(HMCC Web Editor's note: One of the best things about the Web is it allows people to work together across time and geography. Dan Stern wrote to add some details to Bob's original article. I've included Dan's comments using a * symbol and italic text.
...This [article] will deal with the venerable slant six,
and its history. My friend Howard Fischer describes the slant
six as the 300,000 mile motor. The
machine shops don't see many of the engines because they run forever.
Most of you who know me, know that I lean toward the musclecars.
Most of you don't know that my daily driver is a 1963 Dart GT.
There was no V-8 option in the A-body until 1964. That makes mine
a 225 cubic inch slant six. It was found in a shed in Sebastian,
TX. It had not been started in 5 years. Gas down the carburetor,
new battery, and light the fire. After removing the gas tank,
and cleaning the sludge, new front brakes, set of used tires,
over 10,000 miles have been put on the car/engine with only new
plugs. No rebuild, no oil burning, no leaks no trouble.
The slant six started life as a 170 cubic inch replacement
for the old flathead Mopar six in 1960.
* [T]he 170 and the 225 were both released simultaneously in late
1959 for the new 1960 cars.
New overhead valves, rocker
shaft setup, solid lifters, individual porting for each cylinder,
gently curving exhaust and intake manifolds, and a somewhat strange
30 degree slope to the passenger side. Everyone who looked at
the engine said that it looked like it was slanted to the
side. It was a name that stuck the slant six.
* Chrysler Engineering came up with the term in early 1958 during
preliminary design of the Slant-6.
170 cubic inch version had a bore of 3.40 inches and a stroke
of 3.125 inches. The rod length was 5.7 inches. The main reason
that the engine was tilted to the side, was to allow the water
pump to be positioned to the side of the engine. This made the
overall length shorter. You can run outside and look at yours
to confirm this after reading [this]. another bit
of trivia, the first production car to receive the slant six was
the Valiant prototype.
* The first production cars to receive the Slant-6 were
the 1960 Valiant, the 1960 Plymouth, and the 1960 Dodge Dart series.
Again, this was all simultaneous. Also note that the '60 (and '61) Dart
was not the compact, but was an intermediate car.
This was not a Plymouth Valiant. The original
Valiant was proposed as a separate car line. The prototype Valiant
also received the first alternator in the entire auto industry.
* Prototype means it's not a production car. The 1960 Valiant was not a
prototype. It was a Valiant (by Chrysler), and not a Plymouth Valiant,
but it was not a prototype. In addition, it wasn't the first alternator
in the entire auto industry. It was the first use of the alternator as
standard equipment in a regular-production automobile. Alternators had
been used for several years prior in heavy-duty (police, emergency, etc.)
vehicles as an option.
In 1961 Dodge brought out the Lancer. Along with the Lancer,
came a somewhat useful item. The 225 cubic inch slant six from
the big car line of 1960. This engine featured a one inch stroker
crankshaft. This made the bore the same 3.40, but the stroke was
increased to 4.125. Talk about torque. There is also a third version
introduced in 1970 that displaces 198 cubic inches. The bore again
remains at 3.40, with the stroke at 3.640.
I can't tell the whole story, without mentioning the performance
aspects of the dependable engine. In 1960 NASCAR sanctioned a
race for the new compact cars coming out of Detroit. Chrysler
had developed a Hyper-Pak version of the 170 cubic inch engine.
It featured a four-barrel aluminum manifold, cast headers, milled
* The head was not milled. The full-race version of the Hyper-Pak featured pop-up pistons.
and hotter cam. The advertised horsepower on the Hyper-Pak
170 was 148 ponies. Seven Valiants were entered in the race. They
finished 1,2,3,4,5,6, and 7. Not bad for a first showing. Oops!
I almost forgot to mention that the lap speeds at Daytona International
Raceway exceeded 130 MPH. Next time you get close to a Valiant,
look at the frontal area. Imagine the power needed to push this
thing 130 MPH! The calculations work out to almost 200 horsepower
from 170 cubic inches. The 225 received the Hyper-Pak treatment
* The Hyper-Pak was never a factory installation; it was sold as a parts package over the parts counter from Day One.
and was advertised at 198
horsepower. The intro two barrel
273 had an advertised rating of only 180 horsepower, when it came
along in 1964.
The dependability and economy role of the slant six continued
for many years. It was the six cylinder engine up
* 1986 in domestic trucks
The last service was in the truck line. The economy
of the engine was demonstrated in the 1975 Feather Duster, and
the Dart Light.
* 1976 only.
These cars featured aluminum front panels and
* Aluminum hood and trunk inner bracing and bumper brackets, only. All the
other sheetmetal and parts were stock steel items.
a four speed overdrive transmission,
* or Torqueflite automatic, per customer choice
and a 225 slant six
engine. The EPA rating on these cars was 36 mpg highway. This
is the highest rating ever achieved by an American six cylinder
For those readers who want the swap information, here it is.
The 225 crank can be put in the 198 block with the 225 rods. The
225 crank WILL NOT fit the 170 block.
* Not without modification to the crank and block, anyhow, but it has been
The stroke increase
hits the block. All three engines share common pistons. All three
have different rod lengths. The last forged 225 crankshaft was
produced in 1976. The displacement identification is on the top
right side (passenger) of the block, near the front. The number
is clearly marked ... 170, 198, 225 etc., just below the head.
* This numbering system is only used on later (sometime in the '70s and
later) Slant-6s, and this location for the number was only used until
about '78 or so, when it was moved to the rear of the block. Other
numbering systems were used from '60-'7x, and the '60 engines were stamped
in one of three different places.
Any cast crank will be indicated by the letter E, following the
displacement (225E). Any reader needing more information is welcome
to call or write. Thanks for the time.
Gary Hamel, HMCC Web Editor
July 12, 1997
Updated, November 11, 1997; April 16, 2006
Return to the HMCC Tech Page
Return to HMCC Home Page