Car popping/sputtering on the juice; any ideas?
 

Since MSD hasn't sent my broken Digital 6 back to me, I only ran a 75 shot at the track yesterday.

I made 7 N/A passes, all of them the car running just fine; smoothly all the way to 7000.

On my nitrous pass (test both solenoids and window switch couple weeks ago; A-okay), the car was popping the whole way down the track. It was fairly strong to the 1/8th (7.731 @ 92.80, spinning to a 1.86 60'....my best 1/8th time and trap ever on a worse 60'), but fell on its face in the 1/4 (only 11.978 @ 115.99). Comparing to my slips from last year, my 1/4 MPH should have been AT LEAST 118 MPH, but more likely 119 MPH.

Any ideas on why it would have been sputtering? I was shifting at 6500-6600 (I think I'll need to start shifting it at 6800, though....car seems to go faster shifting higher). N/A the car was running a little rich above 4k RPM. Jetting is standard NX 75 shot jets. I'll take a look at it this week, and pray my Digital 6 comes back, so I can spray a 150 shot at the strip next Sunday. I just don't get why it would sputter like that; never has done that before!

Sounds like you may be dropping fuel pressure (what fuel pump) or perhaps you are blowing the spark out (what coldness and gap), both at bigger loads (deeper gears as you shift)?

Just some thoughts.

I doubt I was dumping fuel pressure (Walbro 255), but I'll make sure I watch the pressure the next time out.

Plus are Autolite 103's, gapped .040.

The gap may be too big without your D-6 hooked up. I run .040 too, but with an Accel 300+. You might need .37 or so until you hook the MSD back up. What do you think?

What was the bottle pressure. It ssounds like you're running rich

I'm inclined to go with snow2000SS, sounds rich, did you pull a plug and look?

If it was popping through the exhaust, then you were running rich. You said the motor N/A was already running rich, so that added to the kit running a little rich, makes it alot FAT. Make sure your bottle pressure is at 1000psi. It runs good through the 1/8, then starts popping, cause the bottle pressure starts dropping, and the kit is going fat.

Yeah, I was only at maybe 950psi tops when I launched......forgot to turn my bottle heater on soon enough.

Looking at the plugs won't tell me much now, since I've driven and raced on them more since then. If the weather would behave, I'll take the car out and spray her w/ my car leaned out a bit more and see how she behaves.

Now if only MSD would same my damn ignition back to me; UGH!