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sbc 350 wont stay running

mudhog

mudhog

THEGAME
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ok im having problems keeping my sbc350 running. it will start just fine but if i try and let it idle or if im driving when i let up off the gas going slow it will just die. if im driving and on the gas it runs just fine. i can change the timing and get it to idle then lock it down and within 10min its doing the same thing again. here is some video of it doing it when i was trying to pull someone out. it is a mild built 350 with a edelbrock 1405 carb
 
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I'd guess a vacuum leak---why you can change the timing and get it to idle then it starts stalling again doesn't make sense though..:confused:

I'd look for any vacuum hoses that split,came off,and if they all look good,check the PCV valve hose (and see that the valve itself "rattles" and isn't stuck open)--the base gasket under the carb could be letting air get sucked in,squirting carb cleaner or oil on any suspected areas with it idling will change the idle (you might have to crank the idle speed up or have someone in the truck to keep it running)...
The power brake booster can make a big vacuum leak if the diaphram fails,you would hear it hissing when you step on the brakes though,and feel the loss of power assist...

It could be flooding at idle maybe too--any black smoke out of the tailpipes when you re-start it?..could have a float sticking or sinking maybe..
 
no black smoke when restarting no smoke at any time. i did try the cup your hands over the carb to see if the rpms go up for a vacuum leak but the rpms dont go up it just stalls out. i will try the starting fluid though. pcv is good and new.
 
Maybe and I'm grasping at straws here,the secondary butterflies are sticking open slightly...or if it has an EGR valve it might not be closing fully due to carbon deposits perhaps..
 
Kinda strange. I wonder if your centrifugal advance is mucked up and sticking. And slowly work there way back?
 
Have you tried checking your fuel filter?

Also, Edelbroke carbs are notorious for having issues with the brass floats bending out of adjustment. They are an ok carburetor on the street but a couple hard bumps is all it takes to throw them out of whack. Get a Q-Jet.
 
If this wasn't caused by someone fiddling with the adjustment screws on the front. Take the top off of the carburator and, turn it upside down and check the floats.
It's easy, the specs and adjustment instruction are readily available online.
It's just a big lawn mower carburator. Not much to them.
 
from the video, it sounds like it fires right back up. to much fuel it would blow black out the tail. To little (clogged filter or stuck float) / it would take a while to start/off idle it would fall on its face...
I'm with AR, pull it apart and check everything. I bet you have little chunkys in the bottom of the bowl. While your in there check the floats, then reset the idle mix screws when you get it back together.
 
If the Edelbrock has been put on a Q-jet intake or has a spacer/adapter under it,its highly possible the gaskets have failed ,often they dont have much contact area on the manifold to adapter or to the carb,and a piece of it fails and lets vacuum leakage occour...it could be crud in the bowl or the floats,but it shouldn't run "great" at higher than idle speeds in that case if they were at fault either...
 
one other thing it is doing is if it sets for more then like 2 days then i have to crank it over and refill the carb with gas before it will start. once thats done i can just turn the key and it fires right up
 
I'd see if you could scrounge up a different carb to though on it. Or else rebuild yours. I also am in the vacuum leak camp. Pretty typical that with a vacuum leak it takes a high idle to keep them running in gear. Usually what you end up with is a engine that idles way high in park, and then still dies or tries to die in gear.
 
Sounds like stuck float or needle and seats are off. I did the spring loaded needles and it helped a lot. When you take the top off check the floats got fiel inside them. Shake it and listen for fuel inside the float.
 
I am pretty sure that edelbrock carb on an edelbrock performer intake still requires an adapter plate. Otherwise you get a vacuum leak.
 
No the performer will accept a qjet or edelbrock without adapter. I know. I have had both carbs on the performer on both my current 78 and old 80.
 
It may have worked for you, but I would double check it. A little carb cleaner will tell you if it is your problem. It was needed on my 70 which has a edelbrock 1406 and a performer manifold.
 
Rule out vac leaks, brake booster, bad carb mount gaskets/ loose carb mount bolts/nuts. The basic tune up stuff. Intake gasket leaks first.

No flooding or black smoke on start floats are not too high. Runs fine otherwise, floats not too low.
Starts right up with turn of key but won't idle(weird).
Bowl goes dry after a couple of days, no biggy, methanol in fuels can cause that.

Carb idle circuits clogged, carb body gasket blown. Recheck your fuel filter, rebuild the carb blow out all passages or try another carb if you can like was suggested earlier.
Idle it up and go around with spray brake cleaner to find vac leaks. Plug off brake booster line at carb and try that( brakes will be hard to push).
And please tighten up that noisy belt.
 
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