Thanks,

Rono

Rono.

No argument here, I think it's a good idea to re-torque any bolt/stud gasket combo.  You may find that they don't need it when you do it but you'll be glad you checked if you find one that needed it.

At the start of this thread Rono asked if he should lubricate the threads and the answer is yes, lube both the threads and the surface of the head where nut or bolt head seats. This reduces the friction in these surfaces so that the mechanical action of the threads yields the maximum amount of stretch of the fastener.  I haven't used studs but I expect that the directions included suggest the kind of lubricant to use. 

        It's usually just engine oil for a lubricant, and, yes, it makes a difference in the torque readings. Boy Howdy does it ever.

Are there any auto makers that ask you to bring in your new car so the head bolts can be checked?

I was going to write a little more about how Torque is really just a crude measurement of tension in the fastener but it was late. Head bolts aren't as critical as rod bolts which I understand now are routinely tensioned by measuring the stretch of the bolt with torque as a guide as to when to stop tightening.

When I worked on nuclear reactors the head bolts were tensioned by 4 large hydraulic jacks on a lifting rig one in each quadrant of the vessel. This rig had one small hydraulic pump so the four jacks were applying equal force.  After the jack force was applied the nuts were run down to contact the head with a relatively small wrench just to make sure there was good contact. I think the stretch of the studs was something like 0.100" or so. There were something like 32 studs total. The studs were maybe 6" dia and around 6' or so long,  so you can get some idea of the force the jacks were capable of and the force holding that head on! 

Rono

    Doug, you are of course correct. It is very crude. New fastners on current engines are tensioned by measuring the bolt stretch. Most of the current specs are given that way. I still have not figured out a way to check the stretch of a head bolt though? Much simpler when you can access both ends of the fastner. Grade 8 studs are probably strong enough to not show much stretch at the level of torque we use, although I've never honestly checked.

      The diesels we used in Subs had 2 inch or so studs, the torque wrench weighed more than I do. Get Vargo to chime in here, he was an engineman. 

Blind stud or bolt stretch can be measured if they are hollow to below the block engaging threads.  But if you tension the stud by a certain amount and the gasket crushes a little more after the initial stretch then the stretch is less by that amount.  This would not occur with say main bolts which are metal to metal.  I don't know of any hollow fasteners used in automotive work but they were/are used in some critical reactor applications.  Anyhow this is way beyond what a Y block needs.

I’ll only retorque head bolts if the opportunity arises.  I very rarely retorque as a result and sure don’t go out of my way to do it unless I’m using a non-composition style head gasket.

I put together a 312 out of parts back in August and used the original grade six bolts torqued at 70 lbs with the Best Gasket head gaskets.  I normally recommend grade eight bolts but this engine was done on the cheap so I just reused the half a century old bolts.  No retorquing after warmup and the engine started being flogged on the dyno back in August.  I just had the rocker arms off this week to change the pushrods out to a longer set (another test) and decided to check the head bolts for grins.  I did this largely in part due to this particular thread.  Torque of the head bolts was rechecked again at 70 lbs. and there was no twist or movement in the bolts so I’ll stick to my original thought process and continue to not retorque after running.  If I had found some movement of the bolts, I would have looked seriously into changing out the head bolts to a new set of grade eights but that wasn’t the case here.

I’m also not a stud advocate on street driven vehicles.  Simply makes the heads difficult to remove in the vehicle.  I do not have any gasket failures due to using bolts and as such, bolts are my fastener of choice in both street and high performance applications.

          Told ya I'd get arguements! I still feel that it's a good idea, as the gasket compresses and is heat cycled a few times, I'd be hard pressed to imagine that the tension doesn't relax a bit. Newer gaskets, like the Best brand may not. Habit, I still worry until I check.

                                                        frank

 In my mind that would depend on the actual Gasket construction and material. Modern (Best in particular) may not compress anough for it to be worthwhile. I had an "event" at the pure stock drags a few years ago where I blew both head gaskets in the same pass. Too much timing, not enough octane booster. We ( Feistritzer, Gordon Payne, and I )removed the heads and installed two of John Feistritzers spares in the pits. I thought I was being super careful on the torque readings, which is difficult with the engine in the car. Things like the hood and the heater get in the way. When I got home I re-torqued everything, found several loose. Doesn't prove anything except that I personally need to check my work very closely. Guys like Mummert and Eaton and Feistritzer (and others) probably don't, and that may be the actual reason for the discussion. Not the gaskets.

Don't include me on your "don't" list.  I always retorque after a few heat up/cool down cycles.  Often find one or more have relaxed.

But when torqueing a new set of gaskets 3 plus times to make sure the fire ring compresses, are the bolts supposed to be loosened before retorquing?  That is the process I went through, and if wrong may be the cause of the initital seepage.  And yes I worked up to the torque spec in three steps, 30 55 and 70 lbs each time.

Thanks,

Rono

       I knew you did, with blown engines we pretty much have to sure (as I found out). but I'm guessin' I make more mistake than you will. Mike, interesting that ARP suggests oil. I'll bet with your cars you retorque AND use the oil.

Ok, that made sense when I was doing it and now.  All the bolts torqued in sequence, then one bolt at a time loosened and retorqued, again in sequence, at least three times.  If the bolts are supposed to be backed off one by one when retightening a head after run in, then I am not doing it right by not backing them off one by one?

On the same engine, I had gone through the process and had Felpro gaskets in place.  3 rounds of torque.  The engine was on a stand and nothing was done to it for a couple weeks.  For a reason I dont remember the heads needed to be taken off again .  As the first bolt was loosened it was obviously not 70 lbs. tight.  Adjusted the torque wrench to get an idea of the breakaway torque for the remaining bolts and they ranged from 50 - 60 lbs, most 50-55 lbs.  Bolts were Ford grade 8.

The feedback I received was that the bolts must have stretched.  At least as plausible, I think the fire rings did not compress initially, but did sometime over the next couple weeks.  Not wanting to take a chance the bolts were replaced with ARP studs and the gaskets changed to John's design.

Mike