I cannot recommend the two barrel progressive carb for the VW Bug (Weber DFEV, aka Weber progressive). The DFEV is a good carb, but it is not ideal for the Bug. The DFEV might be a poor choice on a non-stock engine, and may be hard to tune even on a stock engine. Unfortunately, this is the carb I have. I have managed to tune my carb, and it runs fine since I started heating the intake air.

Here are the options as I understand them. I'm not really a carb expert, but I've owned several Weber carburetted cars, and I've done a ton of reading. In the following list, keep in mind that the only carb I have hands on experience with is the DFEV/DGAV series.

Here are 5 options, each with Good and Bad points.

Option One: Dual Weber ICT single barrel carbs (34 mm venturi) .
Good: reasonable price, rumored to have great performance, reasonable fuel economy, works well on mildly modified engines, rumored not to need a choke even in cold climates, rumor is that you won't have to rejet on a mildly modified engine, probably easier to install than the center mounted carbs.
Bad: rejetting requires removing the top of the carb, chokes do not seem to be available.

Option Two: Single Weber IDF two barrel synchronized opening throttles (40, 44, or 48 mm venturis).
Good: reasonable price, easy to rejet, rumored to be well suited to mildly modified engines, much less expensive than dual IDF systems, reasonable fuel economy, rumored to drive well and have no flat spots, different venturi sizes may allow you to better match the carb to your engine modifications, IDF-XE has ball bearings and double seals on the throttle shaft.
Bad: may use more fuel than dual ICTs or a single DFEV, center mount install can be somewhat tricky, may have the same intake manifold heat problems as the DFEV (Non-stock exhausts do not send significant heat to the intake manifold heat risers on any center mounted carburetor.) I have not had a chance to drive a Bug with a center mounted IDF. The manifold is a smoother design than the manifold for the DFEV, so fuel may vaporize better even if the manifold is cold.

Option Three: Weber DFEV 32/36 two barrel progressive (32 mm primary, 36 mm secondary venturi). "Progressive" means that the smaller 32 mm venturi opens first, and is used for most driving. The larger 36 mm venturi opens at about 3/4 throttle to Wide Open Throttle (WOT) and provides top end power.
Good: reasonable price, good performance, many of these have been installed, easily fits in the stock engine compartment.
Bad: tricky to tune, rejetting requires removing the top of the carb, really bad running in cold or wet weather (due to a cold intake manifold), poorly tuned uses a lot of gas, center mount intake manifold can be very tricky to install (it requires patience) Redline Weber has a DGV (DFV) snorkle kit, and a DGV/DFV stock filter adaptor. I wish I'd known this before I spent hours fabricating my own (crappy) adaptor. Redline Weber air filter options

Option Four: Fuel Injection.
Good: reliable, more power, better fuel economy, smoother running, many systems have computer interfaces to exactly tune the FI to your engine.
Bad: Expensive (at least $700, most kits are over $1000), probably tricky to install, may be tricky to maintain.

Option Five: Dual Weber IDF carbs (40, 44, or 48 mm venturis).
Good: lots of power on heavily modified engines, easy to rejet and adjust.
Bad: medium expensive (kits start around $500), use more fuel, may have flat spots at lower rpms.

Buy your carburetor from a specialist. As far as I can tell, all the good Weber carbs in the US come from Redline Weber. There are several suppliers that carry Redline Weber products, but it may be best to go directly to Redline. If you have questions, Redline can answer them; the other suppliers may not have the knowledge.

Redline Weber Site Cover

Redline Home Page

Redline Weber Tech Pages Table of Contents

Mail Order Parts Suppliers - When buying a carb kit, ask if it is a Redline Weber kit.

There is more technical info at the Redline site than all the other sources combined I've seen online. Redline has tuning info that doesn't exist in the Weber Carburetor books! The Redline web site is pretty bad (hard to navigate, broken links, pages that consist of large scanned fliers), but the info is very, very good.

