Help in diagnosing my poor track times?


Well-Known Member
Jun 16, 2001
So I made a similar post last year after racing at the Buick vs Ford shootout. Since this thread.

I’ve pulled the trans and went through it while I sent the converter out to PTC be tightened up a bit. It now stalls around 2800 compared to 3100-3200 0 boost yet I’m still getting slippage in the realm of 14-15%. What if anything can cause a false slippage reading? The car makes boost and rpms easily. I also swapped to a recessed plug, new alky pump, and all new alky wiring/control box to replace my original from 04, went back to stock headers due to bad luck with aftermarkets and removed about 40 lbs of weight.

My best pass was this weekend was a pitiful 11.18 @121.72. That was with 27 psi. At 22-23 psi it ran 11.2@121.78 and went 97 in the 1/8th vs 99.8 in the 27 psi pass. The car just doesn’t want to backhalf at all. On my final pass I ran 11.40 @ 121.75 with the car gurgling a bit at the top of 1st and 2nd gear due to going too rich (went to a 10.6 a/f trying to suppress knock) It went 95.8 mph in the 1/8th and picked up to 121.75. The transmission is still shifting early under heavy load on the 1-2 (almost instantly in 2nd gear off the line except for my last run which is hurting my 60 ft but what I’m really concerned with is the back half and lack of mph when turning up the boost.

The engine has been in the car since 08-09 and maybe has 10-15000 miles but when it comes out, it comes out to play hard usually. I plan on a leakdown test soon but the car runs clean and doesn’t smoke. I do have a bit of oil I noticed on the #6 exhaust port when I took the header off a while back but the plugs all looked good before I changed them on race day. The car has been 127-128 just a few years ago on this same motor and setup and has been as fast as 104 in the 1/8th. When I had the trans apart all the clutches looked great and neither the forwards or directs showed signs of slipping so if the trans is not slipping and the converter is showing slippage could the motor be making the boost and rpms and just not the power to push the car to the mph I’m expecting?

The knock is a bit confusing and obviously could be hurting mph a bit. I’m almost 100% positive its false but I have been over the car a dozen times looking for anything loose or banging and there is nothing. It’s so weird that on the street the night before I took it out and with the same gas and alky settings it pulled clean and had no knock. I even dumped a bit of 104 UL in the tank to see if that helped. Turning the alky up equaled an aborted run due bogging and surging. If this is a wall of text let me know and I’ll gladly clarify anything.

1st pass (no power logger run or Time slip) timing: 23/21 boost: 23 psi with a/f set to 10.8 1/2nd and 10.7 3/4th 11.29@121.78

2nd pass timing: 23/21 boost: 26-28 psi with a/f set to 10.8 1/2nd and 10.7 3/4th


3rd pass timing 23/21 26-27 psi was aborted after setting a/f to 10.6/10.5 and turning the alky from 6.5 to 7.5

4th and final pass timing: 23/21 boost: 26ish a/f commanded was 10.6/10.5 and I dropped the alky back from 7.5 down to 6.

I got killed this run both at the tree and ET/MPH. The trans actually shifted correctly into 2nd gear but the surging killed any power in the 1st half of the track.

If I had gotten one more pass in I would have liked to have leaned it back out to 10.9-11.0 just to see what it did. I was also tempted to unplug the knock sensor and if it blew it blew, but I didn’t.


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I'd start w/ the leak down.
Loss of the seal will show up w/ the loss of mph.
Have you considered race gas and throwing more timing at it to see if the car responds entirely differently?