It was running well, so I fixed that - E21 Weber jetting

Help.  Advice, wisdom, or ideas requested...  So following the last fiasco, the car was running pretty well and I drove it around, enjoying it... except for a bit of hesitation at throttle tip in.

So, I did a bit of research, and it turns out that the hesitation is most likely related to the emulsion tube circuit.  First up is to make sure the float is high enough to cover the feed holes for the emulsion circuit.  Turns out I was a bit low, reset the float.

Figured I might as well re-adjust the mixture, since that circuit might play with the rest of them, just do it right.  Procedure is:

- half turn in on idle screw

- mixture screws 1 turn out.

- start car and adjust per spec

And then the car wouldn't idle.  Turned mixture screws out 2 turns, no dice.   Can keep the car running ok with gas pedal, so, ok, no worries, needs more cow be..., er, bigger idle jet.  Upped the jets, repeat, same thing, but requires less gas pedal to keep running.  Ok, up the jets again.  Largely the same thing, but, the car almost idled "tractor like", and requires just a very light, almost non-existent touch on the gas pedal to keep it running.  

It seems to me that I'm going the right direction with bigger idle jets, but, dang, I'll be running a 60 or 65 all said and done.

Why this concerns me and makes me think I'm missing something is a guy who ran a 2002 with a 292 cam and header, and he was running a 50 idle jet, and I'm running a smaller 1.8 motor with a 284 cam, header, and exhaust.  And nobody on 2002faq that I could find was running a 60 (or larger) idle jet for any engine combo I read about.

We are at 2500 ft here, but a) I thought generally you needed to be closer to 5000ft to affect jetting radically, and b), the air is thinner higher up, which means I'd need to reduce fuel, right?  I.e. I'd think a 50 should be fine, but, that's not what the car seems to want.

I'll pick up some jets tomorrow, but, wondering and want to be sure.

If anybody still knows carbs....  Carbs rule  

Opinions wanted.

Wow, is it possible that a vacuum line got knocked loose or something similar?  I haven't played with carbs in awhile, but going from running well with a little hesitation to not idling seems a little extreme.

Any chance you can check for vaccum leaks, put everything back where it was, and start again?

Finally, is there any chance a PO drilled the original jets?  I found a couple in a weber I had once that were not what they said they were.

First, put the jets you started with back in.

Turn your idle screw in further to bring the idle rpm up. 1 turn at least. Don't worry about the idle speed.

Once the engine is warmed up, start bringing your idle speed down to about 800rpm with the idle speed screw.

Then turn your mixture screws in or out until you get the smoothest idle possible.

Set your idle speed with the idle screw.

Now start fiddling with it if you need to.

Weber emulsion tubes almost never need changing. If you've got a stumble on throttle tip-in, I'd look at the accelerator pump circuit first. The pump diaphragm will harden up on these carbs and give you a weak shot.

In reply to ShawnG :

It'll run that way, it's just in contravention to the set up instructions, found here: http://www.redlineweber.com/html/Tech/38_dgas_tunning.htm

I think it'll run as indicated therin if I go with still bigger idle jets, just haven't seen anybody else doing it, and it makes me wonder. 

I can get it to run smoothly now if I up idle speed screw, I'm just trying to follow the recommended procedures.

EDIT: This set up guide agrees with you on 1 to 1-1/2 turns in as the baseline idle screw setting:  https://www.carburetion.com/Weber/adjust.htm

As ShawnG mentioned first get the carb back to its baseline settings and jets etc. Then get it to idle smoothly. This presumes the other systems, like ignition, are in optimal working order and settings.

 Poorly worded initial post, what I was really looking for was confirmation that such a big idle jet might be warranted when the biggest I'd researched being used was a 50.

My question was based on the set up procedure listed in the first of two links above, which is a Redline/Weber instruction.

The second link (looks like an "authorized" dealer) stated no more than 1-1/2 turns.  Strange that two "authorized" instruction sets contain disparate info.   Found an old Weber manual someone pdf'd that said one turn on idle speed screw. 

Shawn G was indeed correct.  It's darn near a case of the old Tim Allen line "Instructions are just the manufacturer's opinion of how to do it."

