carb troubles on a 1600cc?

[Peter - Belgium]

Hello all!

I just installed a set of dual Dell's 36 on a 1600cc engine. These carbs came of another 1600cc but years ago so have been idle for a while.
I have emulsion tubes 122 and idle 46.
009 with points set to around 30deg at full advance
flow is measured at the 4 corners at around 5

what I see/hear:
at fast throttle push if dies for a bit before picking up
after high revs it stays art higher revs for a pretty long time before settling down.
carbs are sometimes coughing and when pushing the throttle it seems like some fuel sprays up out of the carbs?

Any pointers on what I can stilll check matching the symptoms?

Thanks!
Peter
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356 Outlaw built: https://www.thesamba.com/vw/forum/viewtopic.php?t=430774&highlight=

[mcdragracer]

Since you received the Carburetors you say that they had been sitting for quite some time, did you go through the carburetors or rebuild them before installing them on the engine?

[Peter - Belgium]

I have opened them up and blew out what I could, I did not fully rebuild them with new seals.
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356 Outlaw built: https://www.thesamba.com/vw/forum/viewtopic.php?t=430774&highlight=

[modok]

Did you test that the accelerator pumps are working?
May need new diaphragms. just observe that they squirt?

The idle jets are very small,
It might be ok size if the engine has a very strong vacuum signal and high compression, but I think you would also need a vaccum advance distributor to run that lean.
Maybe they have been drilled larger.

[Peter - Belgium]

Accelerator pumps seems to be working very nicely and I see a nice steady flow of fuel coming out when the throttle is activated, no hesitation there it seems.

what would you recommend as better starting point for idle jets?

What are the common reasons the carbs seems to be coughing sometimes when on idle? and when I hit the throttle they sneeze sometimes wit what seems like a mist of fuel puffed upwards?
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356 Outlaw built: https://www.thesamba.com/vw/forum/viewtopic.php?t=430774&highlight=

[67rustavenger]

Popping up through the carb. Is an indication of a lean condition.

Bump the idle jets up one size and see if that helps a bit.

Also make sure to adjust the mixture screws to achieve the best lean idle (BLI).
The BLI adjustment should be done with every change to the engine. Be it, jet change, idle screw adjustment, or ignition timing adjustments.

Note: When the engine is cold. It will pop through the carbs for a minute or so. Once the manifolds warm up a little. It should clam down on the popping.
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[Peter - Belgium]

Ignition and valves I have checked before and were all good... So first next check: increase size of idle followed by the screws potentially!

will try this this evening:-)
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356 Outlaw built: https://www.thesamba.com/vw/forum/viewtopic.php?t=430774&highlight=

[Peter - Belgium]

so took them all apart again and cleaned again, all passages should be clear!
also changed to 52 idle jets, biggest I still had around

not much improvement... besides going worse:-( seems I now have an issue with the float on 3-4side. First was overflowing, now during running it pulled the chamber empty from fuel.

What is the best way to set these floats?

Thanks!
Peter
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356 Outlaw built: https://www.thesamba.com/vw/forum/viewtopic.php?t=430774&highlight=

[67rustavenger]

[modok]

CB performace kits came with

30mm venturi
180 air jet
#2 emulsion tube
122main

60 idle
50 acc pump jets

(tho most agree these pump jet and idle sizes are too large)
I would start with 55 idle jets and 45 pump jets

How do we know it is the same exact model as what CB sold?
Have to check all the circuits to see if it is the same or not.
I think most are all the same.
The 40drlas had several different models tho

set the float to close off fuel 6-7mm from the gasket, make sure the float valve is tight even if you did not loosen it yourself.
Make sure the venturi is not upside down, size number should be visible from top.

[Peter - Belgium]

I have reset the floats to 6mm closed and 12 mm when lowered and that seems to work now.
checked sparkplugs again, rechecked valves, changed gaskets, ... and ordered a compression tester to make sure all 4 cilinders are at teh right compression.

Also reset the carbs as in throttle gap at 0,1mm and idle screws at 3.5 out. Engine starts well and idles well. Flow i measure is 7 in all 4 corners and revs nicely when I open teh throttlle slowly.
It still stumbles when I hit the throttle fast and sometimes have some bang/fire out of cilinder 4 (hence my compression test I want to do)

maybe I should look for some 60s idles to try that?
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356 Outlaw built: https://www.thesamba.com/vw/forum/viewtopic.php?t=430774&highlight=

[modok]

I'd enlarge the acc pump jets.

The "idle jet size" should be judged by how it cruises at 1/8 to 1/4 throttle.

From alfa sud, most came with 33 or 35 pump jets and 32mm venturi, and that works on THAT car, but only because they are very high compression.

LOW compression stock VW engine, those sizes are for sure not going to work.

[Peter - Belgium]

So bought a compression tester and checked 4 cilinders... 1-2-3 are at 8 while #4 is at 6.
So guessing that is why the #4 has more of the ploffing and backfire through the Dellorto? Will this most likely be caused by the valves or the cilinders? Given the effect on the carbs I would guess vales?

Should i buy a leaktester as well to find out, or just remove the heads and lap the valves?

Thanks!
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356 Outlaw built: https://www.thesamba.com/vw/forum/viewtopic.php?t=430774&highlight=

[mcdragracer]

Is that 80lbs and 60lbs?

[j-dub]

Rick,

Peter means 8 bar(116 psi) and 6 bar (87 psi) respectively.

Peter,
Yes a leak down tester could be valuable here to help realize the next direction to go. Have you verified the valve adjustment, especially of #4? Did you try putting a squirt of oil down the spark plug hole and repeat the compression test?
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[mcdragracer]

Ah yes 14.7 bar per pound, little slow tonight.😜

[mcdragracer]

[Peter - Belgium]

[tasb]

Your compression tester will not be harmed by the oil, nor the fuel. Verify that your distributors advance weights are free moving.
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