6 pack carb issue ?? Helppp !!!!!

[dentwizgen]

Hey fellas,
I have a 70 challenger with a 440 6 pack set up. I bought the car as a turn key car this summer and it runs pretty good. The guy told me that the only mods was the biggest cam that mopar makes. Not sure of the lift.
Here is the problem.
When I start the car is seems to run fine about 1000 rpm then after it gets warmed up, it will runs at higher rpm then slower rpm. Bounces all around . If I turn off the car for a little and then restart it, it runs at a lower rpm say, 800 or less then high again. I looked for vacum leaks , tighted all the gas fittings but still can't seem to locate the irregular ideling.
I am not sure if the carbs need rebuilt.
When I got the car, there are 3 feul lines that come from the rear. The main gas line, the return line and also a vent or over flow line. The over flow line was caped off. Could this have something to do with it?

Sometimes , even after that car is warmed up, it will not start right up. I have to pump the gas pedal several times then is slowly starts ?

Any ideas ?????
I had a friend check the timming and he said it was fine.

Should I have the carbs rebuilt. They are original to the motor. Real V code car. Elderbrock manifold. Holley carbs

 

[R/T4speedconv]

Idle is around 1000/900 rpms stock cam. First check the two outboard carbs. Make sure they are fully closed at idle. Do you have the factory manual? It has good instructions on how to adjust them. Both out board carbs should have their idle mix screws capped off. If the lead caps are gone you have to re-adjust them to be lean-idle mix is the job of the center carb only. the idle mix on the two outboard is to keep fresh gas in them by leaking a little bit-thats all Also the return spring is special to the sixpack-very strong to pull all three carbs firmly closed and to keep vacuum pulses from opening the outboards a little bit. One last thought is check your idle vacuum and the power valve to make sure you have the right power valve

 

[Chryco Psycho]

Most of the itme when a larger cam is installed there is not enough vacuum to keep the power valve closed so you will need to take a vacuum readin gat idle in gear & use a power valve lower then the reading you get by an 1 or more , typically you would need either a 2.5 or 3.5 " powervalve to keep it closed at idle , this will smotth out the idle so other adjustments can be properly made such as the mixtures on on 3 carbs

 

[R/T4speedconv]

Another thought-if you have had any back fires (like when starting) and they are OEM carbs and unmolested you will have a bad power valve and it may leak. Newer power valves are more "back fire" proof than the old style. If you can-get some good close pictures and we can see how original the carbs are. There are at least 3 generations of gaskets that Holley has gone through (clear/black/blue) that claim to solve the leakage/drying out problems. My 440 six pack has always had a harder time starting hot (like after a gas fill) but most of my driving was in the south west. I did put back in the valley pan the insulator under the intake manifold which did help. Is your manifold aluminum or cast iron?

 

[Chryco Psycho]

blocking the heat crossover will help for sure
there are the original cork gaskets that shrunk badly , the brown that stuck far too well ,the black ones & the latest blue type

 

[dentwizgen]

6 pac set ups!

First of all fellas,
Thank you guyz so very much for your help and wizdom and taking the time to share your knowledge with us newbies.
Man, I will look into the the problem areas that you all have thought of.

I need a special mopar carb guy. I am such a noob! Anyway, Anyone know of a mopar guru in Dallas texas that works on these cars?

I believe the carbs are stock and manifold is steel (elderbrock)
I dont know any history on the car other than it has the biggest cam that mopar makes i was told when I bought it.. I believe a 509 lift cam.

Thanks again fellas

mark

 

[dentwizgen]

I do not have the factory manual, anyone know where I may get a factory 6 pac manual?
Thanks

 

[R/T4speedconv]

All 70 Challenger shop manuals have the six pack info in them. There was no six pack only manual.

 

[R/T4speedconv]

Can we get some photos of your set up to look at?