WEBER IDF 44 HELP PLEASE

[dan4u]

I have just built a new type 1 engine. 78 mm stroker 90.5 pistons. trying to adjust a single 44 idf is driving me crazy lol to put it nicely.I do know that duals would be better but at this time it is not possible.the problem that i'm having is it runs great at idle but seems to be very rich and the plugs say the same thing.I've tryed to adjust the carb like chirco recommends in one of there forums, but it is impossible to run the engine with the idle screw turned in a quarter of a turn, I think my butter flys are completely closed.anyways when you rev it up it runs great, strong. but when you hold it at 1800 to 2500 rpms it shooting ducks lol busting up.If any body on here has any tips it would greatly be appreciated.. thanks dan

[hemicat]

Im also having issues with my 40 IDF on a 1641 but im running lean. But i will try and help as much as I can. First what dizzy and hows timing? Second what jets are you running and what other jets do you have to work with? Where are your adjustments at now?

[dan4u]

thanks timing is on the money. IM not sure what the term dizzy means. I'm running 38 mm vents 55/60/65 idles mains 150 160 175 thanks hope you can help

[VW_Man_87]

dizzy = distributor

[Marc]

With any single carb setup, including stock, there tends to be a problem with fuel staying atomized over the long trip to the heads. It condenses on the walls of the manifold, leaving the remaining mixture on the lean side. The condensed fuel eventually drips down into the engine, but it's in the form of droplets that are too large to fully burn in the time allotted. In a lightweight sandrail that's used mostly in the heat of summer there's not much of a problem, but it's a lousy setup for year-round operation in a heavier vehicle.
The factory provided exhaust heat to the intake manifold to reduce this effect, but most aftermarket manifolds offer little if any preheat. The larger the cross-section of the manifold the worse it gets, since flow velocity and vacuum are reduced - and here again most aftermarket manifolds are all wrong, with runners far too large for the job.
You're fighting an uphill battle trying to get smooth driveability with a center-mounted 2-bbl. As a rule the mixture will need to be made overly rich at idle and mid-range to cover up for the inherent problems of the arrangement. IDFs ship with F11 emulsion tubes; switching to smaller-diameter F7s allows more fuel present in the well which richens the mixture on initial acceleration, many have found that to be of some help. Redline offers a manifold that provides much better preheat than most, I'd consider that a prerequisite - but even with that manifold, getting enough exhaust flow from an aftermarket exhaust system is a problem. Where a stock muffler runs the preheat flow from one exhaust flange to a low-pressure point inside the muffler, almost all headers simply connect it between #2 & #4 exhaust flanges - that's better than nothing, but the heat transfers mostly by convection since there's no net flow. You need to plumb one end of the heatriser pipe to a low-pressure point (like the collector) in order to get any significant flow.

[Bugfuel]

Exactly what Marc said!

Emulsion tubes have seem to be the ticket, but I can't recommen done over another.
I've had a carb guru modify my #2 tube for a single Dellorto to get it to run somewhat ok.
man what a pain centermounts are.

[hemicat]

Are there any other issues you are having other than just it snapping out the exhaust? Also what air correction jets do you have?

[dan4u]

thanks for the tips. thats the main problem I have is the popping and seems to be very rich. this is not driving down the road as I have not completed the project yet so this is in neutral in my shop @ 2000 to 3000 rpms It runs very rough.It don't matter if it is cold are hot hint manifold heat. my air correctors I believe are 180 r 200. if I decide to bite the bullet and go to duals would the 44's be two big. since I would only have to buy one thanks again guys for all the help as this problem is not solved yet so all input welcome

[Marc]

Dual 44IDFs wouldn't be too big for a 2-liter. Most come equipped with 36mm venturii, though, so you'd probably need to purchase a couple in addition to the manifolds/linkage and aircleaner(s). Need to know more about your combination & application before suggesting which size chokes would be best, but 36's are probably all you need and they're easier to find.

[hemicat]

Before you drive yourself too crazy actually driving is the best way to really tell whats going on. Mine runs ok at idle, a little rough when held just off idle. But when going down the road it runs like a raped ape although its lean. As far as adjusting mixture at 3000+, thats controlled by the main air and gas jet. Messing with the screws wont have much affect (if any) at the upper range. If you know your running rich try going down a size on the main gas jet or up a size on the air. That should help to lean it out. As for running duals it would prob be cheaper to purchase as a kit. The price of just a carb by itself new is half the price as a whole kit. I got mine from webercarbsdirect.com. Half the price of any I found on ebay. With the plates closed, thats about where you want them. I ended up having to drill a hole in my plates and open up the air bypass screws just to get it to idle. If there open too far it will end up sucking through the progression ports and override the idle circuit. Been there, done that. Talk about a nightmare trying to make any adjustments! Anyway you have half the battle solved at this point so with a little more time you should have this thing running like a top. If you can get your hands on a weber tech manual (white book) it could be a life saver. It has a whole troubleshooting section in it and really does help. For your conditions as explained it points to vacuum leaks or fuel starvation. Again this reffers to running down the road. Also did you set the float level at any point in time? Just trying to eliminate some guess work here.

[dan4u]

thanks hemicat and others. No I have not checked float height yet,but fuel pressure is fine @3.5. mine runs good at idle also just smells like it is loading up really bad. If I go from idle to wot it don't heisatate any what so ever sounds like a top fuel dragster lol. i'm try'ed a 60 and 65 idle jet.when I try to tune the idle cuircuit like is recommended I just can't get it to run with the butterflys closed.now when you come off idle runs a little rough maybe it's the c 25 cam,as I creep up to the transition stage 2000 to 2500 she starts popping.now if I decide to go with duals should i go with a 28 30 32 36 vent?does any body know what a 40 idf vent size is out of the box? also I'm running 35.5 intake valves thanks again guys maybe I will get this problem solved are move on to duals...

[hemicat]

Ok first I would suggest checking float. It should be 10mm closed and 32mm open. For the idle it does say that you can open your air bleed screws 2 and a half to 3 turns if necessary which is what I had to do to get my plates closed enough. You may want to check each side with a sync gauge cause with the manifold setup it acts like a true 2 bbl. After opening the screws make sure both sides are pulling the same with adjusting the bleed screws. When you open them up your idle should start to climb. Dont worry this is normal. After getting this adjusted then you should be able to go back and readjust your idle mixture. Turn in till stumble, back out til runs best. Thats it really for adjusting idle. May need to check final adjustments to see if you need to change jets depending on where your screws are when done.

“Simple Rules for Calibration”
If your mixture screw is out more than one turn like 11/2 turns then your idle jet is too lean, go up one half size on the Idle jet.

If you mixture screw is not out one full turn, something like only 1/2 turn out from seated then your Idle jet is too rich, go down one half size on the idle jet.

This is all based on the important fact that your speed screws are not open more than ½ turn if they are then that is also an indication that you have a lean Idle circuit. You are cheating by opening the throttle plates and exposing additional progression holes in the transition.

This came sraight from weber's site. Again this is just a guideline so actual settings may vary. Also vacuum leaks could contribute to some of these symptoms. Make sure to check good for them cause they can hide sometimes. Other than that keep checking plugs and hopefully you can get on the road soon and really find out what its like. It may call for some additional changes when you get to that point. I had to increase my acc pump jets to 80 because of a stumble on acceleration when I got it on the road and put a load on it. So hope this helps some and keep us posted. Im here for ya as much as I can be! And if anyone finds another way please feel free to input. I dont want to sound like im an IDF expert because im FAR from.