Namerow

If you're going to install new seat covers, there's an incentive for replacing the foam at the same time. When rebuilding the bottom cushions for the seats from my 70 Z, I discovered that 'skirt' of the replacement bottom seat covers was considerably 'taller' than the stock seat covers (my replacement covers were manufactured by Distinctive Industries). I chose not to replace my original foams (they were in pretty good shape), so I ended up having to shim the underside of the bottom cushion foam with about an inch of added-in foam sheet so that the cushion would adequately fill the new seat cover. This was the only way I could bring the lower hems of the covers into proper alignment with retaining tangs on the seat frame tubes.

Only one U-joint in the 510's steering shaft?

You've managed to achieve a really nice stance for the car. The match-up of tire size/profile to wheel diameter/offset relative to the wheel openings looks spot-on. I really like those wheels, too. A refreshing change from Panasports.

The designs of the front insulator and the mustache bar bushings were tuned to isolate the chassis from the gear and drivetrain noise/vibration 'collected' by the diff casing. It will be interesting to see whether stuffing the front insulator's cavity with heater hose really does have an adverse effect in the form of gear howl getting into the cabin. Let us know what you discover. If a problem does set up, you might be able substitute something softer than heater hose that would be better able to meet the dual requirements of noise isolation and clunk elimination.

Check the U-joint. Interesting that Nissan offered u-joint rebuild parts for the 510, but did not offer them for the 240Z. If the 510 parts are NLA at Nissan, it's possible that ez-to-source Kawasaki ATV halfshaft u-joints that fit the S30 will also work for the 510. $30 complete (spider, cups, bearing needles, seals, circlips, and grease fiiting) and relatively easy to install. A 64th inch of slop in the u-joint will be greatly amplified at the steering wheel and makes straight-ahead highway driving 'more involving'.

I've now received my rebuild kit from MSA and I've taken a few pictures for reference. As you'll see, the three seals in my kit are all different -- two are lip seals, the third is an O-ring. One of the lip seals (the one on the left in my pix) is lipped on both the inner and outer circumference. The other (in the centre) is lipped on the outer circumference only. Both are about the same in height. The seal on the left with the inner & outer lips is pretty clearly Item 5 in FSM diagram BR-8. By default, that means that the single-lip seal in the centre has to be Item 3. Obviously, placing them in the right locations and getting each one correctly oriented (lips face inboard, flat sides face outboard) is going to be critical to making the valve work properly. I continue to be confused by the way the upper seal (Item 3) is depicted in FSM diagram BR-9. The shape of the seal's section on the left makes sense. However, the sectional shape on the right looks like a completely different seal! Am I missing something here?

Sorry, but what kind of car is this?

The FSM diagram that Zedhead posted is from the 280Z manual, so it's possible that the bolts used for the 240 were stepped rather than tapered. The fact that Nissan's engineers chose to use a stepped/tapered design rather than a plain old bolt says to me that there's a lot more going on here, NVH-wise, than first meets the eye. The m-bar 'bolts' are more like pins with threaded ends. It's an expensive design (compared to a bolt), so it was used for a reason (just like those rubber-ribbed end-washers) It's a little hard to tell from the FSM sectional diagram, but it appears that only the upper 'special washer' (as the parts manual calls them) bears directly on the shoulder of the pin in the radial direction. If I'm right, it means that the 'eye' of the m-bar is solidly located (in the radial direction) only at the top, while the bottom 'floats' (in the radial direction) on the rubber of the lower special washer. It also means that the thick rubber of the big bushing only comes into play (in the radial direction) when the m-bar deflects far enough to bring the inner metal sleeve of the bushing into contact with the pin. My guess is that this is all about isolating high-frequency differential/gear noise from the chassis under light-load/cruise conditions (via the ribbed special washer), with the bushing only coming into play (laterally) to isolate against cornering-induced vibration (when the diff loads up laterally against the pins). Kind of a two-step isolator for lateral loads. In the vertical plane, the special washers and the bushing look they work in unison as a two-mode isolator (that is, they're both at work simultaneously, in series, but have different stiffnesses and natural frequencies and therefore serve to isolate different vibrational frequencies). Another interesting point (to me, anyway): the FSM refers to the m-bar as a 'transverse leaf spring'. That suggests that the bar itself is being used as a spring. The m-bar is only truly flexible in the fore-aft direction, so perhaps it comes into play when the diff is subjected to braking loads. One final thought: All of this suggests to me that it's not a good idea to jack up the rear of the car using the diff casing.

