Imperial Home Page -> Repair -> Engine -> Specifications
CONSULT YOUR FSM, PARTS SOURCE OR AN AUTOMOTIVE MACHINE SHOP FOR MORE DETAILED AND UP TO DATE INFORMATION PRIOR TO BEGINNING ACTUAL MACHINE SHOP WORK.
General Engine Specifications
| Year |
Bore/Stroke |
Cubic Inches | HP | Torque | Compression | Oil Pressure |
| 1935-50 | 3.250 x 4.875 | 323.5 | 135 | @3400 | 6.5:1 | |
| 1937 | 3.250 x 4.125 | 273.8 | 110 | @3600 | 6.7:1 | |
| 1938 | 3.250 x 4.500 | 298.6 | 110 | @3400 | 6.2:1 | |
| 1951-54 |
3.8125 x 3.625 |
331 | 180 330 |
@4400 @2600 |
7.5:1 | 60psi |
| 1955 |
" |
" |
250 340 |
@4600 @2800 |
8.5:1 | 60psi |
| 1956 | 3.9375 x 3.625 | 354 | 280 380 |
@4600 @2800 |
9.0:1 |
" |
| 1957 | 4.0 x 3.90625 | 392 | 325 430 |
@4600 @2800 |
8.25:1 |
" |
| 1958 |
" |
" |
345 435 |
@4600 @3600 |
10.01:1 |
" |
| 1959-65 | 4.1875 x 3.75 | 413 | 340 435 |
@4600 @3600 |
10.1:1 |
" |
| 1966-67 | 4.320 x 3.75 | 440 | 350 480 |
@4400 @2800 |
10.0:1 | 55psi |
| 1968-69 |
" |
440 |
" |
" |
10.1:1 |
" |
| 1970-71 |
" |
" |
" |
" |
9.7:1 | 45-65psi |
| 1972 |
" |
" |
225 345 |
@4400 @3200 |
8.2:1 |
" |
| 1973 |
" |
" |
215 345 |
@3600 @2000 |
" |
" |
| 1974 |
" |
" |
230 350 |
@4000 @3200 |
" |
" |
| 1975 |
" |
" |
215 330 |
@4000 @3200 |
" |
" |
| 1976 |
" |
" |
205 320 |
@3600 @2000 |
" |
" |
| 1977-78 | 4.340 x 3.375 | 400 | 190 285 |
@3600 @3200 |
8.2:1 |
" |
| 1977-78 | 4.320 x 3.750 | 440 | 195 320 |
@3600 @2000 |
" |
" |
| 1981-83 | 3.910 x 3.310 | 318 | 140 240 |
@4000 @2000 |
" |
" |
*NOTE - Horsepower figures given are BHP figures prior to 1972, meaning no power loss to transmissions, alternators,
air conditioning etc. In 1972, SAE figures were net, meaning after all losses were taken.
|
Year |
Engine |
Main Journal Diameter |
Oil Clearance
|
Main
|
Rod Journal Diameter |
Rod Oil Clearance |
Rod End Play |
| 1935-50 | all | 2.700 | .001-.002 | .003-.007 | 2.1875 | .001-.002 | .006-.011 |
| 1954-55 | 331 | 2.500 | .002-.007 | .003-.009 | 2.250 | .001-.002 | .010 |
| 1956 | 354 | 2.500 | " | " | 2.250 | " | " |
| 1957-58 | 392 | 2.690 | " | " | 2.250 | " | " |
| 1959-65 | 413 | 2.750 | " | " | 2.375 | " | .009-.0017 |
| 1966-71 | 440 | 2.75 | " | " | 2.375 | " | .009-.0017 |
| 1972-78 | 400 | 2.625 | " | " | 2.375 | " | .009-.0017 |
| 1981-1983 | 318 | 2.500 | .001-.0025 | .003-.009 | 2.125 | .001-.0025 | .006-.0014 |
NOTE 1: Rod End Play for inline-8 cylinder engines is per rod; for V-8 engines,
it is for both rods on the same journal.
NOTE 2: All figures are nominal, actual printed data may give a range of dimensions such as 2.7495 to 2.7505 for
a given year of crank or rod journal.
Piston and Ring Dimensions
| Year | Engine | Bore | Piston Clearance | Ring End Gap | Ring to groove gap at top of skirt | Compression/Oil |
| 1935-50 | Inline8 | 3.250 | .002 | .007 | .007 | .002-.004 |
| 1981-83 | 318 | 3.910 | " | .010 | .015 | " |
| 1951-55 | 331 | 3.8125 | " | .010 | .010 | " |
| 1956 | 354 | 3.9375 | " | " | " | " |
| 1957-58 | 392 | 4.0 | " | .013 | .013 | " |
| 1972-78 | 400 | 4.340 | " | " | " | " |
| 1959-1965 | 413 | 4.1875 | " | " | " | " |
| 1966-78 | 440 | 4.320 | " | " | " | " |
Note: Actual Cylinder Bore and Piston Diameters in other than stock engines would be determined by the amount of
overbore at rebuild. Nominal figures are listed here.
All Clearances listed are MINIMUM amounts, with rings fitted at the tightest point in the cylinder in the case
of tapered cylinder walls. piston clearance is measured at the top of the skirt, generally at 90 degrees to the
pin.
Torque Table ( in foot-pounds unless noted )
| Year | Engine | Head | Rod Caps | Main Caps | Crank | Damper | Flywheel | Manifold |
| 1935-50 | Inline 8 | 65-70 | 45-50 | 75-80 | ||||
| 1951-58 | V8 | 85 | 45 | 85 | 135 | 60 | 30 | 25 |
| 1959-78 | All BRB | 65-75 | 40-45 | 80-85 | 135 | 55-65 | 50 | 30 |
| 1981-83 | 318 | 95 | 45 | 85 | 135 | 55 | 45 | 30 |
Note: Flywheel/Flexplate bolts are for flywheel to crank flange hub.
This page was last updated January 28, 2003. Send us your feedback, and come join the Imperial Mailing List - Online Car Club
