Coronet 440-340

We have a 1968 Dodge Coronet 440 2dr
hardtop with 57,000 actual miles. It has a
318 with 2-barrel carb, and automatic. It
runs great, just a cruiser. We’ve changed
the gears from 2.76 to 3.23, Sure-Grip.
I have a 1973 stock 340 engine in need
of an overhaul. The heads are “J360s”,
with 1.88˝ intake and 1.60˝ exhaust valves.
The intake is stock castiron (4Bbl) and the
crank is also cast iron (or so I am told).
Question: should I have the heads
redone and put them on the 318, along
with a different cam and intake manifold,
or will I gain more power by rebuilding
the 340? What type of cam, intake, pistons,
and carb would you suggest I use?
Money is tight!

Normally, since you sound like you’re interested
in a street-machine type project, I
would say to go with the 340 (or, even better,
especially in a heavier car, a 360). 22
cubes is…22 cubes. But, in this case, since
the 318 is so cherry, and the 340 is toast,
your headswap plan makes sense, especially
when dollars are a factor. This also
negates balance issues (the ’73 340 was
cast crank—externally balanced).
The stock 340 intake and TQ carb are
fine on the 318 (with the J-heads). You’d
probably want a cam with something on
the order of 270º advt. duration, tops.
A set of ’68–’70 340 exhaust manifolds,
or a set of small headers, will
complete the package.
Keep the 340 shortblock stashed, of
course. Years from now, when the 318
gets smokey, rebuild the 340 and drop it
under the heads—or find a 360.