Barracuda Challenger Forum

Author Topic: Engine stumble  (Read 83 times)

Offline 70challengersix

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Engine stumble
« on: June 18, 2017 - 12:32:06 PM »
Hi guys, any ideas on this one?  Have a 440 six pack that runs great until it warms up and is stopped (engine turned off) and heat soaked.  When restarted and driving, I feel slight hesitations like a subtle misfire and I can see the tach needle responding similar to the hesitation.  Once it cools, it runs great again.  Here are some details about the car

1.  195 degree thermostat
2.   No spacer between carb and manifold. 
3.   After heat soak, fuel line to center carb is 212 degrees (highest)
4.   Vapor canister installed
5.   Pertronix installed in place of dual point distributor.  Flamethrower coil installed with internal resistor, ballast resistor bypassed
6.   Cooling system and fan operational
7.   Plug wires, cap and plugs look good
8.   Stock mechanical fuel pump
9.   Less tendency with non ethanol gas.
10.  Don't see any vacuum leaks.

Any ideas, is that temp getting too high in the fuel line and could this be connected to my problem? 
 





Offline 734406pk

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Re: Engine stumble
« Reply #1 on: June 18, 2017 - 04:01:15 PM »
I have the same issue with mine. After starting with "heat soaked" carbs, it takes 5-10 mins for the incoming fuel to cool things down and stabilize. 212 deg fuel line temp is very high. I'm running an electric fuel pump too. A manual pump will likely take longer to clear. Do you have the bypass line connected?
1973 Challenger 440 6 pack auto 3.91 rear
2012 Dodge Ram 3500 dually 6.7 Cummins Fleece EFI Live
1973 Challenger 318 2bbl auto 2.73 rear 22.5 mpg RIP
1970 Challenger TA 340 4bbl auto-Sold and sad
1999 Dodge Ram 3500 dually 5.9 Cummins Fleece tuned VGT-sold
1995 Kawasaki ZX1100E & still alive

Offline 70challengersix

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Re: Engine stumble
« Reply #2 on: June 18, 2017 - 05:23:42 PM »
Thanks, the bypass is connected (assuming you mean the vapor canister).  I don't know how a spacer would work since the heat is radiating up from the manifold to the fuel tubes.  I might just try insulating those tubes to see if there is a difference.


Offline cudabob496

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Re: Engine stumble
« Reply #3 on: June 18, 2017 - 05:57:02 PM »
insulate all fuel lines, and reroute if necessary.
Make a sheet metal heat reflector to snug up next to carbs.
72 Cuda, owned 25 years. 496, with ported Stage VI heads, .625 in solid roller, 254/258 at .050, 3500 stall, 3.91 rear. 850 Holley DP, Reverse manual valve body.
Up to 4000 RPM, Warp Speed, Up to 5000, Rediculous Speed, Up to 6000 RPM, Ludicrous Speed!

1999 Trans Am, LS1, heads, cam, headers, stall, etc! Love to surprise the rice rockets with this one. They seem so confident, then it's "what the heck just happened?"

Offline cudabob496

  • Sr. Resident
  • ******
  • Posts: 6349
72 Cuda, owned 25 years. 496, with ported Stage VI heads, .625 in solid roller, 254/258 at .050, 3500 stall, 3.91 rear. 850 Holley DP, Reverse manual valve body.
Up to 4000 RPM, Warp Speed, Up to 5000, Rediculous Speed, Up to 6000 RPM, Ludicrous Speed!

1999 Trans Am, LS1, heads, cam, headers, stall, etc! Love to surprise the rice rockets with this one. They seem so confident, then it's "what the heck just happened?"