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**FirstOwner69** · 04-09-2016, 01:26 AM

Here are a series of excerpts from Section 6T "Exhaust Emissions Control Systems" of the 1969 GMC Service Manual that describe the operation and care of the flame arrestor. Most of the excerpts are taken from within paragraphs describing all parts of the emission systems.

This manual can be accessed in the link above in SS Tim's post (#11).

CRANKCASE VENTILATION SYSTEMS
DESCRIPTION
All engines are equipped with closed positive
type crankcase ventilation systems. However, the
system design varies from model to model (figs.
1 and 2). Fumes and vapors which would contaminate
the atmosphere are evacuated from the crankcase
and valve compartment(s) through ventilation
valves (figs. 3 and 4). These valves regulate the
flow of gases into intake valve ports in cylinder
head or intake manifold, where they mix with fuel
mixture from carburetor and are burned up in the
combustion chamber. Fresh clean air enters engine
through air cleaner and passes through hose
to rocker arm covers; it then circulates throughout
engine and is finally drawn out through vacuum
check valves and into intake valve ports. Flame
arresters are provided in the system to prevent
any backfire from air cleaner to engine internal
compartment.
It is extremely important that the system is
functioning properly or serious side effects could
occur, such as poor engine idle, excessive sludge
or contaminants in oil, or excessive oil consumption.

IN-LINE 6 AND V8 ENGINES (Fig. 2)
A flame arrester is installed in right
rocker arm cover on V- 8 engines and in hose between
rocker arm cover and air cleaner on Inline
engines.

INSPECTION AND MAINTENANCE
Flame arresters should be washed
in solvent and pressure air dried if not excessively
plugged. A badly plugged arrester should be discarded
and replaced with new unit.
In some cases where breathers are partially
plugged with carbon, it may be possible to clean breather by applying heat from blow torch, etc. If
this is done air pressure should be used to blow
out excess carbon ash when completed.

UNIT REPLACEMENT
FLAME ARRESTERS
1. Loosen hose clamps and remove hoses
from ends of arrester, remove arrester.
2. Install hoses to ends of new or cleaned
arrester, position hose clamps and tighten making
certain hoses are on arrester fitting completely.

04-09-2016, 01:26 AM	#14
FirstOwner69 Senior Member Join Date: May 2010 Location: Wisconsin & Arizona Posts: 4,854	Re: Is there a filter here Here are a series of excerpts from Section 6T "Exhaust Emissions Control Systems" of the 1969 GMC Service Manual that describe the operation and care of the flame arrestor. Most of the excerpts are taken from within paragraphs describing all parts of the emission systems. This manual can be accessed in the link above in SS Tim's post (#11). CRANKCASE VENTILATION SYSTEMS DESCRIPTION All engines are equipped with closed positive type crankcase ventilation systems. However, the system design varies from model to model (figs. 1 and 2). Fumes and vapors which would contaminate the atmosphere are evacuated from the crankcase and valve compartment(s) through ventilation valves (figs. 3 and 4). These valves regulate the flow of gases into intake valve ports in cylinder head or intake manifold, where they mix with fuel mixture from carburetor and are burned up in the combustion chamber. Fresh clean air enters engine through air cleaner and passes through hose to rocker arm covers; it then circulates throughout engine and is finally drawn out through vacuum check valves and into intake valve ports. Flame arresters are provided in the system to prevent any backfire from air cleaner to engine internal compartment. It is extremely important that the system is functioning properly or serious side effects could occur, such as poor engine idle, excessive sludge or contaminants in oil, or excessive oil consumption. IN-LINE 6 AND V8 ENGINES (Fig. 2) A flame arrester is installed in right rocker arm cover on V- 8 engines and in hose between rocker arm cover and air cleaner on Inline engines. INSPECTION AND MAINTENANCE Flame arresters should be washed in solvent and pressure air dried if not excessively plugged. A badly plugged arrester should be discarded and replaced with new unit. In some cases where breathers are partially plugged with carbon, it may be possible to clean breather by applying heat from blow torch, etc. If this is done air pressure should be used to blow out excess carbon ash when completed. UNIT REPLACEMENT FLAME ARRESTERS 1. Loosen hose clamps and remove hoses from ends of arrester, remove arrester. 2. Install hoses to ends of new or cleaned arrester, position hose clamps and tighten making certain hoses are on arrester fitting completely.