Show your slant 6 a body!

Here's some food for thought....

PART ONE:


Comparison of turbo Slant Six 500 HP build vs.
500 HP 318/340/360 small block build





The following is written in reference to the 225 motor. The 170 is a different kettle of fish.


It would seem that slant 6 motors (remember, this is a 225 thread) were built (though, not intentionally,) to be force-fed air and fuel.
Whether it's done with a supercharger, nitrous oxide, or a turbo, it once-and-for-all, makes an end run around the built-in breathing problem that slant sixes suffer from birth. Because of their small bores, they can never have the kind of breathing that will deliver horsepower in the 1.75 hp-per-cubic-inch range. Not with that original, cast-iron, 2-valve head, at least.

The engine is rpm limited because of the long (4-1/8") stroke, so it's never going to deliver the goods at 8,000 rpm. That's the rpm where most small-block Chevys that are really "built" seem to make big power. I'm talking the small-displacement, short stroke models.

RPM? Forget it.

Because of the fact that the original plans for the slant 6 included an aluminum block (and, the fact that that aluminum isn't as strong as cast iron,) the basic specifications for the slant 6 block were robust, to say the least; they had to be... aluminum needs more mass to be as strong as it needs to be for reliability, than cast iron. Well, the engine that went on to live in Mopars of various descriptions for many years, turned out to be cast iron.

But, the changes in the cast iron version, from the aluminum parameters, were minimal.

That meant that the resulting engine was an unusually strong critter, not unlike a Diesel, in its basic construction.

A forged steel crank with mains the size of a 426 Hemi’s made for an equally-strong bottom end.

Along the way, someone a whole lot smarter than I am, realized that what this all meant was, you could boost the s**t out of this little motor without hurting it. Boost = performance increases!

Tom Wolfe and Ryan Peterson built the prototypes for the engine that is in the '64 Valiant that Freddie and I plan to run. We bald-facedly copied their lead, and we are HOPEFULLY going to run within a second of their cars. There are only minimal differences in their "recipe" from ours. But, they did it first; we're just copy-cats.


In this diatribe, I am going to try to justify why anyone would want to go this route, ($$$$$$$$$$$,) and perhaps point out a few reasons why it might not be such a good idea, after all...


There are (at least) two kinds of people out there; those who just want to go fast, and those who want to go fast and prove something in the process.

Anybody can stick a big engine into a light car with easily predictable results: It's gonna be F-A-S-T!!! Those 440+ cubic inch A Bodies are hard to outrun... and, with good reason! Ma made it pretty easy to drop an RB engine into an A-Body, and beyond getting it to hook, the problems in getting it to go fast are not actually what you'd call "insurmountable." Whoever said, "There's no substitute for cubic inches," said a mouthful!

Senor' Schumacher has made the task of installing a big engine into a Dart or Duster a lot easier, with his motor mounts and custom-fit big-engine-in-a-in small car headers. The appeal is almost overwhelming, if you love "speed."

Some folks, though, look at that operation and say, "Ho Hum... It SHOULD be fast; big block in a small car.... so what?"

Some of those detractors want to produce a fun car with a smaller engine, but not TOO small.. There are the 318/340/360 guys who don't want the hassles that go with the installation of a third-member-breaking big block, but would still like to trim a few Corvettes.

To them, a small-block is the answer; they don't want to mess with a slant six, because 1. They don't like the way they sound, and 2. it's hard to build one that will outrun most Corvettes. They probably have never SEEN an 11-second slant six car. Or, a 12-second one; thirteen second slant six cars are not even that plentiful.... so, they know that they can stick a set of headers on a 340, raise the compression to 11.5:1, go with any one of a hundred different solid lifter cams, and presto," a low 12-second car that will embarrass most street driven anything, Corvettes, included.

Enter the slant 6 turbo, the type of engine that most regular-guy Mopar enthusiasts think is an oddball, weird combination that yeah, may be pretty fast, but has to be expensive!!! Right? I mean, you don't get 2+ horsepower per cubic inch out of a slant six without a ton of costly, cutting-edge technology!

Well, that's just not true.

Let me point out what ~I~ have found out about this turbo six business that has made me wonder whether it might not be actually CHEAPER than building an equal-power small block. Especially, if you already HAVE the /6, but will have to buy a V8.


