Technical Specs
1976 Pontiac W87 | 1976 L75 Package

1976 Pontiac Firebird Trans Am (W87) Technical Specifications

1976 Trans Am production figures(includes SE):
-L78 400cid w/M38(TH-350)- 33,752
-L78 400cid w/M21(4 speed)- 5,424
-L75 455cid w/M21(4 speed)- 7,528

**610775 is the last six VIN digits for the final 1976 Firebird model produced for the model year(TSB 77-PP-2, sect 10, dated 11/76)

Engine specifics:
-L78 400cid, 4bbl, 185hp@3600rpm(net), 310ft/lbs@1600rpm(net), bore/stroke of 4.12 x 3.75", 3" main bearing diameter, 2-bolt main caps.

-L75 455cid, 4bbl, 200hp@3500rpm(net), 330ft/lbs@2000rpm(net), bore/stroke of 4.15 x 4.21", 3.25" main bearing diameter, 2-bolt main caps.

Block codes/applications: -
-WT code, L78 400cid, 067 camshaft, carb# 17056263, distributor# 1112495, manual trans, for both A/C and non-A/C cars. -WY code, L78 400cid, 067 camshaft, carb# 17056263, distributor# 1112495, manual trans, for both A/C and non-A/C cars. -YS code, L78 400cid, 066 camshaft, carb# 17056264, distributor# 1112928, auto trans, for non-A/C ONLY.
-YZ code, L78 400cid, 066 camshaft, carb# 17056264, distributor# 1112928, auto trans, for A/C equipped only.
-ZK code, L78 400cid, 066 camshaft, carb# 17056564, distributor# 1113205, auto trans, both A/C and non A/C cars, California ONLY.
-WX code, L75 455cid, 067 camshaft, carb# 17056261, distributor# 1112923, manual trans, both A/C and non-A/C.

**All codes listed above are for applications with harmonic balancer. According to TSB 76-I-33, sect 6A, dated 2/2/76, a running change was made to 350 and 400 engines with automatic transmissions in which the the harmonic balancer was deleted and replaced with a damper or small balancer. All "Y" code engines were replaced with "X" as the first letter of the block code. This does not apply to "W" or manual transmission coded block. A few block codes such as X7 , have been found to exist.

Head codes:
-6X, L78 400cid head, secondary stamp of 8(known as "6X-8"), 101cc, 2.11" intake valve, 1.66" exhaust valve, 7.6:1 compression ratio, screw-in rocker studs, many varieties of the 6X exist, some have AIR(smog pump) plumbing.

-6S, L78 400cid head, secondary stamp of 7(known as "6S-7"), specific to Calif emissions vehicles, 101cc, 2.11" intake valve, 1.66" exhaust valve, 7.6:1 compression ratio, screw-in rocker studs.

-6H, L75 455cid head, secondary stamp of 6, 124cc, 2.11" intake valve, 1.66" exhaust valve, 7.6:1 compression ratio, screw-in rocker studs.

**Note: Other variations of the 455 head have been discovered for the 1976 model year. Most common has the same specifics as the 6H but are coded 6X-6. 6X-2 has been rumored as a possible head.

Intake:
-Casting number 525355, same 400/455 4bbl cast iron manifold, EGR, "D" shaped secondary openings.

Carb numbers/metering:

Camshaft specs:
-9779066, "066" or "N" cam, 273/282 advertised duration, 197/206@.050, .407/.407" lift w/1.5 rocker, 55 degrees overlap, 111.25 lobe separation angle, 106.5 centerline.

-9779067, "067" or "P" cam, 273/289 advertised duration, 197/212@.050, .407/.407" lift w/1.5 rocker, 54 degrees overlap, 113.5 lobe separation angle, 113.5 centerline.

Distributor specifics(all specs are at crankshaft rpm):
-1112495, WT block w/manual trans, 1100-4400 rpm advance curve, 18 degrees mechanical advance, vacuum advance can #1973493 with 25 degrees advance between 7-12"/hg.

