ok i have an 87 iroc 305 tpi witht the 5 spd. hooker competition ceramic coated headers, no smog stuff, and no cat, ported plenum, and maf screens removed and the rain guard baffles removed.
i finally ran a 14.480 @ 95 with 2.194 60ft at thunder valley raceway in noble oklahoma elivation 1200 ft
i have the 3.08 gears and i am hittin redline in 3rd gear at the traps. what would be the best gear for me to get. or what other mods can i do to get me into the 13's without lifting a valvecover.
thank you guys
Andrew

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Andrew Peery
1987 IROC, 305 TPI, T5
Flowmaster, Ported Plenum, Accell plugs, Wires, Cap, and Rotor
All smog equipment gone and no cat
192hp and 265tq (at rear wheels SAE corrected)
15.20 @ 92.5 mph with a 2.4 60ft

 

beside NO2 I don't know how you'd go 13's or a cam change...an intake won't do squat on your 305, so don't spend money there, a 52mm tb might help you a couple tenth..I'd stick some 3.23 or 3.42 out back...no more than that, that might help, 3.08 are really not condusive...what ever you do don't put 3.73 or 4.10's out back...you got to think that each time you shift, you loose time too...I had excelent results going from 3.73's to 3.23's with my 350 TPI...maybe some slicks or drag radials....but I still don't think it'll put you in the 13.'s...blower would, NO2 would or cam...

later

 

With the 5 speed, you COULD go with 3.73s, but I would recomend 3.42s. I would never go with 3.73s in an auto, but with the manual, its your choice.

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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, Edelbrock TES 1 5/8" Headers, Hooker 3" Aerochamber Cat-Back System, Performance Resource Chip, Accel Ignition, K&N Filters, JET TPI Air Foil, All Free Mods, Falken ZIEX Z-Rated Tires.

Best ET (w/o LT4 cam): 14.32 @ 97.7mph
(corrected for elevation)

Soon to Come: 7.625" 10 Bolt with 3.42s and Accel TPI Intake Base

 

Gear ratio selection is completely dependant on what your ultimate goal is; what your trap speed will be. Knowing that you want to be near redline in top gear ("D" in an auto and 4th in a manual), calculate the closest gear ratio that will get you there. Keep in mind that for an automatic, you must factor in torque converter slippage.

Given information about my car, Desktop Dragster shows my 700R4 equipped car is faster in the 1/4-mile with 3.73's compared to 3.42's.

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Willie

Supercharged 1987 305 IROC-Z, Daily-Driver, Emissions-Legal.
Former Paxton (6-psig): 12.57 @ 111 mph.
Former Paxton (6-psig) & former 50-hp nitrous: 12.04 @ 114 mph.
Current ATI D1SC (Initially 10-psig): Projecting high 11's.
Future ATI D1SC (15-psig): Gotta catch them pesky 26-psig boosted TTA's!!

http://willie.camaro-firebird.org/

1987 "20th Anniversary Commemorative Edition" Z28 Convertible -- Super Chevy Show Class Winner, 1998.

[This message has been edited by Willie (edited May 20, 2001).]

 

guys if he has to shift one more time going down the strip wouldn't that hurt his trap speed a bit?

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Originating member of the SJNEP Crew
Member of the Jersey Fbody Crew(JFA)
Check out MyGTA Nicknamed:The Big Red Machine
***AOL IM RiceEatinGTA***
Moderator at www.transamgta.com
"What does not kill us only makes us stronger"

Tony

 

a paxton would get you there on a stock engine and go with a 3.45 9 bolt

 

I'd recommend 3.42's. When I had my 86 IROC, I had 3.73/ 5-spd and it was a just a little too steep. The RPM's were higher than I wanted on the Highway. 3.42 is the best ratio for a T-5 IMO.

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89' Iroc-Z
ZZ3 short block-355 TPI ZZ9 cam
NOS 150 shot.
blah...blah...blah..
95' T-56, 6-speed
99' Z' rearend w/ 4.10's
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1997 black Trans AM
LT1, A4, basically stock.
13.87 on the G-tech

 

OK this is where it gets hairy, for street use and on street tires you can't run a 3.73 in any Thirdgen without hurting yourself because of Traction. Sure Desktop dyno shows it to be faster, its not taking in the fact of how hard it is to hook a thirdgen.

