Head Bolts -should I lubricate - peter973

I'm changing the head gasket on my car.

Should I lightly lubricate the Head Bolts or could this affect the torque tightening & in long term, tightening stability ?

I was thinking of screwing the bolts in initially using a little oil and then a little copper slip, before I fit the head gasket with the head.

Just wondering what the general concensus or standard procedure is on this.

I'm always slightly worried that bolts will rust over years or be very difficult/impossible to undo, if I need to remove them again, which is what I had with 4 small Torx bolts on the crankshaft pulley, where I had to hammer on a smaller socket to get the rusted bolts off.


Should I lightly lubricate the Head Bolts or could this affect the torque tightening & in long term, tightening stability ?

Head Bolts -should I lubricate - hardway

I do lubricate "stretch" head bolts but on the underside of the bolt face.

I use graphite powder.

If it's correct or not I'm afraid I'm old school and to be honest using these bolts still freaks me out a little.

The little voice screams "it's going to shear!!".

Stupid I know.

But if your worried about rust on the fasteners just give them a little blast of spray paint.

Head Bolts -should I lubricate - skidpan

The bolt manufacturer should give details regarding tightening and lubrication. Using the wrong proceedure will potentially damage the bolt but it will almost certainly result in premature gasket failure since the clamping pressure on the gasket will be either too great or too little.

Read the instructions and also refer to a workshop manual but the tightening proceedure on the kit should be followed even if it is slightly different.

Head Bolts -should I lubricate - craig-pd130

+1 to Skidpan's advice. Check the workshop manual. Usually the advice for cylinder head bolts / studs is clean, dry threads (a can of carb cleaner or brake cleaner is great for giving them a quick blast and it evaporates in seconds) BUT there are exceptions.

Using a lubricant when torquing a nut or bolt can reduce the applied torque by 30% or more - which means you can overtighten the fixing by 30%. So it's best to check.

Head Bolts -should I lubricate - craig-pd130

Oh, and you shouldn't use oil or grease on a stud that goes into a blind hole in the cylinder block etc. If you put on just a bit too much, it can puddle at the bottom of the hole as you wind the stud down. The end of the stud will then be compressing the fluid rather than hitting the bottom of the hole, which means at best it won't be tightened properly.

Head Bolts -should I lubricate - Stanb Sevento

As others have said clean and dry is the default position in the absence of any other specific information. Dont get too hung up about being super scientific about it, its not a precision thing. Makers spec apply to new bolts not old and getting everything absolutly clean is near impossible, but thankfully there is a fair range of tension that will work fine. Correct sequence and eveness are just as important. Many old hands do it by feel rather than use a torque wrench. All bolts strech when under load, the bigger the load the more they strech, the problems start if you go past their "elastic linit". Thats the point where they dont return to their original length when the load is removed. You can feel if that happens, the bolt turns but the torque reading stays the same, or even falls back.

Edited by Stanb Sevento on 14/06/2017 at 11:23

 

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