An Insane Number of Mopar Slant Six Engine Specifications
| Journal Number | 1980 3.7-Liter | |
|---|---|---|
| 1 | 2.75' x 0.877" | |
| 2 | 2.75" x 0.877" | |
| 3 | 2.75" x 1.107" | |
| 4 | 2.75" x 0.877" |
The engine had four replaceable steel-backed (aluminum alloy on steel) babbitt crankshaft main bearings. Oil grooves were in the upper half of the bearings, and in the lower half of the #1 bearing. The connecting rod bearings were aluminum on steel.
In most years, closed-circuit crankcase ventilation was used; crankcase vapors were routed to the combustion chambers through a PCV valve located in the valve cover. Vapors were burned before being expelled into the air through the exhaust system.
Oil pressure ranged from 35-65 p.s.i. @ 2.000 rp.m. Crankcase oil capacity was four quarts (one more when changing the filter).
1968 detailed specifications
| Engines | 170 cubic inch | 225 cubic inch |
|---|---|---|
| Carburetor | Single barrel | Single barrel |
| Bore and Stroke (nominal) | 3.4 x 3.125 | 3.4 x 4.125 |
| Bore spacing (CL to CL) | 3.98 (1-2, 3-4, 5-6); 4.0 (2-3, 4-5) | 3.98 (1-2, 3-4, 5-6); 4.0 (2-3, 4-5) |
| Firing Order | 1-5-3-6-2-4 | 1-5-3-6-2-4 |
| Compres. Ratio (nominal) | 8.5 | 8.4 |
| Cylinder Head Material | Cast iron | Cast iron |
| Cylinder Block Material | Cast iron | Cast iron |
| Cylinder Sleeve | None | None |
| Number of mtg. points (Front) | Two | Two |
| Number of mtg. points (Rear) | One | One |
| Engine Installation Angle | Lateral 0°, Up 3° | Lateral 0°, Up 3° |
| Taxable Horsepower | 27.7 | 27.7 |
| Publishing max. bhp* @eng. RPM | 115@4400 | 145@4000 |
| Publishing max. torque * (lb. ft. @RPM) | 155@2400 | 215@2400 |
| Weight (piston only ) oz. | 16.4 | 16.4 |
| Clearance (limits) Top land | .024 min. | .024 min. |
| Clearance (limits) Skirt Top | .0005 - .0015 | .0005 - .0015 |
| Clearance (limits) Skirt Bottom | -.0005 - +.0005 | -.0005 - +.0005 |
| Ring groove depth No. 1 and No. 2 ring | .179 | .179 |
| Ring groove depth No. 3 ring | .181 | .181 |
| Compression Rings | Twist and taper, tin-plated | Twist and taper, tin-plated |
| Oil Rings | Cast iron, steel expanders | 3-piece abutment-type, stainless steel spacer-expander with chrome-plated segments |
| Piston Pins | 170 cubic inches | 225 cubic inches |
| Length | 2.965 | 2.965 |
| Diameter | .9008 | .9008 |
| Type (Locked in rod, in piston, floating, etc.) | Press-fit in rod | Press-fit in rod |
| Type (Bushing, in rod or piston) | None | None |
| Type (Bushing, material) | - | - |
| Clearance (In piston) | .00045 to .00075 | .00045 to .00075 |
| Clearance (In rod) | .0007 to .00014 interference | .0007 to .00014 interference |
| Direction & amount offset in piston | Right .06 | Right .06 |
| Connecting Rods | 170 cubic inches | 225 cubic inches |
| Weight (oz.) | 25.7 | 26.8 |
| Length (center to center) | 5.707 | 6.699 |
| Bearing (material & type) | Lead-based babbitt on steel | Lead-based babbitt on steel |
| Bearing (overall length) | .985 | .985 |
| Bearing (clearance [limits]) | .0002 to .0022 | .0002 to .0022 |
| Bearing (end play) | .006 - .012 | .006 - .012 |
| Carburetors (Valiant) | 170 | 225 |
| Idle speed – Manual* | 750 | 650 |
| Idle speed– Automatic* | 750 | 650 |
| Idle air-fuel mixture* | 14.0 – 14.4 | 14.0 – 14.4 |
| Transmission | Manual, Automatic | Manual, Automatic |