ShawnG said:

First, put the jets you started with back in.

Turn your idle screw in further to bring the idle rpm up. 1 turn at least. Don't worry about the idle speed.

Once the engine is warmed up, start bringing your idle speed down to about 800rpm with the idle speed screw.

Then turn your mixture screws in or out until you get the smoothest idle possible.

Set your idle speed with the idle screw.

Now start fiddling with it if you need to.

Weber emulsion tubes almost never need changing. If you've got a stumble on throttle tip-in, I'd look at the accelerator pump circuit first. The pump diaphragm will harden up on these carbs and give you a weak shot.

 

 

I agree with all of this except that for the tip in issues I'd be looking hard at the vacuum advance mechanism before the carb. Ported vacuum line from carb to advance or manifold vacuum going to advance?

They're telling you no more than 1/2 turn to ensure that you aren't running the engine on the transition circuit but you need to get it warmed up and idling properly before you worry about that anyway.

Putting it back to the way it ran before is the simplest way to get things sorted out.

Once it's warmed up and idling like it should be, get a light and have a look down the throttle bores, if you don't see fuel coming out of the booster venturis, then you're still running on the idle circuit and you're ok.

I've never seen a Weber that didn't need more than a one or two step change in the jetting to get it to run properly unless the engine had a really wild camshaft installed. 

Carburetors flow fuel in proportion to the air going through them. They don't care what engine they're on, they care how much air is moving through them. You can take a carburetor from a 150ci 4-cylinder and bolt it to a 300ci 6 and it will still be correct or nearly correct in it's jetting.

Has this carb been freshened up with new gaskets and rubber parts or are you working on a crusty, 40 year-old carburetor that has never been touched?

It's been quite some time since I've had a car with a Weber progressive carb on it but I'm in agreement with ShawnG

There is one other element here; define tip in, is it pulling off a light, when you trying to ever so slightly go back to throttle, rapidly increase the throttle etc.?

Also check the throttle shaft to see if it has any play; if it does you have an air leak and that will contribute to the issue you are having.

ShawnG said:

They're telling you no more than 1/2 turn to ensure that you aren't running the engine on the transition circuit but you need to get it warmed up and idling properly before you worry about that anyway.

Putting it back to the way it ran before is the simplest way to get things sorted out.

Once it's warmed up and idling like it should be, get a light and have a look down the throttle bores, if you don't see fuel coming out of the booster venturis, then you're still running on the idle circuit and you're ok.

I've never seen a Weber that didn't need more than a one or two step change in the jetting to get it to run properly unless the engine had a really wild camshaft installed. 

Carburetors flow fuel in proportion to the air going through them. They don't care what engine they're on, they care how much air is moving through them. You can take a carburetor from a 150ci 4-cylinder and bolt it to a 300ci 6 and it will still be correct or nearly correct in it's jetting.

Has this carb been freshened up with new gaskets and rubber parts or are you working on a crusty, 40 year-old carburetor that has never been touched?

Back to original idle jets (45s), about 1-3/4 turns out, probably could do a little leaner, but not really less than 1-1/2 turns or it falls off.

Once dialed in, I backed the idle screw out maybe 1/4 turn or less, idles about 850 give or take (down from about 1100 at initial mixture setting). 

No fuel from the boosters until I crack the throttle (fairly quickly off idle it'll squirt some fuel, though). 

Running well, now. 

Tom1200, it usually would hesitate going from light throttle opening, 2k or so, to stomping WOT.  A little less than immediate and it would run straight through.  It's said that one of the reasons you'll get that is that your float is too low, you don't have fuel entering that circuit. 

My float was I think a little low.   When I pulled the cover  the fuel level was right at or just below feed holes for that circuit, so I reset the float level. 

For whatever reason I wound up pulling the cover after that, and the fuel level in the bowl covered those feed holes. 

I'll drive it around later tonight, see how it does, see if I still get any hesitation now.   I need gas in it anyway, good excuse to run it a bit. 

Well, a trip to In-n-Out  show she's running just dandy. 

No hesitation at all on the way down, pulls well in all the gears. 

Life is good. 

Thanks all.