'73 240z - Project Build

[datsunfreak]

On 10/27/2023 at 5:57 PM, demo243 said:

They are definitely cool little buzzy engines. Aftermarket support especially in the US isn’t huge… but it’s there.

 

One nice thing about these is that unlike the other engines Nissan makes, the FWD and RWD versions are almost identical. And since the FWD version was sold here, you can get things like gaskets, timing belts, etc a little easier. 

[demo243]

Not much to update-

 

Took it for a cruise this morning to the local coffee shop for fun. 
 

Always laugh at these size comparisons -

 

 

 

Swapped the “winter wheels” on the 510 to store the good tires in the warm basement- had to grab a shot of both of them-

 

 

 

Haven’t ordered any parts yet … but Black Friday sales are dropping so stuff will be ordered soon!

 

Trying to decide if I want to just replace the inner/outer tie rods… or just do the full Apex/T3 rack set up- leaning toward the rack set up and I’ll keep the stock one as a spare… Might as well the TC rods then too. Debating on strut tower braces too even though I think they are basically for show… I remember reading 510s don’t need em, but don’t know about the Z… also read that they can do more damage in a small hit by messing up both sides… tbd. --- Nevermind... gonna strike the TC rods and strut braces for now... $$$ adding up to be too much.

 

Waiting for a BC coilover sale hopefully- got a full set of spare donor struck housings now.

 

Gonna grab some odds and ends from Z car depot hopefully- ignition switch, H4 headlight bulbs and LED bulbs (liked the LEDs on the rear so much I’m gonna do em all around), headlight covers - keep going back and forth on these but I think they really complete the car and give it a sleaker racier look.

 

Finally gotta decide on carbs- the siren song of Moto carbs (Mikuni HSRs) keeps calling but the $$$ just aren’t there for that so OER it will be - 45s with 36mm chokes- just need to decide Weber or Oer jets- which Weber is probably the smarter choice…

 

Was gonna get some skillard door cards and center consol but then remembered about the steering shake so if I buy a rack the skillard stuff is out….

Edited November 17, 2023 by demo243

[demo243]

Datsun season has come to an end for me….

 

Swapped the ZX “winter” wheels back on for storage and put the nice sticky tires in the basement to keep ‘em warm.

 

I’ve though a few times as to whether I should have gone with silver wheels, but throwing these back on confirms that car looks much more badass on dark ones.

 

 

I didn’t realize it when I took em off, but looks like one of the POs put the ZX wheels on with acorn nuts…. Sketchy!!!

 

They are back one for now… but it’s time to find a new set of shoulder season/winter storage wheels - ideally a Rota or Konig or something with a 3-500 tread wear tire on it I won’t mind leaving in the garage all winter but can still drive on to sneak a few more Z days in when I can.

[datzenmike]

On 10/27/2023 at 6:41 AM, demo243 said:

I do have a wideband.

 

What’s the throat size on those R1s?
 

I’m still dreaming about Moto carbs. Was reading about the Mikuni rs40s and it sounds like they have issues with the slides sticking under vacuum. Which is a bummer. The fact that they come in a rack of 4 should in theory make it easier to make a rack of 6. I just figure if 2 HSR 45s and fuel an l28 then 6 HSR42s will be too much on the stock engine

 

 

The home made intake and horns are 1 1/2" pipe and they just fit. So just under 38mm? When honking they drown out the exhaust and everything else. Makes you roll the window down.

 

 

 

 

[demo243]

Just some light reading...

 

I was actually hoping for more info from these, but they don't mean much until I have carbs in hand... And the Sudco book was probably not worth the money. Every Harley site said to get it, as it was better then the Mikuni manual - but they are practically the same and the Mikuni one has more info and is free. 

I guess I should add some more info here- 

 

I was sold on OER carbs - but then couldn't decide if OER or Weber jets were the better way to go... In digging for a few weeks I have read they are the best carb ever... and they are cheap cast junk... and there is hardly any info out there on them other then an old SK manual. I also emailed them to both their OER Japan email and their OER outside of Japan distributor but no response from either... which doesn't help their case.  I also messaged a guy in Japan who is running 6 HSR 45s on a very built engine and he said (translation was an issue...) that he could not figure out the right jetting on OERs and that the HSRs were better,

So I am back on the Mikuni HSR train... The best thing to do would be to buy 2 HSR45s and slap em on the SU manifold. But where is the fun in that?!? The siren song of ITBs sings to me. 

