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chatapokai

Thoughts about installing carbs on an na2j?

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While putting together the 2j for the s30 I thought about how cool this thing would sound with ITBs or carbs....and then really started thinking about the possibilities:

 

ITBs would be really cool but I would need an aftermarket ECU (~$1000+$300 for tuning) and the ITBs themselves ($2000 from EFI). Awesome but 3k on top of what the 2j swap and s30 upgrades will cost is a lot (not counting what an aftermarket loom would cost).

 

But what about carbs?

 

I've seen people carb RBs and LSs before, so why not a 2j? So I did some digging and research. Looks like it's not uncommon for people to delete the efi/ecu from some builds for a carb.

 

1. I can fab the intake manifold (~$250-$300) from a very good fabricator near me) to hold the carburetors (free from a friend)

2. The s30 gas tank can be reused and hooked up to an electronic low pressure fuel pump (~3-5psi) and then hooked to the carbs

3. The 2j has a distributor, but it hooks up to the ECU. I would need to find a way to replace the electronic advance (maybe an msd box? Some sort of ignition control is needed).

4. The starter, alternator, pump and ignition could would hook up to the battery.

 

Outside of tuning the carbs it seems doable and I would honestly be much happier with this build as it's much more representative of the 70s. It's the exact build I had in mind.

 

I found an example of this being done: https://engineswapdepot.com/?p=8336

Looks like they used a cam trigger and Ford EDIS but I was hoping to reuse the distributor if I go forward with this.

 

Thoughts? Ideas? Comments? I'm really hoping this is feasible but the ignition seems to be my only stopping point. 

 

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Wouldn't the ECU need a MAP sensor for vacuum advance of timing?  Also, an RPM signal for centripetal advance.  Does the 2J use a crank mounted sensor or does it use the distributor type CAS?

 

Interesting idea.  Might be easier to just modify a distributor that has vacuum and mechanical advance to work in the engine, to trigger an electronic ignition.  Timing control is the hard part.

 

 

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The ecu would indeed need the map sensor etc to run and would throw a code as the efi would not be connected likely running on limp mode.

 

Im 98% sure it is a distributor type cas.

 

The timing is my only stopping point. I believe I'll be able to at least get it to idle with the stock dist. Right now I'm still cleaning up the motor but i think I'll be getting a trio of chinese 40mm idf carbs or 6x 40mm honda bike carbs and trying it out. If it cranks over and runs then I might move on to trying to modify a distributor, or getting a timing control box.

 

Problem is that I have no idea where to get one or how to hook it up. I assume its a box i can wire to the stock dist and vacuum lines and program. Maybe msd has a solution? I know the 4age guys can use another model distributor but I don't think i have that option. 

 

I've seen one other person try it, but they hooked up a crank trigger wheel to a timing control box (megajolt?) and a ford v6 edis system. Maybe that'll be my last resort bc i really really want to do this.

 

 

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Posted (edited)

Update: did some research and I think I'm going to try a Toyota 5mge distributor before trying the crank trigger/megajolt solution. It has a vacuum advance, the firing order is the same, and the gear size looks pretty close to the stock 2j dizzy. I might be able to make it fit with minor modification. Worth the $40 for trying. 

 

I'm also heavily researching carbs. My 2 options are modifying Honda or minkuni bike carbs or getting 3x empi vw 40idfs. It'll depend on whether the dizzy fits.

Edited by chatapokai

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For cheap ITB's the GSX-R throttle bodies were pretty popular in the Honda crowd. They come in groups of 4, but are repeating so you could modify as needed.

 

Some carbs on a 2J would be neat, a lot of effort for not much power, but would be a fun project. 6 SU carbs with velocity stacks would look real neat, but you probably could make do with less. If you have a 2jzge the lower intake runner would be an excellent starting place, some custom adapters and you would be in business. Probably run a thinner head gasket or shave the head and run a bigger cam, might see bit over 200hp to the wheels. Keep in mind depending on the motor that may put you into interference territory if you were not before. Probably one of the few times a 2jz-ge VVTI setup would be preferential, granted then you have a VVTI you would have to lock or remove altogether just for the higher compression. 

 

Interesting for sure, keep us updated!

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@seattlejester So I've decided to pursue the carb route. I still have a month left of grad school but I have started tearing the 260z apart and rebuilding the 2j when I can. I just removed all the accessories and am about to crack open the head and pan to see the condition of the cylinder walls and rod bearings. 

 

I'm 90% leaning towards the VW/Porsche 40IDF carbs and cutting a rectangle down the driver side of the hood so the stacks peek through. Should look and sound pretty cool. 

 

As for the ignition. I found a company that makes dizzys that can be programmed via bluetooth. I think I'm going to send them what I have and see what they can do. I hope it works because I really dont want to deal with a crank trigger wheel and an ignition box. 

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Most excellent! Should have a cool sound, side drafts on an inline 6 have a really nice induction noise.

