I have a 87 IROC-Z that I've been drag racing for a few years. I have slowly made upgrades and changes to the car. Rather than dump in money right off of the start, I got a truck/trailer and made cheaper changes that I knew would improve performance. So I now need to get into the gears and torque converter. I have stock engine parts. I have the stock 3.27 gears in a 9 bolt rear end. I do have slicks/shorty headers and am running 14.15's right now. I know about the aftermarket 3.73 gears and the gears from 9bolt.com. I am concerned about the used gears from 9bolt.com, but want to hear from people who have used them as well. My question is what have people used and how much improvement have they seen with either the 3.73 or 3.9 gears or 4.11 gears if they've swapped them with the 3.27's? Also, what stall torque converter would you recommend? My winter project is the gears and torque converter, so any recommendations/experience would be appreciated.

Thanks for the help!

 

I say step back and look at your overall goals 1st. You said drag racing how serious are you and what class/bracket do you want to run in?

What do you want your HP, ET to be in the end?

I say this and ask these questions cause if your real goal is 9's, 10's 1/4 mile then you will just be wasting money doing anything to the 9 bolt rear.

I make that mistake with my 10 bolt. I wasted over half what a ford 9" setup goes for. I put in a locker, axles, bearings, TA cover, etc. Just to have the thing break as soon as I got some real traction. Put in another 1o bolt and broke it. Then went to a ford 9" and never looked back.

 

leave the 3.27's in there and spend that money on a nitrous kit instead. hit it with a 75 or 100 shot. also leave the converter stock.

 

My car had 3.27 gears and with a 383 SBC and no power adder, I was able to get into the high 11's. I also ditched the 700R4 for a TH350 at the time. Gearing in the diff was still wrong but I still had enough power to use what I had in the diff. Proper gears would have put me into the mid 11's. It was easier to install a 10 bolt than it was to play with the 9 bolt. 10 bolt got me into the mid 10's before I finally installed a 9". Stock 9" almost failed in the mid 9's. All aftermarket stuff now.

Recommended converter stall needs to match the cam grind. For full race, the converter should stall about 1000 rpm into the powerband. If your camcard says 2500-xxxx rpm then 3500 minimum is a good stall speed. Too much stall can be just as bad as not enough.

 

spendy but all so true!

 

my plan is to race in Sportsman for a long time. So I wouldn't go faster than 12 seconds. It sounds like leaving the gears and torque converter may be best. Has anybody used a performance chip? Would that help? I could do a 100 shot of nitrous. How much would that improve my ET in your opinion? Any other recommendations? I appreciate it!

 

Nickel and dime bolt on stuff will not give you large power gains. If you want to go from low 14's to low 12's you need to make at least another 150 HP or shed a lot of weight off the car.

 

Very true.

Like Alky said, the little bolt on chips, air intakes, etc aint gonna cut it.
Converter and gear needs to match your engine combo. You add a converter now and gears that you need now.. 6 mo. from now you change heads and cam, well then you would need a diff converter and maybe gears.. Wait about the converter and gear set untill you have more mods to your engine.

1st things you need are...
Headers
Good exhaust
Better heads
Bett cam.

Heads is the place to look for power. A head swap could gain you 40-75 HP depending on heads you pick.

Then work on your chassis/suspension/tires. With same engine/trans/converter/gear I went from 13's to 11's with just suspension and chassis mods. I was 60 footing in the 2.20's, 2.30's spinning over 200 feet.

Added weld in SFC, adj. LCA, LCA relocation brackets, adj. panhard, adj. jegster TQ arm, KYB AGX adj. rear shocks, drag bags in rear, Nitto 555R drag radials.

60' went down to 1.70's and ET was in the 11.60's range. Done a little more engine and suspension tuning and got 1.60's 60' and 11.40's ET. Got kicked out for no roll bar, so added a 10 point cage.