Dual Weber IDF 40s, Carb Rookie question... Options

[malcolm2]

A BIG THANK YOU to ALL...... great to have the knowledge that is freely given here.

Would have been hard to do it without all the ideas and examples etc...

I will update here as I put some miles on the bus....

[r_towle]

I have a lawn mower that won’t start after sitting for probably 3-4 years.
Carb is filthy.
I went to order a rebuild kit….yet a new carb is $15.00.
Webers should be so cheap

[malcolm2]

I have a lawn mower that won’t start after sitting for probably 3-4 years.
Carb is filthy.
I went to order a rebuild kit….yet a new carb is $15.00.
Webers should be so cheap

Price is going up.... I bought one from China for my Weed Whacker a couple years ago. It was $14 total shipped from China. Zening post or something or other.

Yeah this rig was about $1,000 IIRC. (IMG:style_emoticons/default/WTF.gif)

This group taught me a ton about the L-Jet, I should have looked for all the pieces and parts for that set up. My 914 has that, Now I got Carbs and L-Jet. So much to learn!!!

Happy Muthas day to all you Muthas!!!

(IMG:style_emoticons/default/driving-girl.gif) (IMG:style_emoticons/default/driving-girl.gif)

[r_towle]

I have a lawn mower that won’t start after sitting for probably 3-4 years.
Carb is filthy.
I went to order a rebuild kit….yet a new carb is $15.00.
Webers should be so cheap

Price is going up.... I bought one from China for my Weed Whacker a couple years ago. It was $14 total shipped from China. Zening post or something or other.

Yeah this rig was about $1,000 IIRC. (IMG:style_emoticons/default/WTF.gif)

This group taught me a ton about the L-Jet, I should have looked for all the pieces and parts for that set up. My 914 has that, Now I got Carbs and L-Jet. So much to learn!!!

Happy Muthas day to all you Muthas!!!

(IMG:style_emoticons/default/driving-girl.gif) (IMG:style_emoticons/default/driving-girl.gif)

You have a van that may be stored for weeks/months
To prevent you from having to remove , clean, rebuild each season I would suggest you add in a main shutoff fir the fuel.
You park it, turn off the fuel, let it idle until it dies.
You then do not leave fuel in the bowl which turns into honey, then honeycomb over the winter.
This was a standard item installed on all 356s, because carbs.

[GBX0073]

Appreciate all the Information. in this thread
In the process of Putting a 2056 44/38 valves Engine back together where the Shop put in big 48 Webers
I pulled the 40 MM venturi's and will try to make it work with 36MM. and a AFR
Suspect may be a loss cause ,Tempted to stop throwing money at them and getting some 40's /All of the information in this thread will come in handy when its time to fire the car back up.

[malcolm2]

Well, I had hoped that WE were done. I got the bypass screws set to nearly even and the idle to 1000 with everything flowing nicely.

Test Drive. Cruises nicely, up hills nicely, but I do hear a pop pop, as I come out from a stop sign and there is a bit of a hill or I am accelerating quickly from a stop.

Is that a lean POP? Maybe I didn't quite get one barrel at Best Lean Idle??

[930cabman]

Appreciate all the Information. in this thread
In the process of Putting a 2056 44/38 valves Engine back together where the Shop put in big 48 Webers
I pulled the 40 MM venturi's and will try to make it work with 36MM. and a AFR
Suspect may be a loss cause ,Tempted to stop throwing money at them and getting some 40's /All of the information in this thread will come in handy when its time to fire the car back up.

Exactly, ditch the 48's and get ahold of some 40's with either 28 or 32mm venturi's. Will make all the difference in the world.

Also. agreed this thread has gotten some mileage from many experienced guys

[r_towle]

Well, I had hoped that WE were done. I got the bypass screws set to nearly even and the idle to 1000 with everything flowing nicely.

Test Drive. Cruises nicely, up hills nicely, but I do hear a pop pop, as I come out from a stop sign and there is a bit of a hill or I am accelerating quickly from a stop.

Is that a lean POP? Maybe I didn't quite get one barrel at Best Lean Idle??

You are not tuning for idle.
You are tuning to accelerate going up a hill.
Also timing, advance plates in distributor, vacuum leaks etc

[nditiz1]

Most likely it is a lean pop. The svda distro hooked to your vac line should be increasing the just off idle timing. As the butterfly opens a rush of air is going in effectively leaning out the mixture. The additional timing from the SVDA will help with any popping. If it pops or kicks down when you punch the gas pedal you may need to increase the accelerator pumps to account for it going lean during that rush of air.

This is where you start to data gather. You now have a running baseline. If you end up testing the accelerator pumps just be sure to adjust both the same amount and write down how much you turn them so you can turn back if needed.

[Superhawk996]

Most likely it is a lean pop.

This is where you start to data gather. You now have a running baseline. If you end up testing the accelerator pumps just be sure to adjust both the same amount and write down how much you turn them so you can turn back if needed.

(IMG:style_emoticons/default/agree.gif)

But it’s a lean condition that is transient. Don’t increase the idle circuit mix to go way rich and mask this transient lean condition.

As stated - the accelerator pump is what should take care of the transient.

