US3157168A

US3157168A - Spark control valve for ignition distributors

Info

Publication number: US3157168A
Application number: US83441A
Authority: US
Inventors: Melvin F Sterner; Kalin S Johnson; Fred S Kerr
Original assignee: Holley Carburetor Co
Current assignee: Holley Performance Products Inc
Priority date: 1961-01-18
Filing date: 1961-01-18
Publication date: 1964-11-17
Anticipated expiration: 1981-11-17

Description

Nqv. 17, 1964 M. F. STERNER ETAL 3,157,163

SPARK CONTROL VALVE FOR IGNITION DISTRIBUTORS 2 Sheets-Sheet 1 Filed Jan. 18. 1961 SRN mu m E H V T 0 m is N IN mu m E A MK mm Y N B mm C x/ mm mm; w mm a w mm "a 8 Vb m NM cw in 3 mm 2 mm V. w.

1964 M. F. STERNER ETAL 3,157,168

SPARK CONTROL. VALVE FOR IGNITION DISTRIBUTORS 2 Sheets-Sheet 2 400 ENGINE SPEED R.P.M.

Filed Jan. 18, 1961 S S M N C R O N m a W S we 2 N 0 ONE .l. EH T AA! 9 NTOR H E A K T J ES F 3 "MD 85. N s a LLE w AR MKF Y B a L 0 m u w M 3 C r I! U a: a a F I IHH wll wlw a 2 3 United States Patent 3,157,168 SPARK CUNTRUL VALVE FUR IGNITIUN DISTRIBUTORS Melvin F. Sterner, moonit'ieid Hills, and Kalin S. Johnson, Northville, Mich, and Fred S. Kerr, Reading,

Mass, assignors to Holley @arhuretor Company, Warren, Mich, a corporation of Michigan Filed Jan. 18, 1961, Ser. No. 83,441 15 Claims. (Cl. 123-117) The invention relates to spark advance apparatus for internal combustion engines and refers more specifically to means including a vacuum actuated spark control valve and a throttle operated valve for regulating the vacuum applied to vacuum actuated spark advance mechanism to provide an optimum spark advance over normal engine operating ranges.

In the past spark advance apparatus for internal combustion engines utilizing vacuum actuated spark advance mechanism have been known. Such apparatus usually comprises restricted vacuum line-s connected to the manifold and venturi of an engine fuel and air intake passage, which lines are connected together and to the vacuum actuated spark advance mechanism.

Such prior vacuum type spark advance apparatus has had undesirable characteristics in that the spark advance provided thereby does not conform to the spark advance requirements of the engine at all speeds. This is particularly true at low engine speed.

It is therefore one of the objects of the present invention to provide vacuum type spark advance apparatus for an internal combustion engine including improved means for combining manifold and venturi vacuums to produce optimum spark advance over the normal operating range of the engine.

Another object is to provide improved vacuum type spark advance apparatus for an internal combustion engine including vacuum actuated spark advance mechanism and means to regulate the vacuum applied to the spark advance mechanism during low engine speeds to provide optimum spark advance at low engine speeds.

More specifically it is an object to provide improved