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Sag/bog after shift at WOT #1453971
06/16/13 07:03 PM
06/16/13 07:03 PM
Joined: Jun 2004
Posts: 148
Montgomery, PA
dodge340dart Offline OP
member
dodge340dart  Offline OP
member

Joined: Jun 2004
Posts: 148
Montgomery, PA
I have a '69 Dart with a 340/904 combination. I am having a problem with a sag in acceleration at WOT after the 1-2 shift and as the race night progresses it gets worse with the same problem after the 2-3 shift. There is even some misfiring out the open exhaust. I have gone through the Holley 830 Annular carburetor and found nothing. I reset the float height with no benefit. I have cleaned the fuel cell, installed a new filter (100 micron) between the cell and pump; again no better. I replaced all the braided fuel lines with new lines, no help. I replaced the pump and regulator, no help. I tested the volume of fuel and the pump can provide one gallon of fuel every 19 seconds. I have played with various fuel pressure staying close to about 6.5-7psi, no help. I have been running the same setup for years, an Edlebrock headed 340 with a .557 MP camshaft and for the last three weeks I have had this problem. I have gone from the 11.40s to 11.60s and 114mph to 111-112mph. The entire fuel system has been replaced except the Holley 830. I have gone through the MSD distributor, checking the pickup and it was good. I replaced the cap, rotor, plug wires, and plugs, no benefit. I used another ballast and MP Chrome box to see if the Dart would pick up and that did not work. I have changed the actual fuel I use (93 octane). I did a compression test and it was 75psi on the first puff and 175psi after five puffs (cylinder 6 was only 170psi). I did leak down testing and every cylinder was 3% or less. Any ideas? I am running out of them.

Thanks,

Chris


2011 & 2012 Beaver Springs Dragway Outlaw Street Champion 2012 BSD Friday Street Racer Driver of the Year 3-time Jr. Stock Eliminator 2-time Mean Street Eliminator '69 340 Dart 1.500 60ft, 11.359et, 117.08mph
Re: Sag/bog after shift at WOT [Re: dodge340dart] #1453972
06/16/13 07:58 PM
06/16/13 07:58 PM
Joined: Nov 2009
Posts: 3,410
Belpre,Ohio
C
CHAPPER Offline
master
CHAPPER  Offline
master
C

Joined: Nov 2009
Posts: 3,410
Belpre,Ohio
Quote:

I have a '69 Dart with a 340/904 combination. I am having a problem with a sag in acceleration at WOT after the 1-2 shift and as the race night progresses it gets worse with the same problem after the 2-3 shift. There is even some misfiring out the open exhaust. I have gone through the Holley 830 Annular carburetor and found nothing. I reset the float height with no benefit. I have cleaned the fuel cell, installed a new filter (100 micron) between the cell and pump; again no better. I replaced all the braided fuel lines with new lines, no help. I replaced the pump and regulator, no help. I tested the volume of fuel and the pump can provide one gallon of fuel every 19 seconds. I have played with various fuel pressure staying close to about 6.5-7psi, no help. I have been running the same setup for years, an Edlebrock headed 340 with a .557 MP camshaft and for the last three weeks I have had this problem. I have gone from the 11.40s to 11.60s and 114mph to 111-112mph. The entire fuel system has been replaced except the Holley 830. I have gone through the MSD distributor, checking the pickup and it was good. I replaced the cap, rotor, plug wires, and plugs, no benefit. I used another ballast and MP Chrome box to see if the Dart would pick up and that did not work. I have changed the actual fuel I use (93 octane). I did a compression test and it was 75psi on the first puff and 175psi after five puffs (cylinder 6 was only 170psi). I did leak down testing and every cylinder was 3% or less. Any ideas? I am running out of them.

Thanks,

Chris





Valve springs..?? How old?


If you like drag racing, support your local track.
Re: Sag/bog after shift at WOT [Re: CHAPPER] #1453973
06/16/13 08:07 PM
06/16/13 08:07 PM
Joined: Jun 2004
Posts: 148
Montgomery, PA
dodge340dart Offline OP
member
dodge340dart  Offline OP
member

Joined: Jun 2004
Posts: 148
Montgomery, PA
I was thinking that as well. The springs are Comp 985-16 dual coil springs. They have 245 runs on them; I installed them new in March of '12. I would think it would impact high RPM but I am planning on checking them anyway. Thanks for the thought.

Chris


2011 & 2012 Beaver Springs Dragway Outlaw Street Champion 2012 BSD Friday Street Racer Driver of the Year 3-time Jr. Stock Eliminator 2-time Mean Street Eliminator '69 340 Dart 1.500 60ft, 11.359et, 117.08mph
Re: Sag/bog after shift at WOT [Re: dodge340dart] #1453974
06/16/13 08:31 PM
06/16/13 08:31 PM
Joined: Oct 2003
Posts: 11,684
W. Kentucky
justinp61 Offline
I Live Here
justinp61  Offline
I Live Here

Joined: Oct 2003
Posts: 11,684
W. Kentucky
I had the same problem, a new coil fixed mine.

Re: Sag/bog after shift at WOT [Re: justinp61] #1453975
06/16/13 11:57 PM
06/16/13 11:57 PM
Joined: Jun 2004
Posts: 148
Montgomery, PA
dodge340dart Offline OP
member
dodge340dart  Offline OP
member

Joined: Jun 2004
Posts: 148
Montgomery, PA
That makes some sense; I replaced the coil in March as I replace all the ignition components at the beginning of each race season. I tested the coil when the problem first started but I may have to revisit the testing but this time add heat to the coil and test it as the problem occurs as I go rounds and the engine bay heat may be impacting the coil. I will swap last year's coil to see if my results are better.

Thanks for the idea,

Chris


2011 & 2012 Beaver Springs Dragway Outlaw Street Champion 2012 BSD Friday Street Racer Driver of the Year 3-time Jr. Stock Eliminator 2-time Mean Street Eliminator '69 340 Dart 1.500 60ft, 11.359et, 117.08mph






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