W108 "Beverly" head installation questions

[K-Jet]

Good morning!

I am in the middle of recommissioning a 1971 280SE, Beverly. This recommissioning includes building a new 2.8 motor to replace the installed 2.5, and we're ready to install the cylinder head. Last week I test-fit the head to the block, to include the full cold torquing sequence and ran into some things that I need someone much smarter than me to answer.[/img]

1. My much more experienced friend tells me that the new, still unused head gasket should not be used as it has now been compressed. I haven't heard that before. Thoughts from the group?

2. The Mercedes manual is silent on this, but the Hanes manual says to torque the head without the cam installed. This means torquing the 8 pedestal head bolts and then the 6 oil line support bolts. Not matching up with the beautifully numbered 1-14 diagram given! The wisdom I've heard here is to have the cam removed while torquing to avoid breaking the camshaft.

3. Before torquing, the cam doesn't spin as freely by hand as the words "spin freely" imply. I measured the torque as 0.36 Nm to start the cam turning and 0.18 Nm to keep it turning. Are those reasonable?

4. When I had the head fully torqued with cam in, I couldn't turn the cam by hand. What do I look for to resolve that situation?

Many thanks.

[MikeSimon]

For one thing, you can only torque the head with the camshaft out, if the engine is not installed in the car. If you R&R the head with the engine in the car, the camshaft has to be in the head before it goes on the engine and is being torqued....food for thought!

[ja17]

The head gasket is not normally torqued, removed and re-used. The seal strips and metal compression rings on the head gasket compress and may not seal as well the second round. If the head has been warped and then re-surfaced flat again, The top deck of the head may still be warped. Shims are available to install under the cam shaft towers to align the camshaft so that is rotates easily. If the camshaft can be turned by hand after the complete torque sequence, then it is fine. Some resistance can be tolerated. Use the shims to adjust. You can check the flatness of the top surface of the head with a machinist straight edge before you begin.

[Benz Dr.]

The head gasket is not normally torqued, removed and re-used. The seal strips and metal compression rings on the head gasket compress and may not seal as well the second round. If the head has been warped and then re-surfaced flat again, The top deck of the head may still be warped. Shims are available to install under the cam shaft towers to align the camshaft so that is rotates easily. If the camshaft can be turned by hand after the complete torque sequence, then it is fine. Some resistance can be tolerated. Use the shims to adjust. You can check the flatness of the top surface of the head with a machinist straight edge before you begin.

Sorry Joe, no way.  Cam shims will not get the cam to turn easily. Even minor deviations can make the cam turn hard mostly from the top side of the head being warped. We often mill the top of the head to get everything level. Cam shims won't get you there, or at least, not easily. I use cam shims to raise the height of the camshaft so that the rocker adjustment comes back into range - trying to level out a warped head using cam shims isn't a good use of time.

Never reuse a head gasket - it's a one time deal. Always have all of your cam bearings and valve cover hoops in place before you start. Why would anyone install a head and not put the cam on? That's just silly.

[ja17]

That's fine Dan, it's worked for me plenty of times and it is a procedure described in Mercedes factory literature. Shaving both sides of the head is more work but probably the best way. These days, straightening the head is even better to get it as close as possible before machining-off any material. Yes using a head gasket over could be a disaster especially on a M130 engine!

[Leester]

Dumb question here.  What's a Beverly head?

[Jonny B]

I think that is the personal name the owner has for the car. Check the first line of the original post.

[Leester]

Yup Johnny B - after re-reading I think you're right. Toldja it was a dumb question.  Lee

[K-Jet]

Beverly was owned by a Swedish film producer in Beverly Hills before my German neighbor bought her. Hence the name. My neighbor did some work on her, as she came with a ventilated block. Hence the 250 motor.  Then she sat in the carport for the better part of a decade until I bought her as a pre-pandemic project. I'm still fiddling with it, as is my neighbor. He's the brains in this operation.

Thank you all for the clear, knowledgeable feedback. As I understand it, I need to buy a new head gasket. I need to return the head to the machine shop for them to check the thickness of the head and parallelism of the top and bottom surfaces. When the time comes, I need to install the head with the camshaft in place.

Did I miss anything?

Dru

[K-Jet]

So the head is back at the local machine shop. I agreed to this under the condition that they would do no machining until they made measurements and came to me with a plan.

The machinist would now like to machine the cam pedestals so that the cam turns freely. I suspect I need to go get the head back, drive it to a M130 specialist halfway across the country, and take the financial consequences that come. Thoughts?

[K-Jet]

No thoughts about machining cam pedestals to correct for non-parallel head surfaces?

[Benz Dr.]

That's fine Dan, it's worked for me plenty of times and it is a procedure described in Mercedes factory literature. Shaving both sides of the head is more work but probably the best way. These days, straightening the head is even better to get it as close as possible before machining-off any material. Yes using a head gasket over could be a disaster especially on a M130 engine!

Oh, you can do it that way if you have several different thicknesses of shim stock, all the time in the world to fuss with it to get it right, and time spent is of no consequence. 

I would NOT, under any circumstance, remove anything from the bottom of cam bearings. If your cylinder head is slightly warped, you should have it planed on top to correct the defect. If it's really warped, have it straightened in an oven before milling either side of the head.

 Most cams will turn well enough with a slight warp on the top of the head as the cam bearings will usually be worn a bit which can give you a bit of latitude. 

[K-Jet]

Well, it doesn't matter what I think because the machine shop (despite promises to the contrary) went ahead and shaved the middle cam pedestals. The cam does turn nicely now. They are so very German.

So what next?

[K-Jet]

What next was to take the head to the specialists at Väth Motoren https://www.vaeth-motoren.com, where they made some incredulous faces when I described what had been done, made some observations of the work that hadn't been done, and went to work. Three days later, they are finished and I will go pick up the head after Christmas. Assembly can then proceed!