Head Gasket tech

[Dr S]

Pulled the head today to fit the decompression plate. Good news, the head is about the spec I thought it was 33mm by 29mm valves. Not bad for a small bore motor.

So now I’ve got two head gaskets, a plate and slack nuts.

So reading HBOL it says I think off the top of my head 50ft\lb of torque on dry nuts. My nuts are lubed up (inside the box)

Should I lube the front nuts? Or try and dry the rears? The nuts were b@stard tight do hi spec motors run different studs?

I’m thinking two HG’s will give me more squish so more re-torquing needed but no more load.

[Peter Laidler]

Oily nuts...... I know the feeling Doc. Even engineers disagree - or agree to disagree - about torque figures for nuts. It's another silicon brake fluid type point to ponder over. The general consensus among the wise, those with current engineering certification is that for the sort of low torque figures we're talking about in this simple form of heat machine - a car engine - that it has no significance whatever. And I stick by that rule of thumb. So if it says 32ft/lb say, I slightly grease the thread and nip it up to THAT figure.

[111Robin]

If the torque figure is specified dry and you take it to the same value lubricated you do run the risk of exceeding the allowable tensile stress in the stud. In my line of work we do lots of testing with different coatings and lubricants to determine the friction coefficient to enable to accurately calculate the torque required for a specific preload. It really depends how close to the limit the studs are, may not be an issue but it is a risk.

[Earwax]

On the matter of decompression plate plus 2 gaskets, have you done your sums including all thicknesses ( or as near to as you can). It would be sad to end up with a CR of 6.5 ( just checking , again , before finalising)

I haven't heard or seen any specific alterations regarding torquing in a more than one gasket environ.. AFAIK The torque is a factor of the stud and thread, and i agree with you stick with the recommendation and dont be tempted to over stress the stud ( agreeing with what was suggested above)
OEM figure is 50 ft/lbs ( your figures) and ARP is 42 ft/lbs IIRC ( with their slippery moly lube) ( so i am sitting on the fence on this one, I use ARP)

Regarding retorquing down, I tend to think you are correct .
Using Multi layer steel gaskets ( Cometic type), I was told to go around a few more times on each step of the way ( so torque to 28 and then 35 then to say 42) But add an extra checking torque round once each level of stasis has been achieved. I am still amazed at the 'creep' that exists in these type of gaskets. I have found the initial 'creep" is where the movement comes and that after heat cycles etc the retensioning is reassuring.
Good luck

[MrNoo]

Some of the old petrol Ferguson engines used a double head gasket and spacer plate in order to run on TVO, we always torqued them to standard (cold) and then we again would do them when hot, surprising how much they went down, never had a gasket issue or stud issue but then suspect the studs were probably way over engineered to start with.