1973 Rebuild

[Matthew Abate]

Very pretty. 

Compared to the many photos I've seen in various L engine rebuild threads, the ones shown here seem to capture 'Nissan Engine Blue' the best.  It's more of an 'industrial' blue than an 'automotive' blue.

Also: Those may be the first photos I've ever seen (anywhere) that document the installation of the crankcase vent screen inside the block casting.

Thanks!

An important side note on that screen topic: I may have mentioned before that I picked up a brand new screen from Courtesy Parts. Well it turns out that the guy I talked to was incorrect when he told me that the L24 in a 1984 Maxima has the same screen as a 1983 280ZX Turbo. The Maxima screen is smaller and trapezoidal whereas the ZX screen is rectangular. So we restored the ZX screen, which was not easy given the 34 years worth of baked in sludge.

Maxima

ZX

[Takhli]

2 hours ago, Namerow said:

Very pretty. 

Compared to the many photos I've seen in various L engine rebuild threads, the ones shown here seem to capture 'Nissan Engine Blue' the best.  It's more of an 'industrial' blue than an 'automotive' blue.

Also: Those may be the first photos I've ever seen (anywhere) that document the installation of the crankcase vent screen inside the block casting.

Thank you, Namerow.

Since the screen installation isn't documented well, I suppose I should also follow with the cleaning method I used. Its not rocket science but what the heck... When parts aren't available we need anything to save a few bucks and share what we learn. 

Note: The Factory Repair Manual provides neither a torque value for the retaining screws nor a method to clean the screen.

First, the screws holding the baffle in place should be hard to remove. The screw heads accept a #3 Philips drive tip and a little gentle persuasion with a hammer and impact driver gets them out easily but Go easy with the hammer! On one of our engines these screws were also covered in an epoxy for a bit of extra security but I'm not certain that is needed if the screws are installed correctly.

Second comes the cleaning. NOTE: The wire wrapped around the folded wire-mesh may be bonded to the screen with something like JB Weld epoxy, or it may be micro-welded - I've seen both methods. The micro-welded part does not come apart easily without damaging the wire-mesh, so a new part should be considered if available.

If the wire mesh has never been removed from a high-mileage engine, expect the screen material to be covered in a baked on hard varnish. For me, the best way to get this off is a very long soak in carburetor cleaner. Drop the screen in the cleaner and forget it for a week. I lucked out and have the screen that used epoxy. When it comes out of the cleaner the bond should be loose enough to separate the wire from the mesh. That's a good thing because you can now unfold the wire-mesh and really inspect it for damage and debris. Rinse the mesh in hot soapy water then rinse it again with a spray carburetor or brake cleaner.

Next, re-fold the mesh into its original shape making sure that the folded screen retains the original shape and fits into the cavity properly. Use JB Weld to rebond the retaining wire around the mesh and let the JB Weld cure.

The threaded holes for the retaining baffle, as well as the screws themselves, must be clean and dry before installing the screws. I clean the hols with a rifle cleaning brush when I clean the block but, if you're not doing a rebuild that requires machine shop work, the threads can be cleaned with spray carb or brake cleaner. When the breather baffle-retainer goes back into the block, apply Red Lock-tite to the screw threads and torque them securely. 

[Matthew Abate]

A couple of updates:

Painted one of the oil pans

Looks pretty great for rattle can in a garage. We're going to use the turbo pan because the non-turbo one we have is way to rusted and I am not dropping $500 plus shipping on an Arizona Z Car cast aluminum oil pan, no matter how rad it might be. We'll plug the tube with a nice looking plug until I think of a use for it (catch can return?).

---

I also decided it's time to sign the DNR on my L24.

I feel a teensy bit uneasy about this. I had intended to keep it intact until after the cars was driving under it's own power and then figure out what to do with it, but we need to scavenge parts because both my furnace and water heater failed in December, and I have house insurance and property taxes and federal taxes all hitting at the same time, so time to say goodbye.

Bummer.

---

However!

In the process of disassembling the manifolds and such in order to get the various parts we need to make the L28 work, I realized I needed to get educated on some details about the carburetor systems for each year Zs didn't have FI. As many of you probably already know, the 260Z intake manifold we have in Arizona has square attachment points and does not route water into the carbs, the same as the early, 4-screw SU round tops. The manifold on my E88 head above has 6-sided attachment points with water routed through the 3-screw SU round tops I have. I can't speak to the 73 manifold or the flat tops since I don't have any.

