71 Duster Dyno

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rumblefish360 said:
If the manual trans (& or the whole drive train) eats 25% of the power, then you have roughly 485/490 crank HP when the wheel dyno says 364 wheel HP.
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Just wondering if you were using 25% as a hypothetical and/or ease of number calculations? I've always heard a safe bet for automatics is 15-20%.... but I'm no expert. Just wondering if the thinking on that has changed?
 
I'm surprised at your torque numbers. Most la builds like your's tend to have a very similar hp/tq. Ex 400Hp/420TQ. It's just how these blocks are.

I'd run it again on another dyno. See what it spits out. Take the average and run with that till you put it on the track.
 
So 403nm ATW is a low reading? I can re run it at another shop i suppose. Not to fussed though car goes well. Real test will be down the 1/4
 
Dyno numbers don't mean squat..run it down the track:burnout::burnout:
 
stroked340 said:
Dyno numbers don't mean squat..run it down the track:burnout::burnout:
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I was going to say you can run on the dyno all you want, might as well through that out the window as soon as you hit the track though.

And yeah, 403nm seems low to me. Like I said, these small blocks are notorious for putting up very close hp/tq numbers. Traditionally a 340 will put hp above torque, and a 360 will put torque above hp. It's just the design of the motor. 403nm = 297 ft/lb as someone else mentioned. If you're putting 367 RWHP down in a 360, i'd expect RWTQ to be in the area of at least 380lb/ft, if not closer to 400. Maybe you're overcammed a hair and it's hurting your torque. Where did HP peak? I'm gunna guess 6200. What convertor you running?
 
25% is too much for a standard trans., like if the chassis dyno said 750 it's 1000 at the crank? figure about 50 hp more at the crank
 
Heres a pic of one of the dyno runs. 314 is from an old run when it had ported J heads and a mopar purple cam.
It definetly feels torquey, who knows. Once i run it ill post results
 

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L4staero said:
Might be hard with the manual though
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Practice practice practice !!!!!
Lightning quick foot pump, balls out quick slamming the shift stick foward quickly and more practice!
Learn where the pedal is and how far you need to go to disengage the clutch and then! Remove your foot to the left to in gauge the clutch. Let that pedal slam up a micro fraction of a moment before the trans teeth crash and crunch together.
This takes time and practice! Go slow and then build speed.

There was a time, long long ago, people would ask me what shift kit I was running. So I'd tell'em, the shift kit is call a "Left foot express." And left it at that, Pointing at the clutch pedal.

DakotaDuster said:
Just wondering if you were using 25% as a hypothetical and/or ease of number calculations? I've always heard a safe bet for automatics is 15-20%.... but I'm no expert. Just wondering if the thinking on that has changed?
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A super over est. I do not know how much power the 833 manual consumes. Automatics consume what you wrote. A lot depends on the specific transmission. According to other members here, there is a huge difference between the 727 & the 904, which is kind of evident due to the switch made many years ago by the pro's in the sport of drag racing by the well known tune of a tenth in the 1/4 or better.
 
[ame="https://youtu.be/iu447kSmPGE"]https://youtu.be/iu447kSmPGE[/ame]Finally had a chance to take it to the track, was super nervous for a first timer but had a blast. I ran with street tyres and a very conservative launch spun through 1st and most of 2nd once it hooked up it went really well but could never hold 4th flat past 150kmh because it was swaying violently. Ive attached a vid for your reference any advice on why its swaying so much would be appreciated.

Ran a 13.4 @ 109mph
 
http://www.hughesengines.com/TechArticles/11360dynotestfeb2000.php
Go to Hughes dyno build-up #11

From your pics, you are running the rear pretty low. Is that cuz the springs are soft, or cuz you like it that way?From the dyno video, the rear looks pretty soft.When you lifted at the end, the back did a little dance. I'm betting the pinion angle is going from waaay wrapped up to waaay pointing down, and hauling the shocks around wherever it goes.
Sway would be chassis; be it springs,shocks,air-pressure,or steering components. Could also be air getting under the front, or a heavy crosswind.New springs with a little rake in the back, will help keep the wind from getting under the front, while planting the rear.Perhaps the shocks will be able to control things better then, and reduce the sway, to an acceptable level. If not, new shocks, perhaps all 'round, will do it.(barring steering issues)

From your mph, that engine is sleeping. Either you are short shifting, or your rear gear is way off, or she's lazy. With those skinny tires, that 360 should be spinning to 60/70 plus mph.
If you're in 4th@150,Ima guessing you're running 3.91s/4.10s; or you are short shifting a much smaller gear.With 3.23s you should be trapping in 3rd gear at about 6200. You wouldn't ever get into 4th. 3.55s would put you at 6800 in 3rd, so the shift should occur around 104mph/6500rpm.
What rear gear are you running?What was your 60ft?