 

So I am doing my research.... 6 HSRs may be in the future. Still some research to be done. But the big selling point is current and US availability of parts. OER has an unknown future... and even with the weber jets there are a few OER specific parts that could potentially be required. The lack of response- even if unintentional is frustrating. 

 

HSRs are definitely a gamble... and a big one at that... but if they are good they could replace the Mikuni PHHs on my 510. I should probably start on that car since I only need 4 and not 6, and I have a manifold, but I don't want to mess with that car while its in running order.

TBD

 

Edited November 30, 2023 by demo243

[datsunfreak]

18 hours ago, demo243 said:

The best thing to do would be to buy 2 HSR45s and slap em on the SU manifold. But where is the fun in that?!? The siren song of ITBs sings to me. 

 

Well, I mean, the best thing would be to send your SUs to Z Therapy...  😋

 

If you want to be the coolest kid at the Z meet, I do have a single downdraft manifold for it? 😉

[demo243]

24 minutes ago, datsunfreak said:

 

Well, I mean, the best thing would be to send your SUs to Z Therapy...  😋

 

If you want to be the coolest kid at the Z meet, I do have a single downdraft manifold for it? 😉

I would definitely give two HSRs a shot before that- I'd really just rather have a new carb and a fan of Mikunis.

I think a 4 barrel would make me the coolest kid at the Z meet?!? Hahahaha 

 

I found a Facebook post by MikuniOZ the "Official Australian aftermarket Mikuni distributor" that had one of the engines I've seen running HSRs so I have sent them a note to see if I can get any more info.

[demo243]

Just gonna drop this here….

 

 

Im committed now!

[demo243]

Went 1 for 3 on Z projects today... 

 

We had a nice day so I decided to try and get a few things done.

 

First was throwing on the new 1320 "Twin" exit muffler. Should have measured first... but decided to just try, unfortunately both exhaust and muffler pipes are 2.5" so Ill have to bring it to the exhaust shop to get it welded on. 

 

Next was putting a new valve cover on - snagged this one off Facebook powder coated red. Dig the color although the blue block is a bit much... but oh well.



Finally I decided to try and tear down my spare struts to prep them for coil overs. Got a few of them torn down but having some issues with rust on them. Also realized the driver side spare I picked up is probably no good... who ever took it out cut it out and did a hack job... It was dark in when I picked it up so I missed it... bummer... but really don't think its worth running.

 

 

Leaning toward maybe just grabbing T3s Evolved lowers now that thread in the BC coils I picked up on Black Friday sale... unfortunately T3s sale is over now... so Ill hold out and see if they do another winter or Memorial Day sale.

Played around with the Mikunis a little bit too- grabbed my spare KA manifold for the DCOE spacing. Still waiting on the TWM manifold for any real set up for fabrication. 

The idle adjustment knobs are definitely gonna be trouble. 

 

 

Tried hacking off the wire and leaving the "crimp" since it acted as a nice wrench flat... but no luck.

I think what I will have to do - and have seen done - is drill and tap the screw and drill the brass hat and use a set screw to hold it in place. Then I'll add some knurling to the brass hat to help with adjustment. Gonna be tight... but hopefully something I don't need to mess with much... 

Fuel inlets are gonna be tight but I think they'll be ok.
 

[demo243]

Got all 6 mocked up! And started tearing them down to get prepped for the shared throttle shaft. Shaft should be here Wednesday. Plan is to run it through them all and mark the slide mount for each - mostly just for spacing- then I’ll try and use a straight edge to mark a line down the shaft to get them all aligned- or vise versa…

 

Its figuring out the angle offset of the throttle stop/return spring and accelerator pump pins that worries me… but we’ll see

 

 

Also shortened up the idle adjustment- looks like it should work like this, but I will need to drill and tap the brass hat so I can use it as a thumb wheel. Might add a slot to the end for a flat head… but don’t think I can get one up there anyway so probably not.

