Difference between a 318 and 340

[MoparDuster340]

I am thinking about turning my 318 into a 340 but i would like to know what is
the main difference between a 318 and a 340? thanks

[tonys]

the bore of the engine.......340 is 4.04 the 318 is 3.91

and no you can not bore the 318 large enough to get to a 4.04
bore............most you can get is 3.97 which is a .060 over 318

"MoparDuster340" <mopardu...@aol.com> wrote in message
news:20000212104356...@ng-cq1.aol.com...

[Barry Lee]

The 340 uses a similar 3.31 crank (they can interchange) but a 340 has a .130
larger bore so if you bore your 318 .060 (the absolute max) you would get to 327.7
cubic inches. The big difference is the heads with bigger ports, bigger valves,
bigger runners and the one down side bigger combustion chamber (lowers
compression). but mill the 340 head .060 and the compression's back with the
higher flowing (more horses) heads. A low buck approach is to bore you 318 and
freshen it with 1968 style pistons. Then buy a set of 360 heads (very similar to
the 340 with smaller valves) mill them .060 and a valve job use a decent cam (not
two much now!), aluminum intake and a holley 3310-750 vacuum. don't worry about
over carbing as you run on the front two barrels and its secondaries are vacuum
actuated and only come in at high rpm where they are needed . Lighter springs can
be bought for the secondaries allowing you to taylor the opening time and rate for
optimum performance. A little port matching and bowl porting before the valve job
would go a long way. 1 5/8" headers 2 1/2" dynomax exhaust (flows as good as the
noisy ones but is quieter and keeps the man of your ass)

You can have close to 340 performance out of your 318 as the engine is just an air
pump and the 340/360 parts will let you optimize this with just a few less cubic
inches. I used a similar combination on my old truck but with too much cam
duration and it really kicked ass once it got rolling. Use something in the range
of 220 to 235 duration at .050. ( multiply mopars advertised duration by .850 to
get dur at .050) (example their 280/280 dur 474/474 cam is 280 * .850 = 238 at
.050 not a bad choice but the 268/272 dur .450/.455 cam would be closest to old
340 street performance at 268 * .850 = 227.8 and 272 * .850 = 231.2 would work
best with a 2200 to 2500 stall)
lots to decide?

Barry A. Lee

[Shield Wolf]

A huge difference is the heads. The 340's flow so much better.

Randy

MoparDuster340 <mopardu...@aol.com> wrote in message
news:20000212104356...@ng-cq1.aol.com...

[Clarence Lambert]

The main difference is that with the 340 installation is a direct bolt in
interchange on the 340. Early model, late model small blocks have the water
pump outlet on different sides. Late model on the right, early model on the
left.

[amgt...@gmail.com]

There is one way to make a 318 into a 340 and that is machine all the bores out and insert new sleeves and machine then to a 4.04 inch bore. Can be done but can be costly also

[gary v]

On Tuesday, July 31, 2018 at 5:36:47 AM UTC-5, amgt...@gmail.com wrote:
> There is one way to make a 318 into a 340 and that is machine all the bores out and insert new sleeves and machine then to a 4.04 inch bore. Can be done but can be costly also

You can bore the 318 .90 over fact.