isosceles

I just came back from the strip. With my new 3:36 rear end, I turned the best ET (15.1)and highest trap speed (89.4). Everything was better, even the 60 ft times. My old diff was a 3:70.... who would've guessed? :rolleyes: This was a hotter day than some of my other good runs too!
I might have done a little better as I was eliminated during the first round of the Corvette challenge for dialing a 15.40 and turning 15.2 letting up. I coasted across the line in hopes of making the faster car break out worse than me. Even though he blew by me, it didn't work.


[Modified by isosceles, 4:23 PM 3/27/2004]

Eddie 70

Time to update the sig. Sounds like it got you excited anyway. I know zero about drag racing. But it sounds like you got faster. Isn't that what its all about. :thumbs:

Glensgages

Just out of curiosity, would you mind posting your best run with the 3.70s vs. your best 3.36-geared run? Specifically, the 'splits' (60', 330', 660' & MPH, 1000').
I went from 15.904/86 to 15.209/91 after swapping my 2.87s for 3.73s...

munday

i have a program from mr. gasket that lets you plug in different specs based on a hp/tq curve with certain trannys and such and helps you find you optimum rear end, i was blown away the first time i saw the data. some times higher gears reallly don't help.

Glensgages

I agree, but I'd think that a 'mostly-stock '79 L-48' would need as MUCH gear as possible in just 1320', and that 3.70s would 'gear-bind' the car (run it outta RPM well-before the lights). In-fact, '79 Z28s, with the almost identical LM-1, came equipped with 3.73s in 4-speed versions...
Plus, I'm 'guessing' that even with 3.70 gears, he wasn't turning much more than 4500 RPM before, which isn't TOO-FAR out of the torque-range of a late L-48

I once raced with a competitor who campaigned a Formula Firebird w/ a 406 SBC & 4.56 gears, running 12-flats @ 109 MPH.
He shelled the rear-end in the water-box one day in front of me, & I helped push his 'lump' out of the way.
While doing-so, I casually mentioned that I had a set of 3.42s for his 8.5" 10-bolt carrier/differential, which he accepted, after making the comment " It'll probably slow WAY down with THOSE gears..."
The next week, with 3.42 gears installed, he ran 12.09/low-teens @ 111 MPH, and I reasoned that the .56s had the car 'wound-tight' WELL before the traps, but the 3.42-gears made the 406 'GRUNT' down the track, both 'calming-down' the launch (28" x 9"-slicks), and giving a higher MPH speed, too.

isosceles

Glen, I think you are correct thinking the motor was getting winded by too much gear. Power always seemes to die off above around 4200 rpm. Although I was leaning toward a 3.08, I took into condsideration your reply to a previous post of mine vs. all the other posts suggesting a 3.70 and went lower but not all the way to my initial choice. Eventually with my planned future mods, the higher 1st and second of a 200r4, a 2200 stall convertor and a 383 motor, I think I'll really like this 3.36.
Screaming the 100 miles up I75 to the track was much more enjoyable. I ran 85-95 most of the way. I was acutally still getting passed by about 1/4 of the cars. Ex-moonshiners from the south, I guess. :crazy:

with 3.70 gears, my best run was
60' 2.184
330' 6.313
1/8 9.739
mph 71.38
1000' 12.743
1/4 15.275
mph 88.6
My best run yesterday with 3.36's
60' 2.195
330' 6.315
1/8 9.714
mph 72.42
1000' 12.681
1/4 15.187
mph 89.41
last day with 3.70 my averages looked like this(2/14/04 weather was cooler):
60' 2.22
330' 6.42
1/8 9.905
mph 70.17
1000' 12.95
1/4 15.52
mph 86.91

My average yesterday with 3.36's looked like this (diff work only change):
60' 2.208
330' 6.3652
1/8 9.7874
mph 71.798
1000' 12.7754
1/4 15.3056
mph 88.248

Glensgages

isosceles:
While I'm surprised that the .36s out-run the 3.70s, I don't doubt your results; TIME-SLIPS DON'T LIE!!!
Kinda perplexed that the 330' is .06-seconds quicker with the taller gear; I'd think in a side-by-side run, the 3.70s would be ahead until half-track (or further), then the 3.36s would drive-around it on the big-end.....
:confused:
Is it possible that on 14 Feb '04, in cooler temps, that the track and traction wasn't up to par (even the 60' times were quicker with the 3.36s?), resulting in wheel-spin?
:confused:
Either-way, 85 MPH w/ 3.70s & no OD had-to suck; enjoy the 3.36s!!!
:cheers:

isosceles

traction? Oh boy, I WISH that were a problem! I can only light them up sometimes with a powerbrake as long as I don't have a lot of fuel. I never spin them at the track. Bradenton is so sticky that I don't even chirp tires on the 1-2 shift like I do on the street.

These results surprised me as well. I think there must be something weird about my car. Like maybe there's a vaccum leak that I've compensated for with tuning and it produces strange results. who knows?! :rolleyes:


[Modified by isosceles, 8:04 PM 3/28/2004]

cardo0

:eek: Wow this post is a real eye opener. It makes sence though that engine power band plays the bigger role. I just wonder what the 3.70 times would be if you had another geat to pull?
I've been confused why the new ZO6 is running 11's in stock form with much less hp & tq than the old big blocks? My guesstimation says trans gearing has a big part in the quarter mile times. But still torque rules for a fun accelerating machine. ;)