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I think I better start firstly with a quick intro.  


Hello from the Wide Bay area of sunny Queensland in Australia.  I’m a long time ‘guest’ lurker to the HybridZ forums mainly for research and ideas particularly when it comes to round top Hitachi SUs.


I’ve loved Z cars since I first laid eyes on one in my early teens when I went to a historic race meeting at a local track with a friend’s family (who also have an affiliation with Datsun 1600/510).  There was no escaping the ensuing obsession.  This was only made worse by the inception of the Fast and Furious franchise coincidently at the same time I acquired my learners driver licence.  I am shamed to say I have had at least one car with “cool” under body neons….


On to the car!

This particular car is a 1971 chassis number #629 purchased in 2009.  The car was a daily driver retaining the L24 and had a 280ZX gearbox and ignition.  I believe it was Victorian sold in a blue colour and was repainted to red in the late 80s or early 90s (judging by the Australian fashion sense in the photos).  I have maintained continuous registration of the car as well.


The car has had various levels of priority around my life choices and events.  I think I put less than 1000 miles on it between 2010 and 2017, is this considered Datsun abuse?  I am now at a stage where I can tinker with it more and crack on with a long time goal to leave a legacy of my experiences and information on YouTube and lessor so on Instagram.  One immediate goal is to try for 200WHP with only optimisations to fuel, ignition and exhaust.


There are gaps to the story thus far which I intend to fill in with further posts.  I want to keep this post short and sweet.





PS. The current specs are:


ENGINE (currently making 170WHP)
-    Overbored and stroked to 2996cc
-    Approx. 10-10.5:1 compression ratio
-    L28 F54 block
-    L28 N42 head, 1.0mm O/S Ferrea Super Flo valves and match ported
-    ‘V07’ LD28 crank, balanced, knife edge and nitrided surface
-    L24 connecting rods
-    Modified Mistubishi pistons
-    Crow Cam camshaft; 

-    292° duration 0.495” valve lift intake

-    296° duration 0.510” valve lift exhaust

-    Innovate Motorsports LM-2 datalogger and wide band O2 sensor
-    Ebay 75mm alloy radiator
-    2 thermo fans
-    280ZX thermostat with Tridon temp switch
-    Pertronix Ignitor I module
-    MSD 6A ignition
-    L24 distributor with ‘7.5 plate’ and vac advance
-    Rebuilt round top 240Z Hitachi SU carbs with ZTherapy rebuild kit
-    SM needles with higher set fuel float level
-    Holly Red fuel pump
-    ZStory stainless steel Race/Sport headers
-    ZStory stainless steel  Z432 style JDM muffler
-    Recycled mild steel centre pipe and generic hotdog muffler
-    71C RB20DET gearbox
-    Exedy ceramic clutch and pressure plate
-    Standard rebuilt open centre 3.9:1 R180
-    Standard uni joint drive shafts
-    Restored Japan polyurethane front bar
-    Stock (and very worn out)
-    280ZX modified tacho
-    Stock springs
-    Stock brakes
-    Stock geometry components
-    Koni adjustable shock absorbers
-    Rota RB-R







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I’m going to treat this like a steak and vege dinner and drive right into what I think is the steak.  Mechanicals are my steak and all else is my vege....


Crank and pistons.


The motor is a stroker motor using an LD28 V07 crank.  I actually had the crank a few years before I acquired the 240Z.  I paid a handsome some of $150NZD for the crank and $350NZD shipping to Australia back in 2007.  I think these days good V07s cost significatly more?


I had the rods, crank, pistons, flywheel and Ross harmonic balancer balanced to an inch of their life.  The crank was also knifeedged and nitrided and as a bonus was straight as a die beforehand.  I think about 3 kg was cut from the crank.  It might be excessive for a motor that doesn’t rev past 6.5k RPM (due to camshaft selection) but in my mind balancing is cheap insurance for your motor.


