BBB

Two years ago I took my car from a stock ET of 15.2 to 13.7. That was a great drop and a solid time for racing at a track that usually has an air density reading of 7-8000 feet at 10:00pm. I ended up shredding the clutch on a nice hard launch and opted for installing the Mcleod Street twin. Well as we all could predict the 120,000+ mile 10 bolt lasted less than half a dozen fairly soft launches before it started to die. So last fall I added a 12 bolt Moser with 33 spline axles and a 3.5" denny's aluminum driveshaft with 1350 joints (to replace the GMPP 3" aluminum driveshaft). Before the clutch/shaft/rear swap I would launch at 3000' rpm pull 2.2-2.4 60' ET 13.7-14.0, and trap a consistent 103mph. NOW I am running 2.1 60' on a 4500rpm launch, 14.9 is my BEST time with 93mph trap speed. I dynoed the car last fall shortly after the changes and I had lost 10-15hp over my entire curve.

A 10-15hp loss does not explain a 10mph/1.2 secon drop in times especially considering a 1500rpm increase in launch and reduction in 60' time.

Can the extra mass of the drive line account for my time loss? My only other possible explanation is a slight rich condition (perfectly flat 11.5 to 1 air fuel ratio curve). I can't imagine picking up 10mph and over a second by leaning out to 13.5 to 1.


Is anyone else in the same boat. Misery loves company but I also need suggestions on how to get the ET back under control.

BBB