Th350, 4.10 gears, Too deep?

[Ws6Stealthbird]

Im building a 92 firebird with 86/87 motor, my car currently has 4.10 gears, I have a BOP 350 getting built by a good friend of mine who is awesome in GM transmissions, anyways... are the 4.10 gears going to be to deep.

I have not picked my stall yet, I have an Erson 214/214 cam.

I have people saying I will run out of gear at 900ft in the 1/4.

 

[WINDMILL]

i dont run 1/4 much,, but i've got a 350 turbo with a 3.50 gear and it seems real good for my gn in the 1/8 mile..

 

[Ws6Stealthbird]

After I get it going, I thought about putting 3.73's in it.

 

[Nick Micale]

Im building a 92 firebird with 86/87 motor, my car currently has 4.10 gears, I have a BOP 350 getting built by a good friend of mine who is awesome in GM transmissions, anyways... are the 4.10 gears going to be to deep.................

Not if you use 30" tires! :biggrin:

Even 3.73 gears may be too steep also depending on cam and other stuff in the combination?

 

[Ws6Stealthbird]

214/214 Erson cam, unported heads, and unported intake, and stock turbo. I will be going to bigger injectors.

It is not running, I am building the short block right now. This car had the 4.10's in it already

Stall is undetermined right now.

 

[KL Mallender]

I agree with Nick and probably many others that it's all how you apply it, personally if I was running a "low rpm" engine(spending most time below 5500) I would want a gear\converter combo that kept engine tugging at the bit the most and shying away from higher than necessary stall speed converters that cover up poor turbo choice, but not geared over max effective rpm through lights. Tire diameters and trap speed are my guides to gear selection. Good luck.

Kevin.

ps: you are much better off using a very "Tight" or low stall converter to fine tune or diagnoiss spool up, if all leaks are handled and you havent gone stupid with too big of a turbo, you can drive car while watching tachometer and "SEE" what rpm in high gear that it begins building boost and at what rpm it gets "Happy"(usually around 7psi) this will allow you to make proper converter selection.

 

[Ws6Stealthbird]

I figured I could run a tighter stall due to the lower gears. You think I will be ok with a 2400 stall speed? My future goal is high 10's, but I just want to get it on the road for now. The gears will probably come sooner after I realize how unstreetable it will be with such a low gear.

 

[SSedan64]

Here's a few Performance calculators for checking rpm/speed & 1/4mi performance. >> Acceleration Calculators

 

[Nick Micale]

I figured I could run a tighter stall due to the lower gears. You think I will be ok with a 2400 stall speed? My future goal is high 10's,.................

Like I stated, I do not know your build, but have worked with race GN's with up to 4.10 gears, but I do not see how you can get anywhere near your optimum performance with a 2400 stall converter.

These are "torque" engines, they keep pulling all the way to the finish line when set up properly. With that low stall, you will never get up on your torque/HP curve. I have never had too tight a converter, and that includes my current one that started out at 5500 stall.

I tightened it a little when I dropped back to an index class, but it is still ~ 5000 RPM stall even though I leave at much less, it pulls all the way down the track.

If a carbed racer is not ahead of me at 1/2 track, he is done unless he has one hell of a shot of NOS in reserve!

For reference, I now use a 3.42 gear and can run 10.0 @ 137 MPH on 17-18 psi using a 70mm turbo. Took 3 years to get the combo right.

 

[Ws6Stealthbird]

Like I stated, I do not know your build, but have worked with race GN's with up to 4.10 gears, but I do not see how you can get anywhere near your optimum performance with a 2400 stall converter.

These are "torque" engines, they keep pulling all the way to the finish line when set up properly. With that low stall, you will never get up on your torque/HP curve. I have never had too tight a converter, and that includes my current one that started out at 5500 stall.

I tightened it a little when I dropped back to an index class, but it is still ~ 5000 RPM stall even though I leave at much less, it pulls all the way down the track.

If a carbed racer is not ahead of me at 1/2 track, he is done unless he has one hell of a shot of NOS in reserve!

For reference, I now use a 3.42 gear and can run 10.0 @ 137 MPH on 17-18 psi using a 70mm turbo. Took 3 years to get the combo right.

I am taking in consideration of what you are saying. The gears will be changed in the future to achieve my goal. I want the car to be in mid 12's when I get it tuned and running with stock trim. But my overall goal is a high 10, I plan on driving this for awhile slowly modding it,little by little, and when gears start to hurt me, they will be changed.

They might be the 1st thing I do when I start modding it. I don't believe I can achieve my 10.9 goal with those gears unless I have a tall tire, I might run a 28" tall tire to see if I gain MPH. But this is all speculation, the car is still on jack stands, a loooong way from being on the road. I think a 3.42 gear would be a good street gear for daily driving.