impression that any lube on a head bolt would give a false torque reading.
Lube will change the clamp load for a given torque. Clamp load is what we care about, but it is convenient to measure torque. I don't want the bolts to rust to the block so I would like to use never seize which is why I lowered the torque a little.
Interesting past discussion here:
In all the Model T head bolt reading I did, my favorite spec was, "tighten till strips, than back off 1/4 turn"
I will start with 40 ft-lbs and see if everything seals. If not, I can always go up.
Engine Rebuilders' Association guidelines -
You can show all the charts in the world and if you go by what is printed on them you will be pulling the threads out of the block or breaking bolts when it come to the grade of cast iron used and grade of bolts used in the T engine. Under 50 FP is more then enough for the stock T engine. That is my observed opinion because so far, knock on wood, I have been very lucky not to have pulled any threads because I follow that advice of keeping it under 50 FP.
I think the charts agree with you. The one I posted suggests 37 ft-lbs for a lubed thread. That's why I am going to start at 35 or 40 and see if it seals. Would you recommend something even lower?
So, do you know the coefficient of friction between the bolt and cast iron using the material you plan to use? That information is how the original torque charts are derived based on tensile strength of the bolt being used and the alloy of iron it's being screwed into. You'll need that to know if you're providing the same stretch to the bolt (without reaching yield value on the cast iron, as would a torque of 45 lb on dry threads. There are, in fact, guidelines for different lubes (reduced torque by %). However, never-seize is not on any chart that I've ever seen, and is not, per se, a lube. I would suggest that while it seems prudent to start at 35 while using never-seize, you don't really know what the clamping pressure is at that value or any other value, and that is a risk that I certainly wouldn't take given that there is zero upside to doing it.
When I see discussions like this, I ask myself "what problem is the OP really trying to solve?", and frankly, after reading through the question and answers, I just don't know.
On my 11 I used never seize and torqued my head to 35 ft.lbs. I went up in 3 stages 20, 30, and 35. Re-torqued a couple of times after it had been run. Copper head gasket and spray sealant on the gasket.
I've got 1700 miles on it now and all is fine.
I've never used a torque wrench, just the wrench Ford gives you. Never had a problem. I read somewhere a long time ago to smear grease on the gasket so I do that too. I've had the head off several times. Never because of a bad gasket.
I use copper gasket spray, let it dry a half hour or so, spray it again, let it dry at least a half hour, put it back together, torque to 45, run it 'till it gets hot, let it cool down and retorque to 45.
After a hundred or so miles I retorque, then again after a couple hundred miles.
I never let the copper coat dry. I put the gasket on while it's still tacky.
It's my understanding you don't want the copper coat to dry completely before assembling. I could be wrong though!
I use anti-seize too!
Spray Copper Kote and torque it. I also use a high temp anti-seize compound on the threads. It really helps in the event you do happen to snap a head bolt. Comes out much easier than if the threads are dry. Re-torquing is probably more important than most folks think. Re-torque cast heads hot, aluminum cold. I have found most of the times it takes going through 4-5 hot/cold cycles to get the torque where you want want it.
Scott, interesting comment "do you know the coefficient of friction between the bolt and cast iron using the material you plan to use", how does the thread class of fit affect the ultimate coefficient of friction when the two are mated?
Thanks to everyone for pointing out the copper coat should be tacky. The can said wait for solvent to dry and I thought that meant the copper coat would dry. Luckily it was still tacky this morning and I took a day off work and played with the head. Unfortunately, I took a step backwards, but that is a different thread.
I think the torque debate will never end, and the idea is to have it tight enough to seal, but not so tight we strip the bolt or head. If you can do that by feel like they did at the Ford Factory that is great. To ensure everything is even I like to have a measuring device.
To achieve the above, the parameter we care about is clamping load. (bolt tension) Not enough clamp load - head gasket leaks, too much - threads strip...
