What,s a good RPM to launch a 4 speed?

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pettybludart

pettybludart

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I,m gonna install my 2 step rev-limiter,what,s a good RPM pill to put in for launching my 4 Speed?The car is my 73 Dart Sport 340..
340 stroked to 372 dynoed 452hp
833 4 speed'
C.F dual friction clutch,
lakewood s.sheild,
8 3/4 s.g 4.10 with Moser LBP,d.shaft loop,new u-joints
slide-a-link,90/10 shocks,
26 inch slicks.
Thanks.
 
The highest rpm below valve float that the car will still hook at. I would start around 4500 & work my way up.
 
I'd say 8500 and side step the clutch. Just kidding. If you running slicks and hooking up good, I would start at 5k and play with it Plus or minus 500 rpm till you achieve your best 60 ft time.
 
SGBARRACUDA said:
I'd say 8500 and side step the clutch. Just kidding. If you running slicks and hooking up good, I would start at 5k and play with it Plus or minus 500 rpm till you achieve your best 60 ft time.
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5000rpm is gonna make me nervous about breakage?LOL!I might start at 3500 and go up in 500 incramints til it feels right or breakage.I know somethings gonna give,but I,d like to just get some good hard launches a few times.Don,t want to pound this car much anymore,that,s what I got the 66 for!
 
pettybludart said:
5000rpm is gonna make me nervous about breakage?LOL!I might start at 3500 and go up in 500 incramints til it feels right or breakage.I know somethings gonna give,but I,d like to just get some good hard launches a few times.Don,t want to pound this car much anymore,that,s what I got the 66 for!
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Yup is has got to hook or your wasting your time.
 
I dont want to scare you but,I ran basiclly the same compbination in my car when i first built it, The only difference i ran 28 tall mickeys and 456 gears, lanched it at 3500 rpm and shifted at 6000 rpm. I could not keep the diff together, i broke 4 cone style sure grips, 3 clutch ones,, went to spool and then i broke teeth off the ring gear, and the last time i raced it with the 4 speed, i broke the main caps off the centre section. I HAD NO LUCK WITH A 4 SPEED AND A 8 3/4, went to 727 and with 500 plus runs with out any braekage, Then i biult a 416 making almost 600 horses and a transbrake and a 5500 stall and 250 plus runs with out any parts breaking, 4 speeds are very fun but hard on parts. hope you have better luck than i had.
 
Look at my post in the racers forums, "68 Coupe its alive - continued" I have basically the same set up except 383 B block, dana 60 with 4.56 gears and I am launching and sidestepping my clutch @ 6000rpm and shifting @ 5800. I started out at 4500rpm launch shifting @ 5000 then moved up in increments to where I am now.


I have the 2 step set up with a momentary switch off the clutch, works great.
 
Launch at 4000 shift it 6000.I turn my 383 6500 all day long and turn it harder than that once in a while. Jim
 
duster harry said:
I dont want to scare you but,I ran basiclly the same compbination in my car when i first built it, The only difference i ran 28 tall mickeys and 456 gears, lanched it at 3500 rpm and shifted at 6000 rpm. I could not keep the diff together, i broke 4 cone style sure grips, 3 clutch ones,, went to spool and then i broke teeth off the ring gear, and the last time i raced it with the 4 speed, i broke the main caps off the centre section. I HAD NO LUCK WITH A 4 SPEED AND A 8 3/4, went to 727 and with 500 plus runs with out any braekage, Then i biult a 416 making almost 600 horses and a transbrake and a 5500 stall and 250 plus runs with out any parts breaking, 4 speeds are very fun but hard on parts. hope you have better luck than i had.
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Yeah,I snapped an axel in 8 1/4 first,stupid to even have that rear in there!Then 8 3/4 cone-type.I just want to get a couple low 12 runs and some pics.,then it,s all racing the 66 Dart with 360/904.
 
pettybludart said:
Yeah,I snapped an axel in 8 1/4 first,stupid to even have that rear in there!Then 8 3/4 cone-type.I just want to get a couple low 12 runs and some pics.,then it,s all racing the 66 Dart with 360/904.
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With all that damage to the rear, I'd start taking weight off the car, and I might put more gear into it. Racing a stick is a real excercise in give and take, and I don't claim to know any real tricks. What I do know is that the lighter the car and the easier it is to make that drivetrain come along... the less breakage you will have. I think it is extremely difficult to get a strong running stick car at the track to have any kind of manners on the street at all. That is why I have two cars.
 