Pistons were .02” oversized Mistubishi 4G64 8v SOHC pistons decked about 2.00mm for a zero deck height at TDC.  This give 2960cc.  I did not use forged as I think eutectic material is sufficient (i’m not looking to make 100hp/l), not to mention lighter and reduce thermal coefficient of thermal expansion in comparison to forged material.


I have a few videos on the bottom end on my YouTube channel referenced in the parent post.


I’d like to write more but my lunch break is finite.  Thanks for reading.




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  • 3 weeks later...

Fast forward to the present for this post.


Progress is being made to optimise the stroker motor with the round top SUs for a goal of 200hp at the wheels. 


I recycled a piece of the old aluminised steel exhaust when the Zstory race sport header and JDM muffler (looks like a 432 muffler) was installed back in late 2016 to try and save a few bucks but have regretted it since.  That was removed over the weekend and a Zstory connecting centre pipe put in its place.  So now the exhuast system is a full stainless steel system from Zstory and I’m stoked.  It looks and sounds exactly how I want my 240Z to sound!


A question for the round top experts.


Has anyone modified Hitachis round tops to a David Vizard ‘specification’?  I had a comment on the YouTube channel recommneding his work on SUs.  I can find at least one workshop that prepares ‘David Vizard’ SUs for Minis with some photos of the modifications.  I’m keen to investigate further and apply some of the modifications as a backup if I cannot get 200hp at the wheels with the round tops in standard trim just I’m not sure if modifications meant for SUs will be as effective on the Hitachis.



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  • 1 month later...

I turned my attention to optimising the needles in the Hitachi SUs.  I took the functional stations from the SM, RV and RU needles I’ve trialed previously and went searching for a best match.


I went to use the Mintylamb.co.uk resource but found that had closed down some time ago.  Ended up using Teglerizer’s resource http://www.teglerizer.com/suneedledb/ to find SB needles were the closest.


Ended up sticking the needles in without lowering the fuel floats down from the band aid fix to riches top end with the SM needles.  The SB needles worked a treat and the AFRs are offset by the amount that raising the float changed.


Overall very happy.  Next port of call is to lower the floats to factory and I reckon I will have 99% convergence to the best mixture I can achieve without making custom needles.  Fingers crossed that’ll work!



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Following on from the SB needle install I decided to adjust the float level to factory. 


Previously I had the float level a little higher as a band aid fix to richen the top end mixture of the SM needles.  The rear float bowl gave me grief.  I think I had the lid off 20 times before the geometry of the float was massaged so it wouldn’t stick in the bowl not closing the jet properly.  I got there in the end.  When you bending little metal tabs minute amounts you need a good swag of patience.


Using the float sync tool and a trusty bit of clear pine dressed down to 9/16” thick the floats are set to the same level.  The Nissan workshop manual suggests making one float higher than the other, presumably for G forces under acceleration, but I’ve never done this.


Working on the 240Z is not the highest priority in my life (although I wish it could be!) so road testing and datalogging with the Innovate LM2 wideband will have to wait.  Video below.



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  • 2 weeks later...

Slowing chipping away little by little.


I mucked with the Megasquirt 1 this week.  Got the V3.0 board sorted from where I left it two years ago  from a full EFI build.  Flashed MS/Extra and plugged it in to the PC with the stim board (after I installed the USB to  RS232 driver for the cable :-[) and low and behold it worked first time!  


I'm pretty stoked that it worked.  I don't have any special hardware built other than the standard configuration.  It is literally taking the signal from the Pertronix unit and manifold pressure from the vacuum advance pickup and determining ignition advance from the ignition table.  I will have to zero fill all the other tables.


next step is get the wiring loom in order although I won't need a lot of wires for what I'm doing....



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I found some interesting parameters in the Tunerstudio software about launch control and flat shifting which got me thinking and consequently the megasquirt case hasn’t stayed assembled for long!  


