Technical New 350 chev wont idle

Hey,

i have put a brand new 350 chev in my 1963 impala and its been running great but last night it stalled I didn't think nothing of it but today took it for a 45 minute drive and now it wont idle, even if im doing 60kph and take my foot of it sounds like the car is off and goes to stall. drives fine once going but wont idle.

Any ideas?

thanks

 

Idle circuit in the carb got dirty is one possibility. What carb are you using?

 

New carb or the old one? New carbs don’t have a filter, maybe you sucked in some crap from the tank and plugged up the idle circuit

 

New carby mate, brawler 650

 

New carb mate I wouldnt pit a old carb on a new motor haha,

 

New carbs can get dirty too.
Make sure your choke isn't partially closing.
Change your fuel filter.
Check your initial timing.
Look for a vacuum leak by running raw propane from a small torch along all suspected areas. The rpm will increase if it finds a leak.
Then try burping the carb.
Increase the rpm and place your protected hand over the mouth of the carb until it stalls out. Do it 2-3 times.

 

Cant do most of them as it wont idle at all it stalls instantly when i take my foot off the throttle but i will check the choke tomorrow morning

 

Sounds like possibly a large vacuum leak to me as well. You can spray carb cleaner around the base when it’s running or if it’s that bad, you can probably hear it. Does it have vacuum booster for the brakes? Could be the hose leading to it. Does it have a PCV valve? Could be the hose leading to it. It could be the base gasket under the carburetor. Or, a crack in the base plate of your new carby.

 

The distributor could have moved?

 

Vacuum leaks are easy to ferret out. Take off the air cleaner, let it idle if possible, you can turn up the idle screw temporarily. Put a hand over the top of the carb, it the idle picks up, you have a vacuum leak.

 

Have a friend help get it started while you fiddle with the engine or hook up a remote starter button and turn the key on and start it from under the hood and fiddle. You might also check the rubber connection hoses on the suction side of the fuel pump for cracks. Don't forget the hose between the tank and fuel line! Lippy

 

I'd start by just turning the idle screw in until it will idle on it's own. Then it will at least run as you check timing, or other things that could have affected the sudden drop in idle.

 

Power brake booster diaphragm?

Jon

 

Send your old ones to me , I'll use 'em !

 

Nah i enjoy rebuilding them

 

All lines are brand new so I wouldn't think they would be cracked

 

Just checked that and it moved by hand haha dammit

 

Been there. easy fix.

 

Luckily we marked the dizzy and manifold, we mustn't of done the bolt up tight enough

 

Turns out the dizzy wasn't the total problem, its happening after about 10 minutes of driving it wont idle, as soon as the accelerator is backed off the idle slowly comes down till it stalls

 

Vacuum leak would be a good place to start. I hate to even say this but just because it's new doesn't mean it's good these days. To me, it sounds like a bad float adjustment or it's not seating right. Fairly common. Is the carb new or is it rebuilt? Rebuilt parts these days are pretty questionable. Also, if you are running the stock electronic ignition, check out the module in the distributor. They do some funny things that can be difficult to analyze. Check the idle speed screw and the fast idle cam. If the idle speed was set on a cold engine (Choke closed) it will be too slow with the choke open (Throttle plates completely closed) and cause your problem. Check the choke adjustment to see if it's set too rich (too much spring tension cold). Check for sticking linkage on the throttle body. If the timing is set to specs, good fuel pump pressure, idle speed and choke set properly, it should idle fine. One last thing: check the carb base to manifold gasket to make sure it isn't covering any little holes between the carb and manifold. Wrong gasket here will make you pull your hair out.

 

Had 2 Holley 600s crap out on me , barely any miles on them...If i find original NOS Rochester quadrajet im gonna grab one dammit..

 

Hey mate, everythings news ignition, dizzy etc carby is new aswell not rebuilt. It was running fine for a few days its just recently started this and only once i got for a drive after 10 minutes it wont idle so to me its not someththat was done when the motor waspit together, its worth mentioning that it runs fun when driving just wont idle. Idle circuit blocked i thought but of that was the case it wouldn't idle at all not just when it warms up. The dizzy was loose so i timed it again and then it ran great but 10 minutes later it was doing it again

 

Ignition module getting hot and breaking down would be my guess. Have you tried a known good distributor to rule this out?

 

Bad ignition modules can do lots of things that will test your sanity. I have had 3 bad ones in a GM HEI... not all the same car, thank you... and all problems were different. A new module in all cases was the cure.

 

Its a street fure hei dizzy mate brand new

 

Wouldn't that cause it to breakdown all the time once warm? Not just cant idle

 

Something people often overlook is that every new carb at one point is full of dirt - or more accurately, all the metal chips etc. from machining all the carb parts. There's no guarantee it was cleaned out properly before assembly, so finding some of it left even in a brand new, never used carb is quite common.

I've learned the hard way to always take a look inside a carb before using it, even if it's new.

 

The most recent was in an OT '84 Chevy wagon. If I went somewhere, the car could be only started within a 10-minute window of shutting it off. Go 15 minutes, no start and I'd have to wait 2-3 hours before it would start again. I guessed it was a heat-soak thing.

I had another in a different Chevy wagon, I could get down the street 100 yards and it would die on me, no matter hot or cold. It simply shut off. I pushed it back home and changed the module, it was fine from there.

The 1st one I had, yet another Chevy wagon... loved those beasts.. would do it only when warmed up. It would mis-fire a few beats and the engine died. But after a minute it could be started, I may get a 1/4 mile and it did it again. Made the commute to my night gig interesting. On the way home, it was dark and cooler, no issue there.

I would say that they might do more than what I experienced. In all cases, a new HEI module fixed the problem, one I swapped in a new distributor from Napa since I got a new cap in the deal.

 

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