340 Build

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340xduster

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Hello Everbody-
I was wondering if anyone with experience and knowledge would beable to tell me exactly how i should be building my 340 in my 71 duster. I want it to have between 450-500 hp. Its a numbers matching engine so i dont want to put in a stroker kit to reach the goal amount. I want it to be Streetable, and be able to cruise in it without problems. If anybody could tell me how i should built this including what cam, what should be done to the heads, carb/intake, pistons, rods, etc. that would be awesome! Thanks!
 
450 to 500 hp 340 with factory heads and stock stroke and with manners aint going to be easy.
 
i would set the 340 aside and stroke the bejesus out of a 360. save the 340 when returning the car back to stock and forget the risk of putting a hole through the original block.
 
You can get the 450ish HP with the stock stroke, but "Streetable" is a loose term. Also, I hope you're only looking for that power at the crank. If you want that much power at the wheels, God speed.

In summation, you're going to need:
-A good carb. I'd say 750cfm minimum, but don't go overkill.
-A fairly agressive intake manifold. Eddy performer RPM air gap or Holley Strip Dominator are the two most aggressive intakes I know of that are deemed "Streetable".
-Porting and Polishing on the heads. If you do not have them already, install the larger 2.02" intake valves and get an experienced shop to port match them to the intake.
-Pistons for your bore (did you bore it 0.030" over, or is it fine as stock?) with compression upped to about 10.0:1. This is the maximum dynamic compression you will want on pump gas.
-I'm no expert on cams, but I would lean toward Comp Cams, Hughes, or Voodoo. Their techs can usually aim you in the right direction for your combo, or there are several members on here that are pretty good at talking cams.
-Headers. I'd go with Dougs or Tti, and don't bother asking which. Totally up to you. Dougs are cheaper, and cermaic coated.
-Good ignition. Mallory and Accel come to mind, but Mopar Performance makes a good system too. Either way, I'd recommend electronic ignition (I'm not sure if 1971s had switched to electronic ignition yet, but I don't think they had).
-Minimum of 2-1/2" dual exhaust, with an x-pipe.

Most of your power will be achieved through the right cam, intake, and cylinder head combo at 10.0:1 compression. Streetability will be tough at that power, but it is achievable.

Post up what you're working with and I know there are enough people here to help you on your way.

Welcome to FABO, and Good luck!
-Mike
 
73AbodEE said:
i would set the 340 aside and stroke the bejesus out of a 360. save the 340 when returning the car back to stock and forget the risk of putting a hole through the block.
Click to expand...

This reminds me, think ARP studs! You will need all new hardware in order to keep all ~450HP inside of the block and not all over the firewall / inner fenders.
 
73AbodEE said:
i would set the 340 aside and stroke the bejesus out of a 360. save the 340 when returning the car back to stock and forget the risk of putting a hole through the original block.
Click to expand...

I would 100% agree. To make that kind of power and the rpm's required wouldn't be worth taking a chance with that #'s matching block.

P.S. Welcome to the site.
 
Would 400 HP be do-able without having to worry about shooting rods and everything else out the side of the block? Just trying to make a powerful motor for the street, and have some fun!
 
340xduster said:
Would 400 HP be do-able without having to worry about shooting rods and everything else out the side of the block? Just trying to make a powerful motor for the street, and have some fun!
Click to expand...

That's alot more realistic. I know many will disagree with me, but 500 or more horsepower on a street, fun type car is not needed. Cool, but not required for some push you back in the seat fun.

Just to add, HP #'s are fun to talk about and brag if the're huge:D, but that's only part of the combination. If your willing to run some gear and a good torque converter, you could easily have a 12 sec. car without having to go radical on the engine set-up. And that can be alot a fun.
 
