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hi everyone
I have a 1970 Challenger that had a 318 in it but i have a 340 and tranny for it or a 440 and tranny. i would rather try the 440 conversion into it but need to know what is involved into doing it and what i need to do it. im a beginner but complete any challenge and want to do this right and not cut corners. any advice would be awesome thx steve
 

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340 or 440

As I remember it, you need a heavier duty K frame for a big block. The 340 would bolt right in. The 340 is a very good engine and if it is a 71 or earlier one it should have a forged crank stock. If you just have to have the 440, you can bolt in a heavier K frame though. Must be terrible to have that choice. LOL
 

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Discussion Starter #4
that might be a better choice going with the 340 because im buyin a 68 and 69 charger both have 383s and are in real good condition can put the 440 in one of them getting them both for 5000
 

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Go with the 340 it just bolts right in and you can build it for performance mine puts out 500hp on the dyno. the 440 will bolt in but the K-member will have to be changed along with heavier torsion bars
 

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ditto,you will hv to change k frame and heavier front springs
Misinformation

The K frame in the original Challengers is the same one used for all V-8's (except the Hemi). And there are no "springs". You simply raise the torsion bars for the additional weight. The only time you would need to change the K frame is if it was a six cylinder car. The 440 will bolt right in with the big block motor mounts. I had SIX small block Challengers and bolted a big block into all but two of them.
 

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Misinformation

The K frame in the original Challengers is the same one used for all V-8's (except the Hemi). And there are no "springs". You simply raise the torsion bars for the additional weight. The only time you would need to change the K frame is if it was a six cylinder car. The 440 will bolt right in with the big block motor mounts. I had SIX small block Challengers and bolted a big block into all but two of them.
This is a 100% correct. I have put a many of big block in a small block car, no K member change needed. It is an old misinformed wives tale, that has sold a lot of k members over the years. Correct on the torsion bars also.
 

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What transmissions do you have for the two engines? Both Automatics? 727s I'm guessing. I'm also assuming the 318 is mated to a 904. If the trannys you have are both Autos...piece of cake. 4-speeds are more work to swap to but WAY more fun to drive.
 

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440 engine mounts + 1" torsion bars, hook up the exhaust too while you're at it, and away you go. My 73 started out with a 318 setup, now runs a 440. Feel free to pm any questions...
btw, 440source.com may be your friend! You may also want to upgrade the brakes.
 

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were there different size (front) sway bars used depending on engine (LA vs B/RB engine?) There's certainly more weight in the front end going to the big block from a small block...
 

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Like everyone is saying here very easy swap, k member is the same only 440 motor mounts required, assorted pulleys a B 727, driveshaft is shorter(if 904 equipped), need one from big block, radiator size will need to be increased, distributor in front will require elongating wiring harness. I used a 440 sixpak torque converter, but many other styles available, also good time to add electronic ignition. 8 3/4 yoke is a 7260(ujoint) should swap out to 7290 much stronger, front would require same.
Adding a rear sway bar on 70-71 Challengers is also a really good idea.
 

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Another thing, if you are thinking the 440 you will definately want to upgrade the factory front brakes. The ones in it will not stop a 440. I would suggest an upgrade to the disk brakes. There are kits made that will bolt on.
 

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It is not clear what your goal with this car is, but either the 340 or 440 can make sweet street engines with minor mods and a modest budget. The 340 is going to be around 140 pounds lighter so it will handle and stop better. Mod for mod, the 440 will make more horsepower. The 440 will make tons more torque, most noticeably from 2000 to 3500 rpm.

Here are good baseline builds and dyno results for low budget, mild 340 & 440 from Mopar Muscle. They add some simple mods (intake, carb, headers, mild cam) and show results each step of the way. If you go back thru the full articles, you see the cams are similar and quite mild. This should give you a good idea of what type of power difference you would see in a 340 vs 440, mod for mod. Of course, you can make lots more power than this with either engine, these just give a nice, mild baseline to compare / think about.