You should be able to adjust the linkage and get there. If not, the accelerator pump bypass can be changed and so can the nozzles. Very tunable - just be patient. Pull plugs occasionally and see how they look. AFM is even better if you can swing it but remember we all tuned these back in the day without AFM.


Keep notes - don’t try to remember. Hell, I have written notes dating back to the 90s. Can’t tell you how many times I used those notes to reset carbs after rebuilds or to just remember what was done three weeks prior that I thought was helping but later decided wasn’t the fix. Notes let you go back to a known baseline easily.

[malcolm2]

I have been doing some searching about the Pump adjustment. I seem to be leaning toward the CC measurement as well. Gonna be tricky getting a bunch of syringes and wires etc....

Do you feel that is necessary? Even with that, the "nut turning" is required.

I counted threads and got 10 threads or so showing on each.

More threads will equal more PUMP, right?

So i figured I would turn 1/4 turn and drive. Hitting the same stop sign and load point each time until I get no popping.

Sound logical?

TO BE CLEAR.... when you say LINKAGE above, you mean the accel pump linkage, right?

[Superhawk996]

I have been doing some searching about the Pump adjustment. I seem to be leaning toward the CC measurement as well. Gonna be tricky getting a bunch of syringes and wires etc....

Do you feel that is necessary? Even with that, the "nut turning" is required.

I counted threads and got 10 threads or so showing on each.

More threads will equal more PUMP, right?

So i figured I would turn 1/4 turn and drive. Hitting the same stop sign and load point each time until I get no popping.

Sound logical?

Yes, sorry for lack of clarity -- I meant the accelerator pump linkage. At this point, don't mess with your main carb linkages.

I never did the CC measurement thing. Can't be a bad thing. I just never found the need.

I think you'll find that you will need more like 3 (or more) turns (in) to make a meaningful difference that you'll perceive. Also be aware that adjusting the nut has a limited range of increase / decrease. It is usually enough to move the needle so that you can learn what the engine wants. However, to make bigger changes, the accel pump bypass jet (bottom of float bowl) and/or the nozzle will need to be change. Not likely you'll need to do this but if you find that moving the nut in helps but eventually it doesn't help moving it in further, you've reached the limit of what can be done via the nut.

Moving the nut is just tweaking how far the accel pump diaphram is allowed to move as it sucks fuel in.

The accel pump bypass jet varies how much fuel is allowed to flow backwards back into the bowl when the accel pump is activated. I forget how Weber sized these by number. A zero bypass does what it implies, basically a one way check valve that allows fuel in but no flow in reverse direction back to the bowl.

[malcolm2]

In High School, I had a buddy.... used to buy and trade Trans Ams..... He would go drive one and tell me "I'm not gonna get too excited about it...."

Well, I am pretty EXCITED about it tonight.

I moved each side's pump nut in 1 turn..... big help

then a 1/2 turn..... maybe a bit more better (IMG:style_emoticons/default/piratenanner.gif)

+ another 1/2 turn (2 total)..... No POPS.

And I was driving with the hatch off so the engine was roaring right there with me. Remember this is a TIV 2.0 in a 72 bus.

These were short drives, from cul de sac to cul de sac not really any big hills. Enough load to make it pop before, but not now.

Tomorrow I will travel a bit further.... This is great.

Now, who is gonna tell me what adjustment or tweeking will be next??? Is there a next?

Thanks again. Longer drive is coming!!!

[rhodyguy]

I think you got it. Button it up and drive around. I would not stray too far. Carry the appropriate tools. Have fun!

[930cabman]

This is a great experiment for us carb guys. I have lived with pops, sneezes, and the like for many years simply by being lazy. At least now I have one less excuse

A big shout out to all contributors (IMG:style_emoticons/default/beer.gif) (IMG:style_emoticons/default/beer.gif)

[GBX0073]

T (IMG:style_emoticons/default/beerchug.gif) oo US Carb Guys (IMG:style_emoticons/default/drunk.gif) (IMG:style_emoticons/default/beerchug.gif)

[r_towle]

Carbs are better than FI

[nditiz1]

I'm a carb guy and do not think carbs are better than MFI, EFI, CIS

[r_towle]

1) carbs are better than FI
2) you cannot turbo a 914
3) it’s not a real Porsche

@clay what some of the other longer term “laws” regarding the 914?

[Superhawk996]

Now, who is gonna tell me what adjustment or tweeking will be next??? Is there a next?

Thanks again. Longer drive is coming!!!

After driving some more - keep monitoring plugs to determine if running rich or lean.

Really suggest that you find a nice flat stretch of road where you can get up to about 60 mph for a bit. Pull the main jet / emulsion tubes. Super easy to do. Get a feel for how much time is spent driving on idle circuit and where that transition to the mains occurs. Without the mains in place, that transition will be where the car just begins to fall flat the more you open throttle and the higher the RPMs. Don’t drive in that condition for long (you’ll be running lean) but find it then back off / slow down - back to running on the idle circuit.

That transition to mains is dependent on speed, load, throttle opening, and RPMs. It really helps to get an idea of just when you need the mains.

When you’re done playing - just put the main tunes back in and you’ve now learned more about your carbs and tuning them - for free!