Pontiac V-8 Crankshafts

 Feel free to contribute or email us with any corrections or additions you may find. This is a work in progress and not guaranteed to be correct.

Technical Notes

  • Pre-1964 cranks must be machined to fit Turbo Hydromantic torque converters.
  • Numbers on the crank are often the same as the part number, but not always.
  • Replacement cranks may be a different part number or casting number than what came in the original engine.
  • Bearings must be installed in the engine and measured prior to grinding the crank to get clearances right.
  • Pilot bearing is # 7109 (GM part number 15533265)
  • Size is 1.3780"OD x 0.5906"ID x  0.3543"W (35 mm OD x 15 mm ID x 9 mm W)
  • Starting around 1966-1967, not all cranks used with automatic transmissions were machined for a pilot bearing.
  • Bearing is slip fit into crank with shield to the outside.
  • Crank opening is staked with a chisel in 2 places to hold bearing in place
  • A common and cheaper 6202 bearing may be used, but the crank opening may need to be machined 2 mm deeper
  • A 6202 is 35 mm OD x 15 mm ID x 11 mm W
  • The 6202 is available with shields or seals on both sides to keep dirt out.

 

  • ALL 326,350,389 AND 400'S HAVE A 3.00" MAIN JOURNAL DIAMETER
  • ALL 421, 428, AND 455'S HAVE A 3.25"MAIN JOURNAL DIAMETER
  • ALL 265 AND 301'S HAVE A 2.50" MAIN JOURNAL DIAMETER
  • ALL LARGE JOURNAL CRANK SHAFTS HAVE A 2 3/4" FLYWHEEL FLANGE.
  • ALL PONTIAC CRANKS FROM 326 THRU 455 USED THE SAME FLYWHEEL BOLT SPACING AND ARE INTERCHANGEABLE.
  • BE CAREFUL THOUGH AS 389/400 CRANKS COME IN 2 1/2" AND 2 3/4" SO BE CAREFUL WHEN SWAPPING CRANKS OR YOU MIGHT END UP CHANGING FLYWHEELS.
  • FOR STICK APPLICATIONS, YOU CAN ENLARGE THE CENTER HOLE FROM 2 1/2" TO THE LARGER 2 3/4' WITH ANY PROBLEMS.
  • BE CAREFUL WITH THE EARLY 389 "ARMASTEEL" CRANKS AS THE REAR CRANK REGISTER IS TOTALLY DIFFERENT AND THE LATER FLYWHEELS AND TORQUE CONVERTERS WON'T FIT IN THE HOLE. THEY CAN BE MACHINED TO FIT, BUT IT COULD BE AN EXPENSIVE OPTION.

     

