Hi all,
Need some help diagnosing a misfire. Went to test n tune today. The car has a skip that develops at the top of 1st and 2nd gear (powerslide). It runs fine during the burnout (6500 rpm). I leave the line and it leaves sorta lukewarm, but not missing. 60 ft fell off .05-.06 from normal. Then at about 6300 or so it starts to skip. Shifted at 6700 (still missing), ran ok until it hits 62-6300 in 2nd, where the skip started again then I shut it off.
It idles and drives arounf the pits/return road fine.
I don't think it is fuel related. No changes to the fuel system since last year and it has always been enough. It's just 1/8 mile so I don't need a huge amount of volume. It has a Holley black pump and -08 line front to rear.
I went to a tnt a few weeks ago and it did the same thing. Only got to make one pass then. Starter went bad. I thought then maybe it was jetted too lean. That day it was low 50's. Jetted 84/85 no pv's Holley 950HP Today was 75°, I still jetted up 1 size over the 50's temp. It ran fine last fall with the 84/85's in 70° weather. Even after jetting up a little and much warmer weather it still had the skip, so I think it's not too lean.
I'm thinking ignition. Setup is an MSD7AL2, MSD dist with locked timing (have tried 36° and 38°) MSD 8.8 Super Cond wires (4yrs old), MSD Blaster 3 coil, and Autolite AR135 racing plugs. The plugs were left from last year. Have 75 or so passes on them.
The only engine related change that has been made to the car over the winter was locking the timing out. It used to have 18° initial and 39° total. I locked the timing in the dist, but made no other changes. It does idle better and has a little better throttle response off idle (that doesn't matter as I leave of a two step brake.
Today I checked the plugs and they looked all the same, also replaced the MSD chips to make sure I didn't have a bad one. Only made two passes, didn't want to hurt it. Valve lash is also ok.
For those who don't know my combo: 383W stroker, Windsor Sr iron heads, solid roller cam, 13:1 comp, all the usual bolt ons. In my 69 Mustang @3025 lbs with a powerglide/5400 stall converter/5.43 gear/ 32" tall tires it normally runs 6.8x's @ 100 in the 1/8 mile.
Any input would be appreciated. Going to start with new plugs and wires this week.
Thanks,
David Cole
Need some help diagnosing a misfire. Went to test n tune today. The car has a skip that develops at the top of 1st and 2nd gear (powerslide). It runs fine during the burnout (6500 rpm). I leave the line and it leaves sorta lukewarm, but not missing. 60 ft fell off .05-.06 from normal. Then at about 6300 or so it starts to skip. Shifted at 6700 (still missing), ran ok until it hits 62-6300 in 2nd, where the skip started again then I shut it off.
It idles and drives arounf the pits/return road fine.
I don't think it is fuel related. No changes to the fuel system since last year and it has always been enough. It's just 1/8 mile so I don't need a huge amount of volume. It has a Holley black pump and -08 line front to rear.
I went to a tnt a few weeks ago and it did the same thing. Only got to make one pass then. Starter went bad. I thought then maybe it was jetted too lean. That day it was low 50's. Jetted 84/85 no pv's Holley 950HP Today was 75°, I still jetted up 1 size over the 50's temp. It ran fine last fall with the 84/85's in 70° weather. Even after jetting up a little and much warmer weather it still had the skip, so I think it's not too lean.
I'm thinking ignition. Setup is an MSD7AL2, MSD dist with locked timing (have tried 36° and 38°) MSD 8.8 Super Cond wires (4yrs old), MSD Blaster 3 coil, and Autolite AR135 racing plugs. The plugs were left from last year. Have 75 or so passes on them.
The only engine related change that has been made to the car over the winter was locking the timing out. It used to have 18° initial and 39° total. I locked the timing in the dist, but made no other changes. It does idle better and has a little better throttle response off idle (that doesn't matter as I leave of a two step brake.
Today I checked the plugs and they looked all the same, also replaced the MSD chips to make sure I didn't have a bad one. Only made two passes, didn't want to hurt it. Valve lash is also ok.
For those who don't know my combo: 383W stroker, Windsor Sr iron heads, solid roller cam, 13:1 comp, all the usual bolt ons. In my 69 Mustang @3025 lbs with a powerglide/5400 stall converter/5.43 gear/ 32" tall tires it normally runs 6.8x's @ 100 in the 1/8 mile.
Any input would be appreciated. Going to start with new plugs and wires this week.
Thanks,
David Cole