| Carburetors (Make) | Ball and Ball** | Holley |
| Carburetors (Model) | BBS-4414 S (Manual), BBS-4415 S (Automatic) | R-3919 A (Manual), R-3920 A (Automatic) |
| No. used and type | 1, 1-bbl | 1, 1-bbl |
| Barrel Size | 1.56 (Manual), 1.69 (Automatic) | 1.69 |
| Suspension details (Valiant) | 170 | 225 |
| Front spring height by diameter | 35.8 x 0.83 | 35.8 x 0.83 |
| Spring – Rate at wheel (lb. per in.) | 85 | 85 |
| Number of leaves in rear springs | 4 | 5 |
1968 Slant Six crankshafts
| Material | Drop-forged steel |
|---|---|
| Vibration Damper Type | Non-adhesive, rubber, dynamic |
| End thrust taken by bearing (No.) | Three |
| Crankshaft end play | .002 - .007 |
| Main bearing (material & type) | Lead-base babbitt on steel, removable, precision |
| Main bearing (clearance) | .0002 - .0022 specified, .0005 - .0015 desired |
| Main bearing (Journal dia. and bearing overall length) No. 1 | 2.75 x 1.034 |
| Main bearing (Journal dia. and bearing overall length) No. 2 | 2.75 x 1.034 |
| Main bearing (Journal dia. and bearing overall length) No. 3 | 2.75 x 1.254 |
| Main bearing (Journal dia. and bearing overall length) No. 4 | 2.75 x 1.034 |
| Crankpin journal diameter | 2.187 |
1968 slant six camshafts were hardened cast iron, with the oil pump and distributor drive gears cast integrally; bearings were lead-based babbitts on steel. There were four bearings. The crank sprocket was made of malleable cast iron or sintered iron (Super Oilite). The cam sprocket was cast iron.
1968 slant six valves
| Model | Slant Six |
|---|---|
| Lifters | Mechanical |
| Valve Rotator, type (intake, exhaust) | Low-friction lock on exhaust |
| Rocker ratio | 1.5 |
| Operating tappet clearance (Intake) | .010 hot |
| Operating tappet clearance (Exhaust) | .020 hot |
| Timing (Intake – opens [°BTC]) | 10 |
| Timing (Intake – closes [°ABC]) | 50 |
| Timing (Intake – duration –deg.) | 240 |
| Timing (Exhaust – opens [°BBC]) | 50 |
| Timing (Exhaust – closes [°ATC]) | 6 |
| Timing (Exhaust – duration –deg.) | 236 |
| Timing (Valve opening overlap) | 16 |
| Intake (Overall length) | 4.77 |
| Intake (Actual overall head dia.) | 1.62 |
| Intake (Angle of seat & face, deg) | Seat: 44.5 – 45; valve: 45 – 45.5 |
| Intake (Seat insert material) | None |
| Intake (Stem diameter) | .372 - .373 |
| Intake (Stem to guide clearance) | .001 - .003 |
| Intake (Lift [@zero lash]) | .394 |
| Intake (Outer spring press. & length – valve closed, lb@in.) | 62 @ 1.65 |
| Intake (Outer spring press. & length – valve open, lb@in.) | 154 @ 1.26 |
| Intake (Inner spring press. & length – valve closed, lb@in.) | None |
| Intake (Inner spring press. & length – valve open, lb@in.) | None |
| Exhaust (Material) | 21 – 4N |
| Exhaust (Overall length) | 4.80 |
| Exhaust (Actual overall head dia.) | 1.36 |
| Exhaust (Angle of seat & face, deg) | 47 – 47.5 |
| Exhaust (Seat insert material) | None |
| Exhaust (Stem diameter) | . 371 - .372 |
| Exhaust (Stem to guide clearance) | .002 - .004 |
| Exhaust (lift [@zero lash]) | .390 |
| Exhaust (Outer spring press. & length – valve closed, lb@in.) | 62 @ 1.65 |
| Exhaust (Outer spring press. & length – valve open, lb@in.) | 154 @ 1.26 |
| Exhaust (Inner spring press. & length – valve closed, lb@in.) | None |
| Exhaust (Inner spring press. & length – valve open, lb@in.) | None |
