340 swap concerns

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marianamaya

marianamaya

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I have a 1974 Duster with a 318 / 904 set up. I am considering swapping my 1971 340 into the vehicle, but I want to make sure that I have all my bases covered.

What engine mounts do I need to use?

The 340 will mate to the 904 with no problems, right?

All of the current 318 underhood components are what I meet for the 340, correct?

8.25 axle should be ok?

Thanks for the help. If I have missed something please let me know

Pete
 
You'll need a drivers side motor mount bracket for a 340/360. Also if the 318 is externally balanced you'll need a neutral balance flex plate. Everything else should be fine.
 
The 318 is an internally balanced engine up thru 1991.
As long as the 340 is '72 & earlier it should work fine.

The left mount can be hard to come by.
I just took to left mounts & made one.
 
Search around here, Crackedback (and others) have detailed how to mod the left mount to fit.
 
marianamaya said:
I have a 1974 Duster with a 318 / 904 set up. I am considering swapping my 1971 340 into the vehicle, but I want to make sure that I have all my bases covered.

What engine mounts do I need to use?

The 340 will mate to the 904 with no problems, right?

All of the current 318 underhood components are what I meet for the 340, correct?

8.25 axle should be ok?

Thanks for the help. If I have missed something please let me know

Pete
Click to expand...

340/360 Spool mount driver's side. I believe your current 318 pass side is good. Easy to source a Schumacher. http://www.engine-swaps.com/

Your 71 340 engine has the same water pump and timing cover setup as on the newer 318. Use the 318 stuff including pulleys if not with the 340. Use the 340 forged crank internal balance harmonic damper.

Starting in 73 model year, the factory axle behind the 340 and 360's was the 8-1/4,
including 4 speeds. Factory did it so you can do it.

904 will bolt to the 340 no problem. 71 340 was internal balance. I believe by 1973 the 318 was external balance cast crank so you may need a neutral balance flex plate.
 
mikedevore said:
The 318 is an internally balanced engine up thru 1991.
As long as the 340 is '72 & earlier it should work fine.

The left mount can be hard to come by.
I just took to left mounts & made one.
Click to expand...
I have an external balance '72 motor. '71 would be safe, '72 is likely external balance. '72 can be build early in June '71.

KosmicKuda said:
Your 71 340 engine has the same water pump and timing cover setup as on the newer 318. Use the 318 stuff including pulleys if not with the 340. Use the 340 forged crank internal balance harmonic damper.

Starting in 73 model year, the factory axle behind the 340 and 360's was the 8-1/4,
including 4 speeds. Factory did it so you can do it.

904 will bolt to the 340 no problem. 71 340 was internal balance. I believe by 1973 the 318 was external balance cast crank so you may need a neutral balance flex plate.
Click to expand...
The last Magnum 318s and everything 318 before them were not external balance. Even cast crank 318s are internal balance. The 340 cast crank actually shares a P/N with some 318 cast cranks- the difference in balance comes from the pistons in why the 340s are externally balanced for '72/3. If it is an external balance motor, it really shouldn't have the flex plate and damper switched if the balance is not altered, that would not be balancing the engine. The external 340s are unique, 360s do not have the same balance. The oddly shaped damper should call out "340 cast crank only" if present.

justinp61 said:
You'll need a drivers side motor mount bracket for a 340/360. Also if the 318 is externally balanced you'll need a neutral balance flex plate. Everything else should be fine.
Click to expand...
If the 340 is external balance it will require a balanced flexplate or the weights put on the converter. All 318s are neutral balance, the only exception is nonstock engines like what someone cheap might've done with a 360 crank.
 
Thanks to all. A little confused still, so let me add this. The 71 340 that o have is a forged crank motor that I had rebuilt. Not sure if it is internally or externally balanced, but I can find out. Does this info effect any of the responses above?
 
marianamaya said:
Thanks to all. A little confused still, so let me add this. The 71 340 that o have is a forged crank motor that I had rebuilt. Not sure if it is internally or externally balanced, but I can find out. Does this info effect any of the responses above?
Click to expand...
An actual '71 motor rather than a '71 build date '72 motor would have a forged crank and be internally balanced the same as all 318s and 273s. Often when rebuilding even the '72 and '73s are rebalanced to be neutral balance and use the more common 273/318 parts.
 
I did the same swap last year 71 340 in a 72 Dart. I used the 318 mounts, just use a longer bolt and spacer for the drivers side. The passenger side mount is the same. You can use the exhaust manifolds, intake and dist. from the 318. I have a 904 lockup in mine bolts up with no issues.
 
marianamaya said:
I have a 1974 Duster with a 318 / 904 set up. I am considering swapping my 1971 340 into the vehicle, but I want to make sure that I have all my bases covered.

What engine mounts do I need to use?

The 340 will mate to the 904 with no problems, right?

All of the current 318 underhood components are what I meet for the 340, correct?

8.25 axle should be ok?

Thanks for the help. If I have missed something please let me know

Pete
Click to expand...
 
Hi Pete. My name is Larry and I live in the Detroit area. (Garden City). I haven't been on the website for awhile and could find the PM (private message) option which I would prefer. I was able to acquire a 71 Dart Swinger from a guy going through a nasty divorce. It's a 318-904 car with all power and AC. The price was right because the wife was ready to call the junk man. Anyway...the front end dress (FEAD) had missing components. The AC compressor and alternator were missing along with the brackets and water pump pulley. Since you're local I was wondering if you had anything I could use. I want to get it up and running so I can get rid of it so I can get back to my other projects. It's an Indiana car. Minimal rust. Lots of bumps and bruises. A perfect 'body man's' car. Let me know if you can help me out. I live a couple blocks from Garden City Hospital. It would an easy drive for me to stop by and see what you've got. Oh yeah...I'm an engine guy and used to run a dyno at the Ford Research and Engineering Lab. Need more power for you small block? How about some bowl ported Magnum heads with 2.02 int. valves for your LA motor? That would really wake things up. That's for another day. Let me know if you have anything to help me out. Thanks.
Larry
 
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