What to do to get a quicker launch...

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DQ81

'73 Dart
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I've got the 318 as descirbed in my sig. now in the Dart.

It's quick, once it's rolling. The launch is kind of misserable and it wont chirp 1st to 2nd :(

Transmission is stock, I've got my old busted 904 which I'd like to build up. Like everybody, on a budget. Budget budget budget.

I've got a 8 1/4 rear end, don't know what gears it has.

I might be getting a 8 3/4 suregrip soon btw :)

Anyway I wan't to accomplish a quicker off the line speed but it's still a street car.

Should I (remember on a budget!)

Build the 904 with the a reverse kit?

Manual valve body? (I'd like a floorshifter anyway)

Just do a shiftkit, and if so which one or is there a DIY one?

Install a higher stall converter (still street, don't wanna be at 3k all the time)

Or do different gears? (I'm at 3k at 75mph)

Love to hear who's done what and what it cost em' roughly.

I'm staying with a 904, not a 727 btw.

cheers,

David
 
Change the rear end gear ratio to a sure-grip with a 3.91 or 4.10 gear set. You`ll lose top end speed but improve your 0-60 time.
 
If your turning 3k rpm at 75 mph now then you`ve got a pretty low numerical gear in your car now. I would think with a 3.9-4.1 gear you`d probably turn 3k rpm at 55 mph. That`s a guess but you get the idea. Perhaps popabear can give you an idea of what rpm he turns at cruising speed.
 
A shift kit won't do anything to improve your launch; all it does is make the shifts firmer and quicker. If you don't do a lot of high-speed driving on the highway you could go to some steeper gears and a slightly higher-stall converter (maybe 500 rpm or so over stock). I'm guessing you have either 2.76:1 or 2.94:1 gears; I'd recommend 3.55:1, 3.23:1 if you do highway driving.
 
A higher stall converter will help alot and contrary to popular belief converter you buy now that are rated at 3,000 rpm don't stall that until you mash the gas. I have a 3K converter in my Cuda and it drives like a stock converter until I floor it from a stop. Made a huge improvement in take off. Like the guy said your gears sound tall too. Sounds like you need both. If you have a 318 you don't really need an 8-3/4 though unless your running slicks. The 8-1/4 is a stout rearend and sufficient and weighs less so the 8-3/4 might actually slow you down a little. I raced a 93 Dakota for a few yrs. and it had the stock 8-1/4 in it and it held up just fine running low 14's. Ran it over 1,000 times I bet.
 
Longgone said:
If your turning 3k rpm at 75 mph now then you`ve got a pretty low numerical gear in your car now. I would think with a 3.9-4.1 gear you`d probably turn 3k rpm at 55 mph. That`s a guess but you get the idea. Perhaps popabear can give you an idea of what rpm he turns at cruising speed.
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Thanks.

fishy68 said:
A higher stall converter will help alot and contrary to popular belief converter you buy now that are rated at 3,000 rpm don't stall that until you mash the gas. I have a 3K converter in my Cuda and it drives like a stock converter until I floor it from a stop. Made a huge improvement in take off. Like the guy said your gears sound tall too. Sounds like you need both. If you have a 318 you don't really need an 8-3/4 though unless your running slicks. The 8-1/4 is a stout rearend and sufficient and weighs less so the 8-3/4 might actually slow you down a little. I raced a 93 Dakota for a few yrs. and it had the stock 8-1/4 in it and it held up just fine running low 14's. Ran it over 1,000 times I bet.
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I like the idea of the suregrip, but perhaps it would be easier just to replace the gears, where to look?

Also what kind of converter are you running now? I was worried about that, but it's good to hear she acts like stock untill you mash it.

Poppabear said:
about 2900 rpm@55mph
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Which gears? Do you use a high stall converter?

What about manually shifting the auto box btw, I'd like a floor shifter at some point and am manually shifting on the column a lot because my trans shift WOT @ about 3800 to 4k rpm, leaving me just under 2k short at WOT.

So the advice is (in order)

Shorter Gears

Higher stall converter (which ones are a good compromise between daily use/fun?)

8 3/4th might be overkill? I don't even know if I can use it, it's under a Ramcharger right now so it's possibly too wide. Anyone know?
 
DQ81 said:
Thanks.



I like the idea of the suregrip, but perhaps it would be easier just to replace the gears, where to look?

If you go with lower gears and/or a stall converter you should add a sure-grip because if you don't you'll probably just spin the right tire and go no where. If you do go with new gears it's the best time to swap in a sure-grip since the labor won't be anymore.
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Also what kind of converter are you running now? I was worried about that, but it's good to hear she acts like stock untill you mash it.

A PTC. Here's the website. www.ptcrace.com
Click to expand...
Which gears? Do you use a high stall converter?

