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Discussion Starter #1
Thought for sure could break 12 seconds with my new 383 stroker. Ran a [email protected] 105 mph.
Contemplating changing my gear ratio from 3.23, to 3.73. Rebuilt 3 speed automatic TH350. It can handle 600 hp. Lightweight driveshaft. My diff is an 8.5" with Eaton posi, ad Moser axles. Running new 555II Nittos.
You think this will put me over? Any other suggestions?
 

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What was your finish line rpm with the 3.23 gear??

What was the 60 foot time??

What's your torque converter stall speed??

Other pertinent info about the car would likely also help...what year or weight, tire diameter, did it spin or not spin on launch with the 3.23, your maximum rpm you want to turn the engine, shift rpm, cam spec.
 

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MPH is a reflection of power vs vehicle weight, gearing changes typically don't change MPH numbers much but will have a big influence on ET.
You've got enough power to run 12's, as witnessed by the almost 106 mph. Backfiguring for actual tire dainneter based off MPH, rear gearing and 4500 rpm says almost 27" tire(26.80").

At the same 106 MPH, a 3.73 gear is going to put you at about 5200 rpm at the finish, maybe a little more if the fact getting it revved a little higher improves power and MPH goes up 2-3 mph....109 MPH wuld put you around 5500 rpm.

You're close enough now that the current gear could get it done into the high 12.90's with some carb or timing tuning or maybe launch technique changes like leaving just above idle and flashing into the converter instead or brake torqueing up to stall on the start.
Have you done any carb or ignition timing changes??
The 3.73 should definately do it.
 

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Discussion Starter #6
A negative. Ran at Ubly for first time this year. Going to Lapeer next week. I didn't try not revving engine up, and holding with brake. A little advance in timing may help, or jetting up 2.
 

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Hey, you're sort of in my neck of the woods, I consider US-131 Martin my home track and have raced Milan Mi.and Osceola, Indiana...I'm 15 miles north of Michigan/Indiana state line right along highway Interstate 69.
Never been north to Lapeer or Ubly, been to Mid Michigan(Stanton) but never raced there personally.
 

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Was the car spinning the tires? The 60' is weak for the ET. More gear will make the spin worse. However, the gear will allow the engine to rpm quicker and get into its powerband faster. What rpm do you shift it at?
 

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If you go to Lapeer, message me. I might meet you there depending on when you go and if I get my car back together. Heck, I'll probably meet you there even if I don't get the car back together. Haven't been there in quite awhile, but I know they have a new owner and I hear it's much improved.
 

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Anytime you get below 2.0 on your 60 in a street car is good!
But I think you might want to get up on the verter more and perhaps not until the tree starts coming down. See what happens. write down results. then try something different if you don't get the results you want.

Did you say you were shifting at 4500? Seems low to me but IDK. have you had the engine or car on a dyno? if so where is peak HP? shift 500 rpm after peak HP.

2400 stall. How was that chosen? might be a bit low, but I honestly have no reason to give, just hunch.

what air psi are you at in the nittos? which tire? the 420s or a Drag radial?
 

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Discussion Starter #13
Was the car spinning the tires? The 60' is weak for the ET. More gear will make the spin worse. However, the gear will allow the engine to rpm quicker and get into its powerband faster. What rpm do you shift it at?
Strictly automatic. I've been revving engine,,and holding with brake till
I reach torque converter rating of 2400. Then just floor it!
 

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Discussion Starter #14
If you go to Lapeer, message me. I might meet you there depending on when you go and if I get my car back together. Heck, I'll probably meet you there even if I don't get the car back together. Haven't been there in quite awhile, but I know they have a new owner and I hear it's much improved.
Yes! They have solved all legal issues. I belong to a club, Twisted Axle Car Club, Detroit Are a chapter. I'll,find out when we are heading up there, and let you know. Lot of Mopars. We have 2 Novas. My real name is Greg.
 

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Discussion Starter #15
Anytime you get below 2.0 on your 60 in a street car is good!
But I think you might want to get up on the verter more and perhaps not until the tree starts coming down. See what happens. write down results. then try something different if you don't get the results you want.

Did you say you were shifting at 4500? Seems low to me but IDK. have you had the engine or car on a dyno? if so where is peak HP? shift 500 rpm after peak HP.

2400 stall. How was that chosen? might be a bit low, but I honestly have no reason to give, just hunch.

what air psi are you at in the nittos? which tire? the 420s or a Drag radial?
R555II Nitto w 30#. Automatic trans. 400 hp dyno. 2400 chosen due to high torque at low rpm.
 

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Mph looks okay
Quick answer: yes more gear is a quick fix to get into the 12’s. 3.73’s might gain a few tenths.
id like to see more consolidated numbers so we don’t have to chase them.

what is cam operating range 2500-6500rpm?
Trap speed?
Shift rpm?
60Ft?
I suspect converter may be too tight but would like to see cam rpm range.
foot braking and leaving at 2400rpm you likely aren’t letting the engine leave on much power.
People don’t realize their converter can cost them. You can look up torque converter slippage but it doesn’t mean everything. Shift rpm drop info may be helpful as well.

you might do what you can to stage as shallow as possible: barely trip the second bulb when staging may speed you up a couple to few thousandths.

as stated: maximizing timing and fuelare important.
 
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Lower gears will make it worse. Your 60’s are pretty slow and your tire spinning is hurting your ET.

Do you get wheel hop too? Did you end up ordering the cal tracks?

IIRC you went to a drag radial, something like an ET street bias tire might hook better but I understand not wanting to ditch a brand new set of tires. When I first started drag racing I ran a MT street tire and spun off the line going to a bias dot slick helped. Went from high 12’s to low 12’s Off the foot brake.
 

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I think you would see a dramatic improvement with a 3000-3500 stall convertor and 3.73...you have the right tires they just grip too much to let the motor rev ...4500 is way too low a shift point also...you could see 11.89
 
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