 

I would run a compression test to before taking the head off to see if there are any problem areas that may need additional scrutiny. Make sure you buy the 10 point socket for the head and clear out the bolt heads of any gunk, these strip very easily. There is also a technique to removing them that leads to less breakage that I would try and find.

 

If you do have to go a different route, the crank trigger wheel isn't too bad. A 1JZ crank pulley has 4 centered holes that can be used to bolt a DIYautotune wheel to. 

 

You will run into the whole seal preference thing. I'd be tempted to just take the mainstream advice and go with OEM seals when the time comes.

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@seattlejester super helpful and I'm glad you didnt talk me out of it.

 

Update: I've been slowly gathering the parts needed to swap to carbs. Just finished grad school so I can finally jump into this more. The following is what I've done to this point:

 

  • Removed L26 and started cleaning up the engine bay (removing surface rust and will start painting the bay)
  • Started rebuilding the 2jz. The head is almost off and I will be doing the following
    • Cold compression test got me values from 135-150 so it seems ok considering the motor was not hot and expanded according to some na-T supra/sc300 friends I have
    • Changing every gasket possible. Going to buy an OEM gasket kit and swap everything out (head/front and rear main seals/valve cover, stem seals, etc) I'm not out for power so OEM will be ok.
    • Water pump and alternator will be changed, not sure about oil pump yet. 
    • Will be upgrading to ARP studs since I liked them so much on my mr2
    • Might get a solid crank pulley instead of reusing the harmonic balancer (unsure)
    • EGR deleted, with 9/16th expansion plug
  • Purchased a set of 6 GSXR carbs and manifold to bolt them to the head (They look so good https://www.instagram.com/p/CFvE_cbnlXe/?igshid=dv6y0l5nxurb)
  • Sold the AR5 for a nice profit and got a cheap w58 trans. I can now use a stock sc300 slave and clutch to run the car
  • Bought an interrupter style motorcycle fuel pump so I dont have to run a return line back to the tank (so glad the carbs only need 4psi to run)
  • Talking with123ignition to see if I can get a programmable alternator

 

Next Steps once the engine is built up and bay is painted:

  • Install the apexengineered subframe
  • Going to get the universal wiring harness from zcardepot (https://zcardepot.com/products/wiring-harness-universal-240z-260z-280z-510) and I will be splicing the 2jz accessories to it (hope that works, Im assuming splicing the 2jz alternator, starter, ignition coil, bike pump, etc to the new s30 harness should work???)
  • Find a 2jz to W58 bellhousing somewhere....then ill be able to measure for the trans mount

I'll stop there but I'm pretty happy. So far it looks like splicing that universal harness will be my best bet for keeping it simple while still upgrading to a modern fusebox. 

 

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OEM seals are used on 1000hp builds so power level isn't much of a concern.

 

Interesting point with the trans, you are running less weight and not much power so a W58 may be perfectly fine.

 

If you do oil pump, worth looking into modified ones with front seal retainers. I did a whole write up on the FMS, differences between the seals and how I think it should be installed, but everyone has their own opinion.

 

Also make sure to run good crank case venting. You won't have the normal problem with pressurizing the crank case, but you will have the problem of not having much of a vacuum source unless you can tie all the runners together.

 

Ooh does danst make a conversion manifold?

 

I think this would honestly be inline with my next build now that I've more or less scratched the turbo monkey. I'd hope for something fairly high compression, maybe even keep the VVTI, and throw in some balancing and try and run the motor a bit more towards higher RPM. That would probably involve crank cradle and all sorts of balancing, but one can dream.

 

Would love to see how you get along. Keep us updated!

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10 hours ago, seattlejester said:

 

I think this would honestly be inline with my next build now that I've more or less scratched the turbo monkey. I'd hope for something fairly high compression, maybe even keep the VVTI, and throw in some balancing and try and run the motor a bit more towards higher RPM. That would probably involve crank cradle and all sorts of balancing, but one can dream.

 

Would love to see how you get along. Keep us updated!

 

What you want is Kazuaki Kadowaki's build. It's so goooood.

2JZ-S30-Fairlady-8 copy

2JZ-S30-Fairlady-2 copy

 

 

He was in an accident that totalled the car a few years back, but I've been following his progress on Instagram for a long time and it's coming back better than ever. 

You'd be able to understand some of his posts far better than I can, but I enjoy seeing his progress pics.

https://www.instagram.com/kazuakikadowaki/

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1 hour ago, seattlejester said:

I forgot that car existed! Granted I think I like the sound of sidedrafts over ITB's.

 

Yeah we've talked about the side drafts vs ITBs haha. Huge horsepower JZ engines are all the rage, but it's nice to see more out of the box stuff like this being more seriously considered. I think a lot of people get too caught up in numbers games and often don't even finish their builds or lose sight of the fact that modest engines with fewer issues and less $$$ can be so fun.

 

Keep updates coming on the progress Chatapokai! excited to see it.

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