 

 

This is with no pressure on the slide- so it would likely be threaded in further- although… realistically I only need one adjuster since they are all attached on the same throttle shaft… there is a slight bit of play in the stock throttle shaft/slide linkage so I’ll plan on running them all for minor adjustments at idle.

 

Also ordered up some 5mm Dcoe spacers - I’ll port match the the manifold to those and then I can port the spacers to match the mikuni adapters since the mikuni adapters are slightly oval. This way if I decide to bail on the HSRs the manifold isn’t jacked…

Edited January 1 by demo243

[demo243]

Not much to update - waiting on some metric drill bits and taps and a few other things.

 

Got lucky with the rod I ordered- it seems like it will be almost the perfect length without needing to cut it down.

 

 

Had an “epiphany” about the idle adjusters. They are quite thin- only 5mm so I would need a very small set screw… then I had the idea if I’m going to join the brass hat to the screw body itself why not just expoxy it! Much easier then all the extra drilling and tapping. So I think I’m going to go that route- there isn’t much force needed for them- and realistically I only need one- so I’ll scuff up the mating surfaces and put a little epoxy in there.

 

Also tried to add a brace under the float bowls but that didn’t work… going to use a small piece of angle aluminum along the back of the carb above the float bowl. Kinda like this but I don’t plan to cut as much out to clear the throats

 

 

Ordered up a Lonely Driver throttle arm- finding a nice one for a 10mm shaft is hard… just need to figure out the cable bracket but gonna try and sort something out like this-

 

thinking about the fuel system right now- simplest is to just get some 5/16 brass “T”s and do it that way - but the nice way would be to make a proper extruded fuel rail… tbd.

[demo243]

Back to the drawing board on the brace for the carbs... My fabrication tools and capabilities are just not up to my original plan. I could have made it work, but it just wasn't going to be as clean as I want it to be... Only out $5 and about an hour, so no big deal.

 

 

Ive got another rough idea that involves a 2x6 and a hole saw.... but that is likely to come out rougher then I would like as well... hole saws just don't make clean cuts easily. But I might try it, only a couple bucks for that small piece of aluminum. Also looking into send cut send or a similar site, but need to find a free cad software for that.

The other option would be to run individual pieces between each carb - I guess better then not having a brace at all, but definitely not as stiff as I was hoping for. I mostly want this brace to have another plane of alignment beyond the throttle shaft; this should help ensure that the carbs stay synced together; because if all the slide mounts are in a precise row, if one carb is slightly off angle in the rubber mount then it would likely have a slightly different sync, the downfall of having them all on one shaft. 

[demo243]

R&D continues! Was tied up all weekend, but snuck out this evening for a little bit this evening. 

Here was my inspiration for this round - Bonneville Performance's dual Mikuni kit... ultimately he is one of the big reasons I decided to give this thing a try overall! I figured the partial circle would be much easier fabricate then the notches I tried before.



First I drilled the carb mount holes; then screwed it to a spare 2x6; used a spare piece of metal as a guide to avoid scratching up the angle piece and went to town with the hole saw.

 

 

Came out looking really good!

 

Unfortunately it wasn't all meant to be.... I mixed up some measurements somewhere.... and the clearance holes were slightly off on all but one (I swear I triple checked measurements...) - The good news is my carb mount holes were good.

 

The bad news was as soon as I tightened it down it got all wonky.... 



It seems that I missed an important little detail --- a spacer! I had noticed the small machined section for the screw head- but missed it later on, and missed it in this photo from Bonneville. Here you can see there is a spacer to off set the bracket. 



Overall not a total failure - functioned as a proof of concept; both in the process and that it did stiffen the whole structure up. The next question is whether it is really needed or not - my hope was it would help align the carb bodies and therefor the throttle shaft mounts... but is it worth chasing right now? It really did help it stay together as a "rack" of carbs, but the throttle shaft is not connected and there are no return springs... once those are in place they will hold together better. Not sure if it will make it easier or harder to mount the carbs to the rubber adapters as right now it is quite hard. 

 

I think I am going to work on the throttle shaft next- for that I only really need the carb spacing - the rest will be based off a straight line on the shaft... 

But I am not abandoning the bracket. Next one should be quicker to make. 

