Help me build my 340

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Austinsguns

Austinsguns

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Be easy on me now, I am just getting into this. I am 22 years old and just purchased my first mopar project a couple months ago. I am looking for suggestions on my engine build and torque converter.


Here it is:

http://www.forabodiesonly.com/mopar/showthread.php?t=271231

I have a 1971 Duster 340. All original, numbers matching. I am going to redo this car. I am going with all stock interior, paint etc. It will be very close to original. I want to build the motor to have better performance than original. But I want a stock vibe. When the hood opens I want it to look very close to original.

Specs on the car:
Original 71 340, currently mechanically sound with 90,000 original miles
727 auto
3.91 Sure grip
Upgrade to 15" rims / taller tires
Will be a street car /cruiser, but with a wild side. Not a strip car


Here are a few build parameters I have in mind:
Run on 91 octane gas
Stock carb (800 Thermoquad)
Stock Intake - improve flow?
Stock Heads - improve flow/new ss valves?
Stock Manifolds - improve flow?
New pistons
New cam - Which one?
Stock rods?




Questions I have:
With the stock components above, what can I do to ramp up the power?
What is the max HP I can get with better internals and porting?
Oil mods that should be done as long as I am redoing the motor?
Would running headers totally kill the restoration theme?
Torque converter recommendations?


Please let me know your opinions.
 
You got a hell of a car there. While i can't attest to the mechanical improvements you're wanting to make, don't forget that this is YOUR car. Build it like you want it. :)

You will get a TON of help on here from the engine building gurus. I personally wouldn't do much to a 340, maybe look at a beefier cam, aftermarket intake and carb. Headers are always a good way to free up some power.

You can always just keep the stock parts should you ever decide to sell it and want to claim it's all original.
 
Were you saying you wanted to keep the intake carb and manifold stock? If not then throw a air gap and 750 dp on it with some headers and flat tops. You will not be disappointed. Oh yea and a good cam!
 
Im thinking you wont be runng 87 octane gas unless you lower the comprresion.and that will take a bit of the wild side away..
 
doogievlg said:
Were you saying you wanted to keep the intake carb and manifold stock? If not then throw a air gap and 750 dp on it with some headers and flat tops. You will not be disappointed. Oh yea and a good cam!
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I want to use stock intake, heads, manifolds. But am not opposed to porting/modifying for better flow.
 
You can run everything to appear stock. Pocket and port match intake and exhaust. Back cut intake valve and get a good valve job, cut guide stems for positive guide seal.
Go with adjustable rockers. Do not over cam a street car, 230@50 for hyd, 240@50 solid. .500 lift with a true 1.5 rocker minus small block geometry loss = .485 lift. Your limiting factor for HP is going to be the exhaust manifolds, run a split duration cam to help the exhaust. If you limit yourself to 87 oct don't go over 9:1. even at 9:1 the ign and fuel will have to be spot on for 87.
 
Damned if I wouldn't build it back STONE stock, but blueprinted to spec. The 71 340 was perhaps the best one. It would be a very well mannered driver that would haul *** and last a long time. But again, decide what YOU want and do it. It's your car.
 
RustyRatRod said:
Damned if I wouldn't build it back STONE stock, but blueprinted to spec. The 71 340 was perhaps the best one. It would be a very well mannered driver that would haul *** and last a long time. But again, decide what YOU want and do it. It's your car.
Click to expand...

If your keeping stock parts I would sent everything to a good shop and have them clean it up and put new bearings in it and maybe check the balance then restore it to stock specs. If I had a street 340 that would be my route.
 
I know you said with stock parts but Stock appearing stroker is my vote, 416 CI with stock intake and exhaust manifolds, with the right cam it will make nice power and torque.
 
JMO here, I'm with Rusty: a blueprinted 340 with aftermarket light weight flat tops, plus a little work on the induction (portwork in the heads) and some tweaking on the carb, and a ~220-225 ish @ 050" (260-270* total) cam on a 112-114 LSA would make a great daily driver, run on pump gas, and run really well. And should you choose to upgrade later, it'll be ready for different cam/intake/carb/header swaps.

In any case, I'll keep an eye on your build
 
Thanks for all of the suggestions. Keep em coming.


I understand it is entirely up to me. I just like seeing what your thoughts are. Maybe a few internal upgrades and a complete overhaul will be best. Keep it close to stock just a bit refined for more performance. I do not want to do a stroker, It would seem like sacrilege to to do that to a nice original setup like I have.
 
Like Rusty said, the 71 340 is quite a formidable package--and that was out of the factory with all the potential inequities. If you put everything in the build the way it's spec'd to be, it'll perform very well. Blueprinting and proper application of parts within the package make reliable power and performance.

If you want to, and the engine needs it, then sure-rebuild it. But if your compression is good across the board, doesn't consume or leak oil, make weird noises, and it runs well after a decent tune up session (timing and carb adjustments), I'd just run it as is until such time that you need to rebuild it.
 
Just tossing this out there since I have been in your shoes. Before you add any power, go through the suspension and brakes.

All the power in the world is useless if you can not apply, control, or stop it.
 
Cam would make a big difference the stock 340 cam is pretty tame, a high lift 268 from voodoo or comp would make a big difference, and X2 on porting, manifolds will be the main power limiter.
 
dano said:
Just tossing this out there since I have been in your shoes. Before you add any power, go through the suspension and brakes.

All the power in the world is useless if you can not apply, control, or stop it.
Click to expand...

Very true...I should practice what I preach...I've said the same thing before.
 
Austinsguns said:
Thanks for all of the suggestions. Keep em coming.


I understand it is entirely up to me. I just like seeing what your thoughts are. Maybe a few internal upgrades and a complete overhaul will be best. Keep it close to stock just a bit refined for more performance. I do not want to do a stroker, It would seem like sacrilege to to do that to a nice original setup like I have.
Click to expand...

so so true

340's rule:cheers:
 
A thorough rebuild on the stock 340 is all I would do. Have hardened seats put in for todays gas. That car is light and that 340 rebuilt, timed and tuned properly will boogie boogie!!! You might find 3.91's not very highway friendly. If you plan on cruising at highway speeds you might consider 3.23's, or maybe even 2.94's. It will take away some low end punch, but gas mileage will go up and the rpm's will go down at 55 mph. Should you ever decide to do a performance build, I would grab a 360 for the making, and leave the original motor intact and stock, and unmolested.
 
I used this exact build, a TF904 with Hughes 3000 stall, Transgo TF2, and a set of super stock springs; 8-3/4 with 3.91 Richmond gears with an Auburn sure grip and TTI headers with a cross pipe with 2-1/2" exhaust.

Dynoed(bench) 410hp and 411lb lbs of torque.

In my 69 Dart I ran 11:98@112 with drag radials @ 18lbs with 68 degrees of ambient temperature.

The machining is the most important part along with cleanliness.

http://www.compcams.com/information/...MM0201-001.asp

Very good article for the beginner and has the motor has served me well. And I drive it one the street every weekend.
 
I know you want to keep your exhaust manifolds but headers and dual exaust free up a lot of ponies and some mpg with no side effects. Other than 340's sound BITCHIN with headers.
 
"I understand it is entirely up to me. I just like seeing what your thoughts are. Maybe a few internal upgrades and a complete overhaul will be best. Keep it close to stock just a bit refined for more performance. I do not want to do a stroker, It would seem like sacrilege to to do that to a nice original setup like I have."


Yes use your best judgement, if you have a numbers matching engine and you are into that kind of thing, pull out the original and use a different one to stroke.
 
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