1970 340 High Performance Mill Dyno - Dyno Results - Mopar Muscle Magazine

Buildup '69 440 Magnum Engine - Dyno Test Numbers - Mopar Muscle Magazine
 

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If you have a 340 and it's just a fun car to run around in, I'd put that in. I built a 340 very similar to what is in that post above me and it was a stellar performer and very reliable. I put it into a 69 Dart with a 4speed and 3.55 gears. It was my daily driver 4 years in college.

I also had stock 340 6-pack engine/car 70 T/A and that car was a blast to drive stock with a Slapshift Auto. It would not win any drag races, but a very reliable and fun driver.

If you are going to the track, then the choice is obvious. Big Block...

I'd also buy a complete suspension upgrade package from Hotchkiss or someone like that. That stock suspension is just awful. 40years of knowledge has really improved what that car is capable of, and it's not that expensive to make a very good/comfortable street performer that is almost on a par with todays cars.

Good Luck!
 

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what i havent seen mentioned is what i experienced in my own swap;i had to shorten the drive shaft. it was a few inches too long and was double walled which made it a little tricky.you can get the combination u-joint from napa for the differential and yoke.i did upgrade to hemi torsion bars and had to add a front sway bar as my 318 car didnt have one,it requires making brackets on the lower control arms for the end links.nothing like 440 power in a e body! i also added a rear sway bar and superstock springs in the rear with longer shocks, it handles and launches very nice with 3:91s but 3:23s are better if you plan on cruising very far on the interstate
 

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either way you go you need to evaluate the whole driveline, suspension, cooling system, brakes. If you go with an automatic then you'll need a 727; what rear is in the car? That'll likely need to go and you'll also need better rear springs and brakes. Sure you can drop in either engine but the whole car needs to be set up right to be both safe and reliable to perform and enjoy properly.

Pick up some copies of Mopar Muscle magazine. There are lots of after market vendors as well as their website. Look at what other people have done with their cars.What you are really talking about is making an RT clone if you go with the big block. Make sure you understand the total package - it's more than just the engine.

I've had both 340 and 383 Challengers and I preferred the small block. Today these can be stroked and you can get insane power while keeping the weight down and the handling up.
 

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oh, one other thing to consider: that 318 has a lot of potential; don't dump it "just because". There are stroker kits for them and they can make very good HP if set up properly.
 

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either way you go you need to evaluate the whole driveline, suspension, cooling system, brakes. If you go with an automatic then you'll need a 727; what rear is in the car? That'll likely need to go and you'll also need better rear springs and brakes. Sure you can drop in either engine but the whole car needs to be set up right to be both safe and reliable to perform and enjoy properly.
I agree completely. As we've already seen, you can produce lots of power with either a 340 or 440 with modest, inexpensive mods and keep it reliable. What you are may not realize is all the $$$ getting everything else up to speed to have a fun, reliable car. At a minimum you will want disc brakes on the front. I would also look really hard at something like the Hotchkis TVS for your suspension. I would much rather have a car with less horsepower, disc brakes & Hotchkis suspension than a car with a high dollar drive train and insane power saddled with inadequate drum brakes and the worse-than-a-minivan stock suspension.

One look at this video from Hotchkis and you can see why many people will want the 340. This car looks like so much fun! That being said, improving your suspension (and brakes) will be even more important if you put the heavier 440 in the car.


Here is link to Jay Leno's garage and a video showing the suspension upgrades on a lift, then they take it out for a test drive. More fun.

http://www.jaylenosgarage.com/at-the-garage/muscle-cars/1970-hotchkis-dodge-challenger-340-ta/

Summit doesn't show the e-body version of the kit on their website, but you can buy them from Summit (I did) and get a price below list. Alternatively, I may still have a 20% coupon from Hotchkis - if it hasn't expired (can't recall). If it is still good and you would like to use the coupon, just let me know.
 

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One look at this video from Hotchkis and you can see why many people will want the 340. This car looks like so much fun!


That being said, improving your suspension (and brakes) will be even more important if you put the heavier 440 in the car.
Unless you enjoy power sliding...then leave the suspension alone. I vote for upgrading the brakes as an absolute must though.
 
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