i lost .5 tents in the 1/4 tonight. My car has a zz4 crate motor, lt4 hot cam, #24 injectors, stock tpi, 50 lbs fuel pressure, 5 speed, 3.73. It had bfg drag radials and went best of 13.3 at 103 and consistent 13.4-13.5 at 102. I put slp runners on with ported siamesed plenum, mickey thompson drag radials, and removed the cat and could not get the car faster than 14.0! NO VACCUUM LEAKS. It runs great and feels it pulls harder but i have no clue whats going on. I dont think its anything obvious but need to figure out whats wrong. Anything helps. thanks. Joe.

 

I'd recheck timing first and also why is the fuel pressure so high? You might want to see if it's running too rich. I'd suspect either timing or fuel pressure.

 

More information please... dates and times when you ran those times, and what track do you race at? (City, state, etc) I bet the DA wasn't as good and that is part of the problem. My LS1 car slows down as much as .4 from the fall to the summer. You lost more than .4, but it's a start. Did you adjust your shift points any? I'm sure those mods moved the power band up. How did the 60 foot times compare before & after? Did you do any tuning after the runner install? It might want more fuel & timing now.

Just my $0.02, there's a lot of factors involved here.

 

yea i have ran the car a lot with the first set up that took me to 13.4 and no matter the weather the slowest id run on a decent pass was 13.5. i shifted at 4800, 5200, 5600, and 6000 and went fastest at 5200. I'll try turning down the fuel pressure but thats not high for that motor. I have heard stock run best around 48-49 fuel pressure. Could the tires have somthing to do with it because my best 60 with the mickeys was 1.88. Call me crazy but i think they are too sticky and bogging the car down. It left harder with the BFG's which would spin on too hard of a launch. The mickeys wont spin no matter what rpm i leave the line but the car bogs. I think ill try running the tires at 25psi to get some wheel spin and keep the rpms up in first gear.

 

What do you have for suspension mods? Do you have LCA relocation brackets? People swore up and down I'd go faster with them in the upper hole, my car left soft. I put them down in the lower hole and played with launch RPM, I was rewarded with a solid .2 improvement in my 60' times.

If you don't have access to a wideband, find a safe spot and make a ***** out pull. At the end of the pass, push in th eclutch and kill the engine. Pull over, and check a few plugs. It will give you a good indication of weather or not it's too fat or too lean @ WOT.