Speaking for a manual car with a 305. If you want to get into the 13's you will need a low gear to get you there so plan on a 3.73 or 4.11's. Now to get you off the line and hook with that you will need Nitto or BFG drag radials, preferably BFGs if you are only using them at the track or Nittos if you have to drive them on the road to... I would get a spare set of rims to put my drag radials on, This will help you out tremendously by reducing 60' times, allowing you to acclerate harder and earlier there by increasing trap speed and reducing ETs.
Though this will cause one major problem to surface. Clutch slippage off the line. YOu will also need to get a heavier clutch to comptete with the added traction in the rear. With these three things you should be really close to the 13's without removing the valve covers.
As mentioned before the extra shift will hurt you a little so to combat this you will need to drive better yourself making better launches and quicker shifts.
Also Try getting a GOOD computer chip and bumping your fuel pressure up 1 psi or so. With all that extra air you are flowing you could use a little more fuel ant timing.
Good luck.

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89 Trans Am Turbo 3.8L All stock 43,000 miles #1053 of 1555

Past Thirdgen:
86 Trans Am w/ built 355TPI with SLP goodies and too much other stuff to List. One sweet *** car, wish I would have had a good enough Job to pay insurance on three cars so I could keep it, but for a 89 Turbo Trans Am w/ Low miles, I think I made the right choice!

[This message has been edited by Kyle F (edited May 24, 2001).]

 

Everything Kyle F said is true for my TA. If I could get some traction, my car would fly! I would add one thing: manual cars need a new shifter!

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1989 Trans Am, 305 TPI 5-speed, T-Tops(love 'em),4-wheel disc, 3.73 posi(the toy). '97 Camaro V-6 T-Tops(daily driver)

 

If you are going to get tires for the strip only, dont get Drag radials. Get some M/T ET's.

 

True forgot about that

If you use Mickey Thompson E/T's you will not be able to run in a street class. You have to run on DOT apporved tires! That is if you aere running a bracket race that has different classes, but if you just want to see how fast your car will go get the ETs




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89 Trans Am Turbo 3.8L All stock 43,000 miles #1053 of 1555

Past Thirdgen:
86 Trans Am w/ built 355TPI with SLP goodies and too much other stuff to List. One sweet *** car, wish I would have had a good enough Job to pay insurance on three cars so I could keep it, but for a 89 Turbo Trans Am w/ Low miles, I think I made the right choice!

 

True. That's why I use Hoosier Quick Time DOT's mounted on stock IROC-Z wheels... but ONLY at the track. And if these aren't good enough, there's always Hoosier Quick Time Pro DOT's.

Willie

[This message has been edited by Willie (edited May 27, 2001).]

 

I have a 1988 305 5/sp Firebird with 3.45 gears and listed in my sig are the mods that put me into the 13's with street tires. I have not lifted the valve covers, but I have done all of the free mods like porting the upper plenium to remove the walls behind the throttle body.

The car has 105,000 miles on it and runs as strong as ever.

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1988 Formula 5L/5sp 3.45 gears, SLP cold air kit, MAS gutted, TPIS air foil, TPIS AFPR, MAC headers, Mac under drive pulleys, MAC cat back, Relocated MAT.
Best ET street tires 13.85
Best 60 FT street tires 1.930
Best MPH street tires 99.29

 

3.73 gears are the way to go for your setup, cause you have almost the same exact setup as I have and my 3.73 gears have put me crossing the finish line at 4800-5000 rpms in 4th. Later

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88 IROC-Z 305 TPI 5 speed
Performance Resource Chip, Flowmaster American Thunder cat back exhaust, B&M Ripper shifter, MSD coil, TB bypass, TPIS MAT relocation kit , TPIS 170* t-stat, Richmond 3.73 gears, March Power & Amp pullies, Home made Ram Air, Steve Spohn SFC's, LCA's , Panhard bar, TPIS AFPR, Ported plenum by Daniel Burk, Gutted cat
Best et: 14.232
Best mph: 97.76
Best 60': 2.063
http://hometown.aol.com/famioso15/johnnyiroc.html