Barracuda Challenger Forum

Author Topic: 426 dual 600cfm - suddenly no power  (Read 261 times)

Offline hofilbert

  • Jr. Member
  • **
  • Posts: 53
    • Phil's 1970 HEMI Cuda Convertible
426 dual 600cfm - suddenly no power
« on: July 08, 2017 - 04:20:40 pm »
I have a 426 Hemi with dual 600 Edelbrock carbs that are synchronized (I hope that's the right term) and has a MSD electronic ignition with a MSD Blaster for a coil. I went to a car show on the 4th - all went fine going there. On the way back home, I went about 2 blocks and suddenly I had very little power. I thought maybe I had popped out of gear, nope. I went another 2 blocks and made it to my country road home. I started playing with gears and gas then while driving. The car was slow at take off and never got out of 2nd gear. It stayed in 2nd gear all the way home. I tried changing gears and that all worked fine, even put it in neutral and the engine has a very slow power curve. It would accelerate, but very slowly...even in neutral. It was slow power like driving an old diesel Mercedes from the 60's.

 You could stomp on the gas pedal and it would give a very slow acceleration even in nuetral. It didn't miss, or sputter or cutout...just a slow acceleration. I had a little less than 1/2 tank of gas, so that was good. I did have a very low battery from not driving it. After I was home, I took off the shaker and all hoses were attached. Had a new air filter. Everything looked good and connected. Checked all plug wires to ensure they were connected.
 I did restart it cold later with the elec. choke and it ran fine for about 20-30 secs. I could get a good VROOM and it would go up nicely to 3500 rpms just fine. Then, suddenly it did this "low power" thing again and dropped to below 1K rpms and foot response was slow. Idle was just fine and no missing. My battery was very still low.

 I've talked to a couple mechanics and they are both stumped.
 Any help with ideas is appreciated. I'm not a full-time mechanic so I'll do my best to answer questions. Thanks! Phil
Be sure to check out my 1970 Hemi 'Cuda Convertible web site http://www.packlighter.com/cuda/mycuda.html




Online cudabob496

  • Sr. Resident
  • ******
  • Posts: 6721
Re: 426 dual 600cfm - suddenly no power
« Reply #1 on: July 08, 2017 - 05:31:31 pm »
carbs flooding? float levels bad?

once that happened to me, and I found out I set my rev limiter wrong.

Look under distributor cap to make sure everything is ok.
Disconnet vacuum advance too, to see if things change.
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 734406pk

  • Andy
  • Sr. Member
  • ****
  • Posts: 1664
Re: 426 dual 600cfm - suddenly no power
« Reply #2 on: July 08, 2017 - 07:00:28 pm »
I have a 426 Hemi with dual 600 Edelbrock carbs that are synchronized (I hope that's the right term) and has a MSD electronic ignition with a MSD Blaster for a coil

What kind of MSD electronic ignition do you have? 6AL, Ready to Run distributor etc.?
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 Bullitt-

  • Permanent Resident
  • *******
  • Posts: 12165
  • Better Things To Come Member Since 2/16/06
Re: 426 dual 600cfm - suddenly no power
« Reply #3 on: July 08, 2017 - 07:34:47 pm »
Personally no experience with MSD ignition but I've seen on TV shows multiple times "racers" having issues with them because of a Low Battery. 
I have no idea which model or style they were using.. I'd be getting the battery seen to before doing much more tinkering...
Wade  73 Rallye 340..'77 Millennium Falcon...13 R/T Classic   Huntsville, AL
Screwed by Photobucket!

