318 dodge to a 340 dodge


i have a 1990 dodge dakota with a 318 and was woundering if i could take the 318 out and put in a 340.


Yes you can. The LA blocks 273/318/360/340 are all identical. The only difference that I am aware of is that the magnum 318 (5.2) oiled through the push rods instead of through the rocker shafts. The lifter angle was also changed to accomodate roller lifters. The external block is identical. All holes are in both blocks and it is exactly the same size and shape externally.

What year 340 are you using?



1970 block that is puting out 450 hp

also do you know it the trans in there is a 727 toruqeflite?


how many gears in a dodage dakota in the 1990 trannys


The trans in your truck is probably an A-500 aka 42RH (4 forward gears - 2=“torque capacity” - Rear wheel drive - Hydraulic).
If memory serves the A-500 is a modified 727 with an overdrive. I am not 100% positive but maybe OK4450 or Transman will chime in and correct me.


I can’t correct you because my memory is too fuzzy on this. It seems to me that Dartman is correct about the A-500, although I was thinking there was another version of it that was used behind the V-8s; an A-518 maybe???
Transman would be the ultimate authority on this unless I ask of a friend of mine who has been a trans guy for almost 40 years.

That 340 is a whale of a motor even stock. Are you sure the driveshaft and rear axle are going to survive this?
(I don’t remember which axle they used on this truck, but it’s not likely one meant to be abused by that much horsepower.)


You must live in a area that doesn’t require emissions testing…

I have a feeling traction will be a BIG problem…


I know the A-518 (46RH) was available but I thought it was used in the full size dodge with the 5.9. Again I could be wrong!!! Where is transman when you need him.
As far as the 340 my 69 produces about 400 hp. I have a completely rebuilt 727 behind it with an 8 3/4 suregrip rear end. The first time I got on it a little bit I busted a u-joint (can not believe I didn’t replace them). Makes me wonder how that little 7 1/4 Dakota rear-end will hold.


I used to have a 69 Super Bee and twisted a few U-joints out of that car, including a new one. Funny thing is, the 68 Roadrunner I had got hammered a lot harder and never shucked a U-joint.

The auto trans will provide a cushion of sorts and the 7 and 1/4 may hold up under some abuse, but my guess is that if it gets beat a lot it’s going to peel some gear teeth or splines eventually.

On the other hand, there’s a guy near here who road races with a turbocharged Merkur XR4 and he’s using the stock 3:38 ratio, 7 and 1/4 Ford rear in that one with no problems. And 21 PSI of boost on the turbo too.


for the rear end i have a 8 3/4 3.23 sure grip to repaces it.


I will narrow the 8 3/4 rear-end and use hemi u joints. As far as traction, lots of sand and big meats will take care of it!


Ballast is for sailboats. The secret to acceleration is light weight. Removing weight is cheaper than creating horsepower and is just as effective.


ya but if you have no traction then why take the wight out?