I thought we might get a thread going where we could all share and maybe cover some of the basics and what appear to be the most common challenges that we face when installing a Weber and hopefully get some good discussion going.
This thread will begin with a more focused view on the initial set up, the importance of the base-line settings and general discussion of a Redline Weber carburetor and not really intended to be a troubleshooting guide. It’s rather an offering to a trouble free installation and use thread.
Set up correctly, either the 32/36 DGV or the 38 DGS should provide great performance and mileage on the 4.2 or even the 2.5. I’ve just been tickled pink with my 38 and I know others who love their 32/36 DGV.
Here’s a good link, should you still be deciding which carb will work best for your application.
Making The Right Choice 32 or 36
The adaptor plates need a close inspection and possibly attention prior to assembly to avoid problems with vacuum leaks. They are often delivered with uneven mating surfaces, casting flash and just about any number of abnormalities that you can think of.
It is well worth your time to give them a close inspection before the install. By using a straight edge over the entire mating surface of each side of the adaptor plates, you’ll be able to tell if the surface is flat. They sometimes need some sort of work in this area and some filing and sanding may be needed to ensure a flat surface. Should the plate need some work to flatten out, you can place a sheet of wet/dry sandpaper on a flat surface, oil it and sand away any high spots.
Once the adaptor plates have a good, flat surface to work with, you can go ahead with the assembly of the plates. It’s a good idea to lightly coat some wheel bearing grease over both sides of the mounting gaskets to ensure a good seal. You may want to perform a test assembly to make sure the mounting bolts are long enough. I’ve seen kits that actually required a trip to the fastener store for bolts that were a touch longer than the ones supplied.
Once the plates are secured to the manifold, you can thread the carb studs into the top plate. This is a part of the initial assembly where some mistakes can be made. If the studs are actually tightened down, they will serve to pry the adaptor plates apart and cause an air leak. Rather than tightening the studs down, simply coat the threads with red Loc-Tite, screw them down until they just make contact with the lower plate, back them out 1/8th turn and walk away until the Loc-Tite has set.
A little Teflon tape on the threads of the PCV port and you should be good to go with the adaptor plate assembly.
Curb Idle Throttle Plate Position
Here’s where the vast majority of complaints and confusions arise when it comes to setting up a Weber.
When installing either of the Redline Weber conversions, I suggest the first thing you do is to flip the carb upside down and determine the maximum amount that the throttle plate can be opened for a proper curb idle throttle plate position.
To do this, you’ll need to use your fingers or maybe insert a short piece of 3/8 tubing between the air horn and the choke plate to hold the choke plate open while you move the throttle from idle to wide open. You should hear a ‘click’ as the fast-idle cam loses contact with the fast idle screw and the throttle plates should return freely to their fully-closed position. This is actually my preferred method of holding the choke plate open so you can set the throttle plates...
Yes, that's actually a short length of toilet paper roll. I mean, who can't find one of those in a pinch
From there, use a screwdriver to unscrew (counter-clockwise) the idle speed adjustment screw to the point where it loses contact with the linkage. Then, from the point that the idle speed adjustment screw just makes contact with the linkage, slowly turn the adjustment screw in (clockwise), counting in at least 1/8th turn increments, until just the very outer edge of the first progression hole is exposed and take note of how many turns were required to get there. On the 32/36 DGV, the plate should be just shy of uncovering the edge of the “S” port, which will be a much smaller port off to the side of the larger progression port. Notice how this is illustrated in this photo, it should look similar to a crescent moon, something like this...
This screw setting, what ever it may be, is considered your absolute maximum idle speed screw adjustment and can not be exceeded when tuning otherwise your performance and mileage will surely suffer.
This photo shows just how much of the progression hole is exposed with the idle speed screw turned in only ¾ of a turn. It’s easy to think that a ¼ turn doesn’t really mean much but it makes a big difference, as you can see. This is why Redline so strongly emphasizes the importance of the idle speed screw setting.
For a Weber 32/36, this screw setting should be no more than 1 ½ turns in. For a Weber 38, it will be no more than a ½ turn in. When this screw setting is exceeded, the engine will pull from the progression circuit rather than the idle circuit and will likely have a rich or stinky idle and the engine will often not even respond when the mixture screw(s) are adjusted. This is an indication that a larger idle jet is needed. Conventional wisdom might suggest that "it's rich so I need smaller jets." That, however, isn't the case.
This maximum setting is crucial and a properly sized idle jet will allow your engine to idle without exceeding the above mentioned screw settings.
There are plenty of topics to discuss here like float level, lean-best idle, idle jet size, fuel pressure, ignition requirements, etc. and I know there are some really sharp Weber guys on the forum so hopefully we’ll get some great discussion on here.