Here I are, Don K Dulmage

 donald.htm

 big-d

THE 380 CUBIC INCH MOPAR

For years we've been building 340s and 360s and while they are great engines they

have had a disadvantage in the size department compared to the small block Chevy.

The most popular combination for them has been the 383 version that is made by

placing a 400 small block crank into a 350 block. 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

 

While we have almost a complete machine shop on site it is primarily for my enjoyment.

Our main work was for many years General repairs and Tune up. Here we had a64

Plymouth Max Wedge in for a tune-up and set-up. Other than my own 63 Dodge

which is a 426 Track Wedge (single 4bbl) anyway I figured this would be the only one

we would have in here now that I am retired so I took a picture of it. It belongs to Glen

Cole of Wooler Ontario who is an "old" friend. (53 to be exact)