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1992-’93: There were a number of changes to the head in 1992. The intake ports were arched on top to make room for the injectors, the intake valves were enlarged from 1.693" to 1.732" and conical springs with smaller retainers were used for the first time. Most of the valves in 1992-‘93 heads on them had 8.0 mm stems, but there may be some of these engines with service replacement heads that have 7.0 mm stems.
It really doesn’t matter which one the customer has when you’re selling a long block because the valves are identical otherwise.
All of these heads were 10112391 castings. The two holes for the crossover passage may or may not be drilled and tapped, but it doesn’t matter because the intake manifold for the port injected engines isn’t heated. However, the big hole in the front of the head for the water outlet should always be plugged because the water outlet housing is on the back of the head on all of the FWD engines.
1994-’97: The same casting that was used in 1992-‘93 was used from 1994-’97, but it had two additional bolt holes drilled diagonally in the front of the head for the RWD water outlet housing and it had 7.0 mm valves. Look for a 10112391 head with an "S" on the end of the casting number. The "S" can stand for three different things, depending on where you look.
The "S" means "standard" on the S-10 pickups, according to the truck microfiche, because all of the truck heads came standard with 7.0 mm stems.
The "J" and "L" cars had a first and second design head from 1993-’97 according to the car microfiche, so the "S" indicates that the head is the "second design" version with 7.0 mm valve stems.
The "S" heads were used as replacements for any 1992-’97 vehicle, so the "S" also identifies the later 7.0 mm head as a "service" part according to GM.
Some of the second design heads were used as service replacements on 1992-’93 cars, so the car microfiche spells out the difference between the first and second design heads to make sure the customer gets the right valves when buying them over the counter.
What really matters, though, is that the 10112391S is not a special head for certain applications as some rebuilders have believed. It actually fits all of the 1992-’97 FWD cars plus all of the 1994-’97 RWD applications, as long as the two diagonal holes are drilled in front of the head for the water outlet housing used on the RWD trucks.
Remember that the coolant crossover isn’t used anymore, so the holes don’t have to be drilled and tapped; and, they don’t have to be plugged if they are drilled and tapped.
