NewZed

It's not really a bypass hose. Looks like somebody removed your air regulator and the heating plate that sits underneath it and just connected the tube ends. The AAR is shown on page EF-5, 7 and 17 and other places. The proper hose routing is shown on EM-4. Attached a picture. I can't remember if that coolant flow helps avoid water pump cavitation or not. There are discussions about it out there. Replacing the AAR and plate would be a good idea, it's a convenient mechanism. Could also be that everything's there but somebody couldn't get there fat fingers in to the tiny places to fix a leak so just bypassed it.. Anyway the coolant is supposed to flow underneath the AAR.

One of those triangulated aftermarket strut tower braces might help you on the top of the firewall. TC rods might help on the front of the rail, locating it to the transverse link and bottom of the strut. http://www.racetep.com/automaker/datsun-z/z-car-front-ultimate-strut-tower-brace.html

You should ask "why?". Here's a good swap thread - http://forums.hybridz.org/topic/95965-lst56240z-project-mentor-wanted/

Why would you remove general car function wiring to do an engine and engine management system swap? You're getting distracted. Wires provide power or control signals for functions. Focus on the functions.

Hard to tell what the timing is on your description but if "recently" means essentially right after you installed the new MC, then you probably have the rod from the booster to the MC adjusted too long. It closes the return hole for the fluid, and the fluid heats up and expands in the lines, actuating the brakes. It's actually a fairly common problem. You may not have adjusted the rod when youdid the swap but the new MC might have its seat for the rod closer than the old one. If "recently" meant months after the new MC was installed and it's been fine for many miles, then never mind the above.

The two red things don't go together.

I think so. See attached. You do realize that many people never get their diffs back together noise-free? At least that's what I've seen in the various internet stories. You might be trading bearing noise for ring and pinion noise. Beware. Probably a fun project but a used factory-assembled junkyard diff is probably the most effective, inexpensive, way to solve your problem. Good luck.

These seem to be them - http://www.courtesyparts.com/nissan/300zx/3812006p10/1986-year/base-trim/3-0l-v6-gas-engine/universals-and-rear-axle-cat/differential-scat/?part_name=pinion-bearings

The propeller shaft doesn't care what the ratio is. Spin and count will get you close on the ratio. Finding the stamped tooth count numbers on the ring gear will let you do some division. Are you sure that you want to start this swap? If you have a car that runs you might want to keep it that way. You're going to have a tough go, at your current question rate.

The bolt pattern looks like an R230. Here's a pretty good comparison picture from the back, Post #6. http://www.mgexp.com/phorum/read.php?40,1106874

This guy just keeps building his inventory of Z stuff - https://zcardepot.com/product/search?search=battery

Owen, maybe? http://forums.hybridz.org/topic/78000-71-240z-roller-for-sale/?do=findComment&comment=741673

Looks like he had work done at M and R. They might recognize it. Amateur sleuthing. http://www.mandrauto.com/

I dug a little deeper around the web and it looks like only the Mitsubishi version is available. Amazon only has three types. One page has answers from Precision saying Mitsu only, the other two have MITZ in the part number. Odd. Is there a Brute Force brand diff? Can't find one described anywhere.

Did you mean Power Brute, not Brute Force? Don't know much about the aftermarket products. Seems kind of inexpensive. They might have gone overseas with their manufacturing. If Amazon can hold inventory for them, they can't be expensive, wholesale. "Ships from and sold by Amazon.com." https://www.amazon.com/Precision-Gear-LOM83-Limited-Differential/dp/B005HJQRQK Here are some CLSD's if you do go used again. Should bolt right in with no flange swap. You could still have the CV shaft problem though. https://whiteheadperformance.com/product-category/240z-260z-280z-70-78/240z-280z-diff-differential-axles-lsd/

Here's an odd thought - disconnect the CV's at the diff and let the engine spin it while it's on the stands. The load will be considerably reduced but it will remove any CV-caused noise from the situation. Or remove one CV at a time and do the same to see if one side is tight. If you get both CV's removed and it's still whining, it's probably the pinion bearing. The whine seems too high frequency and too "shallow" to be the typical gear whine.

This is incredibly old knowledge. You probably should go with the V8 swap. Go with what you know, there's a lot of new stuff to learn if you go with the L6 engine. EFI, overhead cam, the inherent weaknesses of the engine design. You'd break a lot of parts trying to work with the L6.

Don't overlook the diff mounts. Urethane will transmit more nose than rubber. The Z car diffs are inherently whiny. A perfectly fine diff can sound terrible if you everything that's going on in there.

The rear main seal can be changed in a few hours from underneath. It's a one-piece round seal that presses in around the crankshaft. Raise car, drop transmission, remove flywheel, change seal. Of course, while it's apart there are other things that would make sense to do. But it doesn't seem like you know how the engine parts fit together. Hard to put a plan together if you don't. Just saying, these aren't domestic V8's. A cheap way to get a clean running car back on the road might be to just find a used L6, swap it in, and drive it while you think. The engines are often in great shape even after 100,000 miles.

Here's some good reading. Most of the good discussions happened before you or I joined the forum. Many of these guys have moved on and don't post anymore. Read enough though, and you'll see who makes sense and who's just in the headers and high CR camp. http://forums.hybridz.org/topic/75978-giving-more-hp-on-a-na/ http://forums.hybridz.org/topic/56128-my-wicked-engine-rebuild-plans-are-progressing-lots-of-new-modspics/ http://forums.hybridz.org/topic/95316-braaps-l6-efi-induction-advice-and-tips/ http://forums.hybridz.org/topic/50208-the-ultimate-l28et-guidewhat-you-need-for-350whp/

Actually, a lot of the V8 power mods are just hype also. The pushback you're getting here is because you're over-simplifying. There are lists of parts to assemble out there, some on Hybridz, some on other sites. Nobody's going to retype something that's already out there. Search "N42 flat tops compression ratio" and you'll get a ton of threads to read through. Find one that looks interesting and retype it, to discuss.. Without actually measuring power or track times, you won't know if they work or not. A loud exhaust will probably feel like 20 HP. At the end of the thread though, you'll have some parts you bolted together and it will either feel more powerful or you'll feel like you should have gone with a V8. Besides that, it's not apparent that you're actually using or really considering any of the suggestions. There's a whole long list of how the EFI system works and which parts can be modified for power n that FAQ page I suggested. does't seem like you've even glanced at it. BRAAP's opus. lol

I might be wrong on 1974. Here are some links to use to see if the desired parts are there. Looks like they changed some things over the years. http://www.carpartsmanual.com/datsun/Z-1969-1978/electrical/distributor/260z Note 7412 is the change point - http://www.carpartsmanual.com/datsun/Z-1969-1978/electrical/distributor/280z

74-77 will probably work also. Electronic ignition, with the pickup coils on the breaker plate..

Never mind. I linked you to your own thread. You should just follow JMortensen's advice. He has dug deep in to this subject.

That's the top of the two-piece plate used with an automatic transmission. The manual transmission plates are one piece, like in your JDM link. You should be able to find a used one pretty easily. All of the manual transmission engines came with one. http://www.carpartsmanual.com/datsun/Z-1969-1978/engine-280z/cylinder-block