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Discussion Starter #1 (Edited)
This thread will be specifically on carbs. Old school technology. As some of you have read from a few threads here and there about my attempt to modify a JDM Dual carb setup. The carbs are Keihins CV (Constant Velocity). I know from those of you in Europe, Asia, Australia, and Africa that have given me most of the help on the Emmissions routings and CV carb mods that there are probably more of us carb guy's out there that might need the info and maybe we can have some decent discussions on carbs.



D-series Carbs

Links:​
Dog's Carb Projects:​




Ignition and Timing for Dual Carbs New!!!
"bricheun's" home page
Carburettor Syncing
Links to discussions: carbed d-series motors?http://d-series.org/viewtopic.php?t=47
Performance Cams for D15B4?
The ZC Engine
DA-series Honda Integra Specifications (1989-1995)
DOHC ZC website
CRX Resource Featured CRX
Downdraft Tuning info:
Manuals dealing with Dual CV Carbed Honda's:
Info from posts: From "Current Dseries projects" thread:
From "Rejetting dual carb Keihin" thread:
Thanks to Dual Carb RedlineWeber Tech page
Thanks to cryz2 for the following links:





!!!NEW!!!custom header, sidedraft carbs,***Dyno Graphs***by lohatch
 
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A Sticky for us carb guys, thanks Dog... EFI gets all the aftermarket attention, so it's good to see something for the carb setups. You are right, there are many of us...
 
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Hondadog said:
I was hoping I would see you. Hows it going? Did you see the pic?
Yeah, I'll come back here often. Hoping others will have lots of useful info. This is the first board to make a sticky out of this topic. :D :D

By the pic, do you mean your pic on your profile...? Is that your setup?
 

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Discussion Starter #5
Yeah. Theres a bigger one on my home page. I will be getting some more with something better than this polaroid camera I used last time. :lol: . Disposable cameras :( . Anyways. thats my setup. I have a fuel pump and a distributor now. Just need to find a place to buy a vac advance for the dizzy. the mount on the old one is broken. I figure out everything else. I took care of the Inner air vent solenoid. The one on the carb next to the dizzy. Since all it does is close off the vent when the car is off I took a dremel and removed the solenoid from the steel plate that holds it to the bottom of the vent housing thing. First of course i took it of by unscrewing the 2 screws that hold the Sol. to the housing mounted on the carb. Filed down the steel plate that was now flat w/o the sol. . Got a brass vac. fitting and JB welded that. The fitting was the perfect size and pretty much screwed into the hole left by the solenoid. After it had hardened I screwed it back into the housing. Looks pretty good and I got rid of that damn solenoid. Less wires and vac lines :lol:
 
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Looks pretty good, like the way you've cleaned them up. I wish I could get a D16Z6 head and plant it on my SOHC ZC. But in this country we never got D-series vtec motors... only on import, and that's pretty expensive...

I bet yours will be quite a monster when it's finished. Carbs deliver a nice, even flow of fuel, and any carb junky knows that you can rev higher and use an aggro'er cam with carb than with EFI... would be interesting to see what happens when you add vtec to it.
 
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What is the bore size of the of the carb and their center spacing?? I'm thinking of using a set from a honda cb400 twin motorcycle with diff. jettings to avoid all the emmision hoses that comes with the Prelude dual carbs setup.
 

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Discussion Starter #8
Havent been able to get bore specs yet but the opening of the carb throat is 50mm but then tapers down to about 40mm. From center of carb to center of other carb is 5 7/16" or 142mm. You could get a couple of Harley CV Keihin's and rig the up easier than a dual carb setup from a motorcycle cycle that you might have to space apart. Or again use the PM4 manifold and make aan adapter that flows from the two intake ports into a custom Holley 2barrel peice.lol. Stick a 4412 500 cfm or a 350 cfm carb on there. Can you say redneck enginuity. :lol:
 
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I'm running a browntop ZC in my 87 Civic wagon. It's came carb'd but I upgraded to a Weber 32/36 DGEV downdraft. Chose downdraft for ease of tuning/reliability/cost versus a sidedraft



 

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Discussion Starter #10
That is a sweet looking engine bay. I have been searching for the D-series single downdraft manifold which I think is close to yours. Thanks for the pics too. Always nice to see what else is available in the carb arena. Any mods to the distributor? Emissions?

I am working on a custom air cleaner assembly for my Dual Keihins. Dont laugh but I had to use a scanner to take a pic of it. :lol: Came out better than I thought it would. Started of with a 18"x12" peice of sheet metal. Marked out a design that will hopefully work within the confines of the engine bay. Using a K&N air filter. 2 3/4" tall. Just about a 1/4 taller than the oem cleaner assemb. . This is what I got done tonight. Looks a little rough but it will get cleaned up tomorrow.
 
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Thanks...considering the before picture:


I'm using a new stock distributor and ignitor.
Emissions are sort of intact...the charcoal canister and cat are hooked up. The o2 sensor looks hooked up but that's because the wire runs into the passenger compartment for a yet uninstalled A/F ratio meter. Other then that, the 10 miles of vacuum tubing, 40 check valves and mysterious black "control box" all got tossed.

The 32/36 is a nice improvement over stock(10-12% I figure) but the next step up would be a 38 and it's supposed to be significant increases in power.

You're looking for a D-series carb manifold...for what year?
They sell adapters for webers that bolt to the stock DX manifolds(both 84-87 and 88-91). I got one for $50, thinking it would fit the ZC carb manifold...it didn't. in case that's not clear...a weber bolts to the adapter and the adpater bolts to the stock manifold.

