Poly A-block Engine Specifications

I have compiled these Poly 277, 301, 303, 313, 318, and 326 specifications from multiple factory manuals, brochures, service bulletins and my personal measurements. See the service manual page for digital service manuals I provide for free download.

Poly A-block Factory Engine Specs

YearCIDModelBoreStrokeComp RatioBHPTorqueNotes
1956277First A-block3.75″3.125″8:1187 @ 4,400 RPM 265 – 272 @ 2,400 RPM
1957301Car, V8003.913.125″8.5:1215 @ 4,400 RPM285 @ 2,800 RPM1×2 Carburetor. 277 crank and rods, 318 block
1957301Car, V800 Super-Pak3.91″3.125″8.5:1235 @ 4,400 RPM305 @ 2,800 RPM1×4 Carburetor. 277 crank and rods, 318 block
1957303Fury modle, Dual V8003.81″3.31″9.25:1270 @ 5,200 RPM310 @ 2,800 RPMFury model, 2×4 Carburetor.
1957 to 1958318Car, Dual Fury V800 3.91″3.31″9.25:1290 @ 5,400 RPM225 – 330 @ 3,600 RPM2×4 Carburetors
1959318Dodge Truck “Power Giant HD”3.91″3.31″8.25:1207 @ 4,400 RPM292 @ 2,400 RPMDomestic trucks only
1959313Export Truck3.875″3.31″7.75:1184 @ 4,400 RPM278 @ 2,400 RPMExport Dodge trucks
1957 to 1962318Car, Light Truck, Fury V800 Super-Pak 3.91″3.31″9.0:1250 – 260 @ 4,400 RPM340 – 350 @ 2,600 – 2,800 RPM1×4 Carburetor
1957 to 1967318Car, Light Truck, Fury V800 3.91″3.31″9.0:1225 – 230 @ 4,400 RPM330 – 340 @ 2,400 – 2,800 RPM1×2 Carburetor, “Standard” with rare option of “Semi-premium” package
1957301Export, V800 Super-Pak3.91″3.125″8.5:1235 @ 4,400 RPM305 @ 2,800 RPMExport Market, 1×4 Carburetor. 277 connecting rods
1959326Car, Dodge3.95″3.31″9.2:1255 @ 4,400 RPM350 @ 2,400 RPMCalled the “Red Ram” Standard in Dodge Coronet
1960318Heavy Truck3.91″3.31″8.25:1200 @ 3,900 RPM286 @ 2,400 RPMHeavy Dodge truck
1961 to 1967318Heavy Truck, Low Compression3.91″3.31″7.5:1200 @ 3,900 RPM286 @ 2,400 RPM“Full-premium” package
1956 to 1957303Export, V800 Super-Pak3.81″3.31″9.25:1240 @ 4,400 RPM310 @ 2,800 RPMExport Market, 1×4 Carburetor.
1957 to 1964313Export3.875″3.31″9:1225 @ 4,400 RPM330 @ 2,400 – 2,800 RPMExport Market, 1×2 Carburetor
1965 to 1967318Export 3.91″3.31″9:1225 – 230 @ 4,400 RPM330 – 340 @ 2,400 – 2,800 RPMExport Market, 1×2 Carburetor
1959 to 1963318Marine Chrysler Sea V3.91″3.31″8.2:1177 @ 3,600 RPMUnlistedTorque likely around 250 @ 4,000. See the marine page for details.See marine and industrial engine page
1959 to 1962318Marine M318A
Fury 190
3.91″3.31″8.2:1190 @ 4,000 RPM270 @ 4,000 RPMSee marine and industrial engine page
1962 to 1967318Marine Fury 1953.91″3.31″8.2:1195 @ 4,000 RPM275 @ 4,000 RPMSee marine and industrial engine page
1962 to 1967318Marine Fury 2103.91″3.31″8.2:1210 @ 4,000 RPM290 @ 4,000 RPMSee marine and industrial engine page
1959 to 1967318Marine Fury 2353.91″3.31″8.2:1235 @ 4,000 RPMUnlisted, likely around 340 @ 4,000 RPMSee marine and industrial engine page
1959 to 1967318Industrial H3183.91″3.31″8.2:1190 @ 4,000 RPMNot listedLight duty “Standard” package. See marine and industrial engine page
1959 to 1967318Industrial HB318 3.91″3.31″8.2:1190 @ 4,000 RPMNot listedMedium duty “semi-premium” package. See marine and industrial engine page
1959 to 1967318Industrial HC318 3.91″3.31″8.2:1190 @ 4,000 RPMNot listedHigh-compression medium-duty model. The Industrial manual specs might have two typos for the compression ratio and BHP. The engine is likely 9:1 compression and higher BHP rating. See marine and industrial engine page
1959 to 1967318Industrial HT3183.91″3.31″8.2:1193 @ 4,000 RPMNot listedHeavy Duty “Full-premium” package. See marine and industrial engine page