I think your engine has a lot of potential left in her, but the chassis issues will have to be addressed to make it a safe trip.

As a comparison, the one and only full run I ever made with my 3650lb(me in it), 68FormulaS, it went 93 in the eighth,with 4.30s in 3rd gear@ about 7000. This works out to a 4.3x1.40(3rd gear)=6.02 final-drive ratio.
My engine is about the same as yours, except; I run 10.7Scr on 87E10, and a smaller cam; an old Hughes 230*@050,which is 276/286/110. I run 1.6arms, so lift is .549/.571
When I left the line, the tach climbed to 7000, and I left it there, to the traps. I thought the clutch was done. The track starter said he never saw the tires stop smoking.I estimate the tires started hooking at 85plus mph. I was running 4.30s(IIRC) and 325/50-15 DRs, and street suspension,as born out by the 2.2 60ft.

Super-nice looking Duster! Keep on keeping on!
 
109mph is real close to 12.00 in a hood chassis.

You are losing a bunch of time/mph with the sway.

Runs pretty strong.
 
You got 400+. I think 25% is way too high for draw though. On our chassis dyno the loss was typically 18% for stick, 20% for auto. That still beats 400hp, but it's closer to 427 than 480.
 
Hey mate have a read of this in regards to torque at the wheels
[ame]http://mainlinedyno.com.au/images/downloads/DYNO_TORQUE_FIGURES_-_THE_TRUTH.pdf[/ame]
 
When working from the chassis power numbers you need to divide by the (1 minus power loss) estimate.
For instance, if you believe the chassis loss is 18%, then you would divide the net power by (1 less 18%). so that would be 356/(1 - .18 ) = 356/.82 = 434 crank hp.
To double check this, subtract the .18% from 434
That would look like 434 x (1- 18%) and that simplifies to 434 x .84 = 356! The actual power loss to the chassis would then be 434 - 356 = 78hp
This seems excessive, considering that the Hughes very similar engine, cranked out 437/437. What I'm suggesting, is that there's still something left in her,to be found in the tune, and the mph seems to bear this out.
The Duster at say;3400 race weight and 434 crank hp maths out to;3400/434 = 7.83 P/W. With a stick car this should go about 119mph and with an unlimited chassis this might go 11.2seconds. A street chassis might add a second or more so I guess 12.2 to maybe 12.5.
Op's (Greg's)109mph, says the engine is lazy(or short shifted,etc), while the 13.4 ET says the chassis is lazy.
At 109, the bulletin #40 says the engine is pulling just 10.0 P/W, which at 3400lbs is just 340 crank hp.
Shifting at peak horsepower,instead of centering the shifts around the power curve,could be a part of that.
With the A833 having spits of 73%, meaning that the revs drop to 73% at the shift,,shifting at 5600(my estimation of where the Peak is) would drop the Rs to 4100, and that is not gonna make for a good ET. The average Hp for a 4 gear run will thus be in the basement.
So what is needed is to rev well past the peak, to keep the average HP up. With the A833, this might work out to 6300. Shifting at 6300 dropping to 73% is about 4600. This puts the peak dead center at 5600, and the average hp up,a fair amount.
Looking at the dyno chart, it is impossible to know at what engine rpm stuff is happening. If we knew the rear gear and tire size, we could recalculate, and convert roadspeed to rpm, and then a better shift rpm could be determined. I just kindof guessed, based on my engine's preference.
So once the correct shift rpm has been selected and worked out with shift- loops, then timing and jetting, will optimize the engine combo. From there the MPH will settle down. Then you get to mess with the chassis.
I was happy with 93 in the eighth, so,for me,chassis be hanged.I don't care if it ain't that quick. I built it as a DD, and need a decent ride.Besides, it's kindof fun to be able to spin 295s anywhere,anytime.....
 
ktm071983 said:
https://youtu.be/iu447kSmPGEFinally had a chance to take it to the track, was super nervous for a first timer but had a blast. I ran with street tyres and a very conservative launch spun through 1st and most of 2nd once it hooked up it went really well but could never hold 4th flat past 150kmh because it was swaying violently. Ive attached a vid for your reference any advice on why its swaying so much would be appreciated.