I’ve build a protective circuit on the prototyping area to ground a 5v signal from JS11 leg of the CPU.  This will be used to trigger launch control and flat shifting functions.  I don’t know how this will function with the SU carbs as the MS1 is only controlling ignition.  I suspect backfiring will ensue!


I’ll have to build a clutch switch if launch control passes testing.  I want the car to be about function not form.  If the launch control doesn’t prove useful, I’ll bin it.

Oh and the wiring loom of less than ten wires is also complete……



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  • 2 weeks later...

Mech advance in the distributor is locked!  It’s slow progress but thats better than no progress.


Next is wiring the megasquirt!  I can’t wait to test the launch control feature and see if I can’t blow up the exhaust....



Share the vid if you know someone who might benefit from it.


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  • 2 weeks later...

Finally got around to mucking with the megasquirt wiring harness.  There isn’t a lot to wire up with the MS1 in ignition only configuration.  


It took nearly a week doing little bits here and there coming up to Christmas.  It didn’t go to plan but the advantage of this being a project car is I can just shut up the garage until next year!


Merry Christmas all and have a happy new year!



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  • 3 weeks later...

I snagged some time over the Christmas break to fault find the Megasquirt MS1 install.  I 100% expected the problem to be something simple.  


Sometimes I hate it when I’m right…


I hypothesised two possible problems.  One being the ECU itself and the other the wiring loom.


The ECU powered up and connected to the Tunerstudio when plugged into the Megastim board.  Happy days that the ECU was not toast!


This left the wiring harness.  Voltage was getting to pin on the harness. That left that the harness was incorrectly made, that the voltage was going to the wrong pin.  A quick review of my notes, physical verification and sure enough power was going to the wrong pin.  


A quick swap of the pin and the ECU powered up when connected to the wiring harness.  I’m glad it was something minor and simple. 


Next stop, ECU tuning!


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  • 2 weeks later...

I was able to play home tuner using Tunerstudio to set put the parameters and rough in an ignition table for the MS1.  There wasn’t a lot to set up with an ignition only configuration, the ECU is pretty under utilised as far as it’s overall capacity.  Even though the hardware does not exist for the injector circuits, I zeroed the injector table data.


To bench test the MS1, I used the Megastim board and a syringe with vacuum tube for the MAP.  A 60ml syringe wasn’t big enough to generate enough vacuum to get to the closed throttle parts of the map but it was helpful still.


I had help from Godzilla Raceworks who saw one of my Instagram posts and offered up an example tuning file from an MS2 used on a similar engine.  I’m very appreciative for their assistance.




There are a few items I need to address before attempting to start the car with the MS1 and new SU needles.  The vacuum line for the MAP needs a home on the intake manifold and the signal wires from the Pertronix unit need a little tweaking to introduce voltage because the Pertronix unit doesn’t generate its only power, its only a switch essentially.


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  • 2 weeks later...

The moment of truth arrived for the first startup with the Megasquirt configured for ignition only and the SB needles in the SU carbs.  The distributor needed to be aligned with the trigger angle parameter in the ECU which was easy to to.


I did hit a road bump with a leak from a MAP vac hose that was larger than the onboard MAP sensor barb.  That was fixed with a smaller vac hose 3mm in diameter from Super Cheap Auto. I had to buy the stand out blue coloured silicon stuff made by SAAS because the roll of non descipt black was empty.


With the problem fixed the car runs but I want to revisit the ignition table before driving and adjust the SU mixture nuts after.  The idle vacuum is a little different to what I thought it would be and revving the engine without load cause some hesitation around the 3k RPM mark which makes me think I have the advance ramping up too fast in the table.



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  • 2 weeks later...

So the little niggling issues continue.


While travelling to a local informal coffee and cars show I discovered a problem with the ignition timing.  It felt like an ignition ‘wall’ at around 3,400 RPM.


My first thoughts were it was something other than the ignition advance.  I’ve had 36 degrees in this motor when it ran the tripled 45DCOE152s years ago.  I just assumed the engine could take the same again.


