Valve adjustment as per factory manual

schrader7032 · Post by **schrader7032** » Fri Sep 21, 2007 2:37 pm

I think Darryl made a good point...the BMW manual assumes you already have factory training and the procedures are more reminders than anything. I also found the same entry in the Haynes aftermarket manual which mentioned the reverse torque on each nut. But no one is going to hold an aftermarket manual up as the gospel truth. The bike's owner manual says to check for tightness but ultimately says to have the dealer do it.

If you suggest that BMW has been very specific in their instructions, where is the precise information for how to check for tightness? They don't say either to back the nut off or to just go ahead and use the torque wrench on the nut as is. It seems to suggest that you should already know what to do, as provided in details instructions in school.

So, I think we're in a gray area. Most general purpose manuals don't really cover the subject or they suggest that you let your dealer take care of it and the official manual doesn't even touch the subject.

Finding specs for other manufacturers, engines, etc., is not going to shed any more light. Someone can always point out that it is for a different engine, materials, construction, etc., and their concepts don't necessarily apply to how BMW designed their engines to be wrenched on.

If we're looking for the final answer, we need Max Fritz to come back to us. Or have some go over to Germany and sit in the Mobile Tradition office until they can find someone who has the necessary background to tell us what BMW intended.

Kurt in S.A.

EuroIron · Post by **EuroIron** » Fri Sep 21, 2007 7:47 pm

finding procedures specified for other engines, including BMW's own......

does indeed support that premise that the procedures are quite specific and leave no guess work as to how a tech was or was not trained

the procedure for checking for tightness is very clear to me

if you loosen it, you aren't checking it for tightness

schrader7032 · Post by **schrader7032** » Fri Sep 21, 2007 9:17 pm

Well, then I guess we have a semantic thing. It might say check for tightness and if that's all it said, then I'd probably agree with you. But it says check tightness to 25 ft-lbs (or whatever the number is). That means more to me in the way I understand things. To me, that means confirm the torque is at 25 ft-lbs. I know of no other way to check it other than to loosen and retighten to 25 ft-lbs. Sure, you can put the wrench on it and it might take 25 ft-lbs but you haven't overcome the static friction so the reading means little, other than the nut is not loose, ie, tight. Once you break the static friction, then you can read the torque. If it reads 25 ft-lbs, you can stop. If it reads more, then you have to loosen and start over.

You have your way, you have your training...I understand my way, and I have no training. I'm an engineer by profession, and while this is not necessarily my speciality, the information provide through these discussions just hasn't provide enough clarity and scientific basis to alter what I do know and have studied about bolted joints. I also know that technical writing, of which writing manuals is a related field, is a difficult thing to do. It's easy to leave nuances out or assume that the reader knows as much as the writer. IMHO, I don't think any of the BMW manuals being referenced has described this process in the appropriate amount of detail for the shadetree mechanic, which I are one!

I've been taking what I've read, added my own experiences and understanding, and doing what I think is best. I guess that's the road I'm on...

Later...Kurt in S.A.

808Airhead · Post by **808Airhead** » Sun Aug 09, 2009 2:54 am

In my line of work,I build some high performance turbocharged engines with over 250hp/liter,and when installing high performance connecting rods,we use the "ARP" lube that looks moly based,and this is supplied with their hardware.They stress that actual tq. is not accurate since some is loss to frictioin,so this supplied lubricant is specified to be used on the threads as well as the face of the bolt/nut so you can get a ACTUAL tq. reading of the bolt/nut.
Is this over thinking/mixing new tech with old tech,regarding this issue?
I want to accurately tq. the heads,but with the reputation of "butter heads" would the lube make too much stress on the threads??

Allan.Atherton · Post by **Allan.Atherton** » Sun Aug 09, 2009 8:10 pm

... I want to accurately tq. the heads,but with the reputation of "butter heads" would the lube make too much stress on the threads?? The butterhead deformation occurs after decades and tens of thousands of miles of containing the firing pulses at operating temperature. I have never heard it connected to the torque used on the headbolts. If you overtorque the headbolts, they will just likely pull out of the head.

schrader7032 · Post by **schrader7032** » Mon Aug 10, 2009 7:34 am

If you overtorque the headbolts, they will just likely pull out of the head.

Actually, since the head bolts go into the cylinder, it would be a problem for the cylinder. Plus the cylinder is steel which is even less likely to be a problem. The head-cylinder combo is bolted to the engine case with separate bolts and studs.

Kurt in S.A.

Allan.Atherton · Post by **Allan.Atherton** » Mon Aug 10, 2009 8:26 am

... the head bolts go into the cylinder... A mental glitch here. There is some consequence of over-tight head bolts mentioned in a forum - maybe is was stretching or breaking of the bolts. I think it was Duane, saying it was better the bolts are under-torqued than over-torqued.

schrader7032 · Post by **schrader7032** » Mon Aug 10, 2009 8:42 am

I think it was Duane, saying it was better the bolts are under-torqued than over-torqued.

Agreed. There's no real reason to crank on these bolts. Probably anything over 20 ft-lbs up to the nomial 25 ft-lbs will be just fine. And also long as they stay tight, that's the goal.

Kurt in S.A.

VBMWMO · Post by **VBMWMO** » Mon Feb 15, 2010 2:51 pm

Can't find my factory manual and I have a little bet going-
I seem to remember the manual says to re-torque the head bolts at every tune-up prior to every valve adjustment.
Yes or No? Thanks