here you go...

from Wikipedia... Hydrogenated nitrile butadiene rubber (HNBR) is widely known for its physical strength and retention of properties after long-term exposure to heat, oil and chemicals. Trade names include Zhanber (Lianda Corporation), Therban (Arlanxeo [5]) and Zetpol (Zeon Chemical). Depending on filler selection and loading, HNBR compounds typically have tensile strengths of 20–31 MPa when measured at 23 °C. Compounding techniques allow for HNBR to be used over a broad temperature range, -40 °C to 165 °C, with minimal degradation over long periods of time. As a group, HNBR elastomers have excellent resistance to common automotive fluids (e.g., engine oil, coolant, fuel, etc.) and many industrial chemicals. The unique properties and higher temperature rating attributed to HNBR when compared to NBR has resulted in wide adoption of HNBR in automotive, industrial, and assorted, performance-demanding applications. On a volume basis, the automotive market is the largest consumer, using HNBR for a host of dynamic and static seals, hoses, and belts. HNBR has also been widely employed in industrial sealing for oil field exploration and processing, as well as rolls for steel and paper mills.

Happy hunting, CO! Still hoping that someone can post those three measurements for the Nissan OE bushing so that we've got a reference point to work from...

Thinking out loud here... Has anyone ever checked to see whether any of the other, still-available Nissan steel-sleeved isolator bushings could be adapted to the moustache bar? The make-or-break dimension would be the outside diameter of the external sleeve, which would need to be pretty much spot-on. Length could be trimmed to suit (or two under-length bushes could be stacked and then cut to length). Inside diameter of the inner sleeve would only need to be within 10%, I would think (could be sleeved up, but not the opposite). The S30 bushes that come to mind are the spindle pin bushes, the front control arm inboard pivot, and the transmission mount. I have all three on hand and can provide their measurements. What I don't have are the the three key dimensions for the moustache bar bushings: Length Outside dia. of the outer sleeve Inside dia. of the inner sleeve Anybody? Even if none of the other S30 bushes will work, there are hundreds of steel-sleeved bushings out there on the market. Captain Obvious has shown an appetite for looking through online parts catalogs, so with the right dimensions in hand, maybe we (I mean, Captain Obvious ) can find a suitable replacement for the NLA Nissan parts. As for the wavy-shaped rubber end washers, I think suitable facsimiles could be cobbled up pretty easily from thick rubber washers, using a small-diameter sanding drum in a Dremel. Fiddly work, but would probably only take 30 minutes to make four. An alternative fab strategy would be to drill a set of radial holes through a double-thickness rubber washer and then slice it in half, creating a pair of the desired washers in the process. The biggest challenge here would be finding the right rubber washer to start with.

Grannyknot's other nickname is, 'Teddy The Torch'.

Sometimes the obvious escapes us all . Now that you know the 'secret', it should be much easier. You'll need to use vise-grips to get a firm hold on the free clip so that you can pull against the strap tension and navigate the pins into their holes in the seat frame tube. When it comes to making the cuts in the strapping, this is a classic case of, 'measure twice, cut once'. One mistake and you'll be feeding more $$ into the coffers of MSA to order another strapping kit.

hmmm... I don't think you're going to like the results if you replace the straps with a metal plate. At least, not unless all the roads where you live are billiard-table smooth. The strapping kit isn't that hard to install. The three fore-aft straps all get cut to the same length. The MSA kit provides you with the details and includes enough webbing to do both seats with about 6" left over (which means there's no forgiveness if you screw up on any of your cuts). When cut to the correct length, you don't really have to stretch the straps very much to seat the end clips into the seat frame. I found the most difficult step was punching holes through the straps for the rivets to pass through. That rubberized webbing is tough! When you're installing the end clips on each strap, make sure they're both facing the same way up before you install the rivets (it's no fun trying to remove the rivets to fix a mistake made here). If you work at it methodically, you should be able to complete the strapping job for both seats in a morning or an afternoon.