Ok i bought a 88 Iroc that has a pretty healthy LB9 in it with a 700r tranny.
It has several things done to it already however im not sure what the car would run in the 1/4. The mods that are done are Flowmaster with 3" exhaust from y pipe back.Dual K and N's,air foil and port work on the intake. In theory if the car was not in the 14's yet would headers and .373 (.273 posi now) gears push into the 14's?
Matt

 

I've read that it takes a 70-90 HP gain to move a ThirdGen from 15.0 to 14.0 in the 1/4 mile.

Headers might gain you 20 HP

 

3.73:1 is too much for a stockish TPI.
You'd be much better off putting money into a very good torque converter.
Headers and converter should get you solidly into the 14's if you have some traction.

 

You might be in the 14s now.

 

Can someone tell me why a 3.73 gear is to much for a mild 305. Ive seen mild 302 fords run with 4.10's and they ran like stink!

 

+1 Torque converters work wonders - provided there is traction.

As for the gearing, a 302 ford is not the same as a 305. The 305 has a longer stroke and smaller bore - it's more RPM limited by the TPI as well. The 302 ford is a short stroke, big bore engine and likes RPM's more than a 305 TPI.

An LB9 w/ a 700R4 behind it has the peaunut cam, it doesn't make much power past 4200-4300 RPM. So, too much gear and you would run out of motor before you reached the stripe in the 1/4.

 

So would a 3.42 or 3.55 be better?

 

3.42 would be much better.

 

NOS and Suspension work (subframe connectos, LCA's, Panhard bar, etc...)

Making cars fast is expensive

Raf

 

you all who say a 3.73 is too big are full of crap.

I ran a 14.861 @ 93.23 mph
I ran at the track 5 times with a consistent 60' times of 2.13
This was fully dressed, even with my sub box in the back hatch.
Street tires
no stall
So I bet if I take my 75# sub box out, get a 2400 stall, and toss some sticky tires on my car....I'll be running some pretty good times with my little 305.

So to continue....You will be at the top end of 3rd gear with your 700r4 tranny at the end of the 1/4 mile.
If you went with a 4.11 you finish in 4th gear.

With all my mods I made 175hp to the rear wheels with 211 eng. torque.
My peek power was around 4800 rpms.
With a AFR average of 11.4 witch is a little high, but I'd rather be rich then lean.

So there you go. Any questions send me a PM or post it up on here.

 

I have an 88 IROC LB9 and I shaved a half second in the 1/4 mile when I went from a 2.73 to a 3.73. A 3.73 is not too much gear. It's perfect in my car. I finish the quarter right at the red line and run a 1.6, 60 foot time.

On motor I run a 14.85. 3.73 gears, Headers, airfoil, flowmaster, and adjustable fuel pressure regulator. The gears were the best mod I did. Put them in you will love it. It will wake the car right up.

A convertor will also do alot.

 

"you all who say a 3.73 is too big are full of crap."

Whatever you say. My old 86' had an L98 swap, cam, full bolt ons, 3K converter. I lost almost .15 & 1+ MPH going from 3.23's to 3.73's. My test was real word, the car hooked well on BFG drags, and I tested in similar weather - ran Wed. night, swapped the rear Thursday - raced it again Friday night. My 60 ft times were all within .02 - .03 of each other.

You may be fine now only trapping 93-94 MPH, wait until you start going faster MPH-wise and you spin the engine past the powerband to the point where it isn't making power. I notice in your sig. - you have a cam and upgraded runners/base. You definately have extended the RPM range of useable power vs. a mostly stock peaunt cammed LB9.

Gear swap < Proper Stall Converter.

 

my 90 formula got into the 14's with headers, full 3" exhaust(w/cat), used replacement K&N. ran a best of 14.7@90 letting off just before the 1/4(bracket racing), this was with the motor at about 200*. also ran 14.8@92/93 all night with temps at 220ish. 140K on motor, 700r4, and 2.73 posi rear.

If it's healthy it shouldnt be hard to get into the 14's

 

well my tests were real world also, so think what you want. How much time do you think I could have shaved off if I had a stall, lost the sub box and bought some sticky tires? I'm just telling people what I did.
Notice I did say a stall....no where did I say a stall was a bad idea.
If any one wants a cheap stall. Have them install an S10 stall converter.
Where our stock stall, stalls somewhere around 1600, a GM S10 pickup converter will stall around 2200. Just a cheaper way to help people out.
But I swapped in a gear 1st. As people know...I even had to change to a series 3 carrier. I'm thinking once my car gets painted, I'll stick in a stall. Although I wont be able to run at the track anymore (I shaved my door handles, pics in the body section) It sure will be fun on the streets!

 

I have no doubt that you have run much quicker times with a set of 3.73 gears compared to the stock 2.73s. The big question is, would you have had better results with something like a 3.42 and stock intake?

 

LOL...maybe if you compare the different flow rates.
5 words though:
"Go big or go home"
Why change things twice? Do it right the 1st time and get it over with.
What happens of he ports his intake or buys an aftermarket one?
Then hes going to say damn...I should have went with a 3.73.
(if hes got a T5 he better be going with a 4.11!!)

I almost went with a 4.11 in my car. But I didn't want to be in 4th gear.
Also, unless you get the tranny worked on. At WOT...it wont shift into 4th gear.

Another fun fact that some people don't know.
Drop your car into 1st gear and give it gas....don't touch the shifter.
I bet it shifts into 2nd gear all by itself at 5500 rpms.
Call me but I know my car pretty well.

 

The intake has been ported already. So 373's better?

 

You can listen to anybody you want to. But if you put in 3.23's, your going to wish you went to 3.73's

If the 1st gear wasn't so short now in the 700r4 with the 3.73's....I'd buy 4.11's and swap them.

I've had my car on the 1/4 mile track 5 times, just to see what it would do. I'm happy.
I wouldn't do it any other way if I had to do it again. Only way is if I had a T5 manual tranny, I would have stuck a 4.11 in there no questions asked.

Right now we have a 68 Chevelle that we have for the drag strip that's all tubed and will be ready this year.
Plus a 70 Chevelle, 69 Firebird, 72 Formula, and my Trans am to goof around in.

But do what you want, I'd go 3.73's if I were you though ported intake or not.

 

Well, the guy advising you that 3.73 is the way to go runs 14.861 @ 93.23 mph. If you're going to be happy with that then there's your answer.

I was assuming that you might want to go faster in the future, so I stand corrected.

 

Yeah with a stock stall converter, 75# speaker box in the rear hatch, street tires.
Plus my bottom end has over 100,000 mile on it.
Hell get me a 100 shot of nitrous and watch me go into the 13's.
LOL...yeah I don't know anything though.