Engine
Reconditioning Overview & Tips
For your 1929-1955 Chevrolet Straight Six Engine
Part
I continued, <<<
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In
1949, with minor modifications and a 6.6:1 compression ratio the
engine developed 92 bhp at 3400 rpm.
In
1950 the Powerglide automatic transmission was introduced and
engines to be used with this transmission had a displacement of
235.5 cu. in. (3 9/16 x 3 5/16 in. bore and stroke). Powerglide
engines had hydraulic valve lifters. An important improvement
on 1953 Powerglide engines was the introduction of full-pressure
lubrication.
The
6 cylinder engines for 1955 are available in two models.- Standard
transmission models with solid valve lifters, Powerglide models
with hydraulic lifters. On account of a different camshaft, the
Powerglide engine develops 136 hp as against 123 hp on the standard
transmission model. Compression ratio is 7-5:1.
Pistons
are cam-ground cast aluminum alloy. Piston pin bosses are bored
5/64 in. off-center to reduce piston slap when the engine is cold.
Two compression rings and one oil control ring are used on each
piston.
The
compression rings are of the deep section twist type. The oil
control ring is composed of an upper rail, a lower rail, a separator
and an expander of zig-zag type. The exhaust valves are of solid
alloy steel and "aldipped" on the seat portion to insure long
valve life. The cast iron camshaft runs in four bearings; a special
high-lift type is used in the Powerglide model.
The
same cylinderhead is used on both engines and designed to give
a 7.5:1 compression ratio. A full-pressure system is now used
on all engines; a gear-driven oil pump maintains 35 pounds pressure.
Lubrication of the valve mechanism is supplied by a drilled passage
from the rear camshaft bearing to a pipe located under the push-rod
cover to a fitting at the top of the cylinder block. A bleeder
hole in each rocker arm supplies oil for lubrication of valve
stems and pushrod sockets. Lubrication control of the inlet and
exhaust valve stems is provided by an oil seal. A synthetic rubber
seal fits in a groove between valve stem and valve spring cap.
Seal and cap are interchangeable between intake and exhaust valves.
On
Powerglide engines a direct oil feed is maintained to the lifters
at all times through a 9/16 in. gallery which runs the full length
of the engine.
Questions
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Read
Part I, overview of the straight six engine
Read
Part II, engine removal and reinstallation
Read
Part III, cylinder block and rod/piston assembly