Additional Information on Armasteel

The 1966-and  Armasteel cast crankshaft are not any stronger than the 1967-up cranks with "N" cast on them. Both are nodular iron. If you have the crank cross drilled, do not use fully grooved main bearings. It can't hurt, but if the rods are prepped correctly and the assembly is completely internally balanced it is not necessary.
The last year that the Armasteel logo was used on a crank was in 1966. The factory determined that it was misleading because the cranks were not steel. The 1967-up cranks had "N" casting, meaning nodular, or the cranks had no logo at all. Nodular cast iron, also known as spheroid graphite iron, is that the graphite is present in ball-like form instead of flakes as in ordinary gray cast iron. This results in a casting of high strength and appreciable ductility. Its toughness is intermediate between that of cast iron and steel. It is more economical to make than steel because it can be cast in molds by the millions.
In the RA IV engines, the crank had "N" cast on it along with the RA IV crank part number. The only difference I could see between a standard 400 cu.in. engine crank and the RA IV crank is that the RA IV crank was machined with .001" more clearance on the rod and main journals. Otherwise they were exactly the same.
Armasteel cast crankshaft were pearlitic malleable iron, with enhancements, they are not drop cast poured, but are centrifugal spin cast. Armasteel is less prone to cracking and pounding damage from detonation, not much, but a little more, and is denser in its basic structure. After the main casting process is done and the basic machining is completed, the fillet radiuses and main/rod journals are rolled in a hydraulic former, to make those areas stronger (about 10 to 15 percent stronger) than either drop cast or machined areas of the cranks. Buick also used Armasteel cast crankshaft, without problems, and all V6 Buick cranks, steel or iron, have rolled, not machine cut or ground fillet radii. Camshafts used to be made in two different materials, nodular and pearlitic malleable iron, non-harden able and harden able, for flat tappet cams, one for hydraulic and the other for solid lifter use.
And to further muddy the waters as to why some Pontiac engines in the mid-sixties got Armor-Steel cranks while others did not, note that "ALL" 65 326 engines (including the 326 2bbl, auto trans engines) got Armor-Steel cranks. Hummmmm.
The 326 Pontiac engines got the stronger "Armasteel" cranks because of the incredible amount of HP they were producing for their size.
The last year the Armasteel designation was used was in 1966. Therefore no 428 or 400 cranks were called Armasteel cranks. They were all "N" cranks.
I had a 1968 428 4 bolt and it has a Armasteel cast crankshaft. It says so on the crankshaft. I know this engine was never taken apart, and all original. There were a few selected engines other than the 421's that they stuck the Armasteel cast crankshaft in, and the 428 was definitely one of those.
The 1963 421 #9770488 and the 1964-66 421 #9783787 crank is Armasteel. Then Pontiac started playing the "switch-m" game with the 1967-69 428 cranks and pistons. The 1964-66 421 #9783787 Armasteel cranks were used until the #9782769 "N" crank was introduced in 1967. The latter was balanced for the different type 1967-69 428 pistons. Apparently a few of the 1964-1966 421 Armasteel cranks and pistons were installed in the 1967-69 428 engines. The 1967-69 #9782769 "N" cranks are difficult to rebalance for replacement TRW 428 pistons. But as a general rule, all 1967-69 428 cranks are "N" cranks and not Armasteel.
The '64/'65 421 HO Armasteel crank is #9773384. The '66 Parts Catalog shows the #9782769 as the 421 & H.O. crank, so it was introduced a year before '67. The RAII had it's own specific crank casting, #9794054. It was marked Armasteel and was also used in the '69 RAIV. The regular '68 400 crank was #9773524, a nodular iron crank. I understand the machining difference, but it makes no sense to have the RA crank cast as "Armasteel" at the same time nodular iron cranks were produced if there is no difference except bearing tolerances.
The standard production and RA 1967-1968 400 cranks were an "N" crank, p/n 9773524. The 1969-1970 RA III crank was a "N", p/n 9795480. The 1968 RA II (w/#96 round port heads) and the 1969-70 RA IV cranks were "N" cranks, p/n 9794054 with .001" more clearance than standard. I observed the "N" on a RA IV crank from a disassembled 1970 RA IV engine.
If the crank was a 1968 428 engine it could be either a Armasteel #9783737 421 crank or a "N" crank, #9782769,depending on the production date. The latter is considered the 428 crank and were used in all the late production 1968 and 1969 428 engines.
The p/n 9783787 is correct for a 1964 Armasteel "421" crank. The #9773384 Armasteel crank was introduced in the 1965-1966 engines. Either of those cranks could have made it into some 1967-1968 "428" engines even after the #9782769 428 crank was introduced in 1967.
Abbreviations and Code information
  • "FS" = Forged Steel
  • "AS" = ARMASTEEL  = PMI
  • "PMI" = Pearlitic Malleable cast iron. ARMASTEEL logo may not be present on all cranks.
  •  ARMASTEEL is not steel, but a form of cast iron.  ARMASTEEL  was a registered trademark (#0393916) GM used starting October of 1937. The trademark was last renewed in 1982 and expired in 2002.
  • "N"  = Nodular Cast Iron. "N" mark may not be present on all cranks.
  • "CFD" = Central Foundry Division. May not be present on all cranks.
  • It appears many cranks do not have a casting date.
    • The normal GM format:  A=January, B=February etc. Second digit or digits is date, last digit is year. D124 = April 12, 1964 or 1974. 
  • Some cranks may have a 3 digit number like 205. It may be a Julian production date, but there is no confirmation of that.


 

Armasteel

Armasteel casting

CFD casting

Stamped type number

N casting

Crankshaft Specification Table
Year Engine Mtl. Part# Crank# Marks Stroke Mains Rods Snout Rear Hub

Notes
1939-1954 all 6cyl   506176 506176              
1946-1949 all 8cyl   508454 508454              
1950-1954 all 8cyl   513513 512512              
1955 287

FS

 518047 518047   3.25 2.50 2.25 2.50 2.600  
1956 317

FS

 521602 521602   3.25 2.50 2.25 2.50 2.600  
1957 347

FS

 530048 530048   3.5625 2.623 2.25 2.50 2.600  
1958 370

FS

 528527 528527   3.5625 2.623 2.25 2.50 2.600  
1959-1962 389

AS

 531369 531369 ARMASTEEL 3.75 3.00 2.25 2.50 2.600  except Super Duty
1959-1960 389 SD

