Stealthmaro

Trying to figure out what gear ratio is best to run with a power glide 1.76 first gear. Was thinking 3.73s to try and keep Rpms down. Shifting at 6400 and want to see around that in the traps. Cast crank with gm rods with arp bolts is why I don't want to turn more than that. Car is a dragcar so street is not a problem because it isn't going on it lol. Rear tire is a 28 tall I know that plays a factor in it as well. Thank you in advance

AlkyIROC

Doesn't really matter about the transmission gears. Tire height and diff gear ratio are what you need to know.

The only advantage to more gears is to increase torque multiplication to get the car moving however every time you shift, you lose a little bit as the rpms drop down to the bottom of the powerband.

I run a 1.76 powerglide. 32" tall tires and 4.86 gears. My converter stall speed keeps me in the powerband all the way down the track. I launch at 4500 rpm and shift at 7400. Engine rpms drop back to around 6400 and I go through the traps at 7400-7600. If I had a 3 speed, the 1-2 shift would come real soon and the deeper first gear would probably spin the tires from too much torque multiplication. Staying in first gear longer keeps me moving with less chance of wheel spin.

Although a powerglide transmission would need to be modified for more clutches in high gear, consistency increases even more if you launch in high gear and never shift. Won't be the fastest run but you could probably paint a number on the windows.

There are a lot of class racers who shift on time, not rpms. Launch and quickly get on the throttle stop before the 60' mark. While on the stop, shift to high gear. When the engine comes off the throttle stop, the transmission is in high gear which reduces wheel spin and they run most of the track in high gear only. Technically a bracket racer could do the same thing but humans are terrible timing devices. Launch the car and before you hit the 60' mark, shift to high gear.

Now depending on your converter stall, you'll have to experiment on gear ratio, tire size and top end shift point.

3.73, 28" and 6400 rpm sound pretty close. Going to a 4.10 gear would move the shift point closer to 6800. 6400 is a little low for drag racing and most properly built engines should be able to reach 6800. Really depends on the rpm range of the camshaft.

If set up properly, you should be crossing the finish line at or just after your shift light comes on.

Stealthmaro

Ok, the motor setup is a follows
ve a early 90s, 350 small block has been bored to .060 over and has stroker crank in it, which equals 388cu. in. X-rods, Seal power hyperutectic flat top pistons with two valve reliefs,10.5:1 compression, Strike force heads which are assembled in Indiana up by Indy 1.60s and 2.02 valves, Crane energyzer full roller rockers, holley 750 mechanical double pumper, msd ignition system . 6al and blaster 3 coil edelbrock performer rpm intake, erson .488/.510 hydraulic flat tappet cam, mellings oil pump. if I calculated it right I think it around 500hp cam stops working at 6400 and I don't want to turn the bottem end very hard to last and I dont think factory gm rods really like high Rpms but itight be ok to around 6800 but durability has to last. This project has taken me years to get what I have and money is tight lol just like everyone else anymore. Any light on what you think the motor should make by given stats can get more info on cam if needed. Goal is to be mid 11's.

Stealthmaro

RPM Range 2000 - 6400
Duration @ .050 Lift 234 / 244 deg int/exh
Valve Lift .488 in / .510 in int/exh
Lobe Separation 112 deg
Advance 5 deg
Cam info