Roland

Pat, you are probably familiar with these links. The first video illustrates something small enough to theoretically work with a driveshaft. Real-world application, I don't know. https://www.centramatic.com/how-centramatic-balancers-work.rhtml https://www.innovativebalancing.com/ Evidently, some truckers and trailer owners are fans: https://www.airforums.com/forums/f438/centramatic-balancers-update-32907-3.html#post399236 https://www.cumminsforum.com/threads/centramatic-or-balance-masters.2115577/

I do understand you sense the noise is emanating from the rear of the vehicle. The fact that you were unable to replicate the sound with the vehicle on jackstands makes me wonder whether you should not broaden your focus to include the front wheel bearings and even the strut mounts. As improbable as it may seem, loose or worn front bearings can easily be overlooked as a source of noise. Admittedly, such noise is generally accompanied by vibration that you can feel in the steering wheel or floor. This does not eliminate likely culprits listed in Toby's post. However, if the problem lies toward the vehicle center or rear, the sound you have heard is typically accompanied by a vibration felt in your hindquarters, - and this is a symptom you did not mention.

Unless it is leaking, its presence is fairly benign. The threaded "hole" into which the sending unit attaches is pressurized when the engine is running, hence the location and purpose of the oil "pressure" sending unit there. Leave the port exposed and you will experience a mini-ecological disaster. The VDO sending unit replaced the stock unit pictured below. Ordinarily, when it is properly functioning, this device sends a signal to and works in conjunction with your oil pressure warning light marked "O", bottom left.

The device pictured appears to be an oil pressure sending unit. If you have an oil pressure gauge in the cabin, this is presumably the device that feeds the gauge info.

I have been trying to follow your travails and still go back to the "easy-to-overlook" subjects. It goes without saying that I may have missed something along the way. You mentioned setting valve lash. What setting did you use, and did you perform the task with the engine cold or warm? As I indicated previously, I have witnessed better M10 engine operation with copper core spark plugs as opposed to fine wire plugs. However, the differences may not have been as dramatic as most seem to experience, assuming similar branding, heat ranges and gaps. You stated that your fine wire plugs did not evidence the same fouling as the replacement copper core plugs. What plug gaps are you using? I am assuming that your iridium plugs had a large preset gap and the NGK's may have been much smaller. Without faulting either plug type, something changed ignition or fuel wise. And, while a vacuum leak or leaks can play havoc with engine operation, are the plug readings the same for all cylinders - or just 3 and 4? I have a little different take on ignition timing settings, considering certain unknowns regarding your engine. A timing light is a wonderful diagnostic tool, but so are your eyes, ears and nose. Your engine has likely changed since it was manufactured, allowing for the possibility that original recommendations are merely baseline settings, so that your engine may benefit from different ignition settings. (Changes can come in all shapes and sizes. This includes reground or worn cam lobes or resurfaced valve rocker heels - any or all of which can be easily overlooked and can affect valve timing.) Using a timing light might inhibit your attempt to experiment beyond normal recommendations, so assuming you are not dealing with a vacuum leak or an obvious jetting problem, I would consider significantly more ignition timing - if nothing else, but to lean things out at idle. Proper attire can be essential for clear thinking

Sorry, but while all of the advice you have received is well intended, diagnosing a problem from long distance is difficult and more pictures may be worth far more than sound clips. First, I have seen many M10 engines employ platinum tipped plugs without misfiring. Yes, conventional wisdom suggests that the standard copper alloy plugs work even better though. (Something to do with the fact that the platinum plugs were intended more for high energy shorter duration sparks produced by modern non-kettering ignition systems.) However, it might have been helpful to show pictures of the firing end of each plug as an indicator of any obvious combustion issues. Second, ignition timing may be related to your problem, but we have no idea what is going on with your distributor, including the cap and rotor condition. New is good, but no guarantee that the parts mate well with each other. Same with your plug wires and - the terminals for each wire. Some new wires may look new, but you cannot always judge a wire by its good looks. Third, your compression numbers are relative and not necessarily inconsistent with a ‘76 low compression engine. Unless you have used that compression gauge on other engines with previously established readings or compared readings with other gauges on the same engine, your numbers offer somewhat less than empirical data. Again, consistency is the important take away from your readings. Likewise, different readings can be obtained with a cold engine, versus a warm one. Compression tests using a new, fully charged battery, can also yield different results too. Compression readings can also be affected by valve adjustments. That is, if your valves are adjusted too tight, they might not seal as well as they are designed to seal and thus lead to slightly decreased compression readings. I am almost afraid to suggest this but another old standby is use of a vacuum gauge. Fourth, involves any number of variables with your fuel system. Everyone seems to assume a baseline, but what is it? Setting aside simple idle adjustments for throttle plate and mixture screws, do you know what jets are in the carburetor? As has been discussed in countless threads, an idle jet that is slightly plugged or too small or too large can have a dramatic effect on idle and part throttle engine operation. A recent thread discussed float types and float settings. For some reason, these things seem to be taken for granted even though they too, can dramatically impact engine operation, by flooding or starving an engine for fuel. Then there are vacuum leaks that come in all shapes and flavors. You mentioned hearing a sucking sound and wondering if that is normal. Virtually all normally aspirated internal combustion engines will emit vacuum sounds from the air intake. Note, in many instances, “air filter housings,” “air cleaner assemblies“ or even "intake mufflers," have often been called “air silencers.” ? My thought would be to perform a major tune up on the engine without necessarily replacing any parts, but rather visually inspecting, and to the extent possible, testing them. Best of luck.

