Weber IDF Jetting Options

[FastFroggy]

I am starting to play around with tuning and plan to start getting some small increments in jetting. Just to see if I can improve drivability for now. I have twin 44s

Simple question for now: I need 4 turns of idle mixture to now stumble off the line. Should I consider jetting richer?

thanks

[McMark]

You're going to have a really hard time without knowing something about the engine size. If it were me, I would shoot for running a little small and then working up from there. Or to be fully honest, I would pull the engine and inspect a few things to find out what's actually in there.

Should mention that car pull smoothly from 3k plus.

This can be a tricky feeling. It makes you think you're close to the correct setup and you only need a little tweaking. I'm sorry to say, you're not close. If you ignore the repeated advice we're giving here because the changes we're suggesting seem drastic, then you're dragging this process out or you'll never actually get it right.

First, I'll agree with the other posters, you're carb setup is WAY too big. You don't need 44mm carbs until you reach or pass 2.3liters. You can choke them down with smaller venturi, but if it really is a 1.7/1.8/1911 the 44mm carbs will always be too big to tune well. If you really want to get it set up right, sell the 44 carbs and get some 40s.

Carbs need airflow speed to work correctly (except for 0% throttle idling). If you have a small engine it naturally only sucks in a small amount of air for each cycle. The smaller the intake piping (and I mean the carb throat size, in your case) the faster the air moves. Too small and it can restrict wide open throttle where you need as much air as possible. But as you go larger you reduce the air speed across the board for all throttle positions. If you go too large, you reduce the air speed so much that the carb stops working, especially at the lowest air speeds (just off idle and low RPM acceleration). There isn't enough air flow to create the vacuum that literally sucks fuel out of the float bowl.

It's also worth touching on that you can't create horsepower from carburetors. At all. None. Zero. Never. What you can do with carbs is get the correct fuel mixture and air flow characteristics for your particular engine setup. And only at the correct air fuel mixture (and the correct ignition timing) will you optimize the horsepower capability of your engine. It's not about throwing MORE MORE MORE, it's about getting air-fuel-ratios and ignition timing correct to make peak HP at all RPM.

This is also why you need to pay attention to your carb linkage and carb synchronization. If all four throttle butterflies aren't opening equally, the air flow and mixture will be different on all four throats. Think of it like this-- only the highest flowing cylinder(s) do the work of accelerating the car. If all four cylinders are equal, they all work together optimally. If two cylinders are opening more (which is almost always the case with cross/hex bar linkages) then you've got yourself a nice 2-cylinder engine with an extra 2 cylinders to make extra heat and use extra fuel unnecessarily. Okay, one final example/analogy-- If you were picking up a heavy couch to move it, would you want four guys of equal strength? Or two strong guys and two children? In the latter case, who's doing all the work? The two strong guys.

Spend time getting your carbs right, and you'll be amazed at how smooth it can run. Try and ask for a quick fix and you're missing out, even if you solve the problem you're focusing on. Invest the time and money to do it right.