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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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