Weber Marine Carb on 360 la engine?

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Liams55belvedere

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I have a Weber (9635sa 3026) on my 360 with an Edelbrock performer 318/360 manifold and I am not getting any vacuum at idle from what is supposed to be the manifold vac port
(drivers side).
I recently rebuilt the carb and it runs a lot better than it did but still has an inconsistent idle.
I do get vacuum from the port under the electric choke at idle.
This is my first project car and I have some pretty gapped knowledge as I just learn as things go bad.
Any info would be extremely appreciated.
 
Daves69 said:
The simple questions.....
How much idle vacuum do you have?
Possible vacuum leaks?
Is the port/circuit plugged/blocked?

Aside from that, some tuning instruction here............
Click to expand...
1-The needle on the gauge doesn't even move at idle at that port but at the choke port I believe it was around 15 inches
2-ive been hunting for a leak but I've been unsuccessful so far in finding it. Would a mild leak cause it to have 0 vacuum at the port though?
3-its possible it's blocked, is there a way to check this without tearing it all off again?
 
I haven't run an afb in decades, and I really don't have a direct solution for you.

15 inches vac should be plenty. I would think you'd have vacuum there if the port is open.

Maybe plug the pcv port and see if it produces a positive result.

Without other more knowledgeable member suggestions, I believe I'd be pulling it off to check.
 
Daves69 said:
I haven't run an afb in decades, and I really don't have a direct solution for you.

15 inches vac should be plenty. I would think you'd have vacuum there if the port is open.

Maybe plug the pcv port and see if it produces a positive result.

Without other more knowledgeable member suggestions, I believe I'd be pulling it off to check.
Click to expand...
If it is plugged; would that be debris or something done by the manufacturer since it's a marine carb? If it's like that from factory is there anything to do about it or should I be in search of a normal carb?
 
The passage must be clogged. You can try carb cleaner in the fitting or remove the carb, flip it over, put your finger in the primary bore next to the buttery fly, put your palm over the welch plug, then blow a couple psi of compressed air with a rubber tip nozzle into the outside fitting. Clean out the large hole then put the welch plug back in. The surface is covered by the gasket when installed.
 
I think you are using to ported nipple . The manifold port is a straight through hole .

You can see the light from my flashlight shining through the port.

IMG_1038.jpeg


IMG_1039.jpeg


IMG_1040.jpeg
 
MV8 said:
The passage must be clogged................
Click to expand...
Is this where a slot should be for that port nipple?

1723918795543.png

^^^^^^^^from a 9635sa on Ebay

a 1406 eddy..........

1723920413877.png
 
Last edited:
It is on an eddie. Horizontal slot. What is the story on that pic?
 
MV8 said:
The passage must be clogged. You can try carb cleaner in the fitting or remove the carb, flip it over, put your finger in the primary bore next to the buttery fly, put your palm over the welch plug, then blow a couple psi of compressed air with a rubber tip nozzle into the outside fitting. Clean out the large hole then put the welch plug back in. The surface is covered by the gasket when installed.
Click to expand...
Well I will try the carb cleaner but if not then I'll take the carb off and see what's going on with that port.
 
The man vac port is on the throttle driver's side of the carb. The ported VA port is on the pass side. Make sure you are checking the correct port. If no vac, then it is blocked.
 
I see how they could tap into the manifold vacuum now on the AFB. There is a diagonal passage (viewed from the mixture screw side) from the linkage are up to just above the large manifold vac port. Under the bottom plug near the primary, they must have drilled vertical to connect the passage. If used for pcv, it could have been gummed up and hard to clean. I wonder how MBaird's AFB is drilled since light shows through. Maybe a retrofit drill due to clogging?

I think if you apply air to the large round hole in the bottom between the primaries, then plug the pcv and manifold ports with your fingers, it will push the bottom plug out or you can try holding the carb inverted and fill the pcv passage with carb cleaner. A little soapy water won't hurt anything and will show bubbles where any air makes it through. A mini 12v tire inflator usually has a plastic tappered fitting you could use.
 
mbaird said:
I think you are using to ported nipple . The manifold port is a straight through hole .

You can see the light from my flashlight shining through the port.

View attachment 1716290632

View attachment 1716290633

View attachment 1716
Click to expand...

Bewy said:
The man vac port is on the throttle driver's side of the carb. The ported VA port is on the pass side. Make sure you are checking the correct port. If no vac, then it is blocked.
Click to expand...
Yes it's the correct side that I'm checking and the other is ran to the distributor
 
It appears that the marine versions do have different vacuum ports .
Can you post a picture of yours ?
 
mbaird said:
It appears that the marine versions do have different vacuum ports .
Can you post a picture of yours ?
Click to expand...
I will give pics of where the ports should be when I take it out again but here is a couple photos from when I rebuilt it
IMG_20240806_025017520~2.jpg
IMG_20240806_003011788.jpg
 
Get some mechanic's wire and see if you can unblock it.
 
If the MVA port is blocked & you don't want to drill it.....
You can use the large port, bottom centre, carb rear. This is also MVA; usually used for vac to the brake booster. If used for the booster, you can put a Tee fitting in the line. If no booster, & there is a plug there, you can a fitting to take 3/16" hose.
 
Bewy said:
If the MVA port is blocked & you don't want to drill it.....
You can use the large port, bottom centre, carb rear. This is also MVA; usually used for vac to the brake booster. If used for the booster, you can put a Tee fitting in the line. If no booster, & there is a plug there, you can a fitting to take 3/16" hose.
Click to expand...
Is the port under the choke mva as well?
 
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