 

[demo243]

Had a little bit of time this morning - so I decided to give it one more to. Simplified it a little bit using a bigger whole saw and based the position off the one good one from the last round.

 

Happy enough with the results. It really does stiffen the rack up so I’ll plan on running it as long as it doesn’t mess with the sync of the carbs.  Looked closer at the back plate of the carb and it is definitely not flat, so that was the issue before. Spaced it out with 2 thin washers which seemed to be enough.

 

Next up - throttle shaft. A little worried about being precise enough but going to give it a shot! First priority is the spacing of the threaded slide mounts- then I need to figure out the angle offset of the accelerator and throttle stop/return spring (both of these have a little adjustment so I don’t think I need to be as precise- but will obviously try!)

 

Anyway here is the new brace-

 

 

 

[demo243]

We'll hit a snag on the HSR project

 

 

Going to need a machinists....

 

Tried to drill the throttle shaft for the carb's today but the rods I got are just too hard, drill bits aren't even making a mark... even if I could get one drilled there is no way I would get all 18 done.... I’d be blowing through bits and there is no way it would be accurate enough.

 

Probably not a bad thing… since hopefully they will be more accurate then I could be.

Edited January 13 by demo243

[demo243]

Still chipping away the carbs, but nothing exciting to update there at the moment. 

 

I did pick up another set of wheels for the Z - These will be shoulder season (spring/fall) and winter storage wheels. The deal from Kansei was pretty good so I grabbed em. Tires on the other hand are tougher to come by. But I ended up with some 225/50r15 Kumhos which are a 400 tread wear all season. Should be perfect for my use. Will likely run these for any road trips too since they will definitely handle any unexpected rain better then my Falken 660s. 

 

 

[demo243]

Set up the overflow drain system. I have read you can crimp these off... but that just forces an overflow out of the upper vent, so I will route these out to a small catch can in case of an overflow.

 

 

Trimmed and epoxied idle adjusters. Ultimately I probably won't use these... but they are needed to seal the carb and prevent a vacuum leak. Working on a idle arm to adjust the common shaft all at once. 


Throttle lever mock up - Picked up a Lonely Driver arm and Protunerz cable kit. Made up this bracket quickly. Originally it was more "complex" but decided it wasn't needed. 

 

 

Edited February 20 by demo243

[demo243]

It was a nice warm day up here in the northeast today. Tried to take the Z for a spin… but it had other plans. Pushed it out to a nice puddle under the driver rear tire. I guess the driver rear caliper decided to give out and puke all the brake fluid out….

 

So now I need to make a decision… these rear brake need help because there is an interference between the parking brake and the body… question is what do I want to do long term… and how long are these remain 240sx/280zx calipers going to be around….  So do I just replace this caliper and run the the set up - should probably do new pads and rotors all around … or do I upgrade.
 

The fronts are non vented Toyota calipers - fine for what they are but I planned to eventually replace them. Likely a wilwood kit of some sort- but which , and I’ve heard their rear parking brake leaves a lot to be desired which could be very problematic for me since Massachusetts tests the parking brake- I think it’s rev to 1300 rpm and let out on the clutch and it’s supposed to hold.

 

So hmmm decisions decisions…

[demo243]

Got a little more sorted on the carbs as well.

 

Picked up an adjustment lever from OER to use an idle adjust for the whole set up.

 

 

Still working out where I’m going to mount it- but here is where I’m thinking.

 

 

 

This is another option- but I don’t really like it pushing off the top cover… there is another way to mount it lower so it pushed off the carb body here, but it also interferes with the carb body so tbd… another issue is the front of the shaft may be too short , I wasn’t planning for this lever when I took my measurements so it may not work…

 

Throttle shaft is in works but under wraps for the moment! 

 

Also mocked up the fuel lines- wasn’t expecting much- but pretty disappointed. It was going to be temporary while I ensured this plan would “work” and then I was going to make a fuel rail for it. But now I think I might just do it right and fab up a custom fuel rail.

 

^^^ ignore the messy bench… it’s usually not this bad… but pressed for space and time right now so it’s gotten a little out of hand
Another sneak peak-

 

 

Edited February 27 by demo243

[datsunfreak]

18 hours ago, demo243 said:

Massachusetts tests the parking brake- I think it’s rev to 1300 rpm and let out on the clutch and it’s supposed to hold.

