Check out my car and talk to me about 318/340 swap

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J

jrjones

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Hey folks! First post here! My dad and I start rebuilding this when I was 16. We just finished last year. It has the original 318 with 360J heads and an edelbrock 4 barrel carb, bigger cam, original 906, 8 1/4 rear end and discs up front.

After we finished building the engine and tranny and getting it set in place and other stuff built around it, we found a X heads 340. The guy we got it from said the number on the block matched to a 69 charger. He had just pulled it from an 80s ram charger.

So now that I’ve been able to cruise with it for a bit I’m starting to think “what if” about the 340. Assuming everything is good in the engine (or I have it rebuilt) it should bolt right in place on the 904 right?

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think youll need 340 specific motor mounts....other than that its a swap! what size valves in your j heads? if there 2.02/1.60s thay just as good as the X's,.. then its just 22 ci difference if your 318 is stock bore! but it be wayyy cool to have a X headed 340 in that pretty A body you got there!
 
Never put a 340 in a 69 Charger. It all depends on if you are happy with the 318. You could always take your time, build the 340 while driving and enjoying your car. Then if you get bored with 318 swap it out.
I think thats correct on the motor mounts.
 
I'm not a B body guy, but I'm pretty sure the 340 wasn't available in the '69 Charger... A body only at that time.
Swapping it in place of the 318 is easy as falling off a log. Use the 318 motor mount brackets- passenger side bolts right on, driver's side needs a ~1/2" spacer (stack of washers works just fine) between the bracket and rear mounting ear of the engine. Or dig up a 340 driver's mount. Drop it in.
If it truly is a '69 340, you'll need to swap the timing cover and cast iron water pump to the '70 and later timing cover and water pump for your Duster (the inlets switched sides), and you'll need to either remark your balancer or get a post'70 neutral balancer (timing marks also switched sides). Alternatively, get a pre '70 radiator.
Flexplate and convertor will switch right over from the 318 for the 904.
 
Ummm...I don't recall a 340 being available in a '69 Charger but if it is a 340 you should do it IMO.
 
Thanks for the info yall! I’ll have to run the code on the block when I have time to verify that.
 
Juz' sayin but in "about" 73 I swapped a 71 340 into my 440-6 70 RR body. Something Chrysler should have made, I might add
 
You can use the 318 mounts on the 340. RH mount fits from 318 to 340/360 as a direct bolt on. The LH 318 mount bolts up on the front 2 340 engine "ears" the aft ear on the 340/360 is moved forward a little but hole bored in it is in the same spot. Measure the gap, and add a spacer and a longer bolt. Heres a pic of a LH 318 spool mount on a 360 block. How it mounts to the engine is the same. Note the spacer and longer bolt to take up the difference. Or you can hunt for a 68-72 340 A body LH mount, and pay a small fortune for it.

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Do you know the compression ratio of the 318? I had a teener with 340 x heads and it ran out of steam at 100 mph. Just not enough compression to push the car faster. Make sure you are getting the most out of your 318. Building a 340 can be pricey. If I was to build a more powerful engine, I would build a 400 big block, more power and not all that much more money.
 
Don't do it! Just leave the 318. I've said this on here before but ill say it again. When I was young I wanted to v8 swap my slant 6 dart. And a wise old man told me "only a fool would pull a perfectly good running engine" he was right and although I didn't pull the slant when it was "perfectly running" I ended up blowing it up and v8 swapping it. And as much as I love my 360 now I sure do miss that slant six I would love to have another abody with a slant six in it again. Im sure you would miss that 318 eventually too.
 
Make sure of the year on the 340..... Some were externally balanced and you'd have to accommodate for that. Your 318 would be neutral balanced, so the converter would be wrong for an externally balanced 340.
 
72 I think it was when cast crank 340s came out, but at this point in time its anybodies guess what crank is in there now until you pull it apart.
 
If the owner of 340 says it's from a 69 Charger check it over CLOSE before buying.
Nice car!
 
