One Big Head
What can you say other than it's heavy? No one makes an aftermarket head, so we'll have to make do the best we can. Angie at Mopar Engines West does all the head work in the shop, and maybe she can squeeze some flow out of this boat anchor. It's going to take quite a bit of time with the grinder, but we'll give it a try.
The Intake Manifold
Fuel distribution is a problem for any race engine, but the Slant Six pushes the limit with this issue. Don't consider using EFI for improved power alone. A well-tuned carburetor will make as much power as EFI. Port-injected EFI will make a little more power because manifold fuel-distribution problems go away, but since most race manifolds are already good, there's not much to gain. Usually, we are talking about a V-8 or a Hemi engine, but the Slant Six might be an exception. The Slant Six's fuel distribution is so bad in stock form, that we wondered how much more power was actually on tap if they switched it over to a port-injected F.A.S.T. EFI system. To find out, we figured we could make a few pulls on the dyno with a carburetor, and then switch to EFI while it's still bolted fast. Nobody has ever done that before.
The Short-Block
There are two crankshafts that were used in the Slant Six. A forged unit was used from the '60s and into the '80s, but then a lighter cast crankshaft was used. The key word here is lighter. We figured the cast crank would be plenty strong enough to handle the power we were after, so a cast crankshaft it is. This is normally 180 degrees from what anyone would normally do when considering a race engine, but again, a cast crank should be adequate for the anticipated power level. The cast crankshaft also has narrower rod journals. This will also help the power level by using narrower bearings thereby reducing friction.
Since we decided to use a custom connecting rod already, we will use a custom forged piston, as well. We want to minimize the piston's skirt length by shortening the compression distance. Also, we might as well use a smaller wrist pin. When the piston decision was made, we then knew what longer custom aluminum rods were needed to match them. But now we are creating problems for ourselves because the bore size on a 225 Slant Six is so small (3.4-inches) that the rods are most likely going to hit the bottom of the cylinder bores. Aluminum rods make this even worse because they are usually much wider at the big end. The solution we came up with is a tad expensive, but we figured we could cut the crankshaft, making the rod journal sizes smaller. Now we could make the outside dimension of the big end of the rod smaller. While we're at it, it also allows us to offset grind the journals to gain a little added stroke. After all, nobody makes a stroker crankshaft for a Slant Six.
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