Gear recommendation needed.

Fox chassis, 2900lbs, 325/50 (28" diameter) MT drag radial.

514 making somewhere over 700hp (flat tops, 4.15 crank, box stock P51s, mafia intake, big roller). Never been on dyno.

2 speed glide, no converter yet.

Any idea on gear out back? 3.90 maybe?

Maybe for the 1/8 mile^^^^^^. I think I would try a 3.25 but, I like Nitrous too.

I think id want around a 3.70. That should get you to about 135-140mph and a 9.50-9.70ish et

4.10 for 1/8 mile!

Four ten for tha win..

So 4.10 for the 1/8 and 3.70 for the 1/4?

I run 3.89's in mine with a 600HP 472" and a C6 at 3022lbs. It's going 133-134mph in the 1/4 out the back door around 6300-6500rpm on a 28" MT slick. I've switched to 275 Pro drag radials this season.

I ran 4.10's in my 514 with a glide and 28 inch mickey's worked good. Ran 6.20's

With the D2ve's.

So is this a Strip Only N/A Only Deal or to you plan on any High Way Cruising?

This will be a 1/4 mile drag car.  May cruise around a bit to a cruise in or what not but will not be driven more than 5-10 miles at a time.  Definitely don't want to spend the $10/gall for fuel to feed it on the street...

So 4.10 or do you think with the torque I may need  to step down to a 3.90? The glide has a 1.80 gearset in it

4:11s here. 180 glide, 730hp, 29.5s , through the traps in the 1/4 at 68-6900. 9.49 at 139.

jbozzelle wrote:Fox chassis, 2900lbs, 325/50 (28" diameter) MT drag radial.

514 making somewhere over 700hp (flat tops, 4.15 crank, box stock P51s, mafia intake, big roller).  Never been on dyno.  

2 speed glide, no converter yet.

Any idea on gear out back?  3.90 maybe?

Somewhere around a 4.11/1 ... even a 4.22/1 if the valve train will handle 7,000 RPM.

Keep the converter on the tighter side of what the camshaft needs or you'll just blow the tires off.

Thanks guys. Still need to get a converter too. I'll be buying that new. I'd like to dyno the engine to get a good idea what it makes to help in the converter selection. But can't find anyone nearby to do it. Nearest guy is about 2 hours away...

I have a single data point which won't help too much, but it's where I am in dealing with a similar question. I had a pump gas 598" in a somewhat heavy (4220# with me in at the line) '71 convertable Mustang with a Lentech AOD, 3.89 gear, 325/50/15 Hoosier DR. The converter would flash to 5700 off a 2000 rpm foot brake launch and I'd spin it 7800+ throught the lights. After a lot of chassis tuning etc. I was consistently at 9.60-9.70 at 140+ in 3000DA dead hooked at well prepped tracks.

I pulled the drive train (engine and trans) out and stuck it in a '87 Fox notch with the same tire, a 3.50 rear gear, slighly bigger headers and an on the track weight of 3440#. It ran very consistent 9.40/148 at 6500 DA and 9.20's at 3500 DA, also well preped tracks, no spin. With the new car the converter would only flash to 4400 and I would go through the lights at 6800. So at ~800# less I'd only picked up 4-5 tenths when I was looking for .8 or better.

I was running the same damn 60 ft times as before, 1.40's, without the extra 800#. So it was lazy out of the gate and well below the power peak in the lights. The shift points were the same.

I broke the AOD and as I plan to spray it 300-400 progressive down the road, I put in a Hughes 1.80 glide with a Gear Vendors and 9.5" converter build for the N/A dyno sheet, and I increased the rear gear to 4.10 to run N/A. I haven't run it yet. I know I'll have tighten the converter and take out gear to spray it with the EFI.

I got all over map advice too in terms of rear gear ratio, and I'll know more when I run it again at the end of July.

Good luck, make your best choice based on the best advice you can get from your chosen supplier, and know that you'll likley be changing gear and converter stators to get where you wnat to be. Good luck.

My gear recommendations are based on current technology converters.

As a good example:
Our current Limited guys are all running a 1.58 first gear with either a 4.10 or 4.30 rear gear based on weight. They are all crossing well under 7800 at 147 mph.

My car with 4.30's and a 1.58 first gear is a little different as we run 10 more mph in the 1/8th. Doesnt change rpm as much as you would think.