340/383 swap question

[74ralley]

Hi Folks, Ive heard different opinions on my question so I thought I would ask here. My car (74 rallyeChallenger) came with the 318 engine, I now have a 73 340 installed. I have come across a nice 383 for what I think is a fair price. Heres the question: if I remove the 340 and replace it with the 383 after the rebuild do I have to change the k frame or just the motor mounts?  I know I have to switch the drive shaft and trans, but what about any other parts like torsion bars ect. Im just trying to figure out which way to go, leave well enough alone and stick with the 340 or down the road switch to the 383? also on a budget so its also a matter of   any help will be much appriciated

[Changin Gears]

The cross member is the same.  You would need a different radiator though, unless you got one of the later big block water pumps that has a right side inlet.  The driveshaft would be OK if you currently have a 727 trans.

[74ralley]

I have the 904 with a hand built torque converter  so I would need a drive shaft also.

[cudax34me]

The brackets that mount to the block are different.The insulators work.As Changing Gears said you need a later model pump housing .If you can find one off a 400 it will work.Also a big block 727.The torsion bars will work but they are designed for a small block. I helped a friend do this in his '72 challenger and in my '70 cuda. 

[swede-cuda]

 :22yikes:keep the 340.thats a really cool engine dont you think?and your car is a small-block car=perfect.so keep the 340,i mean was there ever a low-output 340 made,dont think so,its a keeper.ive got a 383 in my cuda and im not stunned of its power.

[Challenger6pak]

 :iagree:I would stick with the 340 if you are going to drive the car alot.  It will handle better with the small block due to less weight.  In my experience the stock 383 and the stock 340 'feel' the same in the Ebody as far as acceleration. When mods are added you may be able to make the 383 faster cheaper due to cubic inches.  A common cheap mod I used to do to the 383 was to put a 440 crank in it.  There are aftermarket stroker kits now available for both blocks.  Right now you already have a good set up. It will cost money to switch to the 383.  If you modified the 340 with the same amount of money, how quick would it be? What you use will come down to application and your preference.

[Changin Gears]

Depends on what you want.  A 340 and 383 make about the same power, but when you open the hood that big block looks better.  Small blocks look small in an e-body.

[Chryco Psycho]

with equal modifications I have virtually never seen a 383 beat a 340 , even the stroke of the engine is about the same

[shadango]

...when you open the hood that big block looks better.  Small blocks look small in an e-body.

   I dont know...I always thought my 318 looked right at home in the bay.....I always felt like the BB seemed like it was "stuffing" the engine bay.....

Dont get me wrong... seeing a BB stuffed in is a sweet thing.....

But I dont think the SB looks too small....My bro lin law has a chevy 1500 pickup and it has the v6 in it....now THAT engine looks small in that bay.....has a rad shroud that must  be 2 1/12 feet deep! You could fit a small family in next to the engine in that huge bay...LOL

[74ralley]

Guys thanks for all the replies! I will probably stick with the 340 but ya never know down the road  the 383 was offered to me last week and Im still going to buy it just to have, the price is more than fair and im going to sit on it untill some of my projects are completed (Chally, other car, and some work on the house) . I have always wanted to build a big block so now I have the chance!  

[71chally416]

Stick a 4" stroke crank in that 340 and get some good heads and you'll never want a big block again.

[Challenga]

Keep the 340.  It will handle so much better in the corners and when you open the hood, people that know anything about Mopars will say "holy cow....a 340"  Just look at what everyone above me on this thread has said.  There is just something about a 340 that makes people's hearts pound.  At least mine does anyway. 

[Chryco Psycho]

you could always drop in a 440 crank & rods & take the 383 out to 430 CI

[Cooter]

4.280 X 4.250 and you'll never wonder if the swap was worth it again...Yee who begins with more, always ends up with more with the same money spent...

[71chally416]

I guess it depends on how much "useable" hp one wants or needs. It's does little good to have a mega cube BB if you just smoke your tires for two gears and lose to Ricers. If controlling the hp you have on tap in a mostly stock chassis is the goal, it's always easier to do with a small block.