Here are a few things I learned from the Redline site:

  • DGV and DFV are essentially mirror image carbs. The throttle primary throttle plate rotates clockwise in the DFV series. We use the DFV series on the VW Beetle (DFEV).
  • The E in DFEV is for Electric choke. The A in DFAV (or DGAV) is for water choke (agua, aqua? Weber is an Italian company.)
  • DGV series carbs are available with an Integrated Cutoff Valve (ICU). This is the same as the electric idle solenoid on stock VW Solex carbs and prevents dieseling or run-on after you cut off the ignition. I do not know if the ICU is available on the DFV series carbs. I have a DGAV with ICU on my 2000cc 1974 BMW 2002. The ICU is great. I wish I'd had it on my 1600cc 1970 Datsun 510 since that car often had run-on.
  • The DGV series is available as a non-progressive, synchronous opening carburetor. This is a two barrel carb where both throttle plates open at the same time. These carbs are the 38 (mm) DGAS and 38 (mm) DPS. Redline recommends this carb for modified engines (hotter cam, headers, larger engine size, and presumably high flow cylinder heads). There does not appear to be a corresponding DFS, so those of us running VWs would have to do some interesting throttle cable modifications to use the DGS. I cannot tell if the DGS is available with electric choke (I guess it would be called a DGES). Of course, if you want a two barrel synchronous carb, the IDF is a better choice at about the same price.
  • Redline carries a single, center mounted IDF kit, and it looks very cool. Single center mount IDF for VW Bug

 

 

Below is a photo of my carb 2 years after the installation. It is kind of dirty with road salt residue. Note the neceessary extra return spring. This carb was NOT purchased from Redline. I think I would have avoided several problems if I had bought from Redline.

The roughly made box on top of the carb is an adaptor so I can use the stock air cleaner. The stock air cleaner is necessary because the Bug won't run right in cold or wet weather without intake air pre-heating. See the rear photo. Redline carries an adaptor and a thing called a snorkle that allows relocating the air filter to be out of water, dust, etc.

I'm pretty sure that if you have a merged exhaust (aftermarket performance headers) the heat risers do not work. My heat risers hardly get warm, let alone hot.

In removing the old manifold, I found that one end boot wasn't on the end piece, and the other boot had a huge crack (on the front where it can't be seen). I'm guessing that the lean wide-open-throttle and curious flat spots with the Solex were just due to vacuum leaks!

Anyway, my new Weber DFEV is installed. This is a tricky process, and even more tricky on a later engine with the doghouse oil cooler and larger fan. The instructions were wrong regarding the alternator and fan. I had to remove the fan from the alternator shaft before I could get the alternator and old manifold off. It is necessary to remove at least one manifold end piece. I removed the left one. To get to the rear nut on the manifold end piece (the part that bolts to the cylinder head), I used a breaker bar which was a very close fit at an angle.

During reassembly, I discovered that the fan has to go in the shroud before the carb and manifold go on. It would have been best to install the alternator, and finally the manifold and carb. The new intake manifold can go in after the alternator because the heat risers aren't attached; they kind of have a slip fit. The front left nut on the alternator stand is very very difficult to reach with the manifold on. The front right nut on the carb is almost impossible to reach with the fan and alternator in place. Big problem. The solution with the carb turned out to be putting a 13 mm socket on the nut, then reaching in with an extension at an angle. The extension won't actually go in the socket, but it fits in just enough to turn the socket.

The throttle linkage is a problem. The carb comes with an extra arm that attaches to the VW cable. However, the return spring is way too weak, the the arm is at kind of a weird angle and the throttle barely opens all the way. It turns out that there is a separate kit with a different arm, spring, and spring mounting bracket. This wasn't part of the Weber carb kit, and wasn't mentioned when I bought the kit. I've temporarily jury rigged the return spring from the Solex.

The manifold is a pretty cheap item. It had epoxy inside (I knocked this extra loose). It was inside the manifold, and looked like it might restrict air flow. I think this is 1/4 inch (6.4mm) grid paper.

The heat risers needed a lot of bending before they matched up with the header. I still don't know exactly how. I used hi-temp silicon to seal the head risers to the intake manifold. This seems to be working. More on this as time goes along. The manifold has the word "EMPI" cast into it, but it is poorly made and isn't covered by the instructions. Same for the brace that holds the manifold. I had to bend it because it doesn't fit.

I removed the old choke and fuel cutoff wires that had been attached to the Solex, and made a single wire for the Weber choke.

The "kit" does not come with the end piece gaskets. The guys at Larry's Offroad didn't mention this. When I called back and asked why they didn't tell me, the response was, "I dunno." I suggest you avoid Larry's.

The DFEV is a two barrel progressive, which means that the second barrel isn't used unless you need the power. I had this carb (actually a DGV) on my old Datsu 510. Nice.

 Special tools: 36 mm socket, S-shaped box end wrenches, distributor wrenches, terminal crimping tool.

Extra parts: intake manifold boots, manifold end piece gaskets, hi-temp sealant, throttle kit w/spring, wire and terminals.

 

 


 
 
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