I fist posted this to the list back in 2004.
Many of the GMC motorhomes use J heads.
According to information that Dick Paterson published a few years back here is the head information.
Those with “soft” seal areas that require hardened exhaust seat inserts:
455 1966 B
455 67-69 C
455 68-69 D
455 68-70 E
455 1970 F
all of the above were for leaded fuels
Those with hardened seal areas that don’t require inserts:
455 1971 H
455 71-72 G
455 1972 Ga
455 71-72 J
455 73-76 (Cutlass) K
455 73-76 (Marine / Irrigation) K
403 77-79 4A
These all were for unleaded fuels.
Note that this information was for all applications of the 455, not just the GMC motorhome.
I have just created a gmcphotos.com http://gmcphotos.com/ album which has a more comprehensive listing.
See it at:
http://www.gmcmhphotos.com/photos/g7088-olds-big-block-heads.html http://www.gmcmhphotos.com/photos/g7088-olds-big-block-heads.html
Emery Stora
77 Kingsley
Frederick, CO
Many of the GMC motorhomes use J heads.
According to information that Dick Paterson published a few years back here is the head information.
Those with “soft” seal areas that require hardened exhaust seat inserts:
455 1966 B
455 67-69 C
455 68-69 D
455 68-70 E
455 1970 F
all of the above were for leaded fuels
Those with hardened seal areas that don’t require inserts:
455 1971 H
455 71-72 G
455 1972 Ga
455 71-72 J
455 73-76 (Cutlass) K
455 73-76 (Marine / Irrigation) K
403 77-79 4A
These all were for unleaded fuels.
Note that this information was for all applications of the 455, not just the GMC motorhome.
I have just created a gmcphotos.com http://gmcphotos.com/ album which has a more comprehensive listing.
See it at:
http://www.gmcmhphotos.com/photos/g7088-olds-big-block-heads.html http://www.gmcmhphotos.com/photos/g7088-olds-big-block-heads.html
Emery Stora
77 Kingsley
Frederick, CO
