The Dodge Challenger Message Board

All,

Here is something strange, as long as the ambient temp stays below 85 degrees, this issue does not show up, car runs great no issues.

Here is one I need everyone's thoughts on, since it is running 95+ every day here in Atlanta (This is important), I was getting cars ready to take to a show. My 340 idles/runs great for 30/45 minutes and then you can feel hear a definitive miss ultimately leading to the car to stop idling and shut down. It starts right up no problems with the miss........we are bewildered as we have checked compression and all cylinders are good (so feel mechanically were ok), the complete fuel system is new, carb, fuel pump (psi is good), timing is spot on and ampmeter on ballast resistor shows 9.5/9.8. New Plug wires, etc...........

So we are continually messing with Holley (New) but I am starting to think that I have some form of electronic issue.....I can't recall the (Don't no name) ignition modulator on firewall fail or have some type pf thermo problem when the temp both engine bay and ambient temp are very hot?

We are going to blow air on it while this is happening to see if this makes a difference.

Anything in the fuel system at the gas tank or inlet line I might be missing?

Remember the car runs great for 30/45 minutes and I never experience this problem is the ambient temp is 85 or below........Electronic, Vacuum or Fuel? What do you guys say?

All help is appreciated, I will let you know when I figure this one out.....

I would guess the fuel is boiling in the fuel line or in the carb.

I agree with Dave. One nice thing about the B/RB setup is the use of a fuel vapor seperator. Located behind the alternator and near the timing chain cover. I personally havent experienced this and have mine out during very hot days too. 91-93 is the average around here right now with 82% humidity. Reminds me of my time Savannah, Ga

Also have you rerouted any fuel lines or exhaust? Perhaps they're too close to each other, causing vapor lock there. If that is the case, make a heat shield for the affected area.

i am running a demon carb and i rerouted my fuel lines different and pretty much solved the problem it get hot here in denver all tho not the humidity i agree with dave and ed the fuel is boiling in the carb but also if there is any cavation in the lines it will cut out after it gets hot ,
i made sure to run my fuel regulator after the carb and then to a return line, i used to have the regulator before the carb located on the inner fender and it would cavitate between the regulator and the carb, and after it got hot it would stall and i would have to let the pump run fuel in to it until it started hope this helps

Found the issue, seems that I had an electrical short in a connector coming from the firewall and apparently it had to get to a certain temperature to start the missing.

Anyway, did notice when I was looking for other hot areas that I need to move the coil and some other electronics as they were getting almost to 200 degrees.

Yes, i have always wondered why they locate the coil on the top of the engine, right where it gets the rising heat. I would have thought the fender or firewall would be a better place such as where they put the ECU. The coil gets hot enough doing its own work without having to put up with any extra heat. I like to relocate my coil to a cooler place.

Similarly, the electronic module on some aftermarket dizzys is located on the dizzy itself. On the Mopar SB, it is at the back where the hottest part of the motor is, at the back against the fierwall with little flowing air and getting the rising heat from both eng and trans.

See. Told you it wasn't the fuel.

dave-r wrote:See. Told you it wasn't the fuel.

yea me too!

Goldenblack440 wrote:Yes, i have always wondered why they locate the coil on the top of the engine, right where it gets the rising heat.

For ease of installation. The engines were manufactured as complete autonomous units (with trans and K-member), they just needed the engine harness plugged in the firewall connector, the negative battery cable's small wire bolted to the radiator core support, and the fuel hose to be operational. Couldn't be much simpler.

Similarly, the electronic module on some aftermarket dizzys is located on the dizzy itself. On the Mopar SB, it is at the back where the hottest part of the motor is

If you're referring to the HEI, it had its shares of problems, being insufficiently cooled mounted in the cap. Some mount it to a heatsink under the dizzy head.
The OEM mounting spot for the Chrysler ECU was on the firewall, pasenger side, on a bracket one inch away from the firewall itself for good ventilation. Always some air moving there.

Thanks for the info ! Ease of production and saving dollars often got the upper hand to anything else it seems.

Goldenblack440 wrote:Ease of production and saving dollars often got the upper hand to anything else it seems.

Hey, this is Dodge, not Aston Martin! It rarely happens any other way.

On the other hand, getting the engine complete on the K-member, with the trans, air filter, exhaust, when you restore it, well...
I would have one of those just for looks in my dining room if I could get it past the door!

I bet some very rich mopar head has already done that with a Hemi, esp the Ram inlet. Use the aircleaners as giant beer coasters.