Rear end gearing

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Need to know a lot about your combo.
But basically need to figure out the mph and rpm your gonna beturning through the finish line. Then it pretty simple to calculate the gear needed.
 
'72 Demon, glass hood and front bumper, 10pt cage,
440 .030 over, 11.5 comp, 590 solid cam , 850 cfm holley, tf with 4000 or 4500 stall , will have to look again its been a while
8 3/4 rear. Willwood rear disk brakes. Caltrac with old springs and 9 way Shocks. 325/50-15 , I think that's 27.8 tall.
Front factory disk brakes, adust able front shocks. I think it has the small block torsion bars.
 
What gear do you have now ?
And have you race it and if so what times did you run ? And you haven't it's probably better to run a few times to get an idea what it's capable of and the rpm it runs now. So it less of a guess.
 
440 built by Gary Hettler Engines who builds engines for Stock& Super Stock classes.
1966 440 .030 Forged 11:1 pistons, steel crank, MP .590 lift solid cam, 906 heads ported, Crane Gold roller rockers, Edelbrock TM-7 intake, 6 qt oil pan. Balanced and blueprinted. I put an 850 DP on and the distributor is a stock electronic with light springs 36deg timing, MSD 6AL box with a Blaster Coil.

All steel, except fiberglass hood 1972 Demon, full interior with 12pt mild steel cage. 20gal Harwood fuel cell running 1/2" fuel line and a Holley Blue pump.

727 Torqueflite, cheeta manual valve body, 4:10 spool, 325x50x15 BFG's (27.8" tall), Cal Tracs on soft stock springs, Adjustable Koni's set on 90/10.
Car has run 11.83 and now I have to go find the mph and rpm it was running through the traps as I don't remember right now, but seems to me the mph was low for the time.
 
If you got all you can get out of the gears you got. Can't see ya needing to spin that engine too much higher. I'd get friendly with some of the other mopar guys at the track and see someone got 4.56 all ready to go and see if they will let you try it out.
 
I have a 4.56 and a 4.88 limited slip center all set up. Just wondering what would work best.
People have told me this setup should run low 11's high 10's . Just wondering if a gear swap would get it there
 
You are leaving some on the table. 60ft and 1/8 mile if you have those numbers.....

JW
 
Correction, it was 6800 rpm. Car has been parked for many years and going through some old posts on here I'm figuring I need to fix the tranny/ convertor before I get it out. Had 16 or 18% slippage I. The drive train somewhe re
 
If your hitting 6800 with that 509cam........I don't think you want any more gear
I wonder if your TC is still good; My math gets about 17.5% slip. With 4.10s and 27.8 tires you should get 137mph @6800. If you're getting 113, then
1 minus 113/137 =17.5% slip

I don't race, and know dick-all about what a good TC might slip at, but ......it seems to me 17.5% slip is a lot!
EDIT and all that slip is heating up your ATF, instead of motoring you down the road.
 
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with those itybity tires and a 4.10 gear you are just rpming the motor and it's not given it a chance to produce or use any torque. i'll recommend two things. a taller tire (29's) to go with the 4.10 gear or 3.55 gears to go with the itsy-bitsy tires. you need to get the motor to use it's torque. you have an 11 oh to 10.90 car easy.
 
My old 440SP motor around 9.8:1 ported bv 906's, 850DP etc., made 484hp on track, I would think yours is an easy 500hp, probably more?....but just using 500 fly and at a rough guess on your weight of 3300lbs all in?...with a good trans/verter with an average of 5>6% slip and a good hook it works out something like this>

28" tyre, 4.10 gear = 10.93@123mph trap 6039+6% slip = 6401rpm
28" tyre 4.30 gear..................................... 6333+6% slip = 6712rpm
29".........4.56............................................ 6484+............= 6837
that .590 cam is done at about 6900, of course I am only guessing with the HP and weight which will change things some but not so much the ET/mph, its a high 10 sec car as has been said.
I ran through at approx 6600 with 484hp, 3000lbs, 4500 verter and 4.88's/32" tyre at 10.71@125
 
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Thanks guys. Can't wait for it to warm up and get to cleaning her up.
Need to go out to the shed and find the tranny i rebuilt but blew the reverse band due to a crappy valve body, go through it replace the band, swap it out, and see if it slips less. Pain in the butt pulling the trans with these headers .Could be torque converter also. I think it will not be to easy to figure out which one it is.
If i power break the engine and everything holds at xxxx rpm and doesn't keep climbing rpm , would this show the convert or as being good?
 
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Here's another good RPM calculator to play around with, it's been real accurate with all my cars.

Simple RPM Calculator | RANDYS Worldwide

With your 4.10 gear, 27.8 tire, and 113 mph trap speed you should be around 5800 RPM.
After you get your converter built correctly you should trap at a higher mph and probably around 6000 rpm. I would keep the 4.10 gear with that cam and tire.

My 8" ATI converter slipped less than 3%.
 
What headers do you run? I would spend $150 and have that converter cut open and checked out while you have the trans out.
 
ProSport said:
What headers do you run? I would spend $150 and have that converter cut open and checked out while you have the trans out.
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It has the pro parts headers on it, same as the old McCandless headers.
From what i remember the bell housing is very tight coming out from between them.
Wish i knew if it was the trans or the converter , the converter would be easier , as i think i could pull the trans back far enough to get it out.
I think this is an ATI also, have to go see if I can find the info. The guy I got it from said it had 1 free check up. I wonder if he still has the paperwork from it.
 
It shouldn't be too hard to remove the passenger header completely since the headers are in pieces.
 
ProSport said:
It shouldn't be too hard to remove the passenger header completely since the headers are in pieces.
Click to expand...

ProSport is there a calculator to figure out best gearing for the 1/8 mile. All I have seen are for 1/4 . I only race 1/8 mile.
 
D-50394 said:
ProSport is there a calculator to figure out best gearing for the 1/8 mile. All I have seen are for 1/4 . I only race 1/8 mile.
Click to expand...

I'm not sure, if you type in the tire size, the gear ratio, and your 1/8 MPH you might be able to play around with it. I typed in my 1/8 mile MPH from my old 9 second Dart and it seemed pretty accurate.
 
ProSport said:
I'm not sure, if you type in the tire size, the gear ratio, and your 1/8 MPH you might be able to play around with it. I typed in my 1/8 mile MPH from my old 9 second Dart and it seemed pretty accurate.
Click to expand...

Thanks, I will try that..
 
D-50394 said:
ProSport is there a calculator to figure out best gearing for the 1/8 mile. All I have seen are for 1/4 . I only race 1/8 mile.
Click to expand...


There is an 1/8th mile gear ratio calculator on the Wallace site. There is also about 75 other calcs on there so some guys can really geek out on there. I don't remember the address.


Just google Wallace racing calculators and you can pull it up.
 
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