Unfortunately, we do not measure the bolt tension / clamp load. We measure the turning torque. The torque to clamp load relationship is driven by three main parameters:
Friction at the threads
Friction at the head of the bolt
By adding never seize the friction at the threads is reduced somewhat, we don't really know how much. The chart I posted suggested using a K value of 0.17 for threadlocker - but that is not the same lubricity as never seize. (using K=0.17 would suggest 42 ft lbs torque)
When the friction at the thread interface goes down due to lubricant, the clamp load / bolt tension for a given head torque goes up. If we made no correction for that and torqued to the same value as a dry fastener we would increase the bolt tension and increase the likelyhood it would strip. (The dry torque values are based on 75% of minimum proof load so there is a bit of margin)
Based on the fact that I was using a lube, I reduced my torque to 40 ft lbs. If it had leaked I would have gone to 45 ft lbs. unfortunately I didn't get the chance to test it running and had to pull the head. When I did so, I saw what an amazing job the copper coat was doing. It had sealed everything very nicely and it was a real struggle to separate the parts.
Why not just run a dry fastener? Working with turbo car exhaust has made me a never seize believer. The threads just don't rust together and things can be disassembled without breaking fasteners.
For your question: Beyond Class II, coefficient of friction goes up. Torque and preload become more variable the looser the class of fit and also goes up the worse the surface finish of the threads are. For a given torque you might be tight and where you want to be or you might still need more tightening to effect the same bolt load. This is the condition the mechanic is faced with on a 90+ year old engine.
Add a lubricant to the mix, changing the coefficient of friction to a completely unknown value, then you can throw "torque values" out the window. In this case you can get into real trouble. An experienced mechanic used to working on very old iron can get away with this sort of thing, but the average guy doing it for the first time can buy some trouble for his effort. Torque wrenches have stripped a lot of threads on old cars. Joe is approaching this cautiously, but most will not, not realizing how lubricants affect torque vs clamp load.
My answer above refers to Joe, meaning Joe Andulics' question to me
Isn't the reason for a torque wrench UNIFORMITY in pressure so there are not uneven loads on the head, gasket, uneven tensile forces on the bolt, and uneven loadings on the block. Uneven loadings cause load deformation, loose head gasket areas, and warping of the head? It would seem that if all the bolts are treated the same with anti seize, torqued in the correct sequence, and torqued to the same reasonable loading all should be well.
The original in the day shop manuals did not even mention torque wrenches. My recollection is that torque specs became popular with the aeroplane developments around ww2.
Jon, you are on the right path, but still only 1/2 right...you are looking for a specific value, with variability (or uniformity) limited to the repeatability of the wrench (I think that's what you probably meant but I wanted to be clear). However with slippery lube, just the opposite will be true. With high coefficient of friction (dry) the bolt will come to torque quickly and with little after-movement at retorque. With a very slippery part, the torque is much lower as a result, but very importantly, also what happens is the bolt will turn quite a bit with little extra effort of the wrench, placing very large loads on the parts very quickly. Particularly with a "click" type torque wrench, the normal +/- tolerance for any given "umph" on the wrench can have quite drastic differences from bolt to bolt based on the (relatively) wide +/- tolerance of a "click" wrench, if friction between materials is very low. As a side note, not that everyone in "T"s uses them, but in industry, these type wrenches are calibrated on a very frequent basis and it is alarming how high/low they sometimes are after use, which is why I prefer old style beam wrenches. They can go wrong, but not like the "click" type. Now, before everyone jumps on this, I'm not guessing, and it isn't my opinion; there are quite a few studies by folks in the fastener business and they have all come to this conclusion with respect to the fact that high variability in torque is a significant risk with lubricated fasteners. Now, I am speaking from my own reference in the Defense and Space business, where all fasteners are installed "dry" on product. The above mentioned studies plus our own independent analysis are why.
My grandpa told me a story about one time he put a head on a T and just tightened the bolts from back to front. He said when he tightened the front ones some of the back ones popped out. Don't know how, why or if that happened but he had plenty of T stories, like how he didn't have oil and put buttermilk in one to get about 20 miles.