Engine Identification Number Stamped Prefix Specifications

  • “1” after the ID denotes a “Standard” engine package:
    • This is the most common type of engine found in cars and light trucks.
    • Received 9:1 or 8.25:1 compression pistons, steel-backed babbitt bearings, standard timing set, standard volume/pressure oil pump, 4-quart oil pan (1956 – 1958 received a 5-quart oil pan), mechanical flat-tappet camshaft and lifters, adjustable rocker arms, Silchrome intake valves, standard valve-spring retainers and springs, standard distributor.
  • “2” after the ID denotes a “Semi-premium” engine package.
    • The number 2 may also be a superscript after the ID (Figure 1a).
    • These engines when found are often in Dodge light trucks (D/W100, D/W200, D300).
    • These engines usually received 8.25:1 compression pistons, steel-backed babbit crank and rod bearings, “silent” plastic-teeth timing set, standard pressure/volume oil pump, 4-quart oil pan, mechanical camshaft and lifters, adjustable rocker arms, Silchrome intake valves, standard valve retainers and springs, standard distributor.
  • “3” after the ID denotes a “Full-premium” engine package.
    • The number 3 may also be a superscript after the ID similar to Figure 1a.
    • These engine are not common compared to the total production numbers of the A318 and were available standard in Dodge heavy trucks including D400, D500, D600, W300, and W500, Travco motorhomes, and optional in light trucks. The share most of the same components as the industrial HT318 heavy duty engines.
    • These engines received 7.5:1 or 8.25:1 compression pistons, tri-metal crank and rod bearings, roller timing set, high-pressure (standard volume) oil pump, 5-quart oil pan, hardened and shot-peened forged crankshaft, hydraulic camshaft and lifters, non-adjustable rocker arms, Silchrome intake valves, Stellite-faced exhaust valves, sodium-cooled/filled exhaust valves, exhaust valve rotators, special valve springs for rotators (Figures 1b – 1c), and standard distributor.
Figure 1a: Alternative Superscript 2 Instead of 318-2 (Semi-premium Package)
Poly 318 -3 Premium Valves Rotators
Figure 1b: Poly A-block 318-3 “Full Premium” and Industrial HT318 Heavy Duty Valves, Springs, Rotators
Poly 318 -3 Premium Valve Rotators Rocker Arms
Figure 1c: Poly A-block 318-3 “Full Premium” Hydraulic Lifter Non-adjustable Rocker Arms and Exhaust Valve Rotators

