Pulls hard and then quits...

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blackhand

blackhand

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I was merging on to I-5 this afternoon, there were no other cars on the on-ramp so I decided to gun it. She pulled hard through first gear, gave me a nice chirp going into second, shifted into third, and then at about 70 mph (appx. 3000 rpm) she just quit. Other than that, she runs like a top. Perfect idle, no dead spots, no hesitation even when flooring it on the highway from a 50mph roll.

This may be a dumb question, but what might have caused her to completely lose power at 70mph?:-k

It's a stock 400/727/3.23 sure grip except for the following modifications:

- Carter 9605S (600cfm), 0.098" primary jets with .074" x .047" rods, 0.090" secondary jets, 11inHg step-up spring (car has great vacuum, idles at 17inHg)

- Mild performance cam, 214 degrees intake, 224 degrees exhaust at .050" lift, .442" lift intake, .465" lift exaust

-Initial ignition timing is about 16 degrees btdc

- Full length headers

- High-flow air cleaner

- stock 1978 electronic ignition system, intake manifold, 452 heads, rockers, blah, blah, blah...

I'm not expecting to figure this out beyond a reasonable doubt, but any ideas on things that I can start investigating would be great.

Thanks FABO!
 
sounds like 5/16" fuel line delivery problems! Change to 3/8" line even in the tank. This will cure your problem until you decide to add more gear/power and then the 1320!
 

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To tell you the truth it kind of reminds me of the problem I was having. It turned out to be trash in the tank. After I installed a new tank and sending unit the problem went away.
 
You need to define "quits."

Does it run but not pull, IE run out of power?

Does it "quit" as if you shut off the ignition?

Did you try "getting out of it" for a second, two, or three, to see if the pump would catch up?

What do you have for ignition system and fuel?
 
Yeah, I have to agree it's a fuel delivery problem. Stock pump?
A couple of ways to check it........hook up a fuel pressure gauge between the pump and the carb, of course you have to be able to read the gauge from behind the wheel when it quits and see if the pressure dropped off right before it quit. or you can slid it into neutral, shut down the ignition as quick as possible and coast to a stop (not recommended if you have PS or power brakes). Then check to see how much fuel is in the bowls, they'll probably be dry if it's a fuel problem.
 
67Dart273 said:
You need to define "quits."

Does it run but not pull, IE run out of power?

Does it "quit" as if you shut off the ignition?

Did you try "getting out of it" for a second, two, or three, to see if the pump would catch up?

What do you have for ignition system and fuel?
Click to expand...

When it quits, it just runs out of power. The stock mechanical fuel pump is on the engine right now and this was the first thing that came to mind when I started to think about it. I'm pretty sure that I'm just burning through all of the fuel in the bowls by the time I hit 70mph. BTW, I just finished rebuilding the carb so the inlet needles and seats are brand new and the bowl height and drop is perfect.

The ignition is the stock 1978 electronic ignition. A full MSD setup was next on my to do list but I think I'll have to address the fuel delivery issue first.
 
mullinax95 said:
To tell you the truth it kind of reminds me of the problem I was having. It turned out to be trash in the tank. After I installed a new tank and sending unit the problem went away.
Click to expand...

Brand new gas tank and sending unit installed when the car was restored
 
Rob Eppler said:
sounds like 5/16" fuel line delivery problems! Change to 3/8" line even in the tank. This will cure your problem until you decide to add more gear/power and then the 1320!
Click to expand...

Great idea. You're right on the money there, I'm just trying to get all the kinks worked out so that it's ready for a whole quarter mile by this summer.

Nice freaking ride by the way!
 
Flimsy rubber fuel line between metal line and fuel pump or between metal line and tank gettting sucked shut?
 
I think it's tuning. Something isn't right with the carb or ignition.

I had an old chevy that wouldn't pull past 3000rpm because the valve springs were so dead.

Again….. It is not the 5/16 line unless it is crushed or plugged.


My 5/16 line fed a solid roller cammed, 8000rpm turning, Holley 800 double pumpin, 340 for 20 years without issue.
 
Had the exact same thing happen to me after the motor was installed in my dart. I too had the crappy stock ignition box. I swapped to a chrome box and the problem was fixed.
 
340sFastback said:
Flimsy rubber fuel line between metal line and fuel pump or between metal line and tank gettting sucked shut?
Click to expand...


What he said. I forgot about that, it happened to me. It happened all the time on lower radiator hoses and that's why they now put a coil steel spring looking things in them now.

If the fuel line is softened internally by fuel over the years it will suck in and block the flow. Try that first, cheap cure....then go to the next level.
 
could be several things...i agree it's not the size of the fuel line..but perhaps a kink or a weakening fuel pump not keeping up....if it's fuel deprivation (sp?)...check the plugs to see if they appear leaned out...then pump, kink, or carb tuning is the problem.
a 600 seems slightly small..but you have a pretty mild build to be outrunning your carb CFM
ignition also feels like fuel at times...the stock box's are something that have given me problems right out of the box before, had several die at 4000 RPM like a rev limiter...junked the stock box's and ballast setup for a summit brand (MSD manufactured) stand alone digital ignition box...night and day! good luck!
 
i had a very similar problem when i put a 383 in my truck , changed the fuel pump , still did it , then i changed the fuel filter and it ran fine . try the cheapest part first.
 
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