Ran a 13.4 @ 109mph
Click to expand...


At 109 you should be in the 12.10-12.20 range, maybe a tad quicker. MPH is HORSEPOWER and ET is hook.

As you already know, you need to work on the hook first. Then we need to get you to put your right foot on the floor, and never lift it until you hit the stripe or the wall:finga:

You are giving up a bunch in the gear change.
Think about a 2 step.

What clutch do you run?
 
[ame="https://youtu.be/ix8vPh51Wb4"]https://youtu.be/ix8vPh51Wb4[/ame]

Gearing is 3.73 and tyre size is 14x245x60 i was shifting around 6k, i have my limiter set at 6200 i just figured this was a safe rpm, limiter could be set higher. No doubt some of you will have it screaming start to finish but the swaying up top scared the hell outta me.Once i work out the rocking and i put some better tyres on ill try again.My launches are weak my 60ft was 2.3
 
Looking at your graph, it's clear to see that you would want to shift at 200, to come in at 200kph x .73(the tranny spit) = 146
Well with 3.73s and 24.5 tall tires. 200 would be 6350rpm. So that could be rounded either way;6300/6400. And the power peak right around 175, maths out to around 5550rpm.
Ouch on those 60fts.A decent 60ft,and upping the shift rpm, plus a bit of shift technique,and you will be in the mid 12s easy.
You will be cooking in no time.

With the oiling mods I did, my 360 goes 7000plus any time. And it goes there a lot! Just because it can. And it sounds so awesome.

You are not running a spool are you? If you are, the tires have to be aired up the same and it's very important that you get a 4-wheel alignment. If your running tire circumferences(rollout) are not well matched, or the thrust angle is off, the rear will try to steer the car;which you will perceive as a wiggle back there at slower speeds.IDK at 150kph,cuz I've never had that problem.I can imagine the rear steering in one direction, which you would correct for. The rear would then unload one side, and the car would immediately dart off to the other side;which you would again correct for with steering wheel input.Would this sawing on the steering wheel produce a "sway"? IDK. I'm imagining.But I have run a spool on the street. And this is the exact reason I don't anymore.The correctly set up SG, I like much better; I don't even know it's back there most of the time.
The same can be said for a suregrip that has been set up too tight.
 
Thanks for the advice, i kinda like the look of low rear and high ish front but im starting to think this is what could be contributing to the sway, would a hotchkins style sway bar help? Also what are your opinions on caltracs?
 
mopowers said:
I wouldn't make another pass until you get the front end figured out. Did you have car aligned?
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Agreed.

You have something wrong with the car from a front/rear wheel alignment, bad front end alignment setting (toe out) or something. That's dangerous.

Radials on back, bias up front or vice versa. Something isn't liking what's going on. A sway bar isn't going to help that issue.
 
Your going to feel real dumb when you crash and total your car. Fix the front end and rear springs before you get yourself or someone killed. You have been given good advise by people who drive these cars every day and grew up with them. That car is dangerous as it is. I would not drive it around the block let alone down a track. If you can afford to get a duster down under you can afford a front end check and rear leaf springs, shocks. rule # 1 concrete barriers/walls/guardrails are expensive if you hit one. safety safety safety always be safe. That car is NOT SAFE to continue to race/drive as is.
 
Thanks for advice,but thats why i came on here,for advice.Ran it twice then left, never felt the wobble before as ive never taken it beyond 100mph. Im very lucky to have this car i bought it off an old man car collector for less than half of what he paid, when people see the duster they have no idea what it is.I cant exactly go to a auto shop and buy suspension parts like you guys i have to research and research then order online get shafted on conversion and freight rates and still keep smiling cause i own a MOPAR :burnout:
 
You can do a dirty alignment with some very basic tools.

Look on youtube for some of them.
 
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