40 or 44 IDF Webers, size matters Options

[930cabman]

We are converting a stock 2 liter 4 cyl from D jet to Webers. My gut is telling me a 40 IDF with 32mm venturis is the correct starting point. I am considering purchase of a complete set of 44 IDF's, but are unable to locate 32 mm venturis. Assuming 32MM venturis can be found are 44 IDF"s too large for a stock 2 liter?
thank you

[nditiz1]

40 IDFs are best, but 44s will work if you choke them down. I say 40s are best because they already come with 28 venturis. You may have a more difficult time dialing them in with 44s and bigger vents.

[barefoot]

Question: is the diameter air the manifold interface different between the 2 ?

If the carb throat is larger than the manifold port size, a restriction is formed at that shoulder. Carb base diameter should match the manifold throat size.

[johnhora]

930cabman...

what's wrong with the stock D-Jet?
have you tried to get it to work?

If converting a stock engine to carbs use 40IDFs since no change to cam.

[930cabman]

930cabman...

what's wrong with the stock D-Jet?
have you tried to get it to work?

If converting a stock engine to carbs use 40IDFs since no change to cam.

Several years ago I came upon a low mileage rust free Alfa spider (flood car), after rebuilding pretty much the entire car, the D jet stumped me with it's sensors, ECU and a million electrical connections. I found a set of Weber40 DCOE's and never looked back. If/when a FI system is reasonably new and working I would service it, but working from a basket case, no way. Tooo many variables

[roblav1]

At what what RPM is max HP? I'll take a swag at 5800. My Weber manual chart says 36mm venturi. A 36mm venturi is probably better with a 44IDF.

[930cabman]

This is a stock 2 liter 4 cylinder engine. my gut is telling me probably 32mm venturis

[roblav1]

My 5800 rpm swag was off. My 914 spec says max hp is at 4900 rpm. This'll decrease the main venturi size to about 32mm. So I would recommend 40IDF.

I forget how underpowered the T4 is!

[type2man]

I would run 44 Webers. Personally I run 45 dells on a 2.0 with a cam and headers and have no issues. Dells are much better.

[930cabman]

My 5800 rpm swag was off. My 914 spec says max hp is at 4900 rpm. This'll decrease the main venturi size to about 32mm. So I would recommend 40IDF.

I forget how underpowered the T4 is!

Yes, with dished pistons/low compression it's near impossible yp make decent HP. If I live long enough and/or have some spare time I would like to try a twin turbo setup. I have not seen much on this board with this topic.

Yes, my gut is telling me twin 40IDF's with 32mm venturis will work well with a stock 2 liter. 500cc/cylinder volume

[IronHillRestorations]

You want 40's. With that engine the vacuum signal in 44's is going to give you problems. It will probably run very well with 40's and 28mm chokes

[johnhora]

OK so you have:
Stock 2.0L type 4 with stock FI cam and distributor.
And you have dual 40 IDF to install

This is what we used on a customer 914 rebuild in 2019
2.0 L
009 Dist new one
Web Cam... think it was an 86
Dual Weber 40 IDF
Vents 28
AC 200
EM F11
Main 115
ID 55

Ran fine....they wanted just a driver.

Maybe this will give you a start....GLW your project

[johnhora]

CB Performance's Bob Tomlinson's' book shows:

AirCooled VW engines with Dual 40IDFs

1835-2000cc 28mm venturi 145 M /220 AC /F11 E /55 Id
2000-2234cc 28mm venturi 150 M /225 AC /F11 E /55 Id

[brant]

930cabman...

what's wrong with the stock D-Jet?
have you tried to get it to work?

If converting a stock engine to carbs use 40IDFs since no change to cam.

Several years ago I came upon a low mileage rust free Alfa spider (flood car), after rebuilding pretty much the entire car, the D jet stumped me with it's sensors, ECU and a million electrical connections. I found a set of Weber40 DCOE's and never looked back. If/when a FI system is reasonably new and working I would service it, but working from a basket case, no way. Tooo many variables

What year Alfa?