Offline jhaag

  • Full Member
  • ***
  • Posts: 550
Re: 426 dual 600cfm - suddenly no power
« Reply #4 on: July 08, 2017 - 10:34:39 pm »
what you are describing sounds like a fuel issue to me. Plugged filter, collapsed hose, pump going out, etc. First thing to do is replace the filter. If that doesn't help, check pump output. You would have missing or backfires with ignition issues.   :2cents:
love 70 Challengers

Online cudabob496

  • Sr. Resident
  • ******
  • Posts: 6721
Re: 426 dual 600cfm - suddenly no power
« Reply #5 on: July 08, 2017 - 11:15:54 pm »
an MSD box to close to headers will overheat and not work.
My MSD box did not work due to a bad ground wire.
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 hofilbert

  • Jr. Member
  • **
  • Posts: 53
    • Phil's 1970 HEMI Cuda Convertible
Re: 426 dual 600cfm - suddenly no power
« Reply #6 on: July 09, 2017 - 02:31:53 pm »
Well, I don't think its the low battery issue. I just went out a minute ago and after 3 days on a trickle charger and what sounded like a brand new battery, it cranked it over big time and fired up. The choke was fine and ran for a long minute or two then I revved it off. Idled fine, then I revved it again a few times. Revved OK for about 3 times, then she started the no power thing. I put my foot down to the floor and just a slow acceleration. Not much of anything.

 I'm guessing now, it isn't getting enough fuel. I think its getting fuel, just not enough. It idles OK and doesn't seen starved or flooded or hesitations, or anything like that when I'm trying to rev it. It just doesn't want to perform.

I guess filters are next.
Be sure to check out my 1970 Hemi 'Cuda Convertible web site http://www.packlighter.com/cuda/mycuda.html

Offline 73440

  • Sr. Member
  • ****
  • Posts: 1589
Re: 426 dual 600cfm - suddenly no power
« Reply #7 on: July 09, 2017 - 06:57:25 pm »
Have you looked down into the carb when working the throttle to check spray?
67 440
73 Barracuda w/ 68 440
65 Plymouth Fury III , I sold ,was my Nana's car till 92 yo.
51 Ford F1 239 Flathead, flipped , new cab , stolen
59 BelAir 283 4 door original patina
01 Chevy van 380,223 miles
06 Crown Vic Police Interceptor
75 HD Ironhead converted to RH shift
73 HD Ironhead
82 HD Ironhead
74 Norton 850
80 HD Shovelhead
80 Husqvarna WR 390

Online cudabob496

  • Sr. Resident
  • ******
  • Posts: 6721
Re: 426 dual 600cfm - suddenly no power
« Reply #8 on: July 09, 2017 - 07:15:24 pm »
is choke malfunctioning??
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 hofilbert

  • Jr. Member
  • **
  • Posts: 53
    • Phil's 1970 HEMI Cuda Convertible
Re: 426 dual 600cfm - suddenly no power
« Reply #9 on: July 09, 2017 - 11:11:07 pm »
OK.  Problem solved.  I had Herm Petersen, famed top fuel drag racer ('73 Gaternationals winner) stop in and take a look at my car.  It took him about 10 seconds to find the problem.   The carbs are progressive and there is a little small screw on the linkage of the rear carb.  The screw had come apart so the back carb wasn't working.  The little screw and nut was down inside the tunnel humps of the intake so I didn't see them at initial inspection.  I guess when you've done this as much as Herm its all easy to see.
THANK YOU HERM!  All is good and I'm happy.  I'm so glad it wasn't a serious issue.
Thank everyone else for your ideas and the support.  :thumbsup:
« Last Edit: July 10, 2017 - 11:59:49 am by hofilbert »
Be sure to check out my 1970 Hemi 'Cuda Convertible web site http://www.packlighter.com/cuda/mycuda.html

Online cudabob496

  • Sr. Resident
  • ******
  • Posts: 6721
Re: 426 dual 600cfm - suddenly no power
« Reply #10 on: July 10, 2017 - 06:33:39 am »
Glad to hear!
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 Bullitt-

  • Permanent Resident
  • *******
  • Posts: 12165
  • Better Things To Come Member Since 2/16/06
Re: 426 dual 600cfm - suddenly no power
« Reply #11 on: July 10, 2017 - 06:58:20 am »
 :woo:
Wade  73 Rallye 340..'77 Millennium Falcon...13 R/T Classic   Huntsville, AL
Screwed by Photobucket!