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only running on one carb HELP PLEASE


JeffMopar

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Thanx to everyone for the replys.

Mark, Yes, I have flow in the rear carb and I also made sure the chokes were moving smoothly up and down with the lever. Yes pushed up on jets to verify closed when choke is off.

Captain Obvious, Chickenman,  Yes I have the Unisyn balancer. Both carbs are adjusted to equal flow. I think that should have to mean the throttle plates are open close to equal. When I rev the engine it revs up fairly smoothly with a little desitation and the pistons move like they should.

madkaw, I am going to re check the throttle plate movement and make sure the needle and float aren't intermittently sticking shut. I have a few extras to try, it cant hurt, just have to verify float level every change.

 

Thank you to everyone for the help, I will let you know what I find.                   Jeff

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11 hours ago, madkaw said:

Cliff,
Your not really running that filter are you?


Sent from my iPhone using Classic Zcar Club mobile

Yes, without failing.  Ran one on my EFI too, no leaks at 32psi.  I recoated the tanks and wanted to see what was flowing through, no pink gas yet. :D  

I've never had a problem with those filters.

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2 hours ago, JeffMopar said:

Thanx to everyone for the replys.

Mark, Yes, I have flow in the rear carb and I also made sure the chokes were moving smoothly up and down with the lever. Yes pushed up on jets to verify closed when choke is off.

Captain Obvious, Chickenman,  Yes I have the Unisyn balancer. Both carbs are adjusted to equal flow. I think that should have to mean the throttle plates are open close to equal. When I rev the engine it revs up fairly smoothly with a little desitation and the pistons move like they should.

madkaw, I am going to re check the throttle plate movement and make sure the needle and float aren't intermittently sticking shut. I have a few extras to try, it cant hurt, just have to verify float level every change.

 

Thank you to everyone for the help, I will let you know what I find.                   Jeff

 If the pistons are rising equally, I think the butterflys must be opening. It would seem (IMO) that the problem is in either in the linkage, (doubtful) or it's just a basic "out of sync problem". Have you tried going through the synchronization procedure again? 

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Quote

Captain Obvious, Chickenman,  Yes I have the Unisyn balancer. Both carbs are adjusted to equal flow. I think that should have to mean the throttle plates are open close to equal. When I rev the engine it revs up fairly smoothly with a little hesitation and the pistons move like they should.

" Revs up fairly smoothly and pistons move like they should " ... contradicts the subject line and main premise that the engine is only running on one carb. That tends to lead us all on a wild goose chase??

Sounds like it's actually running on both carbs, but not properly. Synch them again and check that the pistons are free. Remove both oil dampers. With engine off, lift each piston to the top position and then let it drop. It should move freely with no sticking and should drop freely and stop with a solid " clunk ".

If there is any binding, remove the Piston cover and make sure jet is centered in jet holder. Check needle to see if it is bent or has score marks. After making any necessary adjustments. Replace the Piston cover and lightly tighten screws. Do the lift and drop test. If any binding, slightly reposition dome cover. There is some assembly variance built in.  Make sure dampers are filled to the correct level with lightweight oil ( I prefer ATF ) and reinstall dampers. Re-synch carbs.

Edit; Be sure to check for any vacuum leaks around intake manifold. Loose Intake manifold bolts, split hoses etc. A Vacuum leak will put the carb synch out of whack.

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Just came in from the garage to have lunch. Started from the beginning and adjusted the RPM at full choke to 1450-1500 and made sure the carbs were balanced. Went through the full Syncing and Balancing process again, same results. Felt like no matter what I did the back carb wasn't getting fuel. Pulled the vent bung off to look inside the float body and used the WD-40 straw to push the float down, fuel immediately filled the bowl and overflowed. So I revved the engine to draw down the fuel level but the fuel didn't go down as much as I would think it should. I am going to pop off the choke linkage from the jet when I go back out and check to see if fuel is flowing freely through the hose from the bowl.     Jeff

Chickenman, you posted just as I was. Pistons are free and moving as they should, needles are not sticking. Checked manifold and carb bolts and sprayed to look for vacuum leak, nothing. Lifting front piston immediately stalls down engine lifting rear does absolutely nothing also covering air flow with my hand doesn't get any response that is why I think there is no fuel flowing as it should.

Adding a pic in case anybody sees something obviously stupid that I missed.

Carbs on car (Medium).JPG

Edited by JeffMopar
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My interpretation of the problem is "I'm only running on one carb at idle. Above idle, everything seems to be OK, but at idle the rear carb doesn't do anything."  Is that correct?

What was the throttle position when you synced the carbs? Do you use one of the adjustment screws to raise the RPM's to something above normal idle while you are performing the sync procedure? If that's the case, then your carbs may be perfectly balanced at a higher RPM (wider butterfly opening), but at dead closed idle, your rear butterfly is too far closed for the carb to work.

Did you manually open the butterfly on just the rear carb with your finger while at idle? What happened? Did the RPMs go up?

Did you or someone mess with the "do not adjust this" stop screws on the carbs?

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