For a better experience, please enable JavaScript in your browser before proceeding. Cylinder Head Bolt oil or not? Thread starter brathnach Start date Jul 7, I have access to the VW service manual and it makes no reference to either lightly oiling the thread or bolt head prior to torquing up.
However, I have read on here that it appears to be the recommended method. Is there an accepted best practice when it comes to torquing these bolts? I don't want to mess up on this part Thanks Jim. It does not matter much because you torque to a relatively low torque and then go a specified number of degrees of rotation after that to establish the proper preload in the joint.
I would oil them so you don't need as much torque to achieve the rotation specified just because it's easier that way. I saw this and was reminded of a thread on a completely different forum where I was MIS-quoted as never oiling head bolts. Regular engine oil is all I use. There are times when torquing bolts, you will get a 'crack' noise as the bolt sticks at the bolt head or the threads, then releases quite suddenly.
A torque wrench reading of 80 ft. The thread pitch acts like a screw jack to multiply the load factor. As a result, each bolt may exert a clamping load of up to times or more the reading on your torque wrench! That also explains how torquing a head bolt can exert enough pressure to actually stretch it as much as. As the head gets hot, thermal expansion is going to stretch the head bolts even more — especially in engines with aluminum heads.
Aluminum expands at more than twice the rate of cast iron, which puts even more strain on the head bolts. In a typical engine, just warming the engine up to normal operating temperature may stretch the head bolts as much as.
Like a rubber band, a head bolt under load will stretch and spring back to its original length when the load is released. But if stretched too far, the bolt will either become permanently elongated or break. Head bolts that have become permanently elongated may deform along the length of the shank or in the threaded area. Reusing a deformed bolt is risky because the bolt may not hold proper torque, and it may fail when you attempt to retighten it. When engineers design a new engine, one of the many tasks they have to do is figure out what size head bolts to use and how much torque the bolts will require to achieve the proper clamping force.
Some of this comes from previous experience, and some comes by trial and error testing. The compressibility and spring-back of the head gasket, the configuration of the cylinder head, the number of head bolts around each cylinder, the comparative lengths of the head bolts all the same length or different lengths , etc.
Torque-To-Yield Advertisement Torque-To-Yield TTY is a term that you should be familiar with because it describes a type of head bolt that is used on many late model engines. Unlike ordinary head bolts, TTY head bolts are designed to deform — but do it in a controlled way.
Like a standard head bolt, a TTY bolt will stretch and spring back up to its yield point. But once the yield point is passed, the bolt becomes permanently stretched and does not return to its original length. Because of this, TTY bolts should not be reused. Why intentionally stretch the head bolts? Engineers discovered they can get much more even clamping on the head gasket if all the bolts are evenly loaded.
Since variations in friction between bolts always causes some uneven loading, stretching the bolts guarantees all the bolts will exert the same clamping force regardless of the torque reading on the wrench.
The result is improved cylinder sealing, longer head gasket durability and less cylinder bore distortion for reduced blowby and more power. TTY head bolts are typically used on engines with aluminum cylinder heads where there is a lot of thermal expansion and with multi-layer steel MLS head gaskets. MLS head gaskets are very stiff gaskets with much less compressibility than standard soft-faced composition head gaskets. On the other hand, MLS head gaskets are almost bullet-proof and produce much less bore distortion than other types of head gaskets because they require less clamping force.
But to seal properly, MLS head gaskets require very smooth almost polished , flat surfaces on the head and block. This, in turn, requires very precise and even clamping loads by the head bolts. How can you tell TTY head bolts from ordinary head bolts? TTY head bolts are typically longer and narrower than standard head bolts. Factory service manuals will tell you which applications use TTY bolts, and you can often tell from the head bolt tightening procedure if the bolts are TTY or standard.
TTY bolts typically have an angle tightening specification rather than a specific torque value which requires using an angle gauge when tightening the bolts.
The torque procedure for tightening a TTY head bolt involves tightening it until a certain torque reading is reached. Then the bolt is given an additional turn to a specified angle say an additional 45 to 90 degrees to load the bolt beyond its yield point for maximum clamping pressure. Or put another way, anything that reduces friction also multiplies the clamping load exerted by the head bolt at a given torque reading.
Always use oil like a non detergent 30wt oil on the threads and under the head if you can it doesnt hurt for any stock type head bolt. I'll put a small amount thru the threads but not on the bottom. As far as the washers that go under the head bolt head, should I oil the bottom of the washer a bit? You must log in or register to reply here. Similar threads. Replies 17 Views 3K. Aug 13, ilikespeeding. Replies 5 Views 1K. Sep 14, turboglenn. Does my block look clean enough to put the head gasket on?
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