Locomotive Phases and Rosters - EMD/IC GP8

The GP8 is an Illinois Central rebuild of older GP7 and GP9 units. The phases below are for the GP8 rebuilds themselves and do not reflect the phases of the original locomotives prior to rebuilding. IC GP10 rebuilds followed similar phases, except with no Phase 4a; see GP10 Phases.

According to the roster at illnois-central.net, all units I've labelled as Phase 1a and 1b (and one Phase 2 unit, IC 7974) are classfied as GP7, though they bear many of the spotting features of later GP8 units.

These phases are of my own making.

Phases

Phase 1a: 1967-1968 (GP7)

The first few units rebuilt in 1967-1968 had inconsistent spotting features. All lack the central air intake of later units, and a couple still had a high short hood.

Phase 1b: 1968-1969 (GP7)

These units were very similar to Phase 2 units, except they had a cab-mounted headlight.

Headlight: Vertical early-style Pyle headlight on cab
Air filters: Horst (above roof)
Cab roof: rounded (original GP7-GP18 profile)

Phase 2: 1969-1971

Headlight: Horizontal early-style Pyle headlight on short hood

Phase 3a: 1971-1977

Headlight: Vertical, recessed early-style Pyle headlight on short hood

Phase 3b: 1977

Air filters: Dynacell (on hood sides)

Phase 3c: 1977-1978

Headlight: Vertical, flush later-style Pyle headlight on short hood

Phase 4a: 1977

Headlight: Vertical, recessed early-style Pyle headlight on short hood
Cab roof: angled (later EMD style)

Phase 4b: 1977-1978

Headlight: Vertical, flush later-style Pyle headlight on short hood

Other details

IC GP8's were not rebuilt in order based on their roadnumber, although some units - all numbered after IC 7850 - were rebuilt from corresponding 8000-series units (ie. 8901 became 7901 and so on).

Lights and air filters

Between the number boards, units prior to Phase 3a generally had a Gyralite (with red top lens and clear bottom lens) while those after Phase 3a generally had an Oscitrol light (two clear, angled lenses above a red lens). Phase 3a units had a mix of both light types. These lights were subsequently removed in most cases.
Horst air filters had various housings. The vertical duct extending over the hood sides varied in height, with either an angled or rounded top. It was also absent altogether on many units (leaving only the housing on the roof). A few very late Phase 3a GP8's (IC 7727, 7728, 7730 and 7906, perhaps others) had an angular, tapered duct with a wider opening at the bottom.
Dynacell air filters had a square panel that was either bolted or hinged, with the latter generally appearing on later units.

Frame and hood

Many GP8's were rebuilt from GP9's. In the process, a majority received early GP7 hoods with 86" engine room doors and full-height hood straps. The rest received late GP7 hoods with 82" doors (unless they were GP9 hoods with GP7 louver arrangements). These units retained the air reservoir piping arrangement and welded coupler pockets characteristic of the GP9.
Most Phase 1 and Phase 2 units retained the 4 groups of louvers at the rear of the hood (2 groups of louvers each on the 1st and 4th doors from the hood end) which was a GP7 spotting feature. Almost all later units (including GP9 rebuilds) had 2 GP7-style louver groups on the rearmost door only.

Misc. details

Depending on the locomotives used for rebuilding, units of all phases may have front or rear fuel fillers and 36" or 48" fans. The latter appeared only as a retrofit on some Phase 1 units, and the vast majority of GP8's had 36" fans.
Earlier rebuilds (up to early Phase 3a units) retained pilot footboards at both ends. These were generally replaced with flat pilot plates after the late 1970s. Late Phase 3a, all Phase 3b (except perhaps IC 7712) and all Phase 3c/Phase 4 units had either flat pilot plates at both ends, or a flat plate at the rear and plow at the front.

Roster

The following illustrates the phases of GP8 production for units with IC numbers. Notes about the roster:

Frame of donor unit: "7" indicates GP7, "9" indicates GP9
Hood: "E" indicates early GP7 hood with 86" engine room doors and full-height hood straps; "L" indicates late GP7 hood with 82" doors.
Note (1): GP7 louver arrangement under rear radiator intake (2 groups of louvers each on the 1st and 4th doors from the hood end)
Note (2): Angular, tapered duct on Horst air filter housing

Rebuild dates are courtesy of the roster at illnois-central.net.