1968 Slant Six Timing
| 170 Manual | 170 Auto. | 225 Manual | 225 Auto. | |
|---|---|---|---|---|
| Timing (Degrees) | 5 ATC | 2.5 ATC | TDC | TDC |
| Timing (@RPM) | 700 | 700 | 650 | 650 |
| Distributor | 2875199 | 2875202 | 2875364 | 2875366 |
| Distributor Part No. | Centrifugal Advance (Crank ° @ RPM) | Vacuum Advance (Crank ° @ Inches of Mercury) | ||||
| Start | Intermediate | Maximum | Start | Intermediate | Maximum | |
|---|---|---|---|---|---|---|
| 2875199 | 0 @ 700-1000 | 0-7.4 @ 1000, 24.4-28 @ 1980 | 34-38 @ 4400 | 0 @ 5-7.1 | 6-12 @ 8.5 | 12-17 @ 10 |
| 2875202 | 0 @ 700-1000 | 0-13.4 @ 1000, 18.4-22.4@1420 | 28-32 @ 4400 | 0 @ 5-7.1 | 6-12 @ 8.5 | 12-17 @ 10 |
| 2875364 | 0 @ 700-1000 | 0-7.4 @ 1000, 18.4-22.4@1740 | 25-29 @ 4000 | 0 @ 6.2-9.7 | 4-10 @ 11.9 | 7.4-12.4 @ 13.8 |
| 2875366 | 0 @ 700-1000 | 0-7.4 @ 1000, 18.4-22.4@1740 | 25-29 @ 4000 | 0 @ 5-7 | 5-11 @ 8 | 7.4-12.5 @ 8.7 |
Joseph Newhouse provided the following chart which applies to slant six powered cars from 1959 to 1978. Trucks could be rated somewhat lower than cars (140 hp vs 145 hp gross). These are Federal numbers and could vary in California by 10-15 hp. The slant six continued in use through to 1987 in Mexico, where, with a rejetted Carter YPF two-barrel carburetor and recurved distributor to reduce emissions by 30%, it was rated at 98 hp net.
Engine Year(s)
AvailableCompression
RatioHorsepower @ RPM
(see note)Torque (lb-ft) @ RPM
(see note)170 1959-1963 8.2 to 1 101 @ 4400 155 @ 2400 170 1964-1966 8.5 to 1 101 @ 4400 155 @ 2400 170 1967-1969 8.5 to 1 115 @ 4400 155 @ 2400 198 1970-1971 8.4 to 1 125 @ 4400 180 @ 2000 198 1972 8.4 to 1 100 @ 4400 160 @ 2400 198 1973 8.4 to 1 95 @ 4000 150 @ 1600 198 1974 8.4 to 1 95 @ 4000 145 @ 2000 225 1960-1962 8.5 to 1 145 @ 4000 215 @ 2800 225 1963 8.2 to 1 145 @ 4000 215 @ 2400 225 1964-1971 8.4 to 1 145 @ 4000 215 @ 2400 225 1972 8.4 to 1 110 @ 4000 185 @ 2000 225 1973 8.4 to 1 105 @ 4000 185 @ 1600 225 1974 8.4 to 1 105 @ 3600 180 @ 1600 225 1975 8.4 to 1 95 @ 3600 170 @ 1600 225 1976-78 8.4 to 1 100 @ 3600 170 @ 1600 225-2V 1977-78 8.4 to 1 110 180 Heavy-duty slant six engines used in industrial and some truck/bus applications used a double-row roller timing chain (but just one chain!), chrome-plated upper piston rings, and other features depending on service duty (polyacrylic valve stem seals, positive valve rotators, stellite-faced exhaust valves, and/or a high-volume oil pump); Rodger also said some fleet cars had these. You can retrofit the double roller chain and gears into car slant sixes, according to some sources; the double row timing chain is NAPA part 9168, used from 1962 to 1975 on the slant six; the sprockets are part S338 and S339 (thanks, Rodger).
1960 Slant Six
vs GM and FordFord 223 Slant Six 225 Chevrolet HyThrift 145 hp 145 hp 135 hp 206 lb-ft 215 lb-ft 207 lb-ft Choke Manual Fast-reaction automatic Tube-fed automatic Recommended links
- Main slant six page
- Interview with engineer Pete Hagenbuch
- Interview with architect Willem Weertman
- Other stories of the slant six's development (at Valiant Varieties)
- Spark plug replacement guide, with spark plug tube seal replacement
- Full 1968 Slant Six specifications with selected specifications from other years
- Slant Six Performance Upgrades (at Valiant Varieties)