Warpy Carburetor

[Bookwus]

Hiya Bill,

Yep, the sandpaper and glass worked quite well for me.

So, tell me about using the file approach. How do you make sure the base flange is absolutely flat?

[Hippie]

I use a piece of granite countertop...

I would think that would be just about ideal because of the rigidity.

[RSorak 71Westy]

Cough while warming up is going lean....i.e. wants more choke/fuel.

[dtrumbo]

Cough while warming up is going lean....i.e. wants more choke/fuel.

That makes sense since these Webers don't have chokes.

[spiffy]

Cough while warming up is going lean....i.e. wants more choke/fuel.

That makes sense since these Webers don't have chokes.

Yeah D, you get the "cat sneeze" too right after cold start-up? The big dual carbed engines definitely are a tad grumpy for the first 10 seconds or so. They wake right up though.

[dtrumbo]

Yeah D, you get the "cat sneeze" too right after cold start-up? The big dual carbed engines definitely are a tad grumpy for the first 10 seconds or so. They wake right up though.

That's exactly the right word to describe it! O.k. that's normal, I'll move on to finding leaks.

[hambone]

Glad to hear Mike. With mine, the excess pressure (over 10 PSI!) leaked out of the bowl after shutdown and dripped down the manifold and in/out, causing rich (!) startups. 4 PSI (according to a budget gauge) is working just fine.
I too would recommend a file for flanges. You can get a pretty good feel for flatness with practice.

[Bookwus]

Hiya Bob,

.I too would recommend a file for flanges. You can get a pretty good feel for flatness with practice.

No kidding! I'd still like to see the technique.

Since I was starting out with a carb that was about .004 out in the middle of the flange, I wanted to go with a process that would be as accurate (read: flat) as was possible. That spelled the glass and sandpaper routine for me.

And since the flange metal (what is that stuff Solex made carbs out of anyway?) was soft the 220 ate it up pretty fast. Came out nice, shiny, smooth, and most importantly, flat.

[vdubyah73]

Dual Webers need the heat from the heads to travel up the manifolds before they work right. I'd imagine that Solexes with no chokes or non functioning chokes would be the same. The gas condenses back to large droplets during warm up, giving a lean indication. Once warmed up, the heat from the heads keeps the gas vaporized. A sneeze or hiccup, that is only present for the first few minutes of driving, and goes away after warmup is an indication that your jetting is close. if it runs like a raped ape cold and gets lazy when warm you are to rich. If the sneezing or hiccuping diminishes but never goes completely away you are either to lean, have an unbalanced linkage, slightly unsynched carbs, or maybe a small vacuum leak, possibly throttle shafts.

Edited to add:
When going with dual carbs on an engine that had FI eliminate the phenolic spacers between the intakes and the heads. You will appreciate why on cooler/colder days, they insulate the manifolds from head heat. Did Type 4's ever use the metal intake gaskets? If so those would be the best to use.

[vdubyah73]

File approach.

A mill bastard file is a flat file with a fine cut. You lay the file flat on the surface of the flange and work the file in a diagonal motion in relation to its length. You don't need to have a perfect finish, file marks are fine, just don't gouge it. I tend to cut my own intake gaskets and use the waxy paper stuff that is about 1/16" thick. Port work is why I cut my own.

[Amskeptic]

Edited to add:
When going with dual carbs on an engine that had FI, eliminate the phenolic spacers between the intakes and the heads. You will appreciate why on cooler/colder days, they insulate the manifolds from head heat. Did Type 4's ever use the metal intake gaskets? If so those would be the best to use.

Factory dual carb buses used metal intake manifold gaskets for the cast iron manifolds, but also used phenolic spacers between the manifolds and the carbs.
Colin