Need more rpm in the 1/4 mile
 

I need some help here, In the 1/4 mile I am going through the traps at 4200 in 3rd gear. My best time is 13.59 @ 99.3 mph w/ a 1.91 60 ft on street tire.I am figuring I need more gear. But what gear? I want to through the traps at least 5000 rpm. Mods are in the sig. Thanks for any help!

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1985 TA 700R4 w/stock converter and Transgo--9 bolt 3.27 rear 406 TPI--9.25 to 1 compression--ported stock intake, plenum--SLP runners--SLP cold air--trick flow 23* heads--compucam #2050--1.5 roller rockers--Accell 24lb injectors--
Ed Wright custom chip

I would go with 3:73's. Not sure what rpm you would be at, but I think 4:10s might be overkill, especially on a daily driver, then again I could be wrong. Use the calculator on the home page to see what your rpm's will be at around 100 mph considering it stays relatively close.

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"Rice burners are like tampons...Every pu$$y has to have one"
'86 IROC
T-TOPS, TINTED WINDOWS, BRAKE LIGHT BLACKOUTS
GM GOODWRENCH 350
EDELBROCK TES HEADERS
3" Hooker CatBack w/Aero Chamber muffler
EDELBROCK 600CFM CARB.
KN AIRFILTER
ACCEL HEI DISTRIBUTOR
160* Stat, just switched to 180* b/c of winter coming and going to college in the mts.
3:73 Posi
Rebuilt 700R4
B&M Megashifter, 5" Autometer Tach w/shift lite

With my old Iroc, my best run was on the 245/50/16's street tires, I hooked great at the track for some reason with them. I had 26"x10" mcreary's and all they did was drop the rpm's through the traps. Anyways, with 3:73's, 700r4, I had a 1.91 60' and a 14.1 quarter time, I think it was 101mph. I went through the traps at about 5600 in third gear. Problem was my stock cam didn't pull that high and it was the same time as hitting OD at 5000rpms.

With the McCreary slicks, I had a 14.17 at about 5200 rpm's through the traps.

With 4.10's you'd be hitting OD well before you got through the traps with your setup.

Hope this helps,

Scott

I would try to find a 3.42 and a little stall converter. The converter will add about 300 rpm and the gear will add about 10percent more than your current rpm.

One of the big factors for u is the first gear ratio of the 700-r4 (like 3.06). A 3.73 gear will just about blow away the tires for the first 60 feet.

At 5500, a 3.73 is pulling 111mph with a 25.5 inch tire (not counting for any converter slipage). A 3.42 is approximately 9percent less than that at 111mph.

You want to be at your peak power RPM in your 1:1 gear (3rd). Like for my car, I'd want to be at about 5000 RPM in 3rd going through the traps. Go to the equations part of this site and figure out what rear end gearing you need to achieve that. I would suggest either 3.45s or 3.70s.

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1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission
Borg Warner 7.75" 9 Bolt Rear End with 2.77:1 Gears.

Current Mods: LT4 HOT Cam, Comp Cams 1.52:1 Roller Rocker Arms, Accel High Flow TPI Baseplate, Edelbrock TES 1 5/8" Headers, Catco 3" High-Flow Catalytic Converter, Hooker 3" Aerochamber Cat-Back System, Transgo Shift Kit, Performance Resource Chip, Accel Ignition, K&N Filters, Jet TPI Air Foil, All Free Mods, Falken ZIEX Z-Rated Tires.

Best ET: 14.32 @ 97.7mph
(corrected for elevation)

Thanks guys for the input!!