RonDori

Hey guys,

Did a search on this but hard to find some solid input regarding the streetability of a weber carb. If the carb was for a daily driver, is the weber a good choice in terms of engine start-ups, idle, and driving in the lower rpm's?

I'm aware that the Holley is a better choice for street applications, but I really want to run the famous Weber . Is the Weber THAT bad compared to the Holley on the street?

This will be going in a 6 port 13b stock port.

Thanks for the input guys!

purple82

I had a 48 ida Weber on my 6port mild street port s5 13b for a couple of years. It's hard to make universal comments because tuning can easily change things, but I'll comment on what I found.

On an engine with an 8000 rpm redline, it couldn't be perfectly tuned for all rpm. My car was pretty strong over 4500 rpm or so, but rough and bucking under than. I think it might have been a little lean near redline as well ifI wasn't flooring it. The lack of choke made it hard to start if it was below 50. Impossible if it was much colder. If it did start, I had to heel and toe for the first 5 minutes of driving to keep it from dying.

My opinion is that this is a great carb for racing, where the flow needs to be high in a narrow powerband. But a more complicated carb is more complicated to be more friendly on a street driven car.

Fuel mileage was pretty sad with the Weber too.

I ended up going to fuel injection and I'm much happier with the way the car runs. Better torque in low and midrange, just as strong at top end, better part throttle driveability and better fuel efficiency.

j9fd3s

iTrader: (3)

its all in the tuning. the carb needs to be setup and functionally working right too (boosters can't be loose, float level can't be too high, etc etc). most people also use the wrong E tube, F11 has no place in a rotary, F7 or F8 is a good start.

on my car, which is a 12A P port, i spent a LOT of time trying things, i worked my way up from idle and i'm surprised at how nice it does run. there are a couple of compromises in mine too, but nothing too bad. the PP has different ones than a stock port, so i don't need to list em, unless you want.

other than that its actually a lot simpler than most tuning guides will tell you. actually you need to learn what does what in the carb, and what the engine likes, once you do that its pretty simple to see what you need to do. oh also, keep a note book so you don't have to remember anything.

for example, i started with the 80 idle jet, then tried the 70 then the 60, and i just made notes, then i picked one. then after driving around with no main jet stack, i started playing with those, then the air corrector. if you took notes, its really easy to see what part does what, which makes it really quick and easy to tune

PercentSevenC

I had no problem with my 45 DCOE as a daily driver once I figured out that what works for one person won't necessarily work for another. For instance, F11 e-tubes were the only ones that made my car drivable, and I have to run way smaller idle jets than what everyone recommends. Dunno why. Point is, you have to be prepared to learn how the carb works so you can figure out what jets YOU need.

Once you do that, they're great carbs. Mine always started up fast, idled reasonably well, and had good power despite the carb being undersized for my engine. You do have to deal with the lack of a choke, but that's not really a problem once you get used to it. It certainly deals with hard cornering and stopping much better than the Holley I used for a while.

Lotus000

I am running a 45 IDA on my 4 port 13b street port. I have not put a lot of miles on it yet so keep that in mind.

It isn't great for low to mid range RPM, but the high end power is nice. bucking or surging at the low end is easily fixed by adding a 3rd progression hole (and a little driving technique). F11's are the devil, I think I'm running F7's or F4's (id have to go look).

Between my experiences with a stock nikki, stock GSL-SE EFI, and the weber carb I would say the weber is the least street friendly (but also my favorite to drive)

t_g_farrell

iTrader: (1)

The sidedrafts (DCOE) will be a little easier for streetability as they usually use a wrap
around manifold thats longer than the downdrafts (IDA,IDF,DCD etc). The longer
intake moves the torque curve down a bit.

rwatson5651

iTrader: (5)

Like J9fd3s says its all in the tuning, if you are not willing to do what it takes to learn to tune it then you could end up with drivability problems.

My suggestion is to get a good manual, ( I bought four different ones) and most importantly a wideband O2 guage. The wideband changes carb tuning from a black art to childs play.

I was told that the sidedraft on my 4 port 13b would always have a stumble just off idle, but once I got the wideband I got rid of the stumble completly and I love it.

j9fd3s

iTrader: (3)

the off idle stumble and low end bucking are jetting problems, no need to add the 3rd progression hole; although that is an option.

i've only done my P port, but i got that to drive so nice, i see no reason why a stock/street port couldn't drive like stock

13x

interesting thread ...
but what if the setup you got is not rotary friendly is there a general base to start at then adjust from there?

granted carbs are not the most difficult thing but after 30ish years of turning wrenches my brain has not had that ah ha!! moment when it comes to carbs.

j9fd3s

iTrader: (3)

the starting point depends on the engine, but yeah generally for the webers there are some decent guidelines.

idle jet should be around 60-65-70, emulsion tube should be about an F7 for a 12A and F8 for 13B i think. the F11 tube doesn't seem to work for anything....

the main jet should roughly correlate to hp, although the BSFC, mixture you are aiming for and fuel pressure matter. a 12A seems to want a 175-180 jet, the 13B is around 200 give or take.

air corrector seems to end up being 130-150. the air corrector helps the main circuit start, so too big = lean bog, too small = rich bog.