FS

 533038 533038   3.75 3.00 2.25 2.50 2.600  Limited production
1961-1962 389 SD FS 541649 541649   3.75 3.00 2.25 2.50 2.600  Limited production
1961-1963 421 SD FS 542990 542990   4.00 3.25 2.25 2.50 2.600  Limited production (approx 2000)
1961-1962 215   542239 542239              Tempest
1961-1963 4cyl   1193645 1193645              Tempest
1962-1963 421 AS 9770488 9770488 ARMASTEEL 4.00 3.25 2.25 2.50 2.600  And HO engines
1963 326 AS 545585 545585 ARMASTEEL 3.75 3.00 2.25 3.00 2.760  Special Tempest transaxle hub
1963 389 AS 544191  544191 ARMASTEEL 3.75 3.00 2.25 3.00 2.760  Pontiac V8 except 421
1964-1965 6 cyl   3864465 3864465              Tempest; supplied without pilot bearing
1964-1965 V8 AS 9773382 9773382 ARMASTEEL 3.75 3.00 2.25 3.00 2.760  Tempest including 389 Armasteel "400"
1964-1965 389 AS 9773383  9773383 ARMASTEEL 3.75 3.00 2.25 3.00 2.760  
1964-1965 421   977384 977384              And HO; might require different connecting rod for balance
1966 421 AS 9773384 9773384 ARMASTEEL 4.00 3.25 2.25 3.00 2.760 1st Type: if using 1965 type piston different connecting rods are  required
1966-1967 326 AS 9782770 9782770 ARMASTEEL 3.75 3.00 2.25 3.00 2.760  
1966 389 N 9782646 9783786 ARMASTEEL 3.75 3.00 2.25 3.00 2.760  
late 1966 421 AS 9783787 9783787 ARMASTEEL 4.00 3.25 2.25 3.00 2.760  
1966-1967 6 cyl   9782279 9782279             Firebird and Tempest; use pilot bearing (P/N3752487) for MT
1966-1968 421-428 AS 9783787 9783787 ARMASTEEL 4.00 3.25 2.25 3.00 2.760  2nd type: AS long snout
1967-1970 400 AS 9795480 97954   3.75 3.00 2.25 3.00 2.760  except Ram Air
late 1967-early 1968 400 N 9773524 9773524 N 3.75 3.00 2.25 3.00 2.760  
1968-1979 400 N 4813 4813 N 3.75 3.00 2.25 3.00 2.760  both "N" crank and standard w/ 2 3/4" flange
early 1968 350 N 9793573 9793573 N 3.75 3.00 2.25 3.00 2.760  
late 1968-1970 350 N 9795479 9795479 N 3.75 3.00 2.25 3.00 2.760  
1968 400 RA AS 9794054 9794054 ARMASTEEL 3.75 3.00 2.25 3.00 2.760  WU, WY, XT, XW  engines
1968-1969 6 cyl   9790154 9790154              Firebird and Tempest; use pilot bearing (P/N3752487) for MT
late 1968-1969 428 N 9782769 9782769 N 4.00 3.25 2.25 3.00 2.760  
1969 303 FS 546270 546270   2.84 2.50 2.25 3.00 2.760  Limited production
1969-1974 400 N 97954 97954 N 3.75 3.00 2.25 3.00 2.760  2 3/4" flange
1969 400 RAIV N 9794054 9795481 N 3.75 3.00 2.25 3.00 2.760  WH, WW, XN, XP engines, 0.001 more clearance.
1970 400 RAIV N 9794054 9795481 N or ARMASTEEL 3.75 3.00 2.25 3.00 2.760
1969 400 RAV FS 545671 545671 V24, $A 3.75 3.00 2.25 3.00 2.760  Limited production
1970 366 FS       3.375 3.00 2.25 3.00 2.760  Moldex forging, Limited production
1970-1979 350/400   9773524 9773524   3.75 3.00 2.25 3.00 2.760  non "N"  with 2 3/4" flange
1970-1976 455   496453 496453   4.210 3.25 2.25 3.00 2.760  
1970-1976 455 N 9799103 9799103 N 4.21 3.25 2.25 3.00 2.760  Approx wt 72 lbs came both "N" and standard
1971-1974 350 N 481379 4813 N, 79 on front wt. 3.75 3.00 2.25 3.00 2.760  
1971-1974 400 N 481380 4813 N, 80 on front wt. 3.75 3.00 2.25 3.00 2.760  
1972 SD-455 FS       4.21 3.25 2.25 3.00 2.760  Kellog forging, Limited production
1973-1974 SD-455 N 490164 490164 N 4.21 3.25 2.25 3.00 2.760  W8, Y8, X8, Z8, ZJ, XD engines
1973-1976 455 N 495030 496453 N 4.21 3.25 2.25 3.00 2.760  Service replacement
1975-early 1976 350 N 496452 496452 N 3.75 3.00 2.25 3.00 2.760  Thin counterweights
1975-early 1976 400 N 496414  496414 N 3.75 3.00 2.25 3.00 2.760  Thin counterweights
1975-1976 455 N 496415 496415 N 4.21 3.25 2.25 3.00 2.760  Thin counterweights
1975-1976 455 N 496415 496453 N 4.21 3.25 2.25 3.00 2.760  Thin counterweights
late 1976-1979 350 N  496452 496452 N 3.75 3.00 2.25 3.00 2.600  Thin counterweights
late 1976-1979 400 N 499864  499864 N 3.75 3.00 2.25 3.00 2.600  Thin counterweights
1977-1981 301 N 525887 525887   3.00 2.50 2.00 3.00 2.600  End counterweights only
1980-1981 265 N 525887 525887   3.00 2.50 2.00 3.00 2.600  End counterweights only