So, ScottyB spent all of yesterday trying to get my carbs properly adjusted.

We can not get it to idle well below 1500 rpm. it sings around 3000, and screams above 4000. Even wthout load, we can tell the carbs are tuned for top end only.

Here is the deal. My motor is a 2056. The carbs are 44 webers. I KNOW that I will have an easier time with 40s. But I don't have 40s. And I know that folks around here have gotten 44s to work with a 2056. (I'm looking squarely at you here, OpaAndy).

So, engine particulars.
2056 motor.
compression test gives a range of 135 to 148psi on a warm engine
WebCam 494 grind
Valves are (freshly) adjusted to .006 in and ex (as per the cam card)
Deck deck height is .040
CR is 9.5 to 1 (calculated here: http://www.cprparts.com/ci_calc.html)
Exhaust is EuroRace header with a turbo muffler
My house sits at ~700feet elevation, but my driving area is between 100 and 1000 feet (I live around foothills)

How should I jet these carbs to work with this motor? What should my venturii size be?

I CAN NOT put my motor under load yet. The motor is in the car as of yesterday, but the car is NOT yet drivable.

Zach

Zach, have you read Harney's Carburetor Clinic on tuning Weber IDF's?
I've got it bookmarked and seem to remember a description of jetting sizes/effects upon power bands and tuning.
Mike

Your venturis are to large.
What size do you have?
32mm is (I think) the smallest vent for a stock 44mm carb.
Aircooled.net can have smaller ones made up...

On 40mm carbs, a 28mm vent is nice for low end grunt.

The 44mm is just the potential size...the vents make it smaller.
The problem is that the stock sized vents for the 44mm body are still to big IMHO....
Call aircooled.net...they are really cool and can help you out.
They have a large spreadsheet of carb jetting setups from customers that WORK...and they will actually SHARE this information.

The last time I did this, they swapped jets and vents with me till it ran perfect...I only ended up buying one set, paid for shipping (USPS cheapo box) each way, just twice.
I ended up with 31mm vents...it was a special motor though.

Rich

http://www.carburetorclinic.com/weber_tech.htm
Mike

bear with me a minute. with the linkage disconnected, you can not achive an idle around 900 with the idle adj screws only ? even if the screws are off the stops? 32mm on the vents.

Zach-

I have dell 40s on my 1.8 (equiv in flow to weber 44s) and I'm doing okay. Your 2056 will be fine with 44s. What vents size are you running right now? Sounds like it is too big. I've got 32s on my 1.8, 30s would be ideal but I couldn't find them. I'm pretty sure this is my approximate jetting setup:

55 idle jets
55 pump jets
140 main jets
180 air correctors

I run kind of rich so this may be an okay baseline for you.

-Chris

Oh, we could get it to idle at 900. But it was lumpy. At 700 it would lump, sputter, and start to die after a minute or so if we did not goose the throttle. It did not start to even out until around 1200, and really smoothed out around 1500.

Zach

Another wrinkle. I don't know my vent size. I can not figure out how to remove them from the carb. I can't find the set screw, and worry that they are staked some how, so I have not applied any force to remove them. Help in this area would be greatly appreciated.

Zach,

Looking at the notes on my 2056 with Weber 44s... cam is WebCam 86A .435 x 290 deg.

Venturi Size: 36mm
Main Jets: 135
Idle Jets: 50
Air Correctors: 200
Emulsion: F11

-Mike

I've go a similar 2056 with 33mm venturis in weber 40's and at 900 foot elevation has good low and top end. I cant remember jet sizes but could easily check.

Jule

Sounds like you have a vacumn leak, get starter fluid and check around carbs and then the intake manifold. On mine I found the intake manifold was not straight where it bolted up to the head.

Are these webers?

The set screws are on the side, about halfway down the outside of each venturi.
Look on all three exposed sides...3, 6, and 9 oclock...

the upper vents, the ones with the round part in the middle are held in by a spring, but that spring is captured by the top cover of the carb...so you need to remove the top of the carb to get the top vent out.

It can be corroded and will take some gently persuasion to remove the top one.

Show a pic of all three sides of the carb and I can show you where the set screw is.

