M30B35 cylinder head bolt/Rocker shaft issues

[Vintagemotorwerks]

Hello fellow first fivers, I have an issue that I need expert advice on. So I recently purchased an M30B35 engine. I had machine work done on the cylinder head. For some strange reason I’m having a hard time getting the rocker shaft to position properly. I understand that the head bolts are used to located the rocket shaft. Somehow the shoulder on the head bolts are a bit too short and not long enough to slide into the grove cut on the rocker shaft for them. Idk if there is a fix for this issue. The head bolts I purchased are manufactured by Ajusa. Bolts from other manufacturers look exactly the same as well. If anyone has encountered this same issue please feel free to chime in. Thank you lads

[HB528i]

I had this issue on a b30 motor, cam would not center the rockers over the valve end. We put a shim in the rear of the head to position the cam, at least I think that is what the machinist did!

[Vintagemotorwerks]

I was thinking of either doing that or putting a sleeve on the headbolt that will be big enough to seat the rocker shaft properly. I wonder if there’s any more options out there. I just don’t understand why BMW would make such a rocker shaft design and then not make the proper head bolt to work with the system.

[HB528i]

Correction, shim was on rear end of rocker shaft.

[Mike W.]

I've never had this problem. How long is the shoulder, might the aftermarket bolts be different than stock?

[maybeillbuyit]

Correction, shim was on rear end of rocker shaft.

Eric, this seems weird to me. The rocker shafts are just slid into the head and are kind of floating there until the head bolts lock them into position. Putting a shim on one end or the other wouldn't really be able to change the position that the headbolts lock the rocker shaft into. Unless I'm missing something

Vintagemotorwerks I just googled Ajusa and those headbolts look the same as oem. Whats the difference in thickness and length of the shoulder? What was the part number you used to order the bolts? 11120621144?

[Vintagemotorwerks]

Apparently the original head bolts had a longer shoulder that would go down deep enough to help locate the rocker shaft. The new ajusa and updated oem ones have too short a shoulder that after you include the washer, it just doesn’t go anywhere near the curve cut on the rocker shaft. I’m experimenting with thin metal bushings. I’m looking into finding a bolt manufacturer that could manufacture the bolts for me.

[Mike W.]

M30 head bolts are reusable. Are you going turbo or something where you need increased clamping pressure?

[Vintagemotorwerks]

Aren’t the stock head bolts torque to yield bolts? I’m doing a stock set up. No plans on big boost or anything. Just trying to squeeze as much power out of a stock 3.5L. So far my only mods planned are Miller Performance MAF swap, Headers, and exhaust.

[maybeillbuyit]

For some reason that misinformation keeps coming up. The m30 headbolts aren't torque to yield. They're reusable. I'm still curious whats the measurement for the shoulder for your aftermarket bolts vs the stock ones? If you don't have stock ones I think I can dig some out

[Mike W.]

No, M20's are torque to yield, but M30s are not, they're reusable.

[maybeillbuyit]

OK Mike, maybe thats why this is always coming up. I didn't know that m20s are T to Y. No experience with that engine

[Vintagemotorwerks]

Only problem is even the bolts that I took off of my cylinder head didn’t have the proper shoulder length to properly set the rocker shaft in place. If you look at the original diagrams from the 70s-80s the bolt in the diagram actually has a long shoulder. I’m not sure if BMW decided to cut costs by shortening the shoulder or if they just didn’t realize it when they made the new head bolts

[maybeillbuyit]

And whats the length of those shoulders?