 

So hmmm decisions decisions…

 

Do they allow hydraulic handbrakes? 

[demo243]

11 minutes ago, datsunfreak said:

 

Do they allow hydraulic handbrakes? 

 Doubtful…. 
 

I personally like the idea of having a mechanical back up anyway.

 

I should just get a new caliper or two - some fresh pads and rotors and be done with it… but at that point it’s pretty tempting to bump up to the T3 set up.

[demo243]

Diving into to fuel system rabbit hole right now…

 

Planning on using -6 fuel rail to feed the carbs. From my reading these carbs like a pretty low consistent pressure ~2.5lbs. I worry about overflow from over pressure, so I want to run a return (unlike my mikunis on 510). 

 

Pump and regulator now need to be decided- seems the only low pressure bypass style return regulator I can find down to 2 psi is Aeromotive. Then just need to decide on a fuel pump- Carter p4070- Aeromotive $$$ - or Holley Red (supposedly very loud)

[Crashtd420]

52 minutes ago, demo243 said:

Diving into to fuel system rabbit hole right now…

 

Planning on using -6 fuel rail to feed the carbs. From my reading these carbs like a pretty low consistent pressure ~2.5lbs. I worry about overflow from over pressure, so I want to run a return (unlike my mikunis on 510). 

 

Pump and regulator now need to be decided- seems the only low pressure bypass style return regulator I can find down to 2 psi is Aeromotive. Then just need to decide on a fuel pump- Carter p4070- Aeromotive $$$ - or Holley Red (supposedly very loud)

I have never been impressed with the Carter.... but it works...

I ended up ditching the regulator and only have a return line now... 

I was able to get the line pressure where I wanted it by changing the orifice size in the return line.....

 

The facet pumps are suppose to be really good....

 

 

 

[Stoffregen Motorsports]

Carter pumps work great and are very consistent, but they are loud.

 

The only think I don't like about the facet pumps, even the cylindrical ones, is the small inlet/outlet ports. 1/8 NPT is tiny. They should be 1/4 or 3/8 NPT. Also, be careful to make the right choice. Some of their pumps flow enough fuel for dual or triple carbs, but some are right on the ragged edge of what a performance motor might require.

 

There's a calculation out there, but I forget what it is.

 

https://performancedevelopments.com/fuel-flow-calculations-for-horsepower/

 

 

[demo243]

I’ve been running the Carter pump in my 510 since I swapped to Mikuni carbs on that. Never had an issue with it and with the Holley regulator it seems to be fine… but agree on the quality of the Carter pump… feels cheap, mount is flimsy and the studs strip easy. It’s loud but once the car is running I don’t hear it anymore.

 

From what I can tell everyone in Japan running this style carb is running a rail and then return line. The Z still has the lines in place so I plan to utilize it.

 

From reading it sounds like a regulator post carb helps to maintain pressure especially during heavy fuel usage (possibly my problem currently with the SUs…) I was originally going to utilize the stock rail along the valve cover but eh not into it.

 

What I am thinking now is filter -> pump-> stock hard line to front of the car -> clear filter -> across the front to fuel rail -> loop return back along fuel rail and across the front -> regulator -> stock return hard line.

 

It’s more then I want to spend - but probably worth spending - so either Aeromotive 13202 regulator (2-20 psi) or Fuel lab 525 (1-3 psi). Leaning towards the Fuel Lab since it’s a better pressure range, also has a port for a gauge right on it.

 

Planning on a Ross Machine -6 rail- should allow me to directly cut threads for a m14 fitting on the ends- although would -6 fittings be able to? Having a tough time sorting this out… Then was planing on m12 to 5/16 barbs for the carbs.

 

With the regulator on the return I shouldn’t need any more restrictions on the line - but I did see Watcom makes a cool in-line one that uses Mikuni main jets to allow for easy adjustments.

 

@Stoffregen Motorsports @Crashtd420

@datsunfreak

 

appreciate any feed back on all this- all these different fittings, lines sizes and everything are all new to me. Everything on the 510 is 1/4” barb and npt.