L$X$10

iTrader: (4)

so i headed to the track last night looking to see some improved track times with the new 78mm Fast intake and 3.90 gear(swapped the ls6 for the Fast and went from a 3.42 to the 3.90)
instead of quicker times i pulled slower times!
previously i was getting an average 1.75-9 60ft and this time around i could only pull high 1.8s(this isnt my normal track so maybe it wasnt prepped as well as the other?)

here's some times from one of my last passes with the ls6 intake and 3.42 gears:
60ft - 1.798
1/8 mile - 7.888
mph - 89.17
and another with a not so good 60ft:
60ft - 1.900
1/8 - 8.101
mph - 87.25

here is the best from last night:
60ft - 1.888
1/8 mile - 8.216
mph - 84.59

now i know there are a lot of variables such as different track, temperature, etc. but do you think i should be losing that much mph with switching to the 3.90s or are there too many variables to even compare these track times?
any informative input is greatly appreciated

TXsilverado

iTrader: (19)

what was the difference in DA between the 2 runs?

L$X$10

iTrader: (4)

im not sure about the exact DA but the track i ran with the 3.90s is 145ft above sea level and the track i ran with the 3.42s is 242ft above sea level..both should have been around the same temp but not sure on the % humidity

bluecajun5.3

iTrader: (31)

its hot and the computer is pulling timing! go back when it cools off.

L$X$10

iTrader: (4)

hoping thats the case..ill probably hit Doc up this weekend to check everything out on the dyno just to be a 100%

TIM Z

iTrader: (12)

Hmmm, im sure something is up,

Your truck runs good and puts down good times, prob the heat like cajun said.

I am having similair issues with timing bieng pulled during run.

Did you log your runs??

fastrt

iTrader: (48)

was it retuned for the intake? The converter was not flashing as much due to the gear swap. A 3.42 should flash higher than the 3.90. So I have been told.

smokeshow

iTrader: (16)

I'd be willing to bet it was just atmospheric differences that made up that difference. Assuming the new intake and gears were tuned for.

SincalT/A

iTrader: (16)

Yank SS converters favor taller gears over what people normally think would be ideal gearing.I'm running a ss4000 in my camaro with 26 tall tires and 3.42's.Without a doubt going over the logs,g-tech,and gps they all show that taller gears would net me quicker/faster times.With the higher engine stall speeds and torque multiplication like that of the SS series.They pull so much harder at the bottom of every gear.The vehicle doesn't require shorter gears that are often used to keep engine rpm's up throughout the run.Now there's obviously gonna be a point of diminishing return using too tall of a gear but,IMO 3.42 or 3.23's are gonna work best for you.
Keep in mind you have also dramatically lowered the stall point by making it easier for the converter to move the truck.You now have higher 60' times cause,the truck moves out before the engine&converters inertia builds to a optimal point.Think of a converter as a energy storage for the rotating mass.The higher stall speed (or point when the turbines release fluid towards the strator)the more inertia is built up.Now this is given the engine is in its powerband at the stall point.Fluid is then released and effectively gets muitiplied by the strator. Giving the engine more mechanical leverage against the vehicle/drivetrain.

SincalT/A

iTrader: (16)

One other thing to consider is fuel pressure drop but,I really don't think the run would be affected quite like you have discribed.