318 dodge dart stumbles 5000rpm

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gah927

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when Im driving the car and i get into it right around 4700 and 5000 rpm the car stumbles really bad, any ideas?? its a 318 with 340 heads mild cam high rise manifold and a holley 650cfm.
 
Could be any number of things. How old are the valve springs? Is the carb tuned correctly. Is the distributor in good shape with the timing adjusted correctly.

Did the neighbor kid put a potato in the tailpipe.

The more info you provide the more we can help.
 
not sure how old the valve springs are, people before me put the 340 heads on. and yes the carb is adjusted right. the people before me only did a top end rebuild. bottom end is still from factory.
 
What ignition box are you running? I had a stock one act up at around the same rpm, it acted like it hit a rev limiter.
 
Is it cutting out or acting like it is shutting off? Mine acted like it was shutting off around that rpm. I swapped to a chrome box and problem was solved.
 
Badart, what do you mean "chrome box"
My 318 with stock cam, heads and carb. Dual exhaust and rebuilt the stock carb a few months back. The car bogs down and feels like a total loss of power. I let of the gas a little and car reacts again and starts driving normally. I don't know the rpm as I don't have a tach. If I ease into the throttle it'll accelerate past 70. It's the sudden mash like from 1/5 pedal to 4/5 pedal where it acts up.

Any ideas?
 
There are different ingnition modules and the chrome box is one.


SafetyFifth said:
Badart, what do you mean "chrome box"
My 318 with stock cam, heads and carb. Dual exhaust and rebuilt the stock carb a few months back. The car bogs down and feels like a total loss of power. I let of the gas a little and car reacts again and starts driving normally. I don't know the rpm as I don't have a tach. If I ease into the throttle it'll accelerate past 70. It's the sudden mash like from 1/5 pedal to 4/5 pedal where it acts up.

Any ideas?
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could be a fuel starvation issue. I had the same issue a year ago and after switching to a new mechanical pump the problem went away.
 
you say you rebuilt the carb a few months ago - maybe floats are a little too low or one of the float needle valves is sticking a little??? Too bad your
now a little closer, I have a Edlebrok 750 on my 360 currently but have
a 600 Edle and a 600 Holley sitting around as spares I would have let you
try just to rule out the carb. Personally, I had to stay with the Edelbrock,
the Holley 600 and another 650 one I rebuilt both had a stumble right off of
idle that I couldn't resolve in either Holley carb, the Edelbrock don't do it.
 
make sure the secondaries r opening fully, the valve springs are good, and that timing and ignition are in spec.

check plugs for color, post pic if you can...it will tell a lot of things about tune/ignition performance.
 
I'd put it on a fuel or ignition problem, with the symptoms really only appearing with a heavy throttle application I'd put it on the fuel side (although that could still be a timing advance issue). Without knowing more it could be rich or lean, but it sounds like either the carb tuning is off, or you're not getting enough fuel to the carb.

I'd check the fuel filter, float levels, and the size of the secondaries. The spark plug condition should tell you if you're rich or lean.
 
Raise the float level 1/4 turn and see if it helps. If it raises the point that the issue shows itself, it's likely a fuel delivery issue. Make sure it's not dripping fuel in the boosters with the higher float level.

Do not run it constantly at the higher float level, do it to get an idea of the root cause.
 
Thanks for all the input guys. Very helpful and nice folks on here! Right now I have the stock 2 bbl carter carb. I can get a remain from the local parts store for 191 dollars. Would it be best to go this route or look into a aftermarket carb?

I'm leaning towards this being a fuel issue. Timing is right, if I remember correctly we set it 8 degrees advanced. New air filter, electric fuel pump that is about to be gone. Going to go back to the mechanical hopefully this week. Previous owner installed the electric pump. When I first got the car it had a smaller volume pump, thinking the car was starving for fuel at the higher rpms I installed a much higher flow pump. No help, actaully had negative effects. The new pump was TOO powerful and ended up flooding my engine and thinning the oil so bad the motor started knocking. At least the internals are clean now lol.

Typed this all out on my phone, sorry if it's hard to decipher.
 
when you installed the new electric fuel pump, did you also install a fuel pressure regulator? If not, you would definitely be flooding the carb.

I wouldn't send close to $200 for another 2bbl carb unless you know for sure the carb you have is junk. If you do decide to buy something else I would safe some money and upgrade to a 4bbl intake and carb, not too hard to find for relatively cheap second hand.

Maybe have a look in the for sale section or start a post about the parts you're looking for. Some great members here that will help you out any way they can.
 
From an old CARtoons magazine......"No deal Honest John (used car dealer)
the valves float at 10,000"..............................................................
 
67cuda360 said:
when you installed the new electric fuel pump, did you also install a fuel pressure regulator? If not, you would definitely be flooding the carb.
Click to expand...

Yep after the engine flooded out I installed a in-line regulator. Another note I should add here, when I rebuilt the carb all I did was disassemble, clean and reassemble. It was filthy inside!!! I'm suprised the thing even ran. I've since installed 2 filters before the pump. When doing the rebuild i idn't check float height or anything assuming it was correct. I'm going to check out the carb further this week and go back to the mechanical pump. Can anybody point me to a good write up on checking float height and whatnot. And excuse this dumb question!! But what are secondaries? I come from the world of CV motorcycle carbs. Car carbs are a whole other beast haha
 
Do we have 2 different dicussions going on here - the 1st tread said he had a 650 Holley, then SafetyFifth says he has a 2bbl carb - a 650 Holley is a 4bbl which has
"secondaries" - 2bbl carbs only have primaries. For the 2bbl carb you can probably
find the carb listed on the web and look up instructions for it's rebuild kit - should tell
you how to adjust the float and such. Holley floats are very easy to adjust.
 
SafetyFifth said:
Yep after the engine flooded out I installed a in-line regulator. Another note I should add here, when I rebuilt the carb all I did was disassemble, clean and reassemble. It was filthy inside!!! I'm suprised the thing even ran. I've since installed 2 filters before the pump. When doing the rebuild i idn't check float height or anything assuming it was correct. I'm going to check out the carb further this week and go back to the mechanical pump. Can anybody point me to a good write up on checking float height and whatnot. And excuse this dumb question!! But what are secondaries? I come from the world of CV motorcycle carbs. Car carbs are a whole other beast haha
Click to expand...
This is pretty uncool! Start a new thread instead of Jacking this one.
 
I had issue with a wiped out lope on my cam on the exhaust side. it would load up and under high RPM it would stumble and pop until it cleared out. The Fix- New cam
 
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