Sort by: Number - Phase

IC Number	Rebuilt	Phase	Model	Frame	Hood	Notes
7700	1974	3a		9	L
7701	1975	3a		7	E
7702	1974	3a		9	L
7703	1974	3a		7	L
7704	1974	3a		9	E
7705	1974	3a?		7	L?
7706	1974	3a		7	E
7707	1974	3a		7	L
7708	1974	3a		7	E
7709	1974	3a		7	L
7710	1975	3a		9	E
7711	1974	3a		7	E
7712	1974	3b		9	E
7713	1974	3a		7	L
7714	1974	3a		7	L	GP9 hood louvers
7715	1974	3a		9	E
7716	1974	3a?		7	E?
7717	1974	3a		7	E
7718	1974	3a		7	E
7719	1975	3a		7	E
7720	1977	3a		7	E
7721	1977	3a		7	E
7722	1977	3a		7	E
7723	1975	3a		7	L
7724	1976	3a		9	L
7725	1975	3a		9	E
7726	1977	3a		7	E
7727	1977	3a		7	L	(2)
7728	1977	3a		7	E	(2)
7729	1976	3a		7	E
7730	1977	3a		7	L	(2)
7731	1977	3a		7	L
7732	1976	3a		7	E
7733	1975	3a		9	L
7734	1977	3b		7	L
7735	1975	3a		7	E
7736	1975	3a		7	E
7737	1975	?		7		Rebuilt to GP11
7738	1975	3a		7	E
7739	1975	3a		9	E
7740	1975	3a		7	E
7741	1975	3a		9	E
7742	1975	3a		9	L
7743	1976	3a		7	L
7744	1976	3a		7	L
7745	1976	3a		7	L
7746	1977	3c		7	E
7772	1977	?
7773	1975	?
7800	1977	4b		9	L
7850	1973	3a		7	E
7851	1969	3a	GP10	7	E
7852	1973	3a		9	E
7900	1977	3a		7	E
7901	1972	3a		7	L
7902	1975	3a		7	L
7903	1977	3b		7	E
7904	1972	3a		7	E
7905	1972	3a		7	E
7906	1977	3a		7	E	(2)
7907	1975	3a		9	L
7908	1977	4b		7	E
7909	1971	3a		7	L
7910	1977	3c		7	E
7911	1977	4a		7	L
7912	1977	4b		7	E
7913	1977	3c		7	L
7914	1977	4b		7	L
7915	1978	4b		7	E
7916	1978	3c		7	E
7917	1978	4b		7	E
7918	1978	4b		7	E
7950	1969	2		7	E
7952	1975	3a		7	E
7953	1973	3a		9	E
7954	1977	4a		7	E
7955	1972?	2		7	E
7957	1969	1b	GP7	7	E
7960	1967	1a	GP7	7	E	high short hood
7961	1968	1a	GP7	7	E	high short hood
7962	1974	3a		7	E
7963	1977	3b		7	L
7964	1968	1a	GP7	7	E	48" fans, (1)
7965	1977	3c		7	L
7966	1968	1b	GP7	7	E	48" fans, (1)
7967	1977	3b		9	L
7968	1969	1b	GP7	7	L	(1)
7969	1969	1b	GP7	7	L	(1)
7970	1973	3a?		9
7971	1968	1a	GP7	7	L	(1)
7972	1969	2		7	L	(1)
7974	1969	2	GP7	7	L	(1)
7976	1969	2		7	L	(1)
7978	1971	2		7	L	(1)
7979	1969	2		7	L	(1)
7981	1968	1b	GP7	7	L	48" fans, (1)
7982	1972	3a	GP7	7	E	To IC 7900
7983	1972	3a	GP10	7	E	(1)
7984	1972	3a	GP10	7	E
7985	1972	3a	GP10	7	E	(1)
7986	1973	3a		9	E
7987	1973	3a		9	E
7988	1973	3a		9	E
7989	1972	3a		7	E
7990	1972	3a		7	E	Additional hood louvers
7991	1972	3a		7	L
7992	1972	3a		7	L	(1)
7993	1972	3a		7	L	Additional hood louvers
7994	1973	3a		7	E
7995	1973	3a		9	E
7996	1973	3a		9	L
7997	1973	3a		9	L
7998	1973	3a		9	E
7999	1973	3a		9	L