Doug,

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

Frank/Rebop

Bristol, In ( by Elkhart) 

All the information I have ever read says threads should be clean and dry when torquing. But I do put some lub under the heads.

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

Ol'ford nutCentral Iowa

56 Vic w/292 & 4 spd.

Hi Frank, 

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! 

Doug T

The Highlands, Louisville, Ky.

Dout T, was that at Chernobyl??

  AussieBill            YYYY    Forever Y Block     YYYY

 Down Under, Australia

Thanks everyone. I'll probably go with the studs,oil both threaded ends and re-tourque them. Maybe a good time to re-tourque would be while on the dyno.

Rono

  Ron Lane,  Meridian, ID

Sounds like a good plan

-Gary Burnette-

    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. 

Frank/Rebop

Bristol, In ( by Elkhart) 

I suspect that the problem with heads primarly comes from gasket compression which is different for different gasket designs and materials and that dirty or non lubed threads giving error in effective bolt tension. I have never had any problems with new steel gaskets and reusing old bolts.  But I always chase out the block threads, buff the threads with a wire wheel and lube with oil and graphite in the threads and under the heads.

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.

Doug T

The Highlands, Louisville, Ky.

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.

 

I do use head bolt washers when possible and always lubricate the threads before torquing.  Also be sure to check bolt length versus the hole depth as Y’s tend to come closer to bottoming out than most other engines.

Lorena, Texas (South of Waco)

Rono,

          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

Frank/Rebop

Bristol, In ( by Elkhart)