https://www.youtube.com/watch?v=6PbKfw8COQs

Unfamiliar with your device. "Played" with similar gauges that were notoriously inaccurate, like cheap analog watches. Sometimes the needle would stick and you would have to tap the unit to free it. Unit could be affected by heat, humidity, vibration or even lack of lubrication. Consider most analog watch movements are "jeweled." Some were made with very few jewels, but the better watches have many. Some jewels were made of semi-precious materials, others, not-so precious. Those jewels also needed lubrication and were in sealed compartments. But even the best watches occasionally require cleaning and maintenance to ensure reliability and accuracy. You probably do not know how your unit was stored and even if it was a dry hermetically-sealed vault, gravity has an affect and older lubricants may dry out and not last indefinitely.

Thoughts? Your new-old analog tach was probably not known for its accuracy when it was manufactured, It was an inexpensive unit not targeted toward professionals. The more reliable/ accurate "professional" equipment was expensive.

Mike, What is the basis for stating that the newer valve guide and seal is improved and superior to the older style? I recently had a head at a machine shop where I asked about this subject. The machinist pointed out that the 30+ year old viton seals removed from the engine were remarkably pliable and functional. The engine was not smoking, nor was there any compression issue, so the work was purely elective rather than necessary. The silicon-bronze guides were within spec too, although there was some measurable valve stem wear. (The valves were original, but the guides and seals were last replaced in the mid '80s.) I asked about the newer style, which I have also used, and was informed that the newer seals may start out soft, but may not be as durable in the long run. Of course, "long run" may mean different things to different people. The machinist also made the point that if the original style worked so well, what was the advantage of the newer style?

All things considered, denser does not necessarily mean lighter in weight, unless you are also equating denser with thinner as you seem to suggest regarding a smaller ring pack. I was not touting one piston design over another as I agree that conventional wisdom still holds that "forged" is stronger and more durable than "cast" whether pistons, rods or crankshafts. However, if there is one historical disadvantage to forged pistons, aside from cost, it is a greater likelihood toward exhibiting piston slap. This, as you note, is not a considerable impediment to their use. Reference to hypereutectic cast pistons was only in connection to the cylinder wall clearance chart and the fact that they are an alternative in situations seeking minimal piston wall clearances favoring longevity versus all-out performance on an otherwise stock engine. FWIW, I have not had any problems with forged and even the lowly cast variety of pistons in M10 and M30 engines that have seen considerable use for thirty plus years.

A chart offered by an engine builder with similar initials seems to suggest a different conclusion regarding operating cylinder temperatures and optimized cylinder wall clearances. This linked chart: https://metricmechanic.com/wp-content/uploads/2016/07/Piston-Clearance-Chart.pdf indicates tighter (rather than looser) cylinder wall clearance for the inner cylinders (nos. 2 and 3) possibly suggesting "cooler" operating temperatures and less expansion. Whether these operating temperature conclusions or assumptions are applicable to all E10 engines across the board (with or without forged pistons), or they are only applicable to that builder's end-product is unknown. A quick look at a typical head gasket supports the notion that the factory considered and addressed cylinder temperature variation when designing the cylinder head water jackets, including location and size of the various cylinder head coolant passages. It bears mentioning that the temperature variations are somewhat theoretical considering that different engines with different fuel delivery systems and operating conditions and thus operational ranges, will produce differing temperatures. Setting that aside, piston design and manufacture has not remained completely static since original M10 production. For all of the supposed benefits offered by forged pistons, they can carry expansion and weight disadvantages. Conversely, although not as strong as forged, cast hypereutectic pistons suffer less weight and expansion issues, and are less likely to suffer from piston slapping.