I was going to check the signal form from the Pertronix in the event that signal noise was causing interference.  I wasn’t real sure how to condition an I/O type signal.


In the end it was the ignition advance.  When the table ramped up to 31 degrees at 3,400 RPM, the engine couldn’t take it.  Trialing lower advance in the same areas of the table allow the engine to rev properly.


I’m glad it was an easy fix and I am surprised that with running the SUs with SB needles that the engine characteristics changed. A new chapter has been added to my ‘book of Datsun’.  

Anyway the ignition table has been revised to lower advance levels and hopefully this will be a suitable base for some road tuning.


If anyone has come across changes in ignition behaviour with different setup ups, I’d love to hear it. 




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1 hour ago, Neubs said:

In the end it was the ignition advance.  When the table ramped up to 31 degrees at 3,400 RPM, the engine couldn’t take it.  Trialing lower advance in the same areas of the table allow the engine to rev properly.


That seems odd.  In 1972 they were at 29 degrees centrifugal by 2000 RPM.  Even higher depending on which spec you look at.  Up to 33 (17 + 16) or higher, 17 + 20, maybe.  (Nissan has conflicting info in their FSM's).




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Thanks @NewZed!  The FSM I have doesn’t have that information.


The original distributor was a D606-52 with a ‘6’ plate.  


I’m not fussed with the behaviour of the engine.  I mean there are a hundred micro things that could be contributing.  Proof will be in the pudding come dyno time.  As long as the engine makes more power I’ll be happy.

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  • 2 weeks later...

Off the back of pre-tuning experience I thought I’d combine the LM2 WBO2 into the Megasquirt so I could log all my data in Tunerstudio.  Why have two screens to look at while tuning right?


It was a pretty simply process simply wiring the analog output 1 from the LM2 to the DB37 harness.


I did have to calibrate the Megasquirt to match the LM2 AFR outputs which I pulled form the LM2 using Logworks.  The prefilled Innovate Motorsport WBO2 sensors in Tunerstudio did not match the LM2.  I think it was 7.32 @ 0v and 22.39 @ 5v.


So ready for some tuning.  But first I want to make a digital det-can beforehand just to check the strange ignition behaviour of the motor.  Stay tuned (pun intended).




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  • 2 weeks later...

Following on from the strange ignition behaviour I thought it worth making up a cheap digital det can / engine stethoscope to aid in determining if something more serious was happening.  I drew inspiration for an old Autospeed.com article I read probably around 2001.




The basis was the Jaycar ‘bionic ear’ Short Circuits kit aimed at junior electronics.  This kit had all I needed only requiring a few little bits and pieces to customise. The kit was assembled as per instructions and recommendations in the Short Circuits 2 guide.  I simply lengthen the single core screened microphone cable and fixed it to a battery clamp.


I tested it on my TD5 Defender daily and I could hear plenty of extra noises in that motor that’s for sure!  As the kit uses a electret microphone it picked up all the noise.  I think I will find it hard to isolate specific sounds, detonation being a primary one.  For a first round its not bad though and I think I will gradually improve it over time such as switch to a piezo transducer and perhaps an alternate amplifier board.


As soon as I can get some Penrite Super DOT 4 brake fluid to replace my stock and bleed the brakes, which is proving difficult in my ‘regional’ area, it’ll be road tuning time!


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On 3/4/2019 at 3:03 AM, bradyzq said:

Re: the ignition wall, what is your trigger angle set to? Sounds to me as if it might be in the mid 30s,which is a no-no.


If this is the case, try reclocking the distributor so you can achieve a trigger angle NOT between 20 and 50 degrees.

Thanks for that.  I currently have the trigger angle set to 0 degrees.  Do you think this might be a problem?


I have wondered if this may be a problem and have thought of shifting the leads around one location in the dizzy cap and setting the trigger angle to 60.

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