Guide to Cylinder Head Casting Dates

GUIDE TO CYLINDER HEAD CASTING DATES:

Because Chevrolet wasn't to concerned about decoding the casting date you can have trouble with this issue. So I have compiled this small guide to help with decoding the Casting Dates.

[1] Valve Cover bolts:

See Valve Covers

[A] If the two upper bolts are closer together than the two lower ones on the edge bolted covers then it is a 1955 to 1959 head.

[B] If the two upper bolts are equal distance apart as the bottom ones then it is a 1959 to 1986 head.

[C] If the bolts are down the middle of the valve cover then it is a 1987 to date head.

NOTE:

[2] Temperature Sending Unit Boss:

See Tempture Sending Unit Boss

[A] If it does not have a temperature sending unit boss in the cylinder head then it is a 1955 to 1967 head.

[B] If the head does have a temperature sending unit boss but it is not drilled and tapped then the cylinder head is a 1968 head.

[C] If the head does have a temperature sending unit boss and it is drilled and tapped then the cylinder head is a 1968 or later head.

NOTE: In 1968 might or might not have a Drilled and tapped Temperature Sending Unit Boss.

[3] Cylinder Head Accessory Holes:

See Cylinder Head Accessory Holes

[A] If it does not have Accessory Holes in the end of the cylinder head then it is a 1955 to 1968 head.

[B] If does have Accessory Holes in the end of the cylinder head then it is a 1968 or later head.

NOTE: Some cylinder heads cast in 1968 did have Accessory holes. Also some trucks prior to 1968 had Accessory Holes but they usually had 7/16 instead of 3/8 holes.

[4] Screw in Studs with Guide Plates:

See Screw in Studs and Guide Plates

[A] If the cylinder head has Screw in Studs and Guide Plates then it is a 1970 or later head.

NOTE: Some cylinder heads have been modified to except screw in studs by other people.

[5] Spark Plugs:

See Spark Plugs

[A] If the cylinder head has the larger 13/16-inch Hex then it is a 1955 to 1970 cylinder head.

[B] If the cylinder head has the "Peanut Plug" with the 5/8-inch Hex then it is a 1971 or later head

NOTE:

[6] Heavy or Light Casting:

See Heavy or Light Casting

[A] If the cylinder head is a Light Casting then it is a 1975 or later head.

NOTE: Not all the 1975 or later heads were Light Castings.

[7] Extra Exhaust Bolt Hole:

See Exhaust Mounting Holes

[A] If the cylinder head has a Third Exhaust Bolt Hole then it is a 1975 or later head.

NOTE: Not all the 1975 or newer heads have the Third Exhaust Bolt Hole.

[8] Valve Size:

[A] The only Intake Valve size through 1961 was 1.71-inch Intake and 1.50-inch Exhaust

[B] In 1962 the 1.94-inch intake valve was introduced.

[C] In 1964 the 2.02-inch intake valve and 1.60-inch Exhaust valve was introduced.

[D] All 400-CID heads used a 1.94-inch intake valve and a 1.60 Exhaust valve.

NOTE: Remember most heads that have a 1.71 or 1.72-inch intake valve will except a 1.94-inch valve and a cylinder head with a 1.94-inch intake valve will except a 2.02-inch intake valve.