To find out what vents you have installed, you need to look down the throttle body and on the top edge of the main venturi is a number stamped into the vent.
If they are custom, you may not have this number.
Otherwise its on the top edge of the lower venturi.

I dont know your camshaft but think of it this way.
Higher HP numbers are only made in the upper RPM range.
One of the guys posted that he has 36mm vents...
That is great for a race application...WOT balls out driving, but it would suck around town...you would have slow air speed, and to much slow moving air.

If your camshaft has alot of overlap then it will run great at the upper RPM range and would be designed for bigger valves, large venturis, and will even out when the overlap is useful...high RPM.
At low RPM, camshafts with alot of overlap will run like a harley...very lumpy or loping...that is ok. They can be tuned.

The key is the amount of air you are allowing into the motor (its an airpump) and from there you figure out your jets to match...not the other way around.

Rich

Doesn't matter.

I will also bet on a vaccum leak. I use the grey RTV from permatex on each side of the phenolic gasket. no paper. Works good. CUZ of course that's what Jake said to use.

What size idle jets????

Are you able to lean out the idle adjustment screws to nearly shut off gas?

Um New engine??? timing set at what?

Ignition set up?
Spark plug gap?
Have the plugs fouled? Very possible as it sounds like a new motor.

Disconnect the linkage on one side and set idle speed. then tweak mixture screws re-set idle speed reconnect linkage and then synch carbs while engine runs at 2500 RPM off the idle stop screws.

OK here's my two cents. Just got finished building my 1.7L to a 2.0L. 2.0L crank, rods, pistons barrels. Mild cam. Empi HPMX 44's. Weber knock-off carbs. Parts are interchangable. When I fired it up it ran and idled very well. It did however pop a little through the carbs. When I drove it, it had a serious low end bog but ran well mid range and top end. Got some advice from the local porsche repair shop as well as an off road shop. Both agreed the venturi size was too big. Carbs came with 36 mm veturies, 50 idle jets and 50 squirters. We went down to 34 mm venturies and the improvement was huge. Still had a touch of bog when I would give it gas at low RPMs. Rather than going smaller on the venturies they suggested going up on the idle jets. Went from 50s to 55s. Low end bog was gone. It responds very well anywhere at low end now. Does seem to idle a little rich though. The way it was explained to me is that if the venturies are too big there just isn't any vacuum being created in the motor, hence the popping back thruough the carbs and the inability to accept fuel. They also said you want the largest venturies that will run well. Too small of venturies will give great response in low RPMs but you will lose top end. So try reducing the venturies slowly. Put a smaller set in and try them. Stop when you get close and go to jetting. I am not an expert here, I just went on these peoples advice and it solved my problems. Word to the wise, when you take off the tops of the carbs if they are still on the motor put something down the carb throats to catch parts. I don't know if webers do it but when I took the tops off the Empi's a couple of spring loaded somethings held in by a crush washers took off on me. They are supposed to stay in the carb body on one side right in the middle and there are two per carb. Hope this is helpful...again just my two cents.

Hope you put the springs and washer back, there for the choke with out them your
engine will run rich.

So that's what those are....one of them went half way accross the garage and I had to take the battery out to get another but I found them and re installed them. Seems like the lock washer looking keepers that seat into the top of the carb body should hold them down better. I got the springs and parts back down the bore and gently tapped the keepers in. I was thinking that if I take them apart again I might put just a dab of RTV glue on top of them and make sure it's smooth and flat. Any other ideas on how to control these little suckers?

I just pulled a carb and took stock of what I had. Many thinks to those that have helped this far, I have learned a lot.

Here is what is in the carb:

Venturi: 32mm (not stamped anywhere as far as I could see, so I measured 1.258 inches (31.95mm))
Aux Vent: 4.5
pump jets: 50
Main jet: 125
Emulsion tube: F11
Air Correction 200
Idle Jet: 55
Inlet Valve: 55

Thanks

Zach

Change the mains to 135 that should help the low end and the idle. The book says
the main are used above 2800 rpm's but the idle circuit gets its gas through the mains.

bigger main jets is compensating for the low air speed created by using a venturi that is to large.

Drop the vents to 28-30...both custom sized but you need to increase the velocity of the intake charge.

Your camshaft, what is it, who made it etc?