What about manually shifting the auto box btw, I'd like a floor shifter at some point and am manually shifting on the column a lot because my trans shift WOT @ about 3800 to 4k rpm, leaving me just under 2k short at WOT.

If you plan on manually shifting it I recommend installing a Trans-go TF-2 shift kit. When manually shifting a torqueflite alot of times there is overlap between gears. That's when one gear applies before the last one completely releases. The Trans-go kit greatly improves the shifting performance by tightening up the shifts and eliminating overlap.
Click to expand...
So the advice is (in order)

Shorter Gears

Higher stall converter (which ones are a good compromise between daily use/fun?)

8 3/4th might be overkill? I don't even know if I can use it, it's under a Ramcharger right now so it's possibly too wide. Anyone know?
Click to expand...

Not sure on the Ramcharger rear fitting without modification but I'd bet it's too wide. Maybe somebody else can verify that.

One other thing you need to consider when selecting gears is the rear tire size. It affects overall gearing just as the gears themselves do. If you have 3.55 gears and a 26" tall tire you'll run approx. 2800 rpm at 60 mph. If you have the same 3.55 gears with a 28" tall tires you'll turn 2600 rpm at 60 mph. Here's a link to a rpm calculator that you can select different gears and change the tire size to see what happens.

http://vexer.com/68rt/speed.html

BTW: When this calculator comes up it's set on 4 spd. Change that to automatic and you'll see and adjustment labeled torque converter efficiency. It's set on 100%. Dial that to 97% for a stock torque converter and 95% for a good street stall converter. Nothing except a lockup torque converter will achieve 100% efficiency.
 
Thanks Fishy68,

You've been helping me out a lot lately with good solid advce.

Thanks man!

I'm hoping the 8 1/4 on the Ramcharger will fit on my A-body, the gearing it has will be either a 3.23 or a 4.10, either (the latter preferably) will suit my needs just fine.

Thanks for that calculator and link.

BTW, where you at in Il? Anywhere close to Danville?

David
 
DQ81 said:
Thanks Fishy68,

You've been helping me out a lot lately with good solid advce.

Thanks man!

I'm hoping the 8 1/4 on the Ramcharger will fit on my A-body, the gearing it has will be either a 3.23 or a 4.10, either (the latter preferably) will suit my needs just fine.

Thanks for that calculator and link.

BTW, where you at in Il? Anywhere close to Danville?

David
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Glad to help. I'm on the other side of the state from Danville. Approx. 45 miles n.e. of St. Louis. I have been to Danville once when I worked for Hyster. Went to their mfg. site for training.
 
Cool, I have family Danville and have spent some time there. Pioria also.

Using that RPM calculator looks like I've got 3.23's in there at the moment...

Isn't there a trick to checking? I always forget how it works,

Jack the car up by the dif. so that both tyres are in the air. then spin one tyre 360 degress and count the driveshaft revolutions and then?

thanks,

David
 
DQ81 said:
Cool, I have family Danville and have spent some time there. Pioria also.

Using that RPM calculator looks like I've got 3.23's in there at the moment...

Isn't there a trick to checking? I always forget how it works,

Jack the car up by the dif. so that both tyres are in the air. then spin one tyre 360 degress and count the driveshaft revolutions and then?

thanks,

David
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Ok. Been to Peoria too. Not much part of the state I haven't been too.

Your close on checking the gears. You can do it by spinning one tire but you need to spin it 2 revolutions and the number of turns the driveshaft makes is the gear ratio. In other words if you spin one tire 2 revolutions and the driveshaft spins 3-1/4 turns you have 3:23 gears. If you spin just one tire 1 revolution the spider gears inside will divide the ratio in half. So a 3:23 geared rearend will only spin the driveshaft 1.62 times if you only spin one tire one revolution. Another way to do it is to spin both tires exactly one turn count how many turns the driveshaft makes and that's the gear ratio.
 
You might not like a low gear on the street. What intake are you running ?
 
The streetmaster is a single plane but it has small runners and a real small plenum so it still has good torque. I wouldn't go through the work to swap it. I don't think there'd be much gain. Maybe a little at best. JMO
 
That's what I figure on the Streetmaster 318... the runners compensate.

I've gotta get back out on the highway and double check those rev to MPH readings and do a manual check...

Using a stopwatch I just did a run and did 0-60 in 10.2 seconds...

I'm not very happy with that.

I did solve the 2/3 slip with the kickdown as advised, cheers.

Only probl now is the Holley can't get WOT, it's about 20% blocked...oh well, enough for one day.

David
 
Checked my gears by hand...

I'm somewhat dissapointed to say that I have probably got 3.21 gears

For 720 degrees of turning the tire give aprox. 6.5 half turns of the driveshaft, so that's aprox. 3.21's right?

I'm bummed on the one hand because I feel like the launch of my Dart isn't what it should be and was hoping it was the rear gears, if this is what 3.21's do I can't imagine how sloooooow a 2.76 or 2.94 must feel.

