318 Mopar vs. 340 Mopar

[goatboy]

I have a 71 dart with a 225 slant 6. I am thinking about putting a v8 in it. After looking at what it would cost to build the 225 I think I might be happier with something bigger. What I am looking at right now is going with a 318 or a 340. Could someone tell me the benefit or difference between the two. Thanks

[DERICKS]

The 318 is more readily available, cheaper and most performance parts are applicable. The 340 is what I have and would not trade but I have been lucky in having a core lying around. For the money and availablility why not build a 360 for the extra stroke and cubes??? makes a good torquey street motor all the way up to a nice race piece and easier to find than a 340. I guess it all depends on your cash flow, what you may have lying around in parts, and what performance you are looking for.

[340butterduster]

340 are scarse and getting pricey, 318 are abundant and cheaper. If you want more power go with a 360.

My .02.
Giles

[70dart]

There's quite a difference here is two links that will help to define the differences
http://www.allpar.com/mopar/318.html
http://www.allpar.com/mopar/mopar340.html

[mooser]

I was also debating this. (with my 74 duster 225 slant six).

I decided to go with the 318 because, with the 340 or 360 you are going to need an 8 1/4 rear end and with a 318 you can use your stock 7 1/4 and also as mentioned all the parts and the actual motor itself are cheaper and easier to find than the 340 stuff.

hope my 2 cents helps

[goatboy]

thanks guys I am so glad the internet is here, You guys have been alot of help. I think I will keep an eye out for both the 318 and a 340 see which one comes my way. Thanks again

[69 Valiant Kid]

goat boy, i have a 340, i was originally getting a deal, engine and trans for $1200. i had to do 1000$ in machine work. if i had to do another one, i would build the nastiest 318. just because thats the kinda guy i am. and having 450hp out of a 318 would be sweet. but youd be spending money their too. the small blocks just fit better than the big blocks as far as making things fit in and around components. if you want headers and such.

[yellowdartdave]

Gain some torque.... do a 360!! 40 cubes more than a 318 means more bottom end, etc.

[rumblefish360]

Well, it boils down to what ever comes your way first? Then I'd wait for a 360. I did a 318 in my '74 Duster and I'm not complaining an Iota, but it is hard to ignore a 42 cube jump and most of it all is in torque.

The 340 is an expensive item to get just in the block itself.

IF you get a 318, you can get them to move well. It'll just move a whole lot better with a 360. The only thing a 360 can do that a 318 can is get better mileage (on equal parts of course)

318 pistons are a tad higher than a 360's. All else is equal really.

[mooser]

Am i the only person that realizes he has a /6 car so probably has a 7 1/4 rearend therefor if he gets a 340 or 360 he has to upgrade to at LEAST an 8 1/4 while if he gets a 318 he can use his 7 1/4.

[Wilnutt]

if i were to do if all again, i would look into a fuelie 5.2, or 5.9

[66dartgt]

Mooser, no disrespect intended - but a mildly built 318 will blow up a 7 1/4 just as easily as a 340 or 360. Trust me, I know - I did it once in an old diplomat.

[abodyjoe]

Originally Posted by goatboy

thanks guys I am so glad the internet is here, You guys have been alot of help. I think I will keep an eye out for both the 318 and a 340 see which one comes my way. Thanks again

don't forget about the 360. easy and cheap to buy and the longer stroke helps in the TQ which is great for the street. just as easy to bolt in as a 318 or 340

[6pk2goDemon]

The 340's are getting very pricey to come by and to build. Remember they haven't been in production since '73.

If you're doing a street car, the 340 pistons are nearly impossible to find at any compression less than 10 to 1 or higher. We looked for 3 months or more just to find new forged 8.5 comp pistons for our 340 Demon. We wanted street use w/ pump gas.

I like the 360 idea as others have suggested. 2nd choice would be the 318

Just my opinion.....good luck w/ the build.

[Longgone]

318`s were really not built around performance, most are lo-po 2 barrel engines while 340`s (68-71) came with 10.5 to 1 compression, windage trays, forged steel cranks, double roller timing chains, 2.02 intake valves, 3/4 cams, HD valve springs, and dual plane intakes. I`m sure I`ve overlooked things too, but you get the idea. No matter which engine you choose to replace your slant 6 with ,whether it`s a 318, 340, or 360 you will need to build the rest of the car to match. The car will get heavier, go faster, and handle less nimbly so an upgrade to brakes, cooling, suspension, and other drivetrain parts will/may be necessary. My vote would be to find a 360 as a building block. They`re still easy to find and have a lot of potential. Figure in some extra bucks though for upgrades to the rest of the car.

[grimreaper]

My first vote would be for a 340 stroked to 416. (All forged and wild!) My second, and way more feasible, vote would be some version of the 360. More commonly available and cheaper to get good street power from. Third would be for the 318. 318s can and do make great engines but will cost you more for a similar result with the 360. 360s are probably the easiest to get your hands on too. Have you read this before????And, as has also been mentioned, figure on an upgrade in the rear axle department as well. A decent running 273 will rip the pinions out of the frail 7-1/4.

[340sFastback]

The torque of a 360 is what makes it a great street motor. And the later 360s have the magnum heads and roller cams already installed.

[69 Valiant Kid]

any burnouts and the 7 and 1/4 gears are ghandi, if you will.

[MOPEkidD-3]

I want to build a high-compression 360 Magnum for my '70 Duster in the future. Iron Ram Magnum heads (home-worked), flat-top zero-deck slugs (10.5:1 comp.), Lunati Voodoo cam, and other goodies, hooked to a Passon A-833 OD and an 8-1/4" rear. Of course you could go with something milder, but 360's are fantastic motors no matter what you do.

[charger70]

I like the 360.
I had a 72 Swinger 360 4bbl mild cam, 904, and an open 2.94 gear 7.25. Where it really shined was on the open road crusin 70-75. And with the small valves and hard seats it ran on 87 cheepo all day long, gettn 18 mpg.
It was my only car for 6 years. Had a hitch on it and used it for towing.
I only raced it a few times but was rough on it on the street, barking the tires into second gear often. Sold it with 140000 on the same rear it came with. If ya want a 1/4 miler ya gotta step it up but for a mild 360 cruizer the 7.25 could last quite a while giving ya time to save up the funds for the tuff rear ya really want.

That same motor ran 14.8 at 93 in my duster with a 727 and 3.23 8.75rear.