Head Bolts

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A-series head bolts are designed to be reused; they are not Torque-To-Yield (TTY) bolts.

Maintenance Schedule

Retighten cylinder head bolts every 24 months or 24000 miles whichever comes first.

600 mile service
24 months/24000 miles

See Changing Head Gasket for torque specifications and procedure.

Overview

BOLT-FIXING CYLINDER HEAD SHORT [9 needed, 97 mm length]
11056-18001 36 lb ft [Original use: A10 & A12]
11056-H1000 43 lb ft [original use: A12]
11056-H2301 58 lb ft [original use: A12GX]

BOLT-CYLINDER HEAD, TO OIL GALLERY [1 needed, longer bolt]
11057-18000 
11057-H1000 'T'
11057-H2300 '13' for 1967-1973 engines
11057-H5700 '13' for 1974-up engines [111 mm length]

Bolts are the same for A12/A14/A15, but A14/A15 require the stronger bolts (marked '13').

1973 A12 (early engine, upgraded H1000 bolts)
Torque: 40-43 ft-lb
CENTER BOLT: 8 mm central portion (head marked 'T')
OTHER BOLTS: 9 mm

Note 'T' bolt for center of early A12 engine. This is a low-torque bolt.

'12' bolts
photo  photo  photo 

Better to use the GX '13' center bolt, which is high-tensile chromoly V steel
photo  photo 
"13" bolts were first used on the twin-carb A12GX Engine, as opposed to single-carb engine bolts. "13" bolts can be used with any early engine (they are simply stronger than the earliest bolts).

Note that A12/A12A/A13/A14/A15 all may use the '13' bolts, but the center bolt differs between early engines and late engines.

Center bolt 11057-H5000 and 11057-H5700 are interchangeable
click

Part Numbers

Original Lo-torque bolts (B10 & early B110 -1172) - 36 ft-lb
* 11056-18001 BOLT-FIXING CYLINDER HEAD SHORT
* 11057-18000 BOLT-FIXING CYLINDER HEAD LONG 
* 11058-18000WASHER-LOCK FIXING CYLINDER HEAD 

Newer medium torque bolts (1272-) - 43 ft-lb
* 11056-H1000 BOLT-FIXING CYLINDER HEAD SHORT (9 needed) $2.90
* 11057-H1000 BOLT-FIXING CYLINDER HEAD LONG [Center bolt] $2.51 
* 11058-H1000 WASHER-LOCK FIXING CYLINDER HEAD $2.28 

A12GX, A12T, A12S, A13, A14, A15, A12A - 58 ft-lbs
* 11056-H2301 HEAD BOLT SHORT (9 needed) $3.96
** NOTE Some newer lo-power (round port) A12S are spec'd for 11056-H1000
** Also used by Z16/Z18/Z20/Z22 (10 per engine)
* 11057-H2301 BOLT-CYLINDER HEAD LONG, TO OIL GALLERY (TO 6/73) $3.88
** one needed
* 11057-H5000 BOLT-CYLINDER HEAD LONG, TO OIL GALLERY (FROM 7/73) $4.03
** one needed
** Also used by Z24, KA24E, NA20P (10 per engine)
* superceeded 11057-H5700

A12: Long middle bolt marked 'T' (low-torque)
A14: Long middle bolt marked '13' (hi-torque)

Hi-torque bolts marked "13" on the head. Remove the valve cover to verify.

head bolts
Cro-Mo-V steel
13T

Lock Washer 
* 11058-H1000 WASHER-LOCK FIXING CYLINDER HEAD -8504 $2.28 
* 11058-21002 Washer Cyl Head 8504- $2.57