Subtle valve cover differences

[visionaut]

I didn’t realize the ribs on the lower unknown cover were straight not curved from your original pic @bob02. That’s a simpler & heavier design.  So I’m gonna reverse my earlier guess the upper cover was newer. I now think it’s older, in fact likely from a NK.

 

Check out these ribs in this pic of an early NK cover.  Look familiar?

 

And digging into it a bit more this morning, I’m also now thinking Steve @Conserv might be onto something with his 6.9 & 7.0 sequence theory (last digits in the cast 118 026 00 xxx number). The NK cover above is a 3.9.

 

And this 73 cover is an 8.0… Bob’s 71 cover was a 7.0.

My caveat is I’d have expected Bob’s unknown cover to have a lower digit than 6.9 if it’s that much older. But MAYBE different suppliers used these extra digits independently??

[Conserv]

4 hours ago, jimk said:

… why did BMW have so much webbing cast into the underside of the covers?  I have my guess, how about yours.

 

I was an English major, Jim, although I did spend my freshman year in the engineering school wondering: “is this what I want to do for the rest of my life!” 🤔

 

I suspect your guess is going to be 100X more valuable than mine! 😉

 

Best regards,

 

Steve

 

[Son of Marty]

My guess is the ribbing helps with heat dissipation, or there for her pleasure.

[Conserv]

19 minutes ago, visionaut said:

I didn’t realize the ribs on the lower unknown cover were straight not curved from your original pic @bob02. That’s a simpler & heavier design.  So I’m gonna reverse my earlier guess the upper cover was newer. I now think it’s older, in fact likely from a NK.

 

Check out these ribs in this pic of an early NK cover.  Look familiar?

 

And digging into it a bit more this morning, I’m also now thinking Steve @Conserv might be onto something with his 6.9 & 7.0 sequence theory (last digits in the cast 118 026 00 xxx number). The NK cover above is a 3.9.

 

And this 73 cover is an 8.0… Bob’s 71 cover was a 7.0.

My caveat is I’d have expected Bob’s unknown cover to have a lower digit than 6.9 if it’s that much older. But MAYBE different suppliers used these extra digits independently??

Wait, Tom! You trash my sophisticated “6.9 comes before 7.0” theory, crushing my self-confidence and now you say “Never mind!” 😟

 

Thanks! 😋

[Son of Marty]

 

 

[visionaut]

32 minutes ago, Conserv said:

Wait, Tom! You trash my sophisticated “6.9 comes before 7.0” theory, crushing my self-confidence and now you say “Never mind!” 😟

 

Thanks! 😋

Ha ha. You might laugh at my current theory, Steve!!

 

Here goes:

There were 2 suppliers, each with their own rib-stiffening designs, one was assigned the .0 sequence and the other the .9 sequences. (!)

 

The .9 supplier made the flat internal ribbed style covers, producing the 3.9 during NK production and the 6.9 much later during 02 or E21 production. The 3.9 has no external rib stripes, the 6.9 is a thick striped ‘BMW’version. This supplier didn’t use a recognizable date marker.

 

The .0 supplier made the 7.0 and 8.0 covers. 7.0 & 8.0 are ‘BMW’ versions, but your similarly ribbed 76 (#?) is a roundel version. This supplier used a typical date marker.

 

Each supplier kept their internal ribbed structural designs throughout their production spans, yet changed the exterior styles several times, and the x.0 & x.9 sequences cover those 

 

LOL.

Edited August 10 by visionaut

[jimk]

35 minutes ago, Conserv said:

I was an English major, Jim, although I did spend my freshman year in the engineering school wondering: “is this what I want to do for the rest of my life!” 🤔

 

I suspect your guess is going to be 100X more valuable than mine! 😉

 

Best regards,

 

Steve

 

I agree that the bastards are a basting feature.  I don't see any need for structural reinforcement except when timing the ignition and the tuner can't find the ball and decides to take it out on the valve cover.

[visionaut]

Why an internally ribbed valve cover?

 

The valve cover provides an open ‘dome’ of free space covering the valve train. It retains oil within the engine, provides for adding engine oil and provides crankcase breathing. It sits atop a complex high vibration environment (the operating cylinder head and engine).

 

The M10 valve cover design is a thin-walled aluminum shell structure with optimized internal ribbing with weighted nodes. The engineers are looking to optimize the part’s topology for structural and vibration resilience. 

 

The ribs transfer the structural and vibration loading of the domed shell structure to its supports, effectively acting as stiffening arches and load paths on the resonating thin shell (and its subdivided sections).  The mounting base acts as the reinforcing frame for the rib network and serves as the stable mounting/sealing surface. The circular weighted rib ‘nodes’ are located to help distribute and attenuate the resonance/vibration loads occurring across the rib network.

 

The ribbing provides:

• Lower weight with the same mechanical stiffness

• Buckling resistance/stability to deformation

• Vibration resistance & control (natural and induced frequencies/resonance).

 

🤓

 

 

[visionaut]

Why an internally ribbed valve cover?

 

The valve cover provides an open ‘dome’ of free space covering the valve train. It retains oil within the engine, provides for adding engine oil and provides crankcase breathing. It sits atop a complex high vibration environment (the operating cylinder head and engine).

 

The M10 valve cover design is a thin-walled aluminum shell structure with optimized internal ribbing with weighted nodes. The engineers are looking to optimize the part’s topology for structural and vibration resilience. 

 

The ribs transfer the structural and vibration loading of the domed shell structure to its supports, effectively acting as stiffening arches and load paths on the resonating thin shell (and its subdivided sections).  The mounting base acts as the reinforcing frame for the rib network and serves as the stable mounting/sealing surface. The circular weighted rib ‘nodes’ are located to help distribute and attenuate the resonance/vibration loads occurring across the rib network.

 

The ribbing provides:

• Lower weight with the same mechanical stiffness

• Buckling resistance/stability to deformation

• Vibration resistance & control (natural and induced frequencies/resonance).

 

🤓

 

 

[Son of Marty]

Well they made them plenty strong, you can and I have stood on them mounted of course with no damage and I'm over 250#

[visionaut]

4 hours ago, Son of Marty said:

Well they made them plenty strong, you can and I have stood on them mounted of course with no damage and I'm over 250#

 

Being able support a Full Marty probably is a bonus, but that’s part of the high stiffness/stability. It’s light and stout - you can’t twist it. The ribs are critical to assuring flatness of the mating surface for the shell — no oil leaks!

 

[NickVyse]

This smooth topped cover from '65 has such deep and flat ribs it doesn't clear the oil spray bar (original cams in '65 were hollow/internally oiled).

 

[Conserv]

39 minutes ago, NickVyse said:

This smooth topped cover from '65 has such deep and flat ribs it doesn't clear the oil spray bar (original cams in '65 were hollow/internally oiled).

 

Thanks, Nick,

 

Is this example ribbed? And is it dated?

 

Best regards,

 

Steve

 

[NickVyse]

In my experience ribs didn't arrive until around '67, and the smooth covers got a more rounded underside bracing to clear the introduction of the spray bar from '66. I've never looked for the date on this one, which after a bit of grinding cleared the spray bar and is now installed on my 2.5 in the touring.

 

[visionaut]

2 hours ago, NickVyse said:

This smooth topped cover from '65 has such deep and flat ribs it doesn't clear the oil spray bar (original cams in '65 were hollow/internally oiled).

 

Nice Nick, thx. Looks identical to the smooth-top NK cover I posted (top of this page). There were no dates I could see in that one, which has the R 118 026 00 03 9 identification. There is another number on it tho’ in the square above -could it be a date code? 31 401.3