cisurfer

I recently switched out my 373 for 410 and i lost mph in the 1.4 mile, i was rippin a 13.4 at 106 before hand, now i have 4,10s with an alumnium ds, ud pulleys, and fixed my valve seals, timing tensiioners and now my best was 13.4 at 103....keep in mind i was running nitto 555R on the 106 run, now im running just the 555 extremes, but that shouldnt take away mph just time, my friend is telling me i need to use a 28in tire for the track and ill gain mph but wont my time go down?

Moonshine

So you're faster at the bottom of the track... That's good. Don't think of a 'slower' trap as a bad thing. You didn't LOSE anything.

cliffyk

If you run 28" tires you'll be right back where you were with the 3.73's and smaller tires--from an overall gearing perspective...

I think what has happened is that with the 3.73s you were going through the trap at around 5250 rpm, whereas with the 4.10's you are up around 5750--which is where the 2V's power starts to drop off significantly. However, since you are accelerating better in the lower gears it's making up the time lost at the high end in 4th and the total ET is a wash.

Do you have a dyno chart for your engine? Ideally you want to hit the traps just at or near your peak HP.

cisurfer

maybe a 27in would be the best option

cliffyk

Or the 28's, without seeing your torque curve it's hard to say for certain.

If the larger tires get you hooked up better in the lower gears, then the 28's, with the 4.10s, would put you at 5150 rpm or so at 105 MPH. If your torque curve is like that of most 2V's then you probably have another 250 rpm of fairly steady HP left.

So, if there's enough track left after you get into 4th (because of gripping the track better), and you can cross the line at 5400 rpm then that would be 108-109 MPH. Even another 100 rpm would get you to 106-107...

Moonshine

I love cliffy. He's got you all figured out.

Bman2000

to be honest when i put the 3.90s in i was happy on the street, but disapointed at the track. because until i learn how to drive it all over again, i lost time and mph. but driving out of the hole on 3.90s isnt easy compared to the 3.27s lol

Cusp

You confirmed what my drive line man told me on gear choice for my car. That was that 4.10s slow guys down compared to 3.73s unless they use larger drag racing tires. But in that case they are moving back towards 3.73s any way. I don't race my car because of a lesson I learned from a friend about 35 years ago. That being to never use your required transportation for your sporting fun. Have your fun machine and your driving machine and use them accordingly. This nugget was earned at the expense of him having a mishap with the truck he needed to get to work with. After. He replaced his ruined 4X4 with a 2X4 pickup and a dirt bike.
Same can be said for racing your daily driver. Bad idea if you can't function without it. So for me it was 3.73s. They work great on my car.

H0SS302

I dont get why people buy lower gears and expect to tear it up on the track without doing supporting mods. you treat your gear choice like you would anything else... You have a higher torque multiplier out back, you need stickier tires, and better lower control arms to handle that, period.

cliffyk

The drive line guy knew his stuff...

You need to make sure that in whatever gear will be pulling you through the traps the engine has not yet gone past it's peak HP. If you are running otherwise neck-to-neck with another car, and you go past your peak HP point with 150 feet to go--and he doesn't--you lose.

You see this all the time on Pinks because many of the cars are not professionally set up--left lane guy (LLG) has 1-1/2 car lengths on right lane guy (RLG), with 100 feet to go, and all of a sudden it looks like LLG has stepped on his brakes and the right lane car sails over the line with a 1/2 car length advantage.

The left lane car was geared too tall and ran past it's peak HP before crossing the finish line...