Help me pick a rear-end gear - SB 390 stroker, 28" tire

My wife's '68 Cuda has been built as a double duty car but since we bought a Challenger a few months ago and I can go borrow my Dad's '66 Cuda to take to cruises we are going to turn her '68 into a 100% drag car.

Here is the info that may be needed to help determine, if you need other details let me know.

Motor:
318 w/ K1 4" crank, eagle H-beams, Ross pistons making 390cid and currently running 11:1 compression
M1 intake
Edelbrock heads OTB (I may get a little porting done and shave the heads to bump up the compression this winter but have to see how the budget for the other project first)
TTI headers
Barry Grant Silver Claw 750 carb
Comp solid .540/.550 252/262@.050 106 lob sep/Centerline

727, Turbo Action reverse VB
Dynamic 9.5 converter stalling to around 4k
28x10 Good Year slicks

Car should weight 3,200lbs after the roll bar is put in, will be removing stock front and back seats and full exhaust system, also remove fuel tank and installing 5 gal fuel cell.

Running Cal-Tracs full system, front/Back shocks, mono-leaf and bars. Braced 8 3/4 housing.

Currently it's ran a best of 11.57 @ 114, 1.587 60' times, with full exhaust and full tank of fuel, I'm currently running a 3.91 gear with 26x10 slicks (17psi), shifting at 5,800 and going through the traps at 5,800.

I think the SB 4" strokers make their power at lower RPMs so we'll probably want to keep the shift points at 6,000 or 6,200 (not sure about that, anyone with input on this would be appreciated)

I'm thinking a 4.30 would be a good gear but it may be too much and may just need a 4.10?

Here is a video of it launching:
http://www.metzinger.oxentenko.com/videos/Abbey.MPG

Honestly, with 11:1 compression and 106º lobe center, I'd run the 3.91s.

I'll bet, it's close.

Nope,...you are right,..... 4.30 is perfect.

I've got 4.30 and 28" tall tire. Trap at 6400rpm with tight converter at 120mph.

3300 lb. Duster, Edelbrock heads on stroker SB,
9" J converter, 29" tire and 4.10s........

1.43 60 ft.
10.53 @ 127 MPH

I'd give the 3.91s a shot before I went to the trouble.

I'm running the 3.91 with a 26" tire now and she is shifting at 5,800 and going through the traps a 5,800 so going to 28" and making a little more power I figured the 3.91 wouldn't be enough figure 4.10 or maybe 4.30.

Wade I would try shifting it at 6400/6600. Also a 950HP carb will help it. With a 28" tire a 4.30 should be real close. As stated with a 28" tire and a 430 gear mine went thru at 6300/6400. Jim

The engine that was in that Duster is 13:1 comp. 421" 274º @ .050" 108º lobe
separation installed @ 104º and ported heads.....so it's making a little more steam.

......but, OOTB Edelbrocks and 252º @ .050" on 106º lobe centers isn't
going to make power very high anyway.



edit: Maybe I should stick with 340s and 5.57 gears?

If you change from 3.91 to 4.10 you won't even be able to tell the difference.

I don't think you will see much difference with a gear change. Those 4" strokers with eddie heads make alot of torque. I think 4.3 might gain you a tiny bit of e.t. but it isn't gonna be enough to justify the change.
Also, I disagree about the 950 carb. A 750hp is just fine and not worth $600 to gain half a tenth.

Quote:

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If you change from 3.91 to 4.10 you won't even be able to tell the difference.

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I run a 28" tire on my Dart. I changed the 3.91s to 4.30s and only picked up a few hundredths. It was all in 60' and carried it all the way through, 1/8 mile. This was when it had the 340 in it. The 408 broke the 4.30s but I did order another set.