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I am going to run dual mikuni/solex 40 sidedraft carbs hopefully soon and am wondering how do you people like these compared to stock downdraft. How is the throttle response? power? How many seconds faster was your auto x time with the sidedrafts compared to without?

Just a hint, but you might want to be a tad more specific.  Like, what kinda car you have etc. 

I have not run dual sidedrafts on my car.  But then again, I have an STi.  I did run twin Weber 36DCNFs on my Yugo.  So in my opinion you will be 3.74 seconds faster.

Chris H.

Sorry. I am going to put my dual mikuni 40 sidedrafts with syncronizers on an 82 toyota starlet (1.3L pushrod 4KC engine) with no other engine mods except for headers.

properly tuned, you will should see an improvement.  What was your stock carburetor?  I know on my car the single barel Solex was the limiting factor.  It just could not breathe enough.  Installing webmer 40 DCOE made a great improvement.  But they have to be tuned properly.  Mine wsa done on a Dyno.  Took a couple hours to get all of the jets and timing right.

steve k.

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[color=#990000]KGB-Racing Merchandise
"Super Karate Monkey Death Car"

This is basically like comparing apples and kumquats, but FWIW:

My 77 MGB has the stock smog cam and low-compression heads. It had the single sidedraft Zenith/Stromberg 1.75" (if I recall correctly).

When the carb died, I replaced it with a Weber downdraft that was supposed to be a mild street setup. I think it was a 36DGV, but I'm not sure about that.. I also installed headers at the same time (mechanically necessary to change both together on a "B"). I never could get that setup to run right.

I finally replaced the Weber with a pair of SU 1.75" sidedrafts. The stock dual carb setup in the 60's used 1.5" carbs, and my engine certainly doesn't breathe as freely with the late model cam. In theory, it should have been over-carbed, but in practice it runs great. Low-end torque and responsiveness was greatly improved.

Note that I used NEW SUs (HS6). The throttle shafts aren't bushed, so old worn-out SUs are notorious for airleaks, but there are ways to fix that.

The SUs are noteworthy for having a dynamically variable throat size, and it works great. I know nothing about the Mikunis, but I think there are some SU copies that were used on some early Japanese sports  cars.

Two 40mm side draft carbs is a LOT of carb fora 1.3L car. That is a 40mm throat for each cylinder, which is probably not much more than 400 mm in diameter. :)

I ran 40 DCOEs on my 1.6L Toyota Corolla for a street setup and found that you could not get the mid range tuned to work properly OR you would get horible ga mileage. The carbs were running on teh intermediate circuit on the street, even at highway speeds (FAST highway speeds). So you had to lean out the intermeidate circuit, which cuaased as stumble when transitioning from idel to main circuits.

You can make it work, but it will be a compromise between on course and street performance.

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Terry Carraway
WDCR
SRF 561 Red/White #4

I run twin 44 Mikuni's on my 2 liter Datsun motor. I can't compare them to a down draft , but compared to the Hitachi SU's they work better at the top end. A few of the people I know who switched from down drafts to side drafts. Mostly in Datsun 510's , used a single 45mm on a single sidedraft manifold. If the double 40's are going on a stock 1300 you will have problems tuning them for the
flow you have. It could be done, but they would be fairly choked down. Way to many factors effect carbs. With injection the ECU adjusts by the parameters they receive from sensors.

Good Luck !

Mike

If tuned properly they are about as good as FI.If you want to put them on a peanut motor just get smaller chokes to slow the flow.Jet down mains ,air ,fuel, pilot jets too.plus the low speed ones.Totally adjustable to what ever you need if you know what to do.There is also an accelerator pump that you can make adjustments to too.

                                            Toddzilla

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srl311

I HAVE DUEL MUKINI 48 SIDEDRAFTS FOR SALE 

WHIT INTIKE  AND GOOD CONDITION. FOR INFO EMAIL TO NACHAPOP@HOTMAIL.COM

IMHO, skip the sidedrafts & put fuel injection on it.  I've done both - dual Webers on a couple of VW motors, my current BMW.

Well set up, I don't think they give up much, if any, power to good EFI. Maybe a smidge here and there, but when properly jetted, they're really good.  

 Thing is, they're NEVER right. 

Ever. 

 Too many variables, constant changes made them a continual source of tinkering. 

 EFI is more difficult to put on a non-FI car; you have to run fuel lines, more wiring, different pump, etc etc etc - but once done and adjusted, voila - the car just works. 

To me, that's absolutely worth the headache on the front-side.  It'd be pretty easy to swap dual sidedrafts onto a carbed car in an afternoon, and it'd run by the end of the day. 

EFI?  Probably not in a day, but once it runs, it'll run pretty well.

Trip to the dyno (pretty much required for EFI or carbs, to do it right), the carbed car will run well that day. So will the EFI car.

Thing is, once it gets cold, altitude change, whatever, the EFI car will adapt - the carbed car will not.  It'll still run, but you'll be making changes here and there and IMHO, it is not worth it - Megasquirt is not expensive, and once done, it is done. 

I got pretty good at making dual Weber DCOEs work.  I'm not anymore; I put Megasquirt on my 2002 3 or 4 years ago, and it just works.

I like that.

As far as dyno stuff - I put a wideband on it, drove around on the street and had my passenger adjust the mixture on the fly, based on what the wideband said.  It worked, it ran well, I was pretty happy.

Brought it to the dyno, did the same thing; leaned it here, richened there, $100 at the dyno netted me 12hp - about a 10% gain, and the car certainly did not feel like it was down 12hp BEFORE we went.

The dyno is your friend.

 I used to like carbs.  I don't anymore, especially considering just how easy/cheap it is to put fuel injection on a motor.

 

Iain


 

Iain Mannix:

IMHO, skip the sidedrafts & put fuel injection on it.  I've done both - dual Webers on a couple of VW motors, my current BMW.

Well set up, I don't think they give up much, if any, power to good EFI. Maybe a smidge here and there, but when properly jetted, they're really good.  

 Thing is, they're NEVER right. 

Ever. 

 Too many variables, constant changes made them a continual source of tinkering.

I'll second that. In the late '80s I had an F-Prepared 240Z that I put triple Webers on it. 40 DCOEs with 34 chokes. The tuning was a nightmare. Getting the chokes right, the mains right, the accelerator jets right and the velocity stack lengths right was like playing battleship. I ended up enlisting a Production racer to help me get it in the ballpark and then spent a year getting it fine tuned. I ended up changing the mains at every event I went to based on the air density.

The last year I had it I swapped to Haltech Fuel Injection. Very crude and expensive compared to what's available today, but it changed the car. Idle was easy, midrange was fatter, and no stumbles or flat spots like the Webers. Plugs lasted longer too. If there's any way to use programmable fuel injection instead of the Webers, do it. The only advantage the Webers had was aesthetic. 

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Aut tace aut loquere meliora silentio.