|
Re: High rpm misfire
[Re: mac56]
#360813
06/28/09 07:10 PM
06/28/09 07:10 PM
|
Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
|
Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
|
Quote:
Has anyone had an issue with a 7al 2 not working properly. Done all the normal checks that msd recommends but still have a problem. I changed the chip, check grounds,replace pick up wires with shielded cable, ohmed plug wires. Msd says boxes usually work or don't work. Has anyone experienced an issue with them?
Thanks
I had my 7AL 2 do exactly that... mine missed(not
real bad but it was missing), like you I checked
EVERYTHING... I also did a A-B-A test with my back
up box and the first box had a problem... I sent it
to them and got it back and they said it was fine.
I again checked the box and found it to be fine
but I know it had a issue before. Mine missed about
7000 rpm
|
|
|
Re: High rpm misfire
[Re: 572stealth]
#360817
06/29/09 07:27 AM
06/29/09 07:27 AM
|
Joined: May 2007
Posts: 1,443
Maryland
Dads426
pro stock
|
pro stock
Joined: May 2007
Posts: 1,443
Maryland
|
Same problem, but only at the 1-2 shift at 5800-6300 rpm with a 7400 rpm chip. It does it randomly; 2-3 rounds are fine, then it feels like it's on the chip for just a moment (enough to kill 0.03 ET). A/F mixture is good, plug gap is 0.045", new Fire Wires, checked grounds; haven't figured out the reason. Would like to try a new box, but don't feel like shelling out $500 for a new one if that's not the problem. I will be interested in hearing what you find.
2012 422 Allstars NSS Champion
2013 422 Allstars NSS Champion
2014 422 Allstars NSS Champion
|
|
|
Re: High rpm misfire
[Re: mopar dave]
#360819
06/29/09 09:55 AM
06/29/09 09:55 AM
|
Joined: May 2007
Posts: 1,443
Maryland
Dads426
pro stock
|
pro stock
Joined: May 2007
Posts: 1,443
Maryland
|
Our's is already in the car. I will look at shielding the pickup leads. What did you use? A braided cover over the wires?
2012 422 Allstars NSS Champion
2013 422 Allstars NSS Champion
2014 422 Allstars NSS Champion
|
|
|
Re: High rpm misfire
[Re: emarine01]
#360821
06/29/09 11:29 AM
06/29/09 11:29 AM
|
Joined: Mar 2003
Posts: 2,497
PA
moparacer
top fuel
|
top fuel
Joined: Mar 2003
Posts: 2,497
PA
|
Well, I have been trying to figure out why my car misses at the finish line from 66-6900 RPM. 7AL2, Pro power coil, MSD wires, pro billet distributor I pulled the cap and wires to check resistance Saturday night and I couldn't make ANY connection with the multi meter through the brass terminals in the cap, and brass tab on the rotor?!?!  They were not corroded, just had a dull looking brass color to them. I cleaned them of with emery cloth and bingo, great connection.... I will find out Friday night if thats what my problem has been....
67 Barracuda street/bracket car 11.27-119
68 Dart 502 BB 8.70s-152
414 cid SB Dragster 7.65-174
|
|
|
Re: High rpm misfire
[Re: emarine01]
#360822
06/29/09 12:28 PM
06/29/09 12:28 PM
|
Joined: May 2007
Posts: 1,443
Maryland
Dads426
pro stock
|
pro stock
Joined: May 2007
Posts: 1,443
Maryland
|
Quote:
my msd is kinda picky on input voltage , works good at 12.5 sucks at 12.3
I suspect the alternator. It's one of those GM one-wire jobs and doesn't pick up the voltage until the rpms come up. MSD says the 7AL works at 12.0 volts, but that is at the box, so as rpm increases, so does the current draw and voltage drop in the wiring to the box will increase. I like the setup we had on the 64 Ply with the Chrysler alt and race regulator. It was cooking all the time.
|
|
|
Re: High rpm misfire
[Re: mac56]
#360824
06/29/09 05:10 PM
06/29/09 05:10 PM
|
Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
|
Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
|
Quote:
I think I am going to buy another box. If it ends up not being it I guess I will have a spare. I have done all the other recommendations.
Where do you live up there?
|
|
|
Re: High rpm misfire
[Re: MR_P_BODY]
#360825
06/29/09 05:11 PM
06/29/09 05:11 PM
|
Joined: Oct 2005
Posts: 976
ontario canada
mac56
OP
super stock
|
OP
super stock
Joined: Oct 2005
Posts: 976
ontario canada
|
Quote:
Quote:
I think I am going to buy another box. If it ends up not being it I guess I will have a spare. I have done all the other recommendations.
Where do you live up there?
I live in London Mr. P
|
|
|
Re: High rpm misfire
[Re: mac56]
#360826
06/29/09 05:17 PM
06/29/09 05:17 PM
|
Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
|
Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
|
Quote:
Quote:
Quote:
I think I am going to buy another box. If it ends up not being it I guess I will have a spare. I have done all the other recommendations.
Where do you live up there?
I live in London Mr. P
If you want to pay the shipping I can send you my
spare to try
|
|
|
Re: High rpm misfire (update)
[Re: mac56]
#360829
07/13/09 08:45 AM
07/13/09 08:45 AM
|
Joined: Mar 2003
Posts: 2,497
PA
moparacer
top fuel
|
top fuel
Joined: Mar 2003
Posts: 2,497
PA
|
Well, I just had a high RPM misfire I pulled my hair out with for a month and a half..... Yesterday I swapped out my 7AL2 box with a 6AL and the misfire went away...... 
67 Barracuda street/bracket car 11.27-119
68 Dart 502 BB 8.70s-152
414 cid SB Dragster 7.65-174
|
|
|
|
|