OldmanRick said:
That's alot more realistic. I know many will disagree with me, but 500 or more horsepower on a street, fun type car is not needed. Cool, but not required for some push you back in the seat fun.
Click to expand...

i would agree here. 500+ horsepower is great and all , but running the street all day with it may get you into trouble LOL . in my experience a great running mildly built 340 will get the job done without sacrificing any reliability or street manners.
 
I want it to have between 450-500 hp.
Click to expand...
Thats reason number 1 to go stroker - i just made 511 hp with stock eddy heads - so 450 out of iron heads should be doable

I want it to be Streetable, and be able to cruise in it without problems.
Click to expand...
reason #2 to go stroker - with a 3.31 stroke you;d have to spin it alot higher to get that hp - with a stroker you still get street manners, and I have 500 ft lbs of torque from 3 grand to 5600 - perfect to save wear and tear, as well as keeping the rpm's down

check out my build thread - mine idles at 750 with a nice rumble, you;d never know it has a stroker in it as you pull up at a car show and could probably run a low 11 / high 10 with the current setup
 
OK thanks guys! It sounds like a should go with a well built 400 hp motor, like i said just looking to have some fun on the street and push a few buddys back in there seat! Now that we have that taken care of lets here ideas on the best way to build it!
 
340xduster said:
OK thanks guys! It sounds like a should go with a well built 400 hp motor, like i said just looking to have some fun on the street and push a few buddys back in there seat! Now that we have that taken care of lets here ideas on the best way to build it!
Click to expand...

A little more info. would help. Is what you have now completely stock? Are you gonna be just driving local or making longer runs on the highway, say 60+ mph? What is you rear end gear ratio now?

I know yours is a 71' but this may be some good reading for you......
http://www.moparmusclemagazine.com/...970_340_high_performance_mill_dyno/index.html
 
OldmanRick said:
A little more info. would help. Is what you have now completely stock? Are you gonna be just driving local or making longer runs on the highway, say 60+ mph? What is you rear end gear ratio now?

I know yours is a 71' but this may be some good reading for you......
http://www.moparmusclemagazine.com/...970_340_high_performance_mill_dyno/index.html
Click to expand...


I will be driving decent distances from time to time 60 mph plus. Yes as of right now the motor is completely stock, i am planning on having the rear end ratio at either 3.55-3.73. Let me know if you need any other info.
 
IMO, the heads will need porting even to flow 400 HP. Just keep that in mind if you do not want to grind on the original heads. I would take the advice given and find a 360 and simply wrap up the 340 and save it. Just my 2 cents.
 
I agree with Strokerscamp about cutting on the heads.

I'm not as up to date on current parts as some other members that have done recent or are doing current builds so i won't provide any part numbers......

But, i would shoot for a comp. ratio in the mid to high nines, have a good competion valve job done, use a hydraulic Comp or Lunati cam with lift approching .500 and something like 235-240 duration at .050, a good set of headers (maybe TTI's), Eddy Rpm intake, a 750cfm carb of your choice ( i'm partial to Holley's) and some form of electronic ignition.

Once you have the specifics down on the engine and along with the 3.73 gear, you can contact a torque converter company and get a recommendation based on your combo. Something streetable that would flash stall up into the 3000-3500 range would be my guess.

Regardless of the horsepower number that should be a great sounding, fun ride for some street play.

This is just one opinion out of many possibilities. Good luck & have fun, Rick.

P.S. make sure you clean and put away all the factory parts you remove, they are like gold:D
 
I wouldn't build to some vague power level for a street car, I'd Start with where you want the powerband to be idle-5500,1000-6000,1500-6500,2000-7000 etc... And pick a cam for that powerband and that will pretty much dictate which gear ratio, compression, intake, stall speed, carb and heads your combo will need. If you need more power than your engine can produce in the powerband that's usefull to you than you need a bigger engine.
 
To the OP - When was the last time you drove a real 400hp car?
 
To the OP, the stock 340 cam power range is from idle to 5800. Something to think about. I say that from experience as much as seeing it in print. I've used the 340 cam in several engines and it works very well.
 
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