Pontiac tempest 1968 Service Manual page 218

6-1
ENGINE MECHANICAL
CONTENTS OF THIS SECTION
SIX CYLINDER ENGINE
V - 8 ENGINE
GENERAL DESCRIPTION
TEMPEST AND FIREBIRD ENGINES
The Pontiac Tempest and Firebird uses a 250 cubic
inch inline overhead camshaft six-cylinder engine as
standard equipment. This engine has a 3 7/8" bore
and 3 17/32" stroke with a compression ratio of
9.0:1. An optional overhead camshaft engine equipped
with a four-barrel carburetor has a compression
ratio of 10.5:1 with the same bore and stroke.
Six optional V-8 engines are available on special
order, two having 350 cubic inch displacement with
3 7/8" bore and 3 3/4" stroke. The compression
rations are 9.2:1 and 10.5:1. Four 400 cubic inch
displacement engines available in the G.T.O. have a
4.120" bore and 3 3/4" stroke. These engines have
compression ratios of 8.6:1 and 10.75:1. One of these
engines is for use in Ram-Air cars only and incor­
porates a camshaft and valve train specifically for
the Ram-Air engine.
Twenty-five different engine transmission combi­
nations are available. These combinations and their
usages are shown on the engine chart (Figs. 6-2 and
6-3).
Engine identification is facilitated by a letter code
stamped below the production engine serial number
on V-8 engines (Fig. 6-5). The code is stamped on
the block in front of the right bank of cylinders. The
engine code for 6-cylinder engines is stamped on the
cylinder head contact surface of the block behind the
oil filler pipe (Fig. 6-4)* By referring to the identi­
fication code and the engine chart, each engine may
be readily identified.
The vehicle identification number is stamped on
the right rear lower side of the six-cylinder engine
block and to the right of the timing chain cover on
V-8 engines (Fig. 6-6).
PONTIAC ENGINES
Pontiac V-8 engine is used in all models. Dis­
placement is 400 cubic inches provided by 4.120"
bore and 3 3/4" stroke in all models. A 428 and 428
High Output are available on special order. Dis­
placement in these special order engines is 428 cubic
inches provided by 4.120" bore and 4" stroke.
Three compression ratios are available: 8.6:1 on
regular fuel engines, 10
o
5:l on premium engines, and
10.75:1 on 428 high output.
Eleven different engine-transmission combinations
are available; these combinations and the major
components of each are shown in Fig. 6-1.
Engine identification is facilitated by a letter code
stamped below the production engine number. By
referring to Fig. 6-1 and using the identification
letters, major engine components can be determined.
The engine features completely machined combus­
tion chambers, overhead valves, ball pivot rocker
arm construction, harmonic balancer, hydraulic lift­
ers, aluminum pistons, straight valve guides, supe­
rior crankcase ventilation and lubrication systems,
and large displacement combined with high compres­
sion ratio for utmost performance and economy.