Bill Boyle's 400 Rebuild
My goal was to
build a powerful but reliable low compression street engine...to do
it right the first time and to keep emissions in proper perspective.
Car: 1979 Trans Am with TA/6.6--400 engine--an original L-78/W-72
220 net hp engine with 6X-4 heads and 8.1.to 1 compression
Technical Data
- Bore and stroke--4.15" x 3.75"--bored .030 to accommodate
forged pistons with moly rings; journals align honed
- Heads--stock 6X (6x-4) heads--3 angle competition valve job retaining
original 2.11" and 1.66" valves; valves reconditioned; bronze
valve guides; heads surfaced to 94 cc's
- Crankshaft--reconditioned .020 undersize; journals polished
- Rods--stock reconditioned with ARP bolts
- Pistons--TRW forged +.030; deck height averages .0065" +/-
.001" on each cylinder
- Rings--moly--Sealed Power (Federal Mogul) SP E-299K 30
- Main Bearings/Rod Bearings/Cam Bearings--Michigan (Clevite77)
- Timing Gear and Chain--Edelbrock
3-key way true roller (PN 7812)
- Camshaft--Comp Cams 270H;
.476" lift Intake/Exhaust; 224/ 224 degrees duration (fair idle, good
low and mid-range torque); cam is "straight-up"
at 106 degrees.
- Valve Springs--Crower; shims on intake to get proper installed height
- Rocker Arms--Comp Cams--Magnum Roller Rockers (1.52)
 with
7/16" rocker studs (ARP) and 7/16" poly lock nuts with set screw
(Mr. Gasket) #921
- Retainers--OEM
- Keepers--OEM
- Valve Seals--umbrella type
- Lifters--Comp Cams (PN 852-16)
- Push Rods--moly--Comp Cams (PN 7262-16)
- Gasket Set--Fel Pro--(note
this engine used 5 tang rear seal)
- Carburetor--1979 Stock Quadrajet (rebuilt original)
- Intake Manifold--Stock OEM for L-78/W-72 (restricted secondaries)
- Emissions--No
EFE; all other stock devices retained including EGR
- Exhaust manifold--Hooker Super Competition Headers 1.75" primaries;
2.5" pipes
- TransDapt remote oil filter--uses AC PF-2 filter; Aeorquip braided
lines/fittings
- All reciprocating parts are balanced; all tolerances meet OEM specifications
Note: These components work well with 4 speed;
3.23 gears to 3.73. More gear is impractical for street use unless gas consumption
is completely unimportant. This low compression engine runs on pump gas.
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