340 performance?

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ir3333

ir3333

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a friend bought a 73 340 4 spd.Duster
Has a '69 340,cast iron intake,x heads and lumpy cam..not much else known about the car
It runs 13.8 with 3.21:1 8 1/4 rear and 25560R15 BFG ta's
i know this is very little to go on but any guesses on et with 3.55 and 4.10 gears?
:
 
Some drag slicks will lower et, but my eventually cause problems for that 8 1/4. Changing the rear end gears may help or hurt depending on likely the cam that's in there and where the peak horsepower and torque is made. But I would listen to others I really don't know crap.
 
My guess is if it doesn't spin more off the line you might pick up a couple tenths. If it doesn't hook you wont pick up anything.
 
et alone doesn't say anything. What does it MPH?

100mph, it's running about right... 108 it's not getting off the line worth a snot.
 
And what tranny?
Here are some estimates for 104mph, and 27"tires
with 3.21s
With an auto he could be trapping in Direct at 4100ish, or 2nd at over 6000.
With a 4spd he could be trapping in 4th also at 4100, or 3rd at 5800.
3.55s would increase these Rs by 10.6%; so 4500/6600 for A/T and 4500/6400, for M/T,
4.10s would increase these Rs by27.7%; so 5235/7700 for A/T, and 5235/7400 for M/T

13.8 sounds pretty good for just a lumpy cam and skinny street tires
 
255R15/60 don't hook that well.Sorry no other info came with the car.
Still i think it should spool up quicker in each gear with 4.10's once it's rolling.
 
13.8 is pretty good for that combo. - My memory says that those, stock, 340s ran low to mid 14s, back in the day. -- Ronnie Sox, and a few others, got them into low 13s, but that was a rare happening, and questionable regarding stock.
 
RPMagoo said:
13.8 is pretty good for that combo. - My memory says that those, stock, 340s ran low to mid 14s, back in the day. -- Ronnie Sox, and a few others, got them into low 13s, but that was a rare happening, and questionable regarding stock.
Click to expand...

Oh they were stock! Just super tuned by the super experts!
 
j par said:
Some drag slicks will lower et, but my eventually cause problems for that 8 1/4. Changing the rear end gears may help or hurt depending on likely the cam that's in there and where the peak horsepower and torque is made. But I would listen to others I really don't know crap.
Click to expand...

I disagree. I have a local friend who ran a 8 1/4 in a Duster that ran 11s leavin with the hoops in the air on drag slicks. He upgraded to an 8 3/4 when he upgraded the rest of the car, the 8 1/4 never broke. He is going to use it in another project. They are plenty strong to do what the OP is asking.

That thing is cookin to have that gear in it. I bet with slicks and a 4.10 it would be a lot of fun.
 
You disagree ? But agree ?? Let's start with were you disagree - and I agree only from personal experience. My 8 1/4 never broke before I sold it and that was with 355's and 26 inch mt cheater slicks and many passes with a 4 speed, the old 318 and new stroker motor ! So I wanted to try 410 gears and 28 inch Hoosier's. Now I felt I was starting to push my luck and the 8 1/4 had served well, it seemed only a matter of time and again I got lucky and sold it before it became worthless or got me hurt. Spent a grand and built a 489 case 8 3/4 , spool, new 410 gears, professional set up- on about my 30th launch ka booom I damn near sent the ring gear through the back of the housing. Now would I have been better off juat leaving the 8 1/4 ?? And of course to the op this has been my experience and remember I don't know crap.
to were we agree - slicks! To this day I haven't spent better money to make my et lower. As far as gears ? I think it depends on really how much you want to bring it to the track? A couple times a month and maybe start bracket racing - sure. Once or twice a year - don't waist your money.
 
3.21 to 4.10 = .25 seconds in the 1/8, might be a bit more in the 1/4. A "good" torque converter could easily give .5 second in the 1/8.
 
sledger46 said:
3.21 to 4.10 = .25 seconds in the 1/8, might be a bit more in the 1/4. A "good" torque converter could easily give .5 second in the 1/8.
Click to expand...

Converter isn't much good in a 4 speed car. :)

But yeah, I agree in an auto car, huge difference is possible.
 
About 3 years ago I broke a 5.14 that I was running in my D50 and bought a chunk out of a Ford truck with 3.55's and put a mini spool in it. I only slowed down a half of a tenth and gained 1 mph and was crossing the finish line in second gear in the 1/8. Went from a best of 6.34 @ 108 to a 6.39 @ 109 in second.
 
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