Chrysler's potent little Slant Six definitely gets no respect! Sure, one of them shows up every now and then, but how many of us have thought about building one for racing? If you do, and want a better e.t, you could always bolt on a supercharger or nitrous, but what's the little beast capable of doing in normally aspirated dress? We know you're saying, what's the point, it's still a six-cylinder? The first strike against it is the rotating assembly is known to be rugged, but heavy, limiting rpm. And that intake manifold . . . . If you were a group of air/fuel molecules you wouldn't like making those sharp turns at the base of the carburetor, and then that long run to the cylinder head. Also, no two runners are the same length, and fuel puddling is common. Then there's that cylinder head-beefy, but not exactly free flowing.
Some guys really enjoy racing their Slant Sixes, and we were curious about what more could be done to one. When Romeo Furio started chatting with Mopar Engines West (MEW), the discussion yielded blank looks from the engine builders. Why would anyone build a normally aspirated Slant Six for racing? Since Romeo is a starch proponent of Slant Six racing, he sent MEW a 225 engine for dissection. The base engine for the build was a mess, and soon it became obvious there are some inherent limitations.
Compress ItThe basic Slant Six has always done well with its 7.5:1 compression ratio. But the good news is the head has so much material in it that whacking off 11/410 inch or so from the surface would be possible (We're not kidding). The math said with a flat-top piston, this combination could yield about a 13.0:1 compression ratio by shaving the heads surface and removing about five pounds of cast iron.
The Rods And SlugsThe Slant Six has a long-standing reputation as being virtually indestructible. One reason for this is the pistons, which have such tall skirts they actually look like beer cans. Slugs would be a better name than pistons. Sure you can have a lighter custom piston made, but it would still be a slug because of where the wrist pin is located in order to use a stock rod. The block's deck height and the rod length fix the compression distance. We got to thinking, what if we spring for a set of custom rods, would the change be worth anything?