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Leon's Other 260Z

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  • 10 months later...

Happy new year! May this one be more fruitful than the last.


Time for an update. The Z had been down from January of 2020 for a "quick" re-gasket, meaning I got it back on the road in... November. There was a fuel drip from the carb insulators so those were replaced along with all carb gaskets. The plastic spacers and gaskets were replaced with the o-ring and thackery washer style.


I went to the dyno in early December to see if I could sort my fueling with Keith's latest jets as well as figure out the high-RPM cut I've been getting. The dyno day was useful in helping see what's going on with the fueling but I couldn't figure out the cut-out. I did note that it happens at 5500RPM consistently. It was making good power though, about 193whp (w/ filters) before the 5500RPM cut. An adjustable cam gear is on its way to help further dial in the motor.


Fast forward to the past week, (temporarily) installed a wideband and reworked the rear brakes (but still having parking brake lockup issues). Then I shot-gunned some things that were at hand in an attempt to remedy the 5500RPM cut-out. A fresh coil didn't do it but fresh plugs did! All it took was a set of spark plugs to get the car running way better than it probably has before. The plugs in the car weren't that old but it seems they'd gotten fuel/carbon fouled enough to cause some problems. If it happens again, I'm going to try a hotter plug but for now I've replaced with the same: BPR6ES-11.


I did some runs up and down the freeway on NYE and got the main jets dialed in for our new years day drive. Swapped back to the ZX distributor from the 123 as the motor seems to run a bit better that way. I'm going to investigate this further on a future dyno day. We took a 150 mile loop around the Santa Cruz mountains, the Z got the most exercise it's ever had given how much time it spent over 6000RPM!


Without further adieu, the obligatory accompanying photos:


12/28/20 - drove over to a buddy's house for the wideband install and other Z things






1/1/21 - Alice's / SC Mountain Drive










Edited by Leon
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I should say, I also FINALLY went to mount my Compe handle (steering wheel) and I may be called a heathen, but I think I prefer my Grant! I like the thicker grip, larger offset, and larger diameter of the Grant. Considering putting the Compe wheel on the market or hanging it on the wall in my garage...

Edited by Leon
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2 hours ago, Leon said:

I think I prefer my Grant! I like the thicker grip, larger offset, and larger diameter of the Grant.


I can certainly see that.  My leather-covered 3-spoke Grant is my favorite steering wheel of all that I've tried over the years!

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4 hours ago, jhm said:


I can certainly see that.  My leather-covered 3-spoke Grant is my favorite steering wheel of all that I've tried over the years!


Nice! Yeah, it just works and fits well with the car.  This feels like a "if it ain't broke, don't fix it" situation. :)

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On 1/13/2021 at 10:52 PM, munters said:

Yes very nice car.

About the 123. The power is not enough for our engines with triples. After adding a hi-6 CDI and power coil. The car behaves nicely.

no more start problems when hot for example.


Interesting, thanks!

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  • 1 year later...

17 month update! The Z hasn't seen much action as I've been dealing with a perpetual throttle-hang problem and inconsistent low-speed fueling--lots of popping out the carbs at low load/throttle openings.


The low-speed fueling was dealt with by a trip to Keith Franck's house on New Years Eve 2021 to use his custom progression-hole drill fixture. The first p-hole in my 45DCOE 152's was too far upstream, you couldn't even see the throttle plate through it at idle. This is a common problem with the 152's and Keith's fixture was the perfect tool to fix it. It turned out to be the correct diagnosis! I was rewarded with virtually no more popping out the carbs during low-load operation, the freeway cruise home was the smoothest it's ever been... besides the fresh rock chip in the windshield.


But now the rev-hang problem was even worse, although the engine would return to idle after a sharp throttle blip which hadn't been the case before. This is an issue I've been dealing with, at various severity levels, for the entirety of the 9+ years I've owned this Z. I was invited to a cars and coffee event this past Sunday, 5/29/22, which was inspiration for the next round of trying to fix it. So the carbs came off for the 132nd time, this time with the intent of resetting the throttle butterflies. I decided to pull the carbs off the manifold while on the car as to not waste the manifold gasket which had been port-matched when I had it apart last year.


What I also discovered were some slight interferences with the TWM manifold (would love to replace this janky manifold with a Datsun comp or Harada piece) as well as a non-functional accelerator pump on the #2 carb. I ground down the manifold in the offending areas with a file and radiused Dremel burr, this worked very well. Swapping accel pump pistons from carb #2 and #3 did the trick for making the #2 pump function again! I chalked it up to slight tolerancing issues. I then spent a good amount of time with a flashlight backlighting the butterflies, trying to get them as sealed as possible. I first set all the bearing preloads with the throttle shaft nuts as to set the throttle shaft in place. Then I loosened the butterfly screws enough to get the butterflies moving. Setting the butterflies was a matter of seeing where the light was coming through and trying to set it in a position where the light "leak" was even and minimize. The butterflies are eccentric in shape so turning them a bit here and there helped find the optimal position, along with snapping the throttle shaft for a bit of self-alignment.