Here are a few ways that the turbo slant six can be a cheaper alternative to an equally-powerful small block.

For purposes of comparison, let's compare two 500 horsepower engines; one normally-aspirated 360, with time-honored, normal hop-up mods to produce 500 flywheel HP and a turbocharged slant six with equal power.


Lets start with acquiring a rebuildable engine "core."

People give away slant 6's all the time. The one we are attempting to build was, in fact, given to us. It was on its way to the dump, if we didn’t want it. “Free” is always good…

That scenario is also possible with small blocks, but not as easy... and virtually impossible to find a "free" rebuildable 340. But, you don't HAVE to start with a 340; it can even be a 318... but that won’t be as easy. A 500-horsepower 318 is not hard to imagine, but probably would need some pretty good heads, and 12-1 compression. It would also need to be rpm capable, to a large degree. (7,000?)

Not so hard with a 360, but they are not as much in abundance for free, I think. Could be wrong about that. More like $150 for a rebuildable "core."

Advantage, slant 6.

There is more of everything to buy for 8 cylinders compared with 6. Pistons, valves, bearings, rings, valve springs... retainers, keepers...

Advantage, slant 6

The driveability of a turbo slant 6 is not much different from a stocker, in that the main thing(s) that destroy driveability, are radical cams with a fast, ragged idle, and big ports that allow the fuel to fall out of suspension (at low rpm) in the ports, due to low velocities brought on by the size of the ports. The turbo slant six cams don't have much more duration than a stock one, and the ports, even in ported heads, aren't very big.

Advantage, slant 6.

The slant six's that have been turbocharged with high-boost (over 20 pounds,) don't seem to like rpm's and don't NEED rpm's to deliver the goods. Tom Wolfe and Ryan Peterson the two examples I am citing here, both contend that their engines have a de-facto red line of about 5,500 rpm. With such a low red line, the reciprocating stresses, even with a 1-and-an-eithth-inch, stroke, are low enough that these engines will never fail due to bearing loads brought on by excessive piston speed, That is MY opinion; nothing more. Making 500 horsepower from a normally-aspirated small block is going to require that you spin it, probably fast enough to put engine life in jeopardy, if you do it very often.

Advantage, slant six (my opinion)

Because of the relatively low rpm operation of the turbo slant six, the valve train can remain, with stock pushrods and rocker arms, due to the low valve spring pressures required. The money you DON'T have to spend on needle bearing, rollerized rockers, special, heavy-duty pushrods and roller lifters is money saved. Cam life is enhanced because the low-rpm redline make possible the use of mild valve springs that are easy on cams...

Advantage, slant six.

The rear axle ratios in the two quickest A Body turbo slant six cars that I have seen evidence of, are 2.76:1 for the strip AND for the street. The turbo motors are weird, in that the car slows down with normally-"steep" rear gears, such as the 4.56:1 units often found in small-block cars. The turbo motor seems to make more power (not unlike a "fuel" motor) when it is "held back" and not allowed to increase rpm quickly. The significance if this is, the turbo motors also can use the same ratio for highway driving AND drag strip action. The small block "built" motor wouldn't think much of a 2.76:1 rear end on the drag strip, nor would it perform up to its potential, with a 4.56:1 on the highway. So, if you build a small block and it does double duty, you really need two sets of gears; one for the drag strip and one of the highway. No problem; you can change third members in a couple of hours (or, less.) But, they don't give away 8.75" A-Body housings these days, and neither is it cheap to buy and maintain two sets of third members, with different ratios; one for racing, blah, blah, blah...

The turbo slant six car can easily make do with a "one-ratio-fits-all" rear end. A late model, A Body 8.25" rear end from a junk yard will be lots cheaper (or, one out of an Aspen/Volare car) and will come with highway (and drag strip) gears already in it.... and is plenty strong for this application. More money saved.

Advantage, slant six

Because a high-stall converter is neither desirable nor necessary, turbo slant six converters are going to be cheaper than a 4,000-5,000-rpm unit that would be probably necessary for a wildly-cammed small block. Once again, the street driveability issue comes to light. The tighter slant six converter would not create as much heat as a high-stall, small block unit would, in daily driving.

Advantage, slant six

End of part one...