4.10's or 4.30's for 8 3/4 gear swap

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Duster Drag Car

Duster Drag Car

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Need some input just pulled the third member on my 742 case 8 3/4 looks to have had a gear swap and a spool not long ago but the gears are 5.13's or 5.17's to low for my 440 build going to change to 410's or 430's the motor is a 68 440 30 over factory forged crank eagle 4340 forged h beam rods je flat tops two valve release high volume oil pump 1/2 inch pick up 7qt pan high tech double roller race timing chain by comp cams solid lifter comp cam 550-570 lift with 1.6 ratio roller rockers to make lift 579-609 power band is 3500-6500rpm's pro comp heads with edelbrock valves and comp cams dual springs mild port job 72 cc combustion chambers 280 runners valves are 1.81 and 2.20 edelbrock victor intake hooker competition plus fenderwell headers gonna buy a 950 or 1050 main body and use the parts from my 850, compression is a bit over 11.1 gonna use a 3500-3800 stall converter with a 727 reverse manual valve body car is 2800lbs did the gear ratio calculater and i think 4.30's will give me the best et slicks are 29.5 x 11.5 x 15
 
Duster Drag Car said:
Need some input just pulled the third member on my 742 case 8 3/4 looks to have had a gear swap and a spool not long ago but the gears are 5.13's or 5.17's to low for my 440 build going to change to 410's or 430's the motor is a 68 440 30 over factory forged crank eagle 4340 forged h beam rods je flat tops two valve release high volume oil pump 1/2 inch pick up 7qt pan high tech double roller race timing chain by comp cams solid lifter comp cam 550-570 lift with 1.6 ratio roller rockers to make lift 579-609 power band is 3500-6500rpm's pro comp heads with edelbrock valves and comp cams dual springs mild port job 72 cc combustion chambers 280 runners valves are 1.81 and 2.20 edelbrock victor intake hooker competition plus fenderwell headers gonna buy a 950 or 1050 main body and use the parts from my 850, compression is a bit over 11.1 gonna use a 3500-3800 stall converter with a 727 reverse manual valve body car is 2800lbs did the gear ratio calculater and i think 4.30's will give me the best et slicks are 29.5 x 11.5 x 15
Click to expand...

i say try both if you can. i have a all steel 73 dodge dart that should weigh around 3500 pounds with me in it.i weigh around 310 pounds my self.I had a set of 4.10 gears in my 742 case 8-3/4 and on my 5 pass i blew up the 4.10 gears. they was a brand new set of richmond 4.10 that were put in the car before i bought it.So i put a set of used 4.30 gears in my dart. i owned them once before.i have a engine close too yours that i run on 93 pump gas except mine has
bowl ported Indy ez heads that are so posed to flow 310-315 at 600 lift
i have wisco flat tops that is right at 11.1.1 compression
comp solid roller that is 264 at 0.050 and 634 lift with my 1.6 roller rockers
i am running a tunnel ram with 2 carter comp 750 carbs soon to install some Holley 650 dp with some pro form main body's.
dynamic 9.5 inch converter that stall around 4500 rpm
m/t 275/60/15 et street drag radials
my best pass with the 4.10 was a 10.67 at 125.00 in the 1/4 before i blew up the 4.10 i never did get to do any tuning. ti was a nice cool day that day. i only got to try out the 4.30 one time last year and it was 96 97 degrees at 12:00 am that weekend. was a very bad nite for racing.to hot and humid.only was running 1/8 that nite which i think my best pass that nite was a 7.03 at 98/99 mph. my best pass on the cool day was a 6.88 at 100.8 mph. here is a pic of my 4.10 gears. good luck with your car and post some pics of it when you get it running.thanks Mopar65
 

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You want to gear for a little past peak horsepower at the stripe. I'm guessing peak power to be around 6500 at most. So you're falling a little in the middle. I think I'd go with 4.10s myself knowing the car is light. Make sure the convertor is very high quality, and I'd also go another 500rpm higher on the flash stall. I think your looking at a torque peak around 4800 depening on how the heads flow.
 
mopar65 said:
i say try both if you can. i have a all steel 73 dodge dart that should weigh around 3500 pounds with me in it.i weigh around 310 pounds my self.I had a set of 4.10 gears in my 742 case 8-3/4 and on my 5 pass i blew up the 4.10 gears. they was a brand new set of richmond 4.10 that were put in the car before i bought it.So i put a set of used 4.30 gears in my dart. i owned them once before.i have a engine close too yours that i run on 93 pump gas except mine has
bowl ported Indy ez heads that are so posed to flow 310-315 at 600 lift
i have wisco flat tops that is right at 11.1.1 compression
comp solid roller that is 264 at 0.050 and 634 lift with my 1.6 roller rockers
i am running a tunnel ram with 2 carter comp 750 carbs soon to install some Holley 650 dp with some pro form main body's.
dynamic 9.5 inch converter that stall around 4500 rpm
m/t 275/60/15 et street drag radials
my best pass with the 4.10 was a 10.67 at 125.00 in the 1/4 before i blew up the 4.10 i never did get to do any tuning. ti was a nice cool day that day. i only got to try out the 4.30 one time last year and it was 96 97 degrees at 12:00 am that weekend. was a very bad nite for racing.to hot and humid.only was running 1/8 that nite which i think my best pass that nite was a 7.03 at 98/99 mph. my best pass on the cool day was a 6.88 at 100.8 mph. here is a pic of my 4.10 gears. good luck with your car and post some pics of it when you get it running.thanks Mopar65
Click to expand...
who installed the 4.10s maybe they wernt set up right i want to install mine but its a little tricky maybe ill pay the shop to set up the ring and pinion in the third member and ill put everyting back togther
 
Duster Drag Car said:
who installed the 4.10s maybe they wernt set up right i want to install mine but its a little tricky maybe ill pay the shop to set up the ring and pinion in the third member and ill put everyting back togther
Click to expand...

dont know but they was noise on the drive side with what little street time i drove it. I set up the 4.30 gears my self and after 15 passes they are still doing fine. but saying that they could blow up the next time i take it to the track.also i am building a 73 duster and was wondering how you got your car down to 2800 pounds? have any pics of your car you could post? thanks Mopar65
 
805 kid??? NO ISSUES??? you have had ALOT of issues since switching gears.Have you even figured it out yet???You are over geared.I think 4.30s would work better in this application.My Opinion.Mark
 
madmax/6 said:
805 kid??? NO ISSUES??? you have had ALOT of issues since switching gears.Have you even figured it out yet???You are over geared.I think 4.30s would work better in this application.My Opinion.Mark
Click to expand...

i ment for street driving... havn't touched it though
 
Roger - I can set them up for you if need be... I also have a set of 4.30s in the Cuda I'm doing steel work on and the owner doesnt want them.
 
mopar65 said:
dont know but they was noise on the drive side with what little street time i drove it. I set up the 4.30 gears my self and after 15 passes they are still doing fine. but saying that they could blow up the next time i take it to the track.also i am building a 73 duster and was wondering how you got your car down to 2800 pounds? have any pics of your car you could post? thanks Mopar65
Click to expand...
there is a basic picture under my screen name will add more when i take some the car has no interior sheet metal dash fender wells are cut out trunk lid backing is cut out fiberglass hood and bumpers lexan front and rear glass trunk and rear fenderwells are cut out and tubbed and replaced with sheet metal the guy who i got the car from said it was 2800 with the 383 in it im going to weight it when i get it all back together has no alternator or power steering etc.
 
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