I had to make my own adaptor out of a 1/4" thick piece of 4x6 aluminum.
Also modified the ZC intake manifold. Had to block off a lot of the stock ports and I trimmed out the carb inlet port to match the weber pattern. In this shot, all the red was shaved out:

 

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Discussion Starter #12
I am looking for any year really as long as its a single downdraft. I think the USA carbed d-series all came before 92. By the way, is that an electric fuel pump? Really nice job on the mods to the intake to adapt the weber.
 
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Yeah, it's an electric fuel pump.
Funny story...I'm a fuel injection/Ef chassis guy. This wagon is new territory as far as model AND carbs so theres been a learning curve.
I gathered the parts it would need to pull the zc swap off. Someone had mentioned getting an electric 85 Prelude pump as a good idea. So I did... but in doing the swap, we decided to wait and see if the stock pump could meet the demand of the larger more powerful engine. I'm thinking the fuel pump is in the tank like everything else I've dealt with. Turns out it's on the old motor, running mechanical off the cam.
Took the old motor out(and fuel pump) and installed the new motor. Got it all plugged in but, duh, we couldn't get it started. We're idiots. Finally realized that the fuel pressure we were seeing was just the pressure that had built up in the tank, not provided by the fuel pump. Someone on the 1st gen board pointed out the cam driven fuel pump. Good thing I got the Prelude pump.
So we wired it up/installed it all nice and neat...we got power off one of the spades in the wiring harness that previously fed that black box. We were looking for something that was hot at ignition. We found one and it started right up. Took it for a test drive...died about three miles from the house. Towed it home. It started the next day. Test drive..dies in the EXACT same spot. CRAP! Yeah...turns out the spade we used on the wiring harness was related to the choke. Car reaches temperature and it quits getting power. Like I said, we're idiots.

All the USDM carb'd stuff stopped in 87
For 88-91 they went with DPFI(Dual Point Fuel Injection). Kind of a carb design but uses two fuel injectors for fuel instead of bowls/jets/tubes. The manifold itself looks like a downdraft carb manifold.
And a the intake manifold bolt pattern on the 88-91 heads matches the '92+ heads so a DX int manifold with the aforementioned Weber adaptor lets you run a single barrel 34 or the two barrel 32/36 and 38.

There were a couple different JDM models carb'd for '88-91.
1.3L 16 VALVE CARB: 82ps/6,300rpm
1.5L 16 VALVE CARB: 91ps/6,000rpm (I believe downdraft)
1.5L 16 VALVE DUAL CARB: 105ps/6,500rpm
 

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Discussion Starter #14
I know where your coming from.lol Ive done crap like that too. But hey you got it figured out. As far as the b2 manifold it looks to be the easiest of the IM to mod. Especially with no injector holes on the flange to plug.
 
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Hondadog said:
I am looking for any year really as long as its a single downdraft. I think the USA carbed d-series all came before 92. By the way, is that an electric fuel pump? Really nice job on the mods to the intake to adapt the weber.
In South Africa and Australia, as well as Oceania, we had a D15B3 motor in our 4th gen civics... Exactly like a D15B2, except for a single carb (twin barrel downdraft), with exactly the same performance specs as the DPFI of the D15B2. But, being carb, I was able to open the second barrel permanently, for better response, and I rejetted her, which gave me pretty decent high-end gains. I will try to find out what the part number the manifold for the single carb is. I will let you know If I find anything, maybe you will find it useful... oh, and it ran on a cam-driven diaphragm pump...
 

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HOndadog !

I got your mail ! thanx a lot for informations :) :)

But, do you know any 'complete' kit to buy that come with intake, 2 carbs, distrubutor adapted with vaccum or other, and fuel pump ?

It sound to be 'hard doing' that kind of setup ? I want to put forged pistons & rod on my y7 ....

go see my car !

http://www.cardomain.com/id/belette

I want to crush mustang en vr6 ! :) (after mods please :p )
 

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Discussion Starter #18
No these things are pretty much a do it yourself deal. Not many people staying with carbs so there really isnt too much of a market for a kit. The dual carbs came on the concerto, you might be able to find a JDM sohc zc dual carb engine for sale that has everything there.
 

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Discussion Starter #19
What are the possibilities of using an electronic distributor from one of the fi cars? Ive seen mods to V/A distributors when they remove the vac. advance diaphragm and use a spacer where the V/A arm normally screws into the advance mechanism on the distributor. Then they screw it down and plug the hole left by the V/A . I just think that it would be easier to use the newer distributor from the EI. Cant you remove the TDC/Cr/CyPos sensors from say a 88-91 dx or a 92-95 dx and still get the ignitor and distributor to work properly? Since the ECU sensors arent needed I dont see a need for them. Could you still run it (distributor) on a carb setup instead of the old V/A?Also, Im planning on using an electric fuel pump since I cant use the cam operated one. Still trying to figure out which to buy.
 

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Dual Carb said:
Looks pretty good, like the way you've cleaned them up. I wish I could get a D16Z6 head and plant it on my SOHC ZC. But in this country we never got D-series vtec motors... only on import, and that's pretty expensive...

I bet yours will be quite a monster when it's finished. Carbs deliver a nice, even flow of fuel, and any carb junky knows that you can rev higher and use an aggro'er cam with carb than with EFI... would be interesting to see what happens when you add vtec to it.
i asked bisimoto if carbs can be used on a vtec motor, and he recommends that if it is for street use, the vtec should be locked out and an aggressive cam should be used. This is because carbs cant compensate for the vtec changeover. Ive talked to someone who has tuned his carbs for just the VTEC part of the powerband, but his car is for drag racing use only.
 
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