is anyone running this combo??? i have everything except for pistons thats why i want to try this has to be on pump gas so trying to keep comp 10.0 or under any suggestions other than build a 360 ?? thanks

it's an odd combo, not many people running it, but I think it was a fairly common swap before stroker cranks were so readily available. Pretty sure you're going to have to machine the mains down on the crank and go with custom pistons.

You'd want to source a piston with ~1.687" CH & would likely need a substantial dish to keep the CR reasonable along with the proper dia of course 3.940 (.030 over 318)

Previous post about stroking 318s

https://board.moparts.org/ubbthreads/show...part=1&vc=1

I built a 341" 318 a couple years back using the mp 3.55 forged 8 bolt crank and 6" mopar aluminum rods and the off the shelf KB flat top 318 pistons. It came up right at zero deck so with only another .03 of stroke that combo should work well too if you go that route. Motor made great power and reved much faster than a factory 340.

http://www3.sympatico.ca/big-d/MYWEBPAGE.htm

Sample quote

For us Mopar folks all we had
available until now was what is known as a Hoover engine (after Chrysler engineer
Tom Hoover who developed it). It involved boring an early (thick wall casting)
360 block to accept .030 + 340 pistons. There was a fair amount of machining
involved in getting the pistons to clear the crank and chamfering the edge of the
crown of the piston to clear the combustion chamber but it was not particularly
difficult work for someone with even high school machine shop skills to do. The real problem was balancing. Since the 340 piston weighs a whole lot more than the
360 piston coupled with the fact that the 360 crank is a cast crank and already
requires external balance it was a real nightmare (but not impossible to balance
these engines properly). Now I know all of these problems can be overcome
with huge amounts of cash or special engine kits but our main focus here is to
develop combinations that can be duplicated anywhere in the average automotive
machine shop so the high dollar route is out of the question.
It was while freshening one of my old Hoover engines to lend to a friend while we
serviced his big block that I realized we were going about this backward. If a 360
crank was installed in a 340 block the whole picture changes. Early 340s will
handle a .060 overbore and pistons are readily available. I sent out a 360 crank to
have the mains reduced to the 340 size. At the same time I asked to have the rods
offset ground .020 which yielded a stroke of 3.600. With the bore at 4.100 and the
stroke at 3.600 that yields 380 cu in. I discovered when the pistons were machined
the necessary amount their weight was very close to the original 360 pistons making
balancing a snap or even an option. This engine is currently being developed and
if there is enough interest I will keep it posted here.
Last fall I sold the prototype parts and block to Mark Rendal who is a skilled general machinist. He has a car to put it in which I do not and the ability and interest to finish
the job. I will be interesred to see how he makes out.
E-Mail me at "big-d@sympatico.ca

the skirts on those pistons will need to be machine so that the 360 journals do not hit them...

also with no valve reliefs..your cam lift is going to be limited.


http://www.forabodiesonly.com/mopar/showthread.php?t=211511&highlight=347