What kind of acceleration should I expect with a 300HP 355ci, 3:42 rear, and a T5 with the gears: 4.03, 2.37, 1.50, 1.00, .76? Ill prolly be able start from a stop in second gear, and have no problem getting up to speed, right? And that 4.03 first gear will make my car seem like it has even more HP?

 

The 4.03 first gear would be good if you have 33" tall tires. That first gear could easily blow the tires off with anything smaller and would have a very short time before the engine maxed out to the red line. That's a rock crawling gear not a street gear.

Launch in second

A deeper gear does nothing for HP but it multiplies torque more.

300 pounds torque through 4.03 first gear then 3.42 diff gears. 300 x 4.03 x 3.42 = 4135 pound of torque to the rear wheels. That's enough to get a heavy truck moving. That's roughly what my car puts to the rear wheels with a 1.76 first gear powerglide. The difference is that my first gear lasts until the 1/8 mile mark. Your first gear "might" last to the 60' mark.

 

That 4.03 first gear is gonna be just about useless. Your gonna need 7000rpm in first to "almost" get to 40mph, assuming your running stock type 26" tires.

If your not running tall tires(29" and taller)I think your better off using it like a 3 speed and start off in 2nd gear. Then again if you go with a taller tire you'll probrobly never hit 4th in the 1/4. Only way to know for sure is head out to the track

HTH,
Steve

 

So will my mph when at the redline(5500) be the same as when the V6 was in? Like 1-2gear@25mph, 2-3@55, 3-4@80ish, 4th toped out@100mph. And what might my top speed be? My tires are just regular tires, Futura GLS SS, P215.

 

Anyone know?

 

The redline of the engine is mostly determined by the cam grind. After that, redline is redline. 5500 rpm with a V6 is the same as 5500 with a V8. The biggest thing is the torque. A V8 will produce more torque than a V6 and that's what you feel when you launch. HP is just how quickly it can use that torque.

On the dragstrip all the torque is used in the first 1/8 mile. That's where you're accellerating the most, getting the weight of the vehicle moving and going through the gears which will multiply the torque. Once you hit the 1/8 mile mark you should be in high gear (1:1 not OD) and the last 1/8 mile is a high gear brute strength (HP) pull to the finish line.

 

ok, so are my shift point speeds gonne be the same as when I had the V6 in? Because I still have the same tranny. 1-2gear@25mph, 2-3@55, 3-4@80ish, 4th toped out@100mph

 

Depends where the engine makes it's power. That's what's going to determine the shift points. If the powerband peaks at the same rpm, then the shift points will be the same but I wouldn't expect it. The engine doesn't care what tranny is behind it. It will make the same amount of torque so tranny gearing means nothing.

Tranny gearing will affect how the engine uses it's torque. A good example is the 700R4. It's a great street tranny but a poor choice for drag racing. The 1-2 shift is too far apart. When you shift into second at the engine's shift point, the engine rpms drops too much and falls far below it's powerband. This means it has to struggle briefly to get back into the powerband. Trannys like a TH350 or TH400 have a closer ratio so a shift doesn't drop the rpms as much and the rpms can stay in the sweet spot easier. Usually there's around a 2000 rpm window you need to stay in. It all depends on the cam grind.

My engine produces a lot of torque and I don't need all the extra gears to get down the track. When I shift from low, 1.76:1, to high 1:1, the rpm drop doesn't affect me so much because I make so much low end torque.

 

My cam is the Iroc-Z cam

 

you should also be aware that the T-5 you have with that 4.03 1st gear is a NON WC...it probly wont last long