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.

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