Any carb specialists out there? I need help with a carb problem.
-1974 2.0 with dual weber carbs
-The car is spitting and popping out the carb on cylinders 1&2and also backfiring alittle. I've rebuilt the carbs and pulled this carb off again completely taking it apart and checking with no obvious issues found
-With the car idling when I put my hand over each barrel on this carb there is no suction at all on my hand. The idle doesn't drop at all. Doesn't respond to any adjustments on the fuel/air mixture screws.
-The carb is injecting fuel streams when I open the linkage by hand
-On the carb on the opposite side when I put my hand over each velocity stack it really pulls air really hard on my hand and the car will bog down and shut off as it should.
-I have new intake gaskets an new carb base gaskets installed. I sprayed carb cleaner around the base of the carb and also at the head with no change in idle. Any ideas? Is this car basically running on 2 cylinders?
-On the opposite carb on cylinders

Sounds like they are way out of sync. Find a good carb sync set of instructions and follow it exactly not skipping any steps.

Try this one:

http://www.aircooled.net/synchronize-dual-...arburetors-103/

,really points to that,maybe the motor needs a good tune-up also,pointless tuning carbs until done.

Sounds like you may have ignition problems as well.

Tune up procedure is: valve adjustment (engine stone cold), ignition (parts as needed-points, condenser, plugs, rotor, cap, plug wires) and ignition timing, carb adjustment (carb balance & mixture)

Search "carb tuning procedure"

Put you're carbs at the initial adjustment starting point. Check your plugs and points for proper gap. Get the engine warm and then check your timing. To me it sounds like your timing is way off. I had the same issue with my car and I kept messing with the carbs thinking that was my issue until I decided to check my timing. Once I fixed my timing issue and then re-synced my carbs my engine quit having those issues.

Cazz mentioned a lack of suction on one side. I see how carb sync or maybe valve adjustment could cause that, but I'm not getting how ignition issues could cause that. (Remember I'm a newbie, just trying to understand.)

FWIW, I had this also and it was carb sync in my case.

Does the engine smooth out, or at least run better, at 3k rpm? If so, the FIRST thing I would suspect are the idle jets. Closing the idle air adj screws one at a time should produce a marked stumble. No change, pull the jet on that throat. The o-rings, metal ring caps and springs must be in place. Did you replace the fuel filter before you installed the rebuilt carbs? The streams you see are the pump jets. Nothing to do with the idle circuits.

Valve adjustment if there's no vacuum....

Clean the idle jets, then install these when you get a chance. http://www.cbperformance.com/searchresults...tor&Submit=

Check your firing order.
You may have flipped the wires on that side.

If your timing is not correct or even close you won't be able to sync you carbs at all. The adjustments will do little or nothing at all and will most likely make your engine run worse.

Get the CSP Bellcrank linkage from CIP1.

This video has pertinent info:

https://www.youtube.com/watch?v=ZS3oNSwkUPk

I suspect an issue related to the "rebuild. Swap carbs to the opposite side and see if the problem follows the carb. if it does then you know the problem is with the rebuild.

I'm having sync problems as well Dell 40's on new build 2056.Web 494 cam valve lash just re-set after cam break-in .006+ intake, .008+ exhaust 115-120 compression across all 4 cyl. Timing set to 27 Deg at 3500 but getting popping back thru #1,2 and suddenly, no idle fuel to #4. have open exhaust thru SSI's so can feel temperature at each outlet. have cleaned carbs several times but no improvement.
Have studied the Dell tech book over & over.
Also can't seem to get idle below 1100, I've insured that butterflies have no more than .003 gap with closed throttle although one carb can't get as tight as the other.

I was having so much trouble with the beat up, fuel leaking, bent throttle shaft DRLA 45s that came with my car. While debugging the problem at a local VW shop, tried his new old stock DRLA 45s and instantly everything was better. After that I didn't want anything to do with my old ones so just bought his.... where they remain on my car.

I'm liking the Dellortos now, but that book could use a rewrite.

I also replaced my worn out hex bar linkage with a CSP bell crank linkage that looks good and is easy to adjust.

Sorry for a newbie question... this is how I learn.

Cazz mentioned lack of suction from one carb, and people are talking about ignition timing. I'm not seeing how that follows. I thought the suction at the carb intake would be a result of each cylinder's intake stroke, piston movement and valve action combined with throttle butterfly position. Since the crankshaft ties piston movement together, I'm not seeing how ignition timing would cause a discrepancy in vacuum from one carb to the other. The way I understand it, suction from a cylinder on the intake stroke would be the same whether or not there was a successful spark during that cylinder's previous combustion stroke. I should be able to pull a spark plug wire and still see the same amount of intake air flow from that carb throat, right?

Or maybe I have it all wrong. Feel free to enlighten me.

You really need to start there and make sure the valves are all within spec.

Part of the suction is created by the rapid expulsion of exhaust.
This is why there are different camshafts, they all use that suction to pull in more fuel and air.

If the plug wires are flipped, or your timing is so far off, you won’t be firing the explosion at the perfect time and you could not only lose that suction, you could blow back up through the intake valve.

I agree with Sir Andy also.
Start by getting your valves set properly, then point gap, then dwell, then timing,
Firing order is 1432 looking down from up top it’s clockwise.

Carbs are stupid simple.
They allow air into the engine, which is just an air pump.
The fuel gets sucked in via the Venturi affect.

So, carbs are NOT the OP real issue.
He needs to make sure all four cylinders are pulling in the same amount of air.

Thanks for the explanation.

Also the suction in one cylinder is created by the firing of another cylinder. So if the timing is off, it will reduce the power produced by that cylinder, and that reduction in power translates to a reduction in suction on the intake-stroke cylinder because the crank isn't turning with as much force.

SO well said Rich,op has gone to ground?no replies,never mind hope its all going in ?
With the resources on here and the net for anyone to question why engine /timing and tune has anything to do with carb tuning amazes me ,without all this being correct any work on carbs is a waste of time.
Jeez its like ''groundhog day''....rant over and out.

Yup.
OR burnt valves.

I had a very similar issue last spring. My car would idle just fine, with no popping or backfiring. It would pop and/or backfire when revved to 3k. Turned out the linkage drop bar on the one side was out of whack by about 1/4 - 1/2 inch (too long). I figured this out after doing a valve adjustment, replaced those same base gaskets, replaced plugs, wires, factory reset carbs, synced them, replaced fuel filter, checked everything under the sun. Every symptom you just mentioned was what I had. Can't hurt to check!

Getting carbs right is ALSO an iterative process. You have to get it running first. Then you have to get it running good enough to perform the "Loping" idle test to get the idle adjustment screws set right (this is actually hard because it is a chicken/egg problem). This is often complicated by the conflicting requirement to break in a cam first thing BEFORE knowing if it is even running on all four. And you have to get it to run good enough to warm all the way up to properly set the valves, etc. etc.

It is not possible to get everything perfect BEFORE getting everything perfect....