Rich

I have been emailing with the guy at Aircooled.net. He seems to think that for my cam (Webcam 494 grind) my vents and jetting is "darned near perfect."

He thinks my issue is either float level or air leaks. I know my 3/4 float is good, and I am pretty sure my 1/2 float is good. So, air leaks.

Now that the motor is in the car, I actually have a lot of hooking up to do before I can start it for more testing. The gas tank went in tonight. Though I may need to fiddle with the fuel lines under it, I am not happy with how they are running.

Zach

well keep on trucking but watch your plugs and smell the oil for the first two oil changes...
If its to rich the rings wont seat.

My personal experience showed me that higher velocity intake charge (smaller vents) created a motor that pulls right off the line and topped out at 5500-6000 rpms.

Slower velocity intake charge created a motor that lugged off the line, ran poorly under 3k rpms but scared the crap out of me (a big smile) from 3k -7k rpms...

The smaller vents are a more managable street driving and MPG setup.
the Larger vents and jets are great for beating the hell out of the car,

For you...just leave the carbs on the shelf...keep them covered with plastic so they dont get dusty and you will be fine...your not gonna drive it, right...

OR .....will I finally get to see your ugly ass at Hershey ....IN THAT CAR..

Rich

Hopefully.
All the major systems are actually in the car now, so all I need to do is tie everyhting together and get it to the state for thier approval.

Zach

Wish I could come over to play...too much stuff to do school wise. Soon, though.

pa build marathon party....

Zach...when is your winter break???
You must get a little time off from school work???

Rich

I get off the week between xmas and new years off, free and clear. From New Years to ~the 14th I have to work, but no classes. I'm hoping to have the car able to be driven down to the titling office the week I have off. Not perfect, but able for the state to say "okay" and get my title ready (can take months).

how lumpy is the idle at 1050? can you live with the off idle response at that rpm? with the cam and what not you may have to live with a compromise if the induction system is well sealed.

k

When we had it idling it would load up so that if you gave it a blip of throttle it would bog down and die. However, if you managed not to kill it with your blip and blipped it again it would rev just fine. You would also see fuel spitting out of the intakes when blipping the throttle.

I think that chasing air leaks would be a wise first step as you will always wonder if that is the problem and it is easy to do. I also agree with the use of sealant instead of gasket between the phenolic block. Jake recommends it, enough said. You can use a MAP or propane torch (un lit of course) to see if you get a jump in RPM when you put the nozzle near a specific spot.

The phenolic gaskets that I have are paper backed on each side. If I find a leak there, I'll add the rtv. Right now, I bet that it is an air leak (or many leaks).
However, I have to get the fuel / electric components put together before I can do more testing. Most of that I can do myself, but I'll need some help with the elecrical bits.
Zach

Is there supposed to be a gasket on one or both sides of the phenolic spacer on FI cars? Mine has none.

I don't remember. Its been 3 years since I yanked and sold all the FI stuff.

Zach

Zach-

Did you actually check the float level at low and high positions? Or did you just check to see if they still floated. If they aren't set right it is possible that gas could be filling up the bowl too high and dripping down the throat. Happened to me. I could see that creating the symptoms you have. Bogging down at idle, eventually rev past it, then the next time you rev shortly afterwards the bowls haven't filled up enough yet to be draining down the throat. Check to see if any fuel is dripping down the throats with the pump on and the engine off.

-Chris

My floats are both ~10 to 11 mm when closed. I have not measured the max open position, but the Weber tech book says that is not very important.

Zach

Have you checked to see if fuel is dripping down the throats with the engine off and the pump on? I thought I had my float height set right and I still had dripping. Sometimes the needle doesn't seat right either. Just some ideas.

-Chris

Fuel pressure can only be 3lbs max any more than that the carbs will will not idle
right.

I know that the pump is a carb fuel pump, but I have not measured the pressure it puts out. Putting a regulator in line may not be a bad idea. That said, i have not noticed any issues with leaking or overpowering the float valve once the bowl is full.

Zach

Is it a rotary (cylinder) or diaphram (box)? Rotarys are usually self regulated, diaphrams are not.

Electric rotary. No clue on the brand or output.