There have been plenty of posts regarding factory-supplied tools, e.g., https://www.bmw2002faq.com/forums/topic/59301-heyco-300-waterpump-pliers/ Somewhat akin to Conserve's experience, the water pump pliers are most useful for slipping and ultimately pinching a user's skin and drawing blood. The parts catalog omitted inclusion of a tetanus shot, although maybe that was an aftermarket dealer option.?

No treasure map required. If you believe what is printed, Mobil1 Syn Gear Lube LS 75W90 has a GL5 rating, but allegedly is safe and even protects yellow metals. That said, there are plenty of other alternatives, from Amsoil, Redline and even the ubiquitous Staylube. Amsoil: " Less Slippery Low Sulfur Formula Compatible With Brass Synchronizers " ]

Ever heard of a wind-driven water pump?

elliptical offset nuts, ✓ centerlock nuts, toplock nuts and partially depitched (Philidas) nuts

giubo ✓ ?

?

I am uncertain exactly what type of locking "clip" is used, but I see single and double row timing chains with masterlinks advertised for sale: https://www.autohausaz.com/bmw-auto-parts/bmw-timing_chain-replacement.html Iwisketten (Iwis) Timing Chain; Single Row with Master Link P/N: 11311716986 Iwisketten (Iwis) Cross References: 11311265040 11311716987 50026987G68WN12 W01331625464 BMW 535i, 528i, 318i, 635CSi, 320i, 735i, 633CSi, 533i, 535is, 733i & more Iwisketten (Iwis) Timing Chain; Double Row; With Master Link P/N: 11310731105 Iwisketten (Iwis) Cross References: 11310731105L W01331622036 BMW 528i, 530i, 2002, 320i, 633CSi, 2002tii, 3.0CS, 733i, 2002 Turbo, 1600 & more

And then . . . there may be exceptions. https://www.bmw2002faq.com/forums/topic/243977-76-bmw-2002-stunning-ground-up-restoration/?tab=comments#comment-1347329

Beg to differ Mike. I think you may have mis-typed. The above may be generally true for most (but not all) Bosch blue coils. Bosch red coils, and OEM black coils employed external ballast resistors.

"Newer" generally means better, but I can think of at least one venerable product you might consider. About a thousand years ago, before mechanics could spell "disposable gloves," I grabbed an old standby collecting dust in my garage to reassemble a Getrag 4-speed. The Sony Trinitron is no longer around but the box is still together and working fine. Back then, I believe the gooey elixir called Aviation Form-A-Gasket came in a metal container. These products may be worth noting. No personal experience, but they seem to fit many of your needs.

As one of many posts on this subject, try: https://www.bmw2002faq.com/articles.html/technical-articles/body-and-interior/odometer-repair-r42/

For most of us, the air filter and its housing is a necessary airflow "restriction." Smoothing airflow to avoid sharp directional transitions clearly could not hurt in aiding free flow. Numerous examples abound of air filter housings that incorporate this concept. However, as MikeA notes, there are many other airflow restrictions that complicate things for a street car, including throttle plates and manifold and port designs. And . . . it has been argued that for some applications, turbulence may be both a good and bad thing. This, of course, raises the numerous par-baked arguments concerning so-called vortex generators. ?

All of the suggestions made in this thread are plausible, but hardly complete. Consider how many times the window has been left down to allow cabin access for loading and unloading of: packages, tools, tables, welding tanks, ski equipment, medical supplies, construction equipment, outboard motors, floor tiles, drive line parts, parachute, landing gear or other items better suited for a truck bed. How about any front and rear seat removal and re-installation? Has someone reached through the window area to turn the ignition key, unlock the steering, adjust the radio, move a chair back, move gear shift or grab a baby? Ever clean the inside glass, especially the easily accessed rear glass? Or try to ensure that a rear quarter window hasp is actually in the closed position? Add a rhinestone, buckle, ring, squeegee or zipper and voila - instant character. While the A pillar generally gets the shoulder treatment when pushing the car forward, the B pillar is clearly the choice of hands (and items they might carry or wear) when pushing the vehicle rearward.