I have a Pontiac Lemans 72 now.

Bigblock 468 with ovalport heads. Viktor intake now with a Holley Injection. 645hp/685ft/lbs.

The car weights 3000lbs. I have a Th400 with shiftkit B/M holeshot converter @ 2500rpm stall. 4.88 rear end with 33" 17" wide slicks.

My time:

1.43 sixtie
5.97/192.5km/h@201
9.32/228,6km/h@402

This is a streetdriven car. So i want it streetable. I overrev after 300m.

I use 150+150 shot of nitrous. 150 on the switch an 150 on my button at my steering wheel. For best times i use both from start to increase stallspeed.

So my choises is:

Better Converter. Mayby around 3500-4000? Capable of 1000ft/lbs of torque.

Another Rear gear? going from 4.88 to 4.56, 4.11? or will the lower gears hurt my 201 times more than it will gain the 402?

More power in engine will not be considered. No more nitrous either. The engine will need to hold up for at least 10000km/h a year and service each 3 year.

The car must be able to go 8 sec times to hold the competition behind. And that at street. On cold nights with +-0 celcius at worst an 15c at best.

Yes, I would suggest a better converter - like a steel stator 9.5 or 10" specifically for nitrous (if that's the way you always run it)

Popular brands for nitrous users here are PTC and Neal Chance. A nitrous converter will be so tight that street driving naturally aspirated will not melt it down - mine goes 5000 on the brake on the motor, 5700 when I leave on the fogger, but on the street, it will spin the tires at just over 2000 and the car will move at 1500.

If you want that thing to live, I would drop the gear ratio so you aren't going hitting the redline at 1000 feet (ok, 300m LOL). It will help with traction on the street also.

@ streetraces we always run for 201m. Will a lower gear help on that part too?

Still on nitrous it hooks very well. So its just to little power away ;)

Lots of times a nitrous car will go faster with less gear cause it makes so much torque. If you have them to try, I'd change the gear and see how it likes that.
Like 66 283 said, a custom built nitrous converter will definitely pick that combo up.

I almost decided on a coan 9" steel stator for nitrous.
In all simluation software i gain ET with nitrous going from 4.88 to 4.11 and i dont loose anywhere on the track.

So going to a 4.11 rear gear and 5000rpm stall will surely get me faster down the track?

//stefan