Anyhoo, looks like I'll have to sacrifice highway RPM's or cough up for a higher stall converter...
 
Yep sounds like 3:21 gears.

I just looked at your signature line and see you have an Eddy cam in it. Which Eddy cam is it? The performer or performer RPM? Did you degree it in when you installed it?

If it were me I'd try the bigger stall converter first before going lower on the gears. Your stock converter only stalls about 1500 rpm so even if you went with a conservative 2500 stall you'd gain alot. What size rear tires are you running?
 
DQ81 said:
I did solve the 2/3 slip with the kickdown as advised, cheers.

Only probl now is the Holley can't get WOT, it's about 20% blocked...oh well, enough for one day.

David
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Your making progress. Back the throttle pressure off just a little so you get full throttle. The trans will still work the same but it'll give you more throttle.
 
fishy68 said:
Your making progress. Back the throttle pressure off just a little so you get full throttle. The trans will still work the same but it'll give you more throttle.
Click to expand...

That's the problem I've been having, I set up the line pressure with max pressure at WOT to start and that yielded soft shifts and slippy 2-3. Shifts are nice and firm now but the only way to get that was to crank up the line pressure. Any adjustment to it inhibts it's ability to go to WOT now. Make sense?

I've got the Performer plus cam in it, I didn't install the cam myself so I don't know if it was degreed... I asked the guy I bought the motor from (it came in a truck I bought for the motor w/ reciepts for rebuild this past winter, the work was done in the UK and I'm not sure they degreed the cam, I'm tempted to think not...)

In principal a more radical cam, not too much more radical, could help along w/ a higher stall converter. I think the latter is the next step.

This question is rhetorical but: no way to check if the cam is degreed is there?

Thanks Fishy

BTW: what initial timing would you run with this setup? I'm at 10* but should be able to get 12* out of it. I want all my timing in by 3k RPM right? Say 36* tops?

Cheers,

David
 
DQ81 said:
That's the problem I've been having, I set up the line pressure with max pressure at WOT to start and that yielded soft shifts and slippy 2-3. Shifts are nice and firm now but the only way to get that was to crank up the line pressure. Any adjustment to it inhibts it's ability to go to WOT now. Make sense?

You should be able to get both max line pressure and WOT. With the engine shut off block the throttle wide open and adjust the throttle pressure so it just slips over the stud. That is how I do it and always works.
Click to expand...

I've got the Performer plus cam in it, I didn't install the cam myself so I don't know if it was degreed... I asked the guy I bought the motor from (it came in a truck I bought for the motor w/ reciepts for rebuild this past winter, the work was done in the UK and I'm not sure they degreed the cam, I'm tempted to think not...)

In principal a more radical cam, not too much more radical, could help along w/ a higher stall converter. I think the latter is the next step.

You really don't want to go alot bigger on a small cube engine but there are some better ground cams out there that'll give you good low end torque and good hp too. After using a few different cams I like Lunati's. Their ground pretty aggressive with a good amount of lift so they have good torque
Click to expand...

This question is rhetorical but: no way to check if the cam is degreed is there?

Only way is to pull the front end off and go through the process
Click to expand...
.

Thanks Fishy

BTW: what initial timing would you run with this setup? I'm at 10* but should be able to get 12* out of it. I want all my timing in by 3k RPM right? Say 36* tops?

Cheers,

David
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I'm sorry but I don't know 318's well enough to know what total timing they like but I'd guess 36 is pretty close. Just listen real close for any spark knock and back it off some if you need too. As far as initial I'd guess about 14-15 degrees would be the best. You should have it all in by 2500. Running more initial timing and having it come in quicker will help your soggy take off.
 
DQ81 said:
I set up the line pressure with max pressure at WOT to start and that yielded soft shifts and slippy 2-3. Shifts are nice and firm now but the only way to get that was to crank up the line pressure. Any adjustment to it inhibts it's ability to go to WOT now. Make sense?


David
Click to expand...


There is an adjustment inside the tranny to increase the pressure without having throttle travel interference. It has been a long time since I was in an automatic tranny but I believe there is an allen bolt adjuster below the servo.
 
Thanks Blownfish, I'll look into that, although for now I've orederd the proper linkage Chrysler linkage for the Holley.

Fishy:

There is really no way to get the transmission to behave the way you've described, that is exactly how I have set up the last 3 Mopar transmission I've done, even TH350 chevy's are the same... the trans just doesn't respond. I think/hope the linkage has too much travel for a Mopar, looks like it's the Ford linkage that's on there...

Lunati is a cam I've looked into and it interests me, I just like the name, especially the Vodoo series. I've heard good things.

I want to play with the timing when it stops raining out, where is the allen head to adjust the vac pod located?

Thanks
David
 
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