<E30> report of head bolt upgrade - more damage (long)

[Michiel van Wessem <jmvw@xxxxxxxxx>]

Hello,

Here is another report from your beginner driveway mechanic. This time I
upgraded my head bolts and adjusted the valve slack. 

For the interested, I've started to built a set of web pages where I keep
this stuff. If you're interested see
http://www.vramp.net/~jmvw/cars/BMW/index.html Unfortunately no pictures
there yet!

Ok, here's my report: 


Yesterday I have upgraded the head bolts on my 1987 325es to the Torx kind
and while the valve cover was off I adjusted the valve play.

Replacing the head bolts wasn't difficult at all, just took a lot of time
and strength. It took me about 5 hours.

I replaced the bolts one by one (so without taking the head off), following
the bolt-on pattern from my Bentley manual. 

Three of the 14 old hex bolts were so loose engine oil had gotten into the
bolt holes and all the way down the threads. I cleaned out the bolt holes
with canned air. The oil jumped out like bits of chewing gum, frozen by the
now cold canned air. I was a little worried here about the cold causing the
block to develop cracks, but figured that if it could stand the explosions
of combustion, it should be able to take it. 

After torque-ing to 22 ft. lbs., I used some white-out to put a dot on one
side of the bolt, as suggested by Rick Gaitley from the BMW list. This
facilitated eye-balling the 180 degrees that the bolts should be turned. To
tighten the new bolts, I used an 8 inch breaker bar and a 2 inch socket
extension. I'm a big guy and it took just about all my strength. If you
need to do this job too, then I suggest you get both a longer breaker bar
and more extension. I twisted the bolts 180 degrees in two goes. Well, in
two goes and a couple of little ones. 

As I said, I also adjusted the valve play. Now at least I could hope that
my car would run a little better after this operation, rather then just
being protected from snapping head bolts. This was the first time I did a
valve adjustment and I liked it, because it's easy and because I got a
better understanding of valve operation. To move the camshaft, my wife
cranked the engine in short bursts, until the camshaft was in the right
position. 
I used a little Allen wrench to move the eccentric on the rocker arms.
After loosening the nut, if I had the feeler gauge under the eccentric, I
could just turn it until I felt resistance. I think the gaps may be a
somewhat less then the specified .25 mm now, but they're certainly more
then .22 mm. So that should be good.

Where things went a little wrong is when I put the valve cover back on. The
Bentley manual had told me to tighten the cover nuts to 11 ft. lbs. That
seemed a little high to me, but I thought I should follow the instructions.
It seemed really tight, but after a lot of turning the torque wrench
finally clicked with the first nut. With the second nut, the head stud
broke off. Here I put the torque wrench aside and just used a ratchet on
the following nuts, until it felt tight. I don't know what I was thinking,
but a little later I picked up the torque wrench again and broke another
stud! Argh! 

I don't know if it was the inaccuracy of my torque wrench or if Bentley is
crazy to list 11 ft. lbs., but I don't think I'll ever torque M6 bolts
again. In the future I'll just go by what feels right. I haven't broken a
bolt that way yet (well, maybe when I was 12 years old or so, on my bike).
The torque wrench is $40 clicker from J.C. Whitney.

I started up the car for a test drive and it started and immediately
stalled out. The only way to keep it going was to use the accelerator. I
thought maybe this was a case of the computer having to relearn the engine
because of the new valve play. rolled out of our driveway and started it
again and drove it for a while. It just couldn't hold it's idle. Even on
the freeway it stalled as soon as I pushed in the clutch (just letting the
clutch come up is enough to make it start again instantly). 

I went home and felt very discouraged. I figured that the valves opened too
early, which made the engine run badly at low RPM's, like with ignition.
After about an hour, I realized that I couldn't remember putting the hose
from the idle stabilizer valve back on. I went out to the car and sure
enough, it was loose. After reconnecting it, the car runs fine. :)

So now I have two broken studs on the cylinder head. I took a look today
and I seem to be lucky - part of both studs still seems to be sticking out.
If I remove the valve cover again, I may be able to turn them out with a
Vise-Grip wrench. Otherwise, it's going to be drilling. I hate it, but I
want to fix this real soon. Probably tomorrow.


Michiel

------------------------------

End of bmw-digest V9 #649
*************************