Detailed Mechanical Specs for Poly 313, 318, 326

CategoryComponentSpecificationNotes
BlockCylinder Out-of-RoundNo more than 0.005” before overbore, and that is very worn.
Cylinder TaperNo more than 0.020” before overbore, and that is very worn.
Lifter Bore Diameter0.9050” – 0.9058” allowableSee oiling modification tech article
Cylinder Pressure, Stock Build120 – 150 cranking psi, no greater than 20 psi variation between cylinders. 110 psi minimum.Cylinder pressure depends greatly on elevation, climate conditions, compression ratio, cam, testing procedure, and component wear.
Cylinder Pressure, Performance BuildAbove 160 cranking psi ideal, no greater than 20 psi variation between cylinders.Cylinder pressure depends greatly on elevation, climate conditions, compression ratio, cam, testing procedure, and component wear.
Deck Height9.603″The deck height can vary from block to block depending on core shift and if the block has ever been milled before. When milling the block to square the surfaces, most blocks clean up at .015″ – .020″. You can usually go up to .040″ before needing to also machine the intake manifold.
CamshaftEnd Play0.002” – 0.006” with 0.010 max
Bearing Clearance0.001” – 0.003” with 0.005 max
Journal 1 Diameter1.998″ – 1.999″Important for measuring core shift
Journal 2 Diameter1.982″ – 1.983″Important for measuring core shift
Journal 3 Diameter1.967″ – 1.968″Important for measuring core shift
Journal 4 Diameter1.951″ – 1.952″Important for measuring core shift
Journal 5 Diameter1.5605″ – 1.5615″Important for measuring core shift
Bearing 1 Diameter2.000″ – 2.001″
Bearing 2 Diameter1.984″ – 1.985″
Bearing 3 Diameter1.969″ – 1.970″
Bearing 4 Diameter1.953″ – 1.954″
Bearing 5 Diameter1.5625″ – 1.5635″
Cooling SystemCapacity w/out heater20 quarts typicalDepends on radiator and heater core size. See cooling system tech articleSee cooling system tech article
Radiator Cap Relief14 – 16 psi (higher with A/C)1956 – 1959 used 12 psi cap. See cooling system tech articleSee cooling system tech article
Thermostat180° or 195°See cooling system tech articleSee cooling system tech article
Normal Operating Temperature175° – 205°See cooling system tech articleSee cooling system tech article
Crankshaft, Con RodsMain Journal Diameter2.4995” – 2.5005”
Main Journal Out-of-round and Taper0.001″ maximum
Main Bearing Clearance0.0005” – 0.0025”
#3 Thrust Bearing Run-out0.002″
Crankshaft End Play Measured at Bearing #30.002” – 0.007”
Rod Journal Diameter2.124” – 2.125”
Rod Journal Out-of-round and Taper0.001 maximum
Rod Bearing to Journal Clearance0.0005” – 0.0025”
Rod Bearing Side Clearance0.006″ – 0.014″
Rod Length6.123”
Rod Journal Bearing Diameter and Width2.126″ x 0.842″
Rod Pin Journal Diameter0.9842 – 0.9843″Bronze bushing
Piston Pin to Rod Clearance0.0001″ – 0.0004″
Rod Ratio1.85
FuelingFuel Pressure5 psi – 7 psiWhen running some Holley (e.g. 4150/4160) and Edelbrock AVS carburetors, pressure over 6.4 psi can lift the needles causing flooding.
IgnitionFiring Order (Figure 2)18436572
Hot idle speed500 – 850 rpmDepends on cam and vacuum requirements. See carburetor selection and tuning tech article
Spark Plug Type 3/8” short-reach Autolite 85, Champion 63 (formerly J12Y), etc. WARNING: Do not install LA-type 3/4″ long-reach plugs, such as Autolite 65. They will contact the piston.
Spark Plug Gap0.035″See ignition timing and points adjustment tech article
Points Gap0.017”See ignition timing and points adjustment tech article
Dwell Angle26° – 28° ideal, 26° – 32° allowableSee ignition timing and points adjustment tech article
Coil Resistance Primary1.65 – 1.79 ohmsat 70°F – 80°F
Coil Resistance Secondary8,000 – 9,200 ohmsat 70°F – 80°F
Ballast Resistor0.665 – 0.735 ohms
Distributor Shaft to Bushing Clearance0.0007″ – .0027″
Distributor Shaft Side Play0.000″ – 0.003″Wear over 0.006″ requires rebuilding
Distributor Shaft End Play0.003″ – 0.017″Check with distributor installed and clamped down. Note that it is common to find the end play outside the factory tolerance on even NOS and quality new aftermarket distributors up to 0.050″, which will not impact the distributor negatively. Excessive end play should be diagnosed and addressed since it may cause wear to the drive tang leading to inconsistent timing and possibly breakage.
Ignition TimingInitial 10° BTDCBaseline for starting engine in order to tune. See ignition timing and points adjustment tech article
Total Advance w/out vacuum at 4,000 RPM34° – 36°Depends on each engine. See ignition timing and points adjustment tech article
Total Advance with vacuum at 4,000 RPM44° – 56°Depends on each engine. See ignition timing and points adjustment tech article
Adjustable Vacuum Advance Screw Midpoint5 turns out from full in (typical)Verify with specific vacuum can
LiftersLifter Angle59°
Lifter Diameter0.9040″ – 0.9045″
Lifter Bore0.9050″ – 0.9058″
Lifter Bore Spacing1.760″
Oil System (Figures 3a – 3b)Hot Oil Pressure at Idle under 800 RPM20 – 30 psi idealLower than 20 psi idle suggests an oiling problem
Hot Oil Pressure above 1,500 RPM50 psi – 65 psiHigh-pressure pumps may run 70 – 75 psi
Capacity 1956 – 1958 with 5-quart Pan5 quarts, 6 total with filter
Capacity 1959 – 1967 with 4-quart Pan4 quarts, 5 total with filter
Capacity 1959 – 1967 Marine with 8-quart Pan8 quarts, 9 total with filter
Capacity 1956 – 1967 Industrial with 5-quart Pan 5 quarts, 6 total with single filter, 7 total with dual filters
Viscosity, Rebuild Break-in30 weight conventional with ZDDP.WARNING: Never use synthetic oil to seat new rings. Always use a ZDDP formula or additive with flat-tappet camshaft/lifters.
Viscosity, Cold Climates below 40°F5W30 conventional or synthetic with ZDDP.WARNING: Always use a ZDDP formula or additive with flat-tappet camshaft/lifters.
Viscosity, Cold and Mild Climates between 41°F – 90°F10W30 or 10W40 conventional or synthetic with ZDDP.WARNING: Always use a ZDDP formula or additive with flat-tappet camshaft/lifters.
Viscosity, Very Hot Climates above 90°F10W40 or 20W50 conventional or synthetic with ZDDP.WARNING: Check hydraulic lifter specs since performance lifters often specify no thicker than 10W30. Always use a ZDDP formula or additive with flat-tappet camshaft/lifters.
Rebuild Oil Priming Prior to StartManually prime with high-torque drill.Figure 5 shows why often times the engine must be turned over by hand while priming the oiling system because the camshaft must rotate to feed both cylinder heads galleries.
Oil Pump Cover Flat, 1956 – 1967 M51 and M720.0015″ maximumSee oil pump blueprinting tech article
Oil Pump Inner and Outer Rotor to Cover, 1956 – 1967 M51 and M720.001″ – 0.004″See oil pump blueprinting tech article
Inner Rotor to Outer Rotor Teeth, 1956 – 1961 M510.001″ maximumFeeler gauge placed between teeth. See oil pump blueprinting tech article Note that the M72 clearance of 0.001″ – 0.006″ may be safely used for the M51 pump.
Inner Rotor to Outer Rotor Teeth, 1962 – 1967 M720.001″ – 0.006″Feeler gauge placed between teeth. See oil pump blueprinting tech article
Inner Rotor Height, 1956 – 1961 M510.998″ minimum
Outer Rotor to Pump Housing, 1956 – 1967 M51 and M720.002″ – 0.012″See oil pump blueprinting tech article
Outer Rotor Diameter, 1956 – 19612.244″ minimum
Outer Rotor Height, 1956 – 19610.998″ minimum
PistonsClearance Top of Skirt 0.0005” – 0.0015”
Ring End GapDepends on ring manufacturer, induction type, and build purpose.

