K1200 belt alignment.
Turbo Mini Forums

I don’t believe that vertically shimming the head at either end will do anything; because you can reverse the rotation and get the travel to reverse direction. If you were to shim it (vertically) enough to stop it traveling in the forwards direction, it would travel HARD in the opposite direction.

There are only two things I believe it can be; the head “rotated” on the block, or teeth cut at an angle on the eBay pulleys.

When I machined my block, it was done on a mill, and I indicated off the outer two bores using dowel pins amd a parallel, then off a 1/8” thick long parallel that I ran thru the main journals, using a dial indicator on the column to verify the crank axis was also square to the bores.

I spent a long time getting it to within 1 thou over the length of the block, because I didn’t want any issues. I even machined tube dowel locators into the block to locate the head accurately (one dowel round and sized as per BMW as the prime location datum; the other is ovaled slightly so it only constrains forwards/backwards so it won’t be fighting as the head expands/contracts relative to the block).

Edited by TurboDave16V on 24th Mar, 2018.

Well, this bugged me.

I went into my garage and pulled out my stack of OEM and aftermarket pulleys.


I then did a simple test using a parallel and one of my “special occasion only” high precision squares.



All but one of them, displayed no rocking of the square. The teeth are, to all intents, normal to the turned face. I repeated several times around, on both sides of the teeth. The one that showed a little rocking has mostly straight teeth, but one or two are off. I can repeat the test and get the same results on the same teeth.

I then repeated the test, in situ, of my current installed pulleys, and the square rocks. Repeated it a few times on both sides, definitely rocking present...

I then came up with what I think is an even better test.
Using two pins gauges (I used .211 and .212”) holding them on almost opposite teeth like this pic, and resting a rigid parallel across them, every OEM and my aftermarket B18 pulleys are perfect. The one I saw a little rocking on allows the parallel to rock in every position, but in some positions has a LOT of angular offset. I also measured over the pins at each face of the pulley, and it is parallel (so the pulley is not tapered), it’s just skewed.



I’ll repeat when the engine is next out, but may as well pick up another pair of pulleys I guess (a different type) and inspect squareness before installing... I see more rocking with the square on my installed pulleys than the “worst” aftermarket one I have in my stack after all.

Edited by TurboDave16V on 24th Mar, 2018.

Was there any progress made with this issue?
Shane

Completely forgot to update this thread, as Turbodave suggest the head is "rotated" in block face, can't remember for sure but at the time, because the head was so tight at the studs I spend a long afternoon removing some studs, one at each time, and rotating the head clock and then anticlockwise bolt everything down, cams, pulleys, timing, etc, lots and lots of turns in the engine, pretty sure that my rings are all seated after now, until the belt as no movement.

From what I remember, from the one at the left back corner stud I remove I could see a half moon from the block deck so at the very least I have a misaligned stud. Its being stat under the bench since last May.

Only update was last week I got in touch whit Alex@TheCarKitchen to have a quote for a new fresh block.

Edited by R.Rodrigues on 12th Feb, 2019.

I had a similar issue when timing and tensioning mine. After checking everything for true and squareness it turned out solely to be an overly tight belt.
What surprised me was at the time was that with amount of these engines that have been built (by both SC and self builds) the belt tension is still vague and no one (that I spoke with SC included) could give a value for deflection (mm per Nm) as you would have on your more typical cambelt change.

Glad you’ve found the issue, how do you propose to resolve it? Could you not fit an over sized plug and redrill the offending stud hole?

Shane

Edited by shane on 12th Feb, 2019.

not such long time ago I replaced the timing belt of my Alfa diesel. That one is with a spring that indicates when you have the right tension. At that moment the longest distance between two rolls / sprockets is checked by torsion. Just could turn it gently a quarter turn. Thats what I also did yesterday on my K head build. Feels fine to me