 

Luckily, I picked up a set of early 240Z SU round tops at the Imports show in Pennsylvania last year for $60. At least I think they are for a Z because the dude who sold them to me said they were and threw in a voltage regulator identical to the one in my car, but who knows. They could be off something British.

So it's all going in the mail to AZ, along with various heater tubes and the stuff that started this whole process in the first place, and we will work it out later.

Edited January 31, 2017 by Matthew Abate

[Captain Obvious]

All of the carbs 70 through 74 use the same mounting bolt geometry. The holes are in the same location on all of them, meaning that any carb will bolt up to any manifold. They changed the thickness of the phenolic spacers at times (70-72 are thicker than 73-74), and hence, the stud length to compensate. But all of the holes and studs are a square pattern and are in the same locations.

They changed the water routing scheme over the years as well:

70 and 71 used the square mounting face (pic of the carbs in the bag), and they did not route any water into the carbs.
72 used the six sided mounting face shape you have pictured above with the holes in the phenolic. They routed water through the holes and into the carbs.
73 and 74 also used the six sided mounting face, and were capable of routing water through the spacer and into the carbs, but they did not do that. Instead, they used a solid phenolic spacer without coolant holes and ran a complete additional independent coolant stream to the carbs. This coolant path is in addition to the one that ran through the intake manifolds.

So about your statement here:

3 hours ago, Matthew Abate said:

As many of you probably already know, the 260Z intake manifold we have in Arizona has square attachment points and does not route water into the carbs

The 260 intake manifolds (the N36's) used a square attachment points (as every year manifold did), but they had the six sided face. It's been too long and I don't remember if they put water holes in the N36 manifolds on the carb mounting faces. I know the phenolic spacers are solid, but I don't remember if they bothered to put the holes in the manifolds themselves. Have you got any pics of the carb mounting faces of the N36's with the spacer removed?

[Matthew Abate]

The 260 intake manifolds (the N36's) used a square attachment points (as every year manifold did), but they had the six sided face. It's been too long and I don't remember if they put water holes in the N36 manifolds on the carb mounting faces. I know the phenolic spacers are solid, but I don't remember if they bothered to put the holes in the manifolds themselves. Have you got any pics of the carb mounting faces of the N36's with the spacer removed?

I realize the bolt pattern is the same on all of them, but the surface they mount to is not six sided on the N36. There is no water routing, so we'll probably use the early-style round tops unless there is an advantage to using the ones with the water channels even though they wouldn't be used.

In all of my research on the N36 manifold I never saw anyone discuss the lack of water circulating through the carbs and whether or not the impact of that offset the advantages of the larger intake.

I assume Nissan was trying to make these things perform as well as possible under the legal circumstances in the US that year, so the potential is there and we can make it work out. Just need to look into it deeper.

More photos if you want to see the rest of it:

[Captain Obvious]

Thanks for the pics. It's been so long since I've seen them from that angle that I didn't remember the details of the face shape or the holes.

I can tell you with certainty however, that the phenolic spacer plates for 73 and 74 have the six sided shape like the ones from your 72. The differences are that the 72's have coolant holes and are thicker. With the flat top carbs of 73-74, they used thinner spacers. Presumably to account for increased girth of the flat top carbs and/or the accompanying air cleaner.

The mounting faces of the 73-74 carbs have coolant holes on the mounting face, but they didn't use them. They drilled and tapped holes underneath for metal hose nipples instead. The whole thing with the carb heating seems like they kept changing it and never got it all worked out. Then in 75, they went to EFI.

Also, unrelated to the above, but if you're interested in amassing info about the early carbs... I haven't researched it in depth, but believe the 70-71's were the four screw round tops, and the 72's were the three screws. Makes it easier to identify quickly from the top without having to see the shape of the mounting flange.

[Matthew Abate]

The mounting faces of the 73-74 carbs have coolant holes on the mounting face, but they didn't use them. They drilled and tapped holes underneath for metal hose nipples instead. The whole thing with the carb heating seems like they kept changing it and never got it all worked out. Then in 75, they went to EFI.

I was wondering what the little tubes on the N36 manifold we for. I'm guessing there are no holes to connect them too on the round tops, and I don't want to be drilling them out.

[Bonzi Lon]

On my 73 with a set of 4 screw carbs and the N36 manifold, the little tube is connected to my vacuume advance on the dizzy.