Factory street is 0.015” for compression and scraper
Always follow ring manufacturer specs.
Floating Wrist Pin Diameter and Length0.9842″ x 2.995″
Pin to Piston Clearance at 70°F0.00 – 0.0005″Use light thumb push to measure
End Play0.004″ – 0.026″
Piston Pin to Rod Clearance0.0001″ – 0.0004″
Rocker ArmsRocker Arm Ratio1.5:1 
Arm to Shaft Clearance0.001″ – 0.003″See rocker assembly rebuilding tech article
Shaft to Bracket Clearance0.001″ – 0.0045″See rocker assembly rebuilding tech article
ValvesIntake Diameter1.844″
Intake Length4.599″
Intake Stem Diameter0.3725″
Intake Stem Clearance0.001” – 0.003”
Intake Tip Length0.213″
Intake Keeper
Exhaust Diameter1.563″
Exhaust Length4.539″
Exhaust Stem Diameter0.3715″
Exhaust Stem Clearance0.002” – 0.004”
Exhaust Tip Length0.0989″
Exhaust Keeper7° 4-groove
Valve AdjustmentMechanical Lifter Intake Lash Hot0.013”See valve adjustment tech articleSee valve adjustment tech article
Mechanical Lifter Exhaust Lash Hot0.021”See valve adjustment tech articleSee valve adjustment tech article
Mechanical Lifter Intake Cold (for initial start)0.015″See valve adjustment tech articleSee valve adjustment tech article
Mechanical Lifter Exhaust Cold (for initial start)0.021″See valve adjustment tech articleSee valve adjustment tech article
Hydraulic Lifter Intake and Exhaust Preload Hot3/4 turn after zero lashSee valve adjustment tech articleSee valve adjustment tech article
Hydraulic Lifter Intake and Exhaust Preload Cold (for initial start)1/2 turn after zero lashSee valve adjustment tech articleSee valve adjustment tech article
Valve SpringsValve Spring Installed Height1.7”Verify proper rocker arm tip position
Valve Spring Pressure Factory Spec.up to 145 in. lbs. at 1-5/16”Follow camshaft’s required spring pressure

Poly 277, 301, 303, 313, 318, 326 Firing Order
Figure 2: Firing Order

Poly 277, 301, 303, 313, 318, 326 Oiling System
Figure 3a: 1956 – 1961 Oiling System (bypass valve)

Poly 277, 301, 303, 313, 318, 326 Oiling System
Figure 3b: 1956 – 1961 Oiling System (without bypass valve)

Mopar Plymouth Dual Fury V800 Poly 318 A-block
1957 – 1958 Dual-quad “Dual Fury V-800” Package

Mopar A-block Poly 318 Fury Super-pak V800
4 -barrel 318 “Fury Super-Pak V-800” Package

Mopar Poly A-block 318 Fury V800
2-barrel 318 “Fury V-800” Package
Poly 318 Marine Engine
Marine A318 “Fury” Series with Dual Carter YH Carburetors
Poly 277, 301, 303, 318, 326 Engine Internal Sectional
A-block Sectional

Poly 277, 301, 303, 318, 326 Canted Valves
A-block Canted Valves