1/4 mile confusion

[barrchr]

I need help. Here is the story. I have in the past run low 14s consistently(14.20s mostly) with factory 3:27s and an Xpipe with a horrible leak at the manifold connection. My 60 ft times were 2.5 and 2.6s and MPH was 96-97. I have recently put back on my factory converter hpipe and new 4:11s along with nitto drag radials. I ran last night at Millington and ran a string of 14.30s with the nottos set at 16psi. My 60ft times were all in the 2.0s. I gained 1/2 second in 60ft but lost a tenth at the end and 1-2 mph. The nittos still take a second to hook after spinning and I did heat them up good. The car made a noise in the upper RPMs like someone was shaking a penny in a coke can. What is this? I believe it had someting to do with it but am not certain. How can I gain 1/2 second only to lose a tenth in the finish? I am a new member and dont really know who to talk to about assistance and advise. The car is a 99GT and 3555 lbs, 5 spd

[barrchr]

Can anyone help me with this?

[lguerra1]

Your biggest issue is if you are hearing, the penny in a coke can sound, then it is probably detonation. Which can burn a hole in your piston and hurt you motor.

In relation to your times slowing down, it is very common for someone to slow down after going with a lower ratio gear. You are going through one more shift than you would if you had the 3.27's. And if you are not great at shifting gears, then that slows you down as well.

Being that your 60 ft times improved, you should have improved your 1/4 mile times as well. Put the off-road exhaust back on, and go back out there for another go at it. Maybe your stock cats are plugged and killing your times. :huh:

[barrchr]

I cant put the off road exhaust back on. The passenger side Xpipe connection did not come close to mating with the passenger side manifold outlet. Xpipe, perfectly circle. Manifold, squared oval. What would you suggest about the detonation problem( plugs, timing, etc.) I have seen your car on the dyno and I know you know your stuff so I am glad I can talk with you about this matter. I have been told that every tenth you take off your 60ft times you will take off 2-3 tenths at the 1/4 BUT that just did not happen for me.

[lguerra1]

Start with plugs and timing. I don't know what type fuel you use, but if you only run 87, I would consider using at least mid grade. That should help your detonation. You definitely want to get rid of it, because running it with detonation will hurt a piston.