The spiders never came with Djet actually
They were spica and then motronic DME

Your car would be worth learning d jet
They are a great and reliable system actually

Almost like they were made for the car....

[930cabman]

930cabman...

what's wrong with the stock D-Jet?
have you tried to get it to work?

If converting a stock engine to carbs use 40IDFs since no change to cam.

Several years ago I came upon a low mileage rust free Alfa spider (flood car), after rebuilding pretty much the entire car, the D jet stumped me with it's sensors, ECU and a million electrical connections. I found a set of Weber40 DCOE's and never looked back. If/when a FI system is reasonably new and working I would service it, but working from a basket case, no way. Tooo many variables

Once again,

Thank you to all who responded for your information. My gut was telling me to go on the "small side" with regards to carb size. Anybody have a twin 40 IDF setup available?


What year Alfa?

The spiders never came with Djet actually
They were spica and then motronic DME

Your car would be worth learning d jet
They are a great and reliable system actually

Almost like they were made for the car....

1985 Alfa spider, maybe it was L jet, but very similar. ECU, sensors, many many connections. When operating correctly the Bosch system is far superior to any carb system, but with 50 years old stuff, it's another story

[Superhawk996]

When operating correctly the Bosch system is far superior to any carb system, but with 50 years old stuff, it's another story

Just for the record. That's what everyone said in the late 80's too.

Not a carb hater by any stretch. Just think it's funny that the debate rages on 30 years later and I hear the same arguments out of both sides of the debate. (IMG:style_emoticons/default/laugh.gif)

[930cabman]

For me, it comes down to simple.

Bolt on carbs, add fuel and go.

50 years old FI stuff = headaches

[nditiz1]

Simplicity for me too. I worked with the black magic of the D-jet, but had more working knowledge of carbs. I had a harder time diagnosing an issue with the D-jet and started to take away things that could potentially cause issues, but were not needed i.e., Cold Start Valve, decel valve. Ultimately trying to get back to a simplistic system.

This does not mean that carbs are simple. They have their own set of rules you must follow and several have spent hours tuning them to the point where - well it gets me down the road. Suffering from poor mpg, bucking, overheating, just to name a few. Most of these stem from dirty carbs, incorrect jets, or linkage setup.

If you start with a good working set and know your engine you can follow the methodical steps to get everything dialed in. What really helps is knowing how everything works together. I learned a big part of this a few years back when trying to tune a set on a new top end 2056. Learning that one could drive around with the main stacks removed was an eye opener. That is how you can set the idle jet and know exactly when the tip in starts for the main so as to not have a flat spot. That combine with an AFR can really help you dial them in perfectly.

[VaccaRabite]

When I had my 2056 carbed I tried 44s and 40s.

The 44s had ALL the power in the top end. If I was racing, it would have been ideal. Car would hit readline and just KEEP GOING until I was floating valves. Not great for regular driving, but fun when I could open it up.

40s were a better mix, but did not have the same oomph that the 44s had. BUT I bet most of that was the defective gasket set I got that did not have all the jet holes punched and caused me to be fighting with the carbs so bad that I eventually went to EFI.

That said, Microsquirt EFI has been the best.

Zach

[930cabman]

When I had my 2056 carbed I tried 44s and 40s.

The 44s had ALL the power in the top end. If I was racing, it would have been ideal. Car would hit readline and just KEEP GOING until I was floating valves. Not great for regular driving, but fun when I could open it up.

40s were a better mix, but did not have the same oomph that the 44s had. BUT I bet most of that was the defective gasket set I got that did not have all the jet holes punched and caused me to be fighting with the carbs so bad that I eventually went to EFI.

That said, Microsquirt EFI has been the best.

Zach

I hear guys talking about Microsquirt EFI, but I have no knowledge of this system, sounds complex (expensive)