And I finally have the crisp throttle response I've always wanted! It could be better but it's a massive improvement over what it was. I'm still missing that "zzzzz" noise on overrun when snapping the throttles closed but at this point, I'm happy. I made it to the C&C yesterday and did about 160 miles of excellent ripping through the East Bay and Santa Cruz Mountains!











Photos from recent drives:












My son likes to service his car while I work on mine, we ensure that safety best practices are always followed.


Edited by Leon
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  • 1 year later...

Looks like a year and a half is about my post cadence these days. :) I've been driving the Z sparingly but with much enjoyment since fixing the throttle hang. It's finally feeling close to getting to the level of refinement I want out of it.


Unfortunately the diff started making some extra whiny noises beyond what it was already making so I pulled it this past Saturday. I got the chance to pop the cover off and found that I'm the lucky winner of 6/8 loose/snapped ring gear bolts. 😱 I'm not sure whether it's salvageable but I'm going to tear into it as time allows. The last time this diff was opened was by a local diff shop but I can't say for certain whether they had removed the ring gear...


This is a Datsun Comp R180 3.9 CLSD so I'm hoping I can save it and run it but it looks a bit grim at the moment.





The cross pin position is not centered and doesn't seem to have any ramps? It's late and I'm confused, will be looking into this later.





The spot faces have heavy embedment from the loose bolts. If this LSD carrier can be reused, it will need machining.





I pulled these bolts out by hand, their ends are broken off and lodged in the ring gear.





Edited by Leon
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Unfortunately, more unhappy diff news this evening. It seems whoever assembled this diff majorly screwed up, to put it lightly. As I said, a local diff shop was the last to touch this diff when I had them inspect it... 10 years ago. So the costs may very well be sunk at this point which is disappointing.


There is heavy embedment of the friction plate ears against the carrier and damage to the cover itself (perhaps due to mishandling during install?), I have a feeling the clutch vs washer vs plate stackup was done incorrectly.







Elongation of clearance holes in carrier due to loose ring gear bolts






And the mystery of where in the world are the LSD ramps was solved... the pressure ring was installed 90° off and the cross pin was put in the wrong place. INSERT REGRET AND DISAPPOINTMENT HERE.



Edited by Leon
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  • 2 weeks later...

I decided to act quickly as to not have the car down too long. After tireless and borderline obsessive searching, I committed to getting a Subaru R180 for availability reasons. The cheapest solution for stub axles turned out to be Kameari which I found for significantly cheaper on Yahoo Auctions Japan rather than buying inside the US: https://www.jauce.com/auction/m1117548805. They were $417 shipped to my door vs anything US-based being $500+. The fresh hardware is a nice value add.


As for the diff, I wanted to retain the 3.9 ratio paired with the late ZX close-ratio box vs the 3.54 which I initially built the car with. I did like the deep overdrive with the 3.54 for highway cruising but the 3.9 gearing is perfect for mountain driving. In the US, the 3.9 LSD was only used in '04-'05 STI's and therefore is quite a bit tougher to find now versus 10 years ago. When they do pop up, they seem to go for way too much, for my wallet anyway. So I started searching other avenues to get one of these...


There are more available on eBay UK but they tended to be missing the rear cover for some reason and condition was not so clear. Then I turned to the JDM which ended up being more complicated to understand as far as which models to target. Long story short, I learned that at least the '01-'05 STI with DCCD transmission got a CLSD 3.9 R180--good enough for me. I ended up contacting Tyler at Magnolia Auto Supply (shout out: https://magnolia-as.jp/) who helped me source a diff from Japan! Japanese dismantlers seem to be very thorough in how the parts are presented, this one came out of an '03 STI with DCCD and has 89k miles on it. This path is likely a bit more expensive than the UK route but I felt good knowing more about the part. The hope is that this diff lasts the lifetime of the car given that I don't put that many miles on it.


The diff is currently on its way and I'm very much looking forward to getting the car back on the road. I've got a fresh diff cover gasket and seals to install once it comes in. I just need to source a Nissan R180 pinion flange and decide on studs vs bolts for the rear cover. :) 






Note the PN: 27011AA860



Per Subaru:


Edited by Leon
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Well done!  I like "After tireless and borderline obsessive searching..."  That describes me more days of a week than not.  I haven't been very active on Hybridz.org for several years, but have been restoring a 240z for 5 years now and that has required a lot of tireless and borderline obsessive searching.  

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Hi! I thought the clutched STI 3.9:1 LSD was available in the years 05-07’? Meh, minor detail. Was just curious if my recollection is wrong. Maybe that’s just the US models. 

keep in mind, now that you have your LSD carrier and stub axles, you can swap out the carrier to different r180 with whatever ring/pinion ratio you like. Sounds like you will be happy with the 3.9, so you’re all set. Just nice to know you have options. I swapped my helical STI LSD carrier into a 4.11 for track purposes. 

im not sure how often the clutched carriers need to be inspected or the clutches replaced, but not a bad idea to do it now before you seal her back up. I have never had a clutched LSD myself, but I know the competitive S30 road racers prefer it. 

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