-1112923, WX block w/manual trans, 1000-4400 rpm advance curve, 14 degrees mechanical advance, vacuum advance can #1973493 with 25 degrees advance between 7-12"/hg.

-1112928, YS(XS) and YZ(XZ) block w/auto trans, 1200-4400rpm advance curve, 16 degrees mechanical advance, vacuum advance can #1973493 with 25 degrees advance between 7-12"/hg.

-1113205 ZK block for Calif emissions, 1200-4400rpm advance curve, 16 degrees mechanical advance, vacuum advance can #1973545 with 20 degrees advance between 7-11"/hg.

Ignition coil:
-1876209 AC Delco coil, for all 400/455 applications listed above.

Spark plugs and wires:
-AC Delco R45TS spark plugs with .060" gap, 8mm AC Delco plug wires.

Idle speed:
-400/455 w/manual trans, 775rpm hot idle, 1800rpm fast idle.
-400 w/auto trans, 575rpm hot idle, 1800rpm fast idle, both Federal and Calif emissions.

Transmission:
-M38, MG code TH-350 for 400cid, research for specifics continues.
-M21, HW code Borg-Warner Super T-10 close-ratio 4 speed manual transmission, 400/455cid applications, 2.43 1.61 1.23 1:1 forward gear ratios, 2.35 reverse rear ratio, 10.4" clutch w/L78 400cid, 11.0" clutch w/L75 455cid, 2.5 pint fluid capacity.

Driveshaft specifics:
-M38, 48.55" long, 2.75" diameter, brown/brown stenciled identification striping.
-M21, 48.00" long, 2.75" diameter, yellow/yellow stenciled identification striping.
-Angles, .9 degrees front, 3.8 degrees rear, 5.2" upward jounce travel.

Axle specifics(1971 to 1981 GM 10-bolt 8.5" ring gear):
-PSG, 2.41:1 ratio, 41 tooth ring gear, 17 tooth pinion gear, M38 w/A/C applications only, limited slip series II carrier.
-PWG, 3.08:1 ratio, 41 tooth ring gear, 15 tooth pinion gear, M38 non-A/C or L78 400cid w/manual trans(either A/C or non-A/C) applications only, limited slip series III carrier.
-LDG, 3.23:1 ratio, 42 tooth ring gear, 13 tooth pinion gear, L75 455cid w/manual trans(either A/C or non-A/C) applications only, limited slip series III carrier.

Speedometer gears:
-part number 3987919, 19 tooth natural color, both L78/L75 equipped cars with M21 manual trans, both 3.08 and 3.23 axle ratios.
-part number 1359270, 36 tooth white color, L78 400cid with M38 auto trans and 2.41 gears. -part number 1362049, 42 tooth green color, L78 400cid with M38 auto trans and 3.08 gears.

Wheels:
-Rally II rim, HW code, 15 x 7", N67 body color or N98 argent color.
-Honeycomb rim, HP code, 15 x 7".
-Space saver rim, XA code, 14 x 5" black rim with inflatable tire.

Tires: -GM tread design with the "Steel Belted Radial" styling. Standard equipment were option code QBX GR70x15 blackwall radial tires. Option code QCY GR70x15 white lettered tires available in Goodyear, BF Goodrich, Uniroyal or Firestone brand names were a $38.40 option.

**Note: All Trans Ams were shipped with 4 radial tires and a space-saver spare. Due to shortage, cars built after 5/17/76 and VIN 580449 were shipped without a space saver spare(TSB 77-PP-2, dated 11/76, Sect 10). Spare was furnished by dealer when supplies became available. A notice was placed on bottom of window sticker on cars shipped without spare.

Starter specifics:
-1108759, starter motor, 400/455
-1114396, starter solenoid, 400/455

Battery specifications:
-R87P, standard L78/400, 350 cold cranking amps, 80 minute reserve, 3200 watts.
-R89SP, standard L75/455, 430 cold cranking amps, 100 minute reserve, 3500 watts.
-R89WP, 400/455 w/UA1 heavy duty battery option, 465 cold cranking amps, 125 minute reserve, 4000 watts.