You don't mention what flywheel you have...Alum or Steel.
if your breakin parts you have too much clutch and flywheel...IMHO
 
I would say use your line lock and load the diff by letting out the clutch a hair, wind it up and let it loose. Most breaks using a 4spd is caused by not preloading the drivetrain. This is a must to reduce the chances of something going boooommmmmm. Just a suggestion
 
Mad Dart said:
I would say use your line lock and load the diff by letting out the clutch a hair, wind it up and let it loose. Most breaks using a 4spd is caused by not preloading the drivetrain. This is a must to reduce the chances of something going boooommmmmm. Just a suggestion
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I do have line-loc and use it.My motor is 452 HP,which is why I broke the 8 1/4.Last year when I broke the cone-type s.g,it was a used,old one.It,s all good now.I have C.F dual frriction clutch,Lakewood s.sheild,d,shaft loop,4.10,s in clutch s.g.,adj. pinion snubber,Bears performance racing axels.I,m not trying to be the fastest,just having fun.After June 5-6 weekend,the car won,t be raced anymore,I have a 66 Dart for racing!
 
Mad Dart said:
I would say use your line lock and load the diff by letting out the clutch a hair, wind it up and let it loose. Most breaks using a 4spd is caused by not preloading the drivetrain. This is a must to reduce the chances of something going boooommmmmm. Just a suggestion
Click to expand...
well thay always told me if your afraid of brakeing it don't race it. becuse with a 4speed its going to brake.and if the cam is makeing power at 5800 i would bring her off at 6200 by the time your off the clutch youl be in the power range.then be man about it put the nee lock on the right leg and shift it like you mean it....MOPAR TO YA!!
 
I was only stating that it will reduce the chance. Of course if you are racing your car, running it hard, make a mistake it will eventually break........That is a known fact for sure. It sure is fun though no matter what!!!
 
Emilio my brother in law launches at 4600. Here is the in car video of his technique
http://video.google.com/videoplay?docid=7528903995676743423&hl=en

2468359_33_full.jpg
 
SGBARRACUDA said:
I'd say 8500 and side step the clutch. Just kidding. If you running slicks and hooking up good, I would start at 5k and play with it Plus or minus 500 rpm till you achieve your best 60 ft time.
Click to expand...


LOL, Back in the day that's exactly how it was done with my car.... Well.... 8,000 rpm against the limiter clutch dump.

But thats how the car was set up. Very violent.
 
halfaed said:
Nice video!!!!!!
Click to expand...

I know what you mean. When I first say that vid I was blown away. That car however is set up to take that kind of abuse. Mine on the other hand close but not all the way. I have optimum u-joints, Yukon axles, scatter shield, and Mcleod clutch and pressure plate but still afraid I'm going to break something.
 
What most have said rings true.
I wouldnt just straight dump the clutch.
Id load it up to point you can feel it about to creep then come
off it if that makes sense. You dont wanna shock the drivetrain,
you want to load it up.
Manuals break running gear more due to shocking it an automatics
less due to loading it up instead.

An id recommend dialing it to the rpm where max torque is.
Not power. But thats me.
You cant really say a given rpm,due to different engines
setups etc having different powerbands.
With stick shift,its all trial an error my freind as i learnt.

Best of luck!
Hope that all made sense!
 
dr, I saw that bad 5-speed car on TV. It runs AND looks great!
Pat:cheers:
 
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