 

Bonzi Lon

[Captain Obvious]

I think we're talking about different tubes. The 73-74 tubes I was referring to are screwed into the bottoms of the carbs, not the intake manifolds. The faces of the 73-74 carbs have these trapezoidal shaped holes for water passageways that they could have used to pass water through the spacer and into the carbs (like the 72's), but they didn't. They chose to plug those holes with rubber plugs and drill and tap new holes into the bottom of the carbs instead. Then they screwed metal nipples into the bottoms of the carbs for coolant inlet and outlet. Here's a plc with a good view of the coolant tubes and the faces of the flat tops:

The holes I think you're talking about are on the intake manifolds - Four holes on the front one, and two on the rear? Four of those holes (the rearmost four threaded ones) are to mount the idle bypass tube for the 73-74 tubes. Note that one of yours has the twisted off remains of one of the idle tube retaining screws broken off stuck in the hole. Doesn't affect you, but that's what that is.

The other two holes (at the front of the front manifold) with the vacuum nipples pressed in are for constant vacuum sources and were not used for distributor vacuum advance. Probably academic, but those vacuum holes were originally used for a) the throttle opener device, and 2) the anti-backfire valve. The vacuum advance should come off a ported source on the carb bodies, not the intake manifolds.

Here's a crowded shot of a mostly stock 260. You can see the mounting screws for the idle screw, and the bundle of snakes of other vacuum lines, etc:

As for what to do with the holes... I believe the holes for the idle tube are blind, and you can just leave them open. The other holes with the vacuum nipples, you'll have to do something with. I don't know how much emissions stuff you're planning to run, but you might need one of them for a throttle opener system? Other one just cap? Or get elegant and pull the tube out and weld the holes shut?

Edited February 1, 2017 by Captain Obvious
I talk to much.

[Matthew Abate]

@/profile/23457-captain-obvious/" id="ips_uid_3816_8" rel="" style="text-decoration: none;" title="Go to Captain Obvious's profile">Captain Obvious Dude. Super helpful Thanks!

So while I figure all that out, here is an update:

Ready for rods and pistons!

Edited February 2, 2017 by Matthew Abate

[Matthew Abate]

Thinking of going in this direction with my paint:

Lamborghini Huracan Spyder in Arancio Borealis 4-layer paint ($267,545 MSRP)

[Takhli]

As you see above, I've done some assembly of Matt's short-block. Those with experience in building engines please excuse the detail but for the rest of you, following is the way it was done:

Before beginning, I wash up thouroughly and take extra care to get my hands really clean. Also, I never build an engine while wearing gloves of any kind. That may seem odd to some but I like to be able to feel my parts as they go together and wearing gloves prevents feeling any grit or the tiniest particals that may find their way onto my clean engine parts. Gloves can also scratch the fine coating on bearing inserts.

Next, comes cleaning my work area. I do not use compressed air in the area near my parts, but a dust pan and wisk boom to pick up the crud. Once the work area is clean comes setting up my organization and cleaning the engine parts. Acetone and dust free cloth are all I use for bare metal engine parts, and GM Engine Oil Supplement is what I use for assembly.

I set all my parts and reference material in a clean dry location close to my assmbly area, then I begin an inspection of parts, regardless of them being used, recondioned, or new. Even if I've done an inspection previously. I also read my instructions several times before I begin.

 

On the six-cylinder L-series engines it's important to note that the number 1 and number 7 bearing inserts are wider than the others.

No so important to these engines is the small additional hole in the block insert that feeds the timing chain oiler. Our set of bearings came with this extra little hole in both the wider block inserts so I only had to make certain the inserts were in the proper bearing saddles.

You may think that because you recieve parts in sealed packages they would be clean enough to install, straight away...  Not so!  The next few photos show the fine grit that came off the bearings and our main bearing caps with a simple wipe with acetone.

Look closely and you will see that there is still residue on the towel after three passes with acetone wetted cloth. A word to the wise... Your parts cannot be too clean!

 

Cleaning includes deburring the caps and making certain the flats on each boss are in fact true. Lay 400 grit wet-dry paper paper saturated in light oil on the CLEAN work bench and dress the flat, to gently remove any burrs that may have arisen during the block's stay at the machine shop. Then use a small fine file to dress the chamffer on the cap.

 When done, I clean the block saddles with acetone.

 

Stay tuned... There's more to come.