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  #1  
Old 12-29-1999, 05:05 AM
deek1965 deek1965 is offline
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I currently have a 318 and have the chance to buy a stock 340. Is the 340 a better engine than my 318? The 340 is supposed to be from a 71 Charger. Is there any way other than the 340 cast into the block under the head to identify the year and what car it came from? If so does anyone know what the numbers should be? Will my trans mount up ok? Can I use the 318 pulleys and balancer? Can I use the 318 torque converter?

Thank you for your input.
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  #2  
Old 12-29-1999, 05:18 AM
cwby cwby is offline
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well where to start...... the 340 is definately the better of the two motors and you should have NO problems doing the swap... they are both small blpcks and use the same mounts and everything....as far as the transmisson goes it will bolt up... the question about torque converter is one i cant answer because the 340 you are bying could have too be balanced from the converter or the harmonic balencer so you need to give more info.... but im sure someone else will address this topic for you... as far as the block numbers go, you should be able to look on the side of the block and it will tell you what year the motor is and what cubic inch the motor is, it is molded on the side of the block, about at the level of the freeze plugs on the drivers side.... good luck with the conversion..CWBY
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Old 12-29-1999, 06:40 AM
Elwenil Elwenil is offline
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I would agree that the 340 is a better engine as there is, of course, no subsitute for cubic inches as we have all said before. If the 340 is trully stock, then your torque converter should be ok to use. 360's were the only ones with the odd balance weight. Of course, if the 340 is not stock, it could have been balanced differently. The casting date on the passenger side of the block should be the year before it was installed in a new car. This isn't always true, but for the most part if your 340 came from a 71 Charger it should have been cast in 1970. If your engine was originally installed in a production car, it will also have the cars VIN number stamped on a small machined boss on the passenger side at the oil pan rail. Of course, if your engine is a warranty block, then this pad will be blank. This swap should be a bolt in deal, although you will need to obtain a new engine mount bracket for the left or drivers side. The 340 and 360 both use this mounting bracket that is different from the 273-318 piece. Good swap!
~Elwenil~ ~.\|/.~
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Old 12-29-1999, 08:16 AM
johnjdodge johnjdodge is offline
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A true 71 340 was statically balanced, solid plain damper and no balancing weights on converter or holes on flywheel. The 72 340 w/auto was a dynamically balanced engine, weights on converter and that special damper that had the cast in words (for cast crank only). A 72 340 w/4spd was still built like the earliers, forged crank, plain damper, but 8.5:1 pistons.
318 engines weren't balanced like 340's. They didn't have any special dampers for "cast cranks use". The dampers may look the same, but be different. Dampers changed at some year ( I can't remeber when) with the pulleys bolts being symmetrical or with 1 bolt hole offset. Keep this in mind.
Mounting tabs changed between the 318/340/360 engines. There are "340" brackets but 360 & maybe 318 brackets can be adapted.
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  #5  
Old 12-29-1999, 12:07 PM
Larry S. Larry S. is offline
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Elwenil is right on this one. You will have to get a left motor mount bracket for a 340/360 as the 318 bracket is a little different. All 340 engines were internally balanced, the same as the 318, so you don't need to change anything as far as the torque converter or harmonic balancer are concerned between a 340 and a 318. I don't know what JohnJ is talking about when he refers to static or dynamic balancing of a motor, they are either internally balanced or externally balanced. The engine balancing process uses both static and dynamic balancing. The pistons and rods are static balanced, and the crank, harmonic balancer and flywheel are dynamic balanced.
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Old 12-29-1999, 04:33 PM
Elwenil Elwenil is offline
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Thanks Larry, I also might add that the mount that is needed is readily available from Schumacher Creative Services. It's a nice welded piece that looks a lot stronger than the factory stamped steel one. I used it on my 72 Charger to swap in a new Magnum 360 crate engine, which by the way, uses the same mounts as the old ones, which is good to know. If anyone has any questions about swapping a Magnum crate engine, feel free to ask me. I ran into just about every problem imaginable with my swap, and know how to fix it.
~Elwenil~ ~.\|/.~
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  #7  
Old 12-30-1999, 01:42 AM
340king 340king is offline
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The cast iron crank 340's were externally balanced. The balancer had the words JohnJ described on it. The balance is different than a 360, hence the need for the wording. The balancer for the forged steel crank engine is also a little different. The ones I have in possession have a small indentation on the back side of the ring. This increased the natural frequency of the balancer to accomodate an anticipated higher rpm range.

As for the year of construction, the date on the side of the block is cast date. The date of use is stamped on the front of the left bank or drivers side of the engine block just below the deck. If you post these numbers, someone here is sure to have the answer to your question.

As for the torque convertor, it should work if your engine has a forged steel crank and is internally balanced.
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