Alternator specifics:
-1102384, standard alt, 37 amp.
-1102385, with A/C or rear defroster, 55 amp.
-1101016, with A/C and rear defroster, 80 amp with idler pulley.

Radiator specifics:
-standard, FI L75/455 w/manual trans both A/C and non-A/C, FQ L78/400 w/manual trans both A/C and non- A/C, FN L78/400 w/auto trans non-A/C, FC L78/400 w/auto trans and A/C, 21.2 quart capacity, part number 3031059.
-V02 Super Cool option, 400/455 both A/C and non-A/C, FA w/manual trans, FU w/auto trans, 23.3 quart capacity, part number 3032109.

**Note: VO2 is required w/manual trans and A/C.

Exhaust specifics:
-260cid catalytic converter, part number 8998244, both 400/455 applications.
-standard muffler, L78/400, part number 547836, single inlet/dual outlet.
-low restriction muffler, L75/455 only, part number 525406, single inlet/dual outlet.
-tailpipe with chromed exhaust splitter, 525321 RH, 525372 LH.

Steering box specifics:
-Saginaw 13:1-15:1 variable ratio power steering unit with low effort valving.

Sources: 1975 Pontiac Service Manual, 1976 Pontiac Service Manual Supplement, 1976 Pontiac Technical Service Bulletin set, 1976 Pontiac Craftsman Service News issue numbers 1 through 4, 1975 Pontiac Craftsman Service News issue number 4, 1967-1975 Pontiac master parts catalog, 1976-1981 Pontiac master parts catalog, and "Pontiac High Performance Handbook" by Pete McCarthy.  Special thanks to John Witzke, John Viale, Jim Hand, Pete McCarthy and Nunzi Romano for assistance with the on-going search for more information.

Updated 6/6/01

1976 Pontiac Firebird Trans Am - L75-455/4-speed package specifics:

Total production:
Base W87 Trans Am:  7,099
Special Edition T/A w/o T-tops:  319
Special Edition T/A w/T-tops:  110
         Total: 7,528

Option added $125 to price of vehicle and consisted of the following:

Block:
-WX code 455, bore/stroke 4.15 x 4.21", 3.25 main bearing diameter,  2-bolt main caps, 200hp@3500rpm(net), 330ft/lbs@2000rpm(net).

Heads:
-6H, secondary stamp of "6", 124cc, 7.6:1 compression ratio, 2.11/1.66" valves, screw-in rocker studs,

Carburetor:
-17056261 Rochester Quadrajet, 70 primary jets, 42K primary rods, DB .0697" secondary rods, M secondary hanger.

Distributor:
-1112923 HEI distributor, 1000-4400 rpm advance curve, 14 degrees total mechanical advance, vacuum advance can #1973493 with 25 degrees of  advance at 7-12"/hg.

Radiator:
-radiator code, FI w/non-A/C, FA w/A/C 21.2 quart capacity.

Transmission:
-HW code Borg-Warner Super T-10 close ratio 4-speed manual transmission,  2.43 1.61 1.23 1:1 forward gear ratios, 2.35 reverse gear ratio, 11" clutch, 2.5 pint case fluid capacity.

Rear axle:
-LDG code, 3.23:1 ratio, limited slip differential rear axle.

Brakes:
-semi-metallic front brake pads and rear drum shoes from Police package.

Exhaust:
-specifically tuned exhaust with #525406 low restriction single inlet/dual outlet transverse mount muffler, #525321 RH tailpipe and  #525372 LH tailpipe, chromed exhaust splitters.

Decals:
-specific "455" engine call-outs on shaker scoop.

Source: 1975 Pontiac Craftsman Service News, issue 4, pages 59-60

1976 Pontiac W87 | 1976 L75 Package

Research by Rocky Rotella