13x

thank you very much, atleast I can see how far off it may be, it has never run right with the Weber since installed ... the stripped Nikki I did was a hell of a lot better as far as power, torque(lol) and milage but would rather try and stick it out with theWeber, I would suspect it has greater potential and it does look better ... I do get that right foot is a key component suck as a 4k stomp with the mechanical secondary Nikki

FunK73

iTrader: (6)

I daily my dellorto side draft. I had no complaints from temps of 110 to 20 degrees. got me to work every day no issues. They can be skiddish when engine bay temps are low (intake icing issues). Its just gonna take some time to fine tune the tune itself, and be ready to make adjustments occasionally. I also NEVER needed to use the choke, even at 20 degrees. Just play with the gas for a little bit and then she'd idle no issues. My tune was rich and timing was set to stock. Ran fine.

rwatson5651

iTrader: (5)

I also have had occasions when the intake manifold would, for a short time during warmup, would get covered with a thick covering of ice! Never was a serious problem though, as it would go away after a brief period and was more of a interisting curiosity than a problem.

13x

I've seen the frosting .. soon as bay temps would go up it was gone ... does make ya ask why it happens

rwatson5651

iTrader: (5)

It happens when the ambient air is laden with moisture and is drawn into the carburator venturi it is cooled to the freezing point. The temperature drops for three reasons, first because of the expansion caused by the engine suction, secondly because of the increase of speed through the venturi and thirdly the liquid gasoline introduced into the airstream must evaporate, and the heat of evaporation is extracted from the airstream, causing it to further cool. The temps in the intake can easily drop below freezing and when it is sufficiently humid, it freezes. This is why airplanes have carburator heat so that during periods of partial throttle operation carb icing is prevented.

13x

wow well put,

rwatson5651

iTrader: (5)

I copied from wikipedia., but I know about it cause Im a pilot.

13x

LMAO

was going to say, but I'm in Sin City and you said moisture in air, but didn't want to come across as being a jerk lol

Siraniko

iTrader: (13)

stick with Nikki and lemme have your webber so I can put it to better use.

13x

hey wacky ,,i,

Siraniko

iTrader: (13)

grow some ***** and say it LOL

j_tso

iTrader: (2)

I've been driving a side draft for a bit over a year now, on an S4 13B 6 port, first with a 45 DCOE and now with a 48 DCO/SP. Tuning is not going to be the same for every engine, I've found out I needed smaller jets than what's recommended. There are several threads with people's jetting, though it's mostly with 12As.

I've found no trouble driving mine any day, but since there's no choke warm up is a little longer. Not sure why, but the 48 DCO seems to start up better than the 45 DCOE. When it's really cold I had to keep the engine at 1500-2000 rpm for about a minute before it would idle on its own, whereas with the 48 I only had to do that for about 10 seconds.

Biggest drawback is fuel economy suffered quite a bit compared to the 2nd gen EFI I had on it before. I switched to a Weber because I already had the carb for another engine and for over a year I couldn't solve the problems EFI was giving me.

Adding to the tuning discussion, I like the F3 emulsion tube best so far. It's exactly the same as F11, but a little narrower letting more fuel in. F7 made my engine bog while cruising or lower rpm, maybe it's better for an IDA set up.

deadphoenix52

iTrader: (2)

my 7 isnt a daily driver. but ive had no issues starting even in the cold. 30-40F. i have a 47 OER which is basically the same as a 48weber DCOE. like people have said you may have to hold the gas for the first ten or so seconds the engine is running.

and be prepared for 12-15 mpg.

13x

thanks guys,

first my car is by no means my daily she's a very low vin and dailying it would just tear her up

as far as starting thats not an issue, pump pump, crank, fire, hold at about 1500 for several seconds. Thats cold starting warm starting say when we are wrapping up one of weekly meets reach in the window crank, fire, let run for a couple minutes and go


Oh and Wacky ... oh hell no crazy sob you must have hit your head lol

patmac6075

iTrader: (26)

Ha Ha ....cold 30-40F!!!

was -2 last night...my kid was wearing shorts and a hoodie to basketball practice...My 7 (nikki) started right up though.