Now that the milder 2056 is in the car, I could use some advice on carb tune.
compression is at 8.8:1, valves are 44/38, cam is Webcam 86a.

Weber IDF 40's have
37mm venturis,
135 mains
airjets 200
F11 emulsion tube


I am told by the builder that I should step down to 34 venturis, but, have no idea where else to start. Car will go to a good tuner soon enough, just want o have a good starting point.

I would start with 115 mains, 28 vents, 50 idle.

Once you get the baseline for the engine then you can move up and down with the vents and mains. Vents will move your powerband. The higher vents you go the less punch off the line you will have, BUT you will carry the power to redline, whereas with 28s you will have a lot of punch, but fall on its face ~4700

Agree with above
Venturis are fir airflow volume and speed
Smaller venturis offer faster yet less air at low rpm
28mm is right for Street application
I think it has always been up by 2mm each time.

I have a box of multiples of each part….each motor is different, and your elevation also matters.

28mm vents
Tune idle jets, f-tube, and main jets to your needs.

Starting small generally works better in my experience. With a 37 venturi you may not be getting the necessary signal. My recent 2056 with similar specs runs great with 28 vents. I have considered 30's but too many other fish to fry these days

Yeah. 37mm and 34mm vents are HUGE. They make sense for a race car running WOT all the time, but not for a street driven car. Vent size will change your powerband also. I had 44's on the car with (I think) 32 vents and the car made a ton of power above 4K and was a total dog until 3500 rpm. When I necked down to 40s with 28vents powerband moved to a much more usable range.

Start at 28mm.

50 idles. You may need to go up to 55 idles. I tried 60 and started coking up spark plugs. Most of your driving is on the idle jets.

I had 120 mains on my 2056 and it liked those.
F11 is fine for emulsion tubes.
Zach

I have a very similar engine combo in my '73 currently aside from the heads having stock valve sizes. At sea level I am running 40 IDFs with 32mm vents, 125 mains, F11 tubes, 50 idles, and 200 air correctors. Power band starts waking up at about 2500 and pulls strong through to 5700 or so. My engine also has AA forged rods, Web single coil valve springs, solid rocker spacers, MSD ignition, 2.0 SSi's, and a Triad muffler. The whole combo seems to work pretty well for a carbed car. Runs relatively cool, has good idle performance, and great response in the power band.

Anyone have some 32 vents to sell? Cant seem to source them right now.

Looks like they may be in stock at CB

https://www.cbperformance.com/product-p/6395.htm

Or Pegasus, generally has most any Weber stuff

Unplaced on order but they only had 2.

Pierce manifolds is my go to for all weber parts. I'm pretty sure i have 32s. You can try them out. If you want to use them then buy me a replacement and have them shipped to me.

.


^^^^GOOD GUY^^^^^^^
I just checked my 40s for 32’s for the same reason this morning....

+1 with Pierce, they always have

Randy Congrats on getting your engine back looking forward to all the future updates as you get her Tuned.
Reach out to Rick Hunt on FB thinking he may have a source of printed venturi's
Edit
Update talked with Rick 3D printed venturis still in development phase.

Hijack:

On my 2056, I have some popping when the engine is pre-warm. No popping after warmed up. If I run anything less than 93 octane, I get a lot of popping.

Carb settings:

Weber IDF 40
28mm venturis,
115 mains
Idle Jets: 50
airjets 200
F11 emulsion tube

Recently adjusted valves (didn't change anything)
No vacuum leaks.
No info on cam or valves. (2L heads)

Suggestions for adjustment?

For starters get a set of 32mm Venturi. Go thru the preinstall procedure. Baseline the carbs. Timing must be set and valves adjusted correctly.

@spoke

I get popping out of my carbs until fully warm. It's worse during the colder months. Everything is probably fine.

Only other thing i could think of is linkage, what linkage are you running? Almost seems like it could be related, but usually the hex bar goes out of adjustment warm, not better

@nditiz1

Nick, I have the cable system by Racer Chris. Both sides seem to open at the same time. I'll go back and check all adjustments and synchronize the carbs.

@nditiz1

Checked all adjustments and synched the carbs. No popping on the drives today.

Not sure if it was the adjustment or the fact that one of the studs on cylinder 1 holding the carbs on the head had completely backed out and was laying on the tin. It must have been off for some time. Put it back in and tightened all 5 other studs. None were tight...

"none were tight"

many of us have been there before

I'v got a 75 914 2.0 unknown piston and crank with

Weber 40 DNCF 101-250 4D
Venturis: 30mm
Mains: 145
Idle Jets: 65
Airjets: 210
Emulsion Tube: F36

When I bought it it had 57.5 Idle Jets and back fired at idle and at 2500 RPM. I went down to 50s and it got worse. It runs lots better with 65s. Theres some popping when coasting in gear. I'm at ~4300ft elevation. 50s should be the right size from what I've read but they are not working in my car. My idle mixture screws have to be turned way out also for it to run good. They were between 10 and 11 turns with the 57.5s when I got it. I've got it at 5 turns with the 65s. Big idles and lots of turns. It doesn't seem right but its running way better.