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OK - that would explain the torque lowering also, since it "squishes" the whole thing tighter together.

And the rockers move closer in toward the engine block/push rods.

And there goes the valve lash.

Retorquing actually pushes in a bit more and makes it tighter still I asssume...

I have been following this thread with interest. I have some info on my website about this procedure.

The first retorque is when brand new. We would do a quick check at 500-600 miles. It was typical to find that upon retorque the valves would be off a couple of thou. I don't recall finding the torque off by much, or the valves either. After that, they would be stable and only vary a little, but not enough to worry about.

To find that the valves had closed up to near zero would alarm us greatly. Either we failed to assemble it correctly, or a stud is pulling out.

While BMW calls for a cold check, it matters none. Just to test this for yourself, next time you wish to check valves, pull in hot and remove both covers. Check the valve lash and write it down. Then the next morning after it is "officially" cold, check again. You should find no significant difference. A stable engine can be set hot or cold.

We only used a beam type torque wrench because you get the most information that way. You can see what is typical for backing off on the head nuts. Don't back them off with a breaker bar, or you will lose info. Record your findings in your log book each time. We would only back off the head nuts if we found a large change in valve lash. It would be typical to go 20-30 k miles without ever finding a large change in valve lash.

To find that the valves had closed up to near zero would alarm us greatly. Either we failed to assemble it correctly, or a stud is pulling out.

I'm fine with all the thoughts, but this one is getting to me

From everything I read, doesn't a stud pulling out cause the opposite?

The head pulls away from the block and the valve lash gets larger?

How would a stud pulling cause valve last to become less?

pkboxer wrote:
I'm fine with all the thoughts, but this one is getting to me

From everything I read, doesn't a stud pulling out cause the opposite?

I had the same thought

Major Softie wrote:

pkboxer wrote:
I'm fine with all the thoughts, but this one is getting to me

From everything I read, doesn't a stud pulling out cause the opposite?

I had the same thought

The stud pulls out, releasing tension when the engine is hot and running. Even in its weakened state, it retains enough integrity to pull the head in a bit when cold and retorqued.

The clamping force that the studs must withstand when hot in an air-cooled motor is a multiple of what they get torqued to when cold.

melville wrote: The stud pulls out, releasing tension when the engine is hot and running. Even in its weakened state, it retains enough integrity to pull the head in a bit when cold and retorqued.

The clamping force that the studs must withstand when hot in an air-cooled motor is a multiple of what they get torqued to when cold.

I'm not saying you're wrong, but I am saying that this makes no sense to me at all.

Major Softie wrote:

melville wrote: The stud pulls out, releasing tension when the engine is hot and running. Even in its weakened state, it retains enough integrity to pull the head in a bit when cold and retorqued.

The clamping force that the studs must withstand when hot in an air-cooled motor is a multiple of what they get torqued to when cold.

I'm not saying you're wrong, but I am saying that this makes no sense to me at all.

I don't understand it either.

OK, I'll try again. I thought we were discussing this:

Duane Ausherman wrote:The first retorque is when brand new. We would do a quick check at 500-600 miles. It was typical to find that upon retorque the valves would be off a couple of thou. I don't recall finding the torque off by much, or the valves either. After that, they would be stable and only vary a little, but not enough to worry about.

To find that the valves had closed up to near zero would alarm us greatly. Either we failed to assemble it correctly, or a stud is pulling out.

Cold motor gets built, torqued to spec. Tension on studs that the case threads must withstand is X. Vroom! It runs, heats up, the AL parts expand more than the steel studs, tension on case studs is 2X or 3X. One of them starts to give, opening valve clearance on that valve. Motor is allowed to cool--stud is still out a little. Mech checks clearance (it's loose), torques heads, stud holds at room temperature, valve clearance tightens up.

Here's where Duane and other smart mechs say, "Aha, we must fix those case threads!" even though the customer is saying, "But didn't the clearance resolve itself with the retorque?" "How much $$$ is this going to run?"

Cold motor gets built, torqued to spec. Tension on studs that the case threads must withstand is X. Vroom! It runs, heats up, the AL parts expand more than the steel studs, tension on case studs is 2X or 3X. One of them starts to give, opening valve clearance on that valve. Motor is allowed to cool--stud is still out a little. Mech checks clearance (it's loose),

This is as far as I was when I asked my original question and lash was tighter, not looser...

Then among other things that Duanne said that made sense he also said..

To find that the valves had closed up to near zero would alarm us greatly. Either we failed to assemble it correctly, or a stud is pulling out.

That was what was confusing me and you seem to be supporting my questioning of Duanne's statement.

A stud that is pulling out when the engine is hot will make the gap open up.

This was all after installing newly redone heads (new seats, guides, springs new exhaust valves) and new base and head gaskets.

If a stud starts to pull out...it won't really get up to torque and feel mushy. I had one do that just before a 600 mile ride. I left it alone and did the ride. I checked the valve clearance during the ride. It opened up and was a bit louder than usual. But it moved less than one might think.

Once home, I tore it apart and put inserts into all eight stud holes.