Zach

If its the rotary pump from Aircooled its set at 3lbs other wise the other brands youbuy from a automotive store is set for 5-7 lbs so you need a regulator. To make sure but on a pressure gage and measure the pressure.

Slower velocity intake charge created a motor that lugged off the line, ran poorly under 3k rpms but scared the crap out of me (a big smile) from 3k -7k rpms...


EXACTLY what Zach's engine was doing on the ground with no load on it


Have you checked to see if fuel is dripping down the throats with the engine off and the pump on? I thought I had my float height set right and I still had dripping. Sometimes the needle doesn't seat right either. Just some ideas.


Checked that and no it's not dripping when off


Something else to note. I was having a HELL of a time getting 3-4 to balance, had a hard time even getting any pull. Then I checked the spray....looked like poo. I ended up pulling the diapragm out of that carb and it was stretched more than Madonnas twat. Zach found a new one and I put that in. NOW 3-4 acted right. 1-2 had a " decent " spray but I think he still should replace that diaphragm as well.


Zach if you do rtv the gaskets just rememnber how I did the other gaskets. Just a thin layer spread out evenly, you don't want it oozing out like it was a rednecks 350

I agree: The jetting sounds like it's in the ballpark and a vacuum leak is probably your problem. I know I chased mine for quite a while. I don't want to open a can of worms here so take this with a grain of salt...................for some stupid reason I didn't install the phenolic spacer between the manifolds and the head. I felt that a little heat on the manifold would help idle and low end. It may not be too good for top end ultimate power, but I'm very happy with the way it runs! I always thought the phenolic was a FI thing. Also don't expect to get the thing tuned to perfection before you've broken in it! Good luck!

In the old days a 48mm intake valve was the way to go...that is what FAT did...
Bigger was better. Bigger carbs, bigger valves.

Well, now we are here, today.
The smaller valves matched with the smaller venturi creates a faster speed, or higher velocity intake charge. 44-46mm intake valves are more the norm nowadays...44mm intake valves with the right cam are amazing if tuned right.
This introduces more air speed and a finer atomised mixture into the intake valve.

the larger carb venturis that Zach has do two things.
the air moves slower and so does the fuel...so the atomization is not good until you hit the VE of that venturi...so when you hit 3k rpm it takes off because NOW you have the velocity to actually do a decent job of atomising the fuel...

Big vents require big main and idle jets and a bigger qir correction jet.
All of the larger jets are just compensating for the slower intake charge.
The net result is the car will run, but not optimal.
It will get worse gas mileage.
It will run like a raped ape at WOT.
All of that is basically how you tune a race car/autox car that gets trailered to the event. These cars get 10 mpg.

For street you want smaller vents, more intake velocity and smaller main/idle/air correction jets.
Also think about the F7 emulsion tube that tends to produce a better transition circuit for street...again the F11 is great for a race car/autox car but sucks for the street...this is the classic 2800-3200 stumble that people speak about...

Rich

learning a lot in this thread

another thing to consider if you go chasing leaks. check the bases of the intake manifolds. used ones have been torqued countless times. overly so i think. if the bases are out of true the leak will be built in.

k

Standard setup is like this
head<>gasket<>spacer<>gasket<>intake manifold<>gasket<>optional spacer<>gasket<> carb

where you see the <> I use red, high temp rtv gasket material...a light coating so it does not ooze out..

Rich

and...do not use steel cut washers under the intake stud nuts. this is where the (overly so) factor comes into play. what works real slick are the schnorr (sp?) washers used on the cv joint bolts. is does not take alot of pressure for them to do their job.

k

I also had a leak on my carbs which I chase for over 2 months. Found out that
the cooling tin which goes around intake on the heads was not recessing correctly
when the gasket and intake manifold were bolted on, the sheet medal was holding
the gasket and manifold up, although it look sealed. I lossen the sheet metal and
position so it was fitting right, below intake ports, added new gasket with rtv, No
more leaks!

[/quote]
My floats are both ~10 to 11 mm when closed. I have not measured the max open position, but the Weber tech book says that is not very important.

Zach
[/quote]


Max open is important. The lower the float goes the farther the valve opens. If you limit the opening you limit fuel volume when you need it the most. When the float bowl is almost empty.