Six Pack Issue - Hey Chryco!

[VTMopar]

I just had my 6 pack set up completely rebuilt, along with new wires, plugs, etc.   She was a real mess before the tune-up, and would hardly run (sticky float).   A Local Mopar Mechanic did the work (whom I trust) and spent a fair amount of time (and my $$) on the tune. I took her out and she runs terrific.... Idles great and with a slow,to hard press, she responds very well on the road.   However, when I cranked her hard at about 45 and into passing hear, she coughed pretty hard and a lot of black smoke out the rear.    Tried it one more time - a hard acceleration - and she coughed, hesitated before catching.   Decided it best to just take her back on Monday, but does anyone have any thoughts on cause?   

Neal - this is the same set up you gave a fiine-tune at Carlisle on years ago this weekend.    Hope all is good with you!

VT Mopar

[DocMel]

Id take it back asap, and dont touch the set up as it is now.  You paid for the tune and I am sure your mech will make it right

[VTMopar]

Rest assured..... I have no intention of touching it...... Just curious if anyone here might know if there is an obvious cause/fix.     

VT Mopar

[BarracudaDave]

The hesitation, before the engine takes off, sounds like the secondary springs probably need to be changed to a stiffer spring.  This will delay the tip-in of the two end carbs, making the transition smoother.

[Chryco Psycho]

well to me it obviously is loading up fuel so yes it could be the secondaries are opening to slowly & need a lighter spring but it could also be a power valve issue where the vacuum drops quickly opening the power valve adding too much fuel in as well so you mght want a lower rated PV

[VTMopar]

Thanks for the ideas.....   I'm taking it back this afternoon.... Will see what he comes up with.   

VT Mopar

[VTMopar]

As happens too frequently, during a 20 minute test drive, we could only get it to "cough" once.....   So he's less inclined to think it is the springs or power valve....   

 Funny thing is on the way over, I lost all "power" to my dash gauges (fuel, temp, oil pressure) and the tach was going crazy.    Never had this happen before.    We did experience an issue with the positive batter cable when I picked her up (had to move it around to get her to "connect".    I had this issue a year ago with a fresh build on the 68 Charger and we found a new cable had an issue in the connection.    Another after-market parts issue. 

Anyway, I've cut off the connector and installed one of those (ugly) bolt types so will see if that cures it. (I also ordered a new cable).   

Anyway, he thought the one time it coughed when he was driving it happened after the carbs opened.....  So we want to eliminate any possible spark/ignition issue before he goes tearing those carbs apart again.....    I'm going to drive it and see how often it sputters/coughs....     

More to follow.   

[VTMopar]

Update:    Since fixing the battery cable connection, I've noticed the engine is more responsive.    I've not had any issues with it coughing or backfiring nor any issues with the gauges.    I'm convinced the culprit was the battery cable connection, causing voltage issues....     

So - this is the second time (two different cars) where I've had a battery cable connection fail.....   Something for others to think about.

Thanks again for the suggestions......

VT Mopar

[moper]

Ive had some connection issues over the years onnmy own and customer cars. Glad you found the culprit.