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dartfreak75 said:
Don't do it! Just leave the 318. I've said this on here before but ill say it again. When I was young I wanted to v8 swap my slant 6 dart. And a wise old man told me "only a fool would pull a perfectly good running engine" he was right and although I didn't pull the slant when it was "perfectly running" I ended up blowing it up and v8 swapping it. And as much as I love my 360 now I sure do miss that slant six I would love to have another abody with a slant six in it again. Im sure you would miss that 318 eventually too.
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i can see saying that with a 318 but not a slant. nothing more boring and slow then a stock slant.. best thing i ever did to our dart was trash that slant for the 360. if it was an original 318 car i'd probably of left the 318 and slightly modified it to where i wanted but there was no way that the slant was ever going to satisfy me.
 
Theres a reason why I call them a "slant sux" because unless really souped up, they suck. Chrysler coulda made the back of em the same as a V8 bellhousing and saved us the extra hassle of finding V8 transmissions for swaps
 
abodyjoe said:
i can see saying that with a 318 but not a slant. nothing more boring and slow then a stock slant.. best thing i ever did to our dart was trash that slant for the 360. if it was an original 318 car i'd probably of left the 318 and slightly modified it to where i wanted but there was no way that the slant was ever going to satisfy me.
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I guess it depends on the individual. And the mindset of the individual some people's priority is a tire fryer and getty up and go others just love the nostalgia of an original classic car the way it was back in its day. My priorities have changed thru the years. I guess it also depends on how many cars you have lol.
 
dartfreak75 said:
My priorities have changed thru the years.
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so have mine.. they went from lets go fast in a straight line to nice and peppy and handle, stop and drive nice.. slant six was in the car for the first 6 or 7 years we owned it.. hated driving it because it was so slow and boring. 360 was night and day difference.. it now has passing power and doesn't take 3 miles to catch up to traffic..:) still has all the nostalgia of a classic car. hell most look at it and think its all original. still wearing its original paint.. just not the original driveline..
 
318willrun said:
Make sure of the year on the 340..... Some were externally balanced and you'd have to accommodate for that. Your 318 would be neutral balanced, so the converter would be wrong for an externally balanced 340.
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(Some) Late ‘72 & all of ‘73

moparmat2000 said:
72 I think it was when cast crank 340s came out, but at this point in time its anybodies guess what crank is in there now until you pull it apart.
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IDK why they changed the balance over for the 1 year only 340, but very late ‘72’s were also done this “odd” way.
 
i'd sell the 340 to a numbers matching guy who 'needs' it and use the cash to add a 390 stroker kit to the 318. you can upgrade the heads later as that's an 'in situ' job. the stroker kit will give a bigger bang for the buck than the 340, it's just a simple matter of inches (which give torque). 22 extra or 70 plus, i know what i'd do.
 
dartfreak75 said:
I guess it depends on the individual. And the mindset of the individual some people's priority is a tire fryer and getty up and go others just love the nostalgia of an original classic car the way it was back in its day. My priorities have changed thru the years. I guess it also depends on how many cars you have lol.
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I agree to a point, but a stock 318 2 barrel at least has a decent amount of pep, a slant sux is like a stock air cooled 1300cc VW bug. Anemic as hell. BTW those air cooled bugs suck too. I had a 66 coronet 2 door hardtop with a slant sux. ****** couldent get out of it's own way.
 
dirty white boy said:
think youll need 340 specific motor mounts....other than that its a swap! what size valves in your j heads? if there 2.02/1.60s thay just as good as the X's,.. then its just 22 ci difference if your 318 is stock bore! but it be wayyy cool to have a X headed 340 in that pretty A body you got there!
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There's more to it than the 22 cu inch difference 318s have lousy heads...low compression etc. Sorry had to chime in saying the only difference is 22 cubes is a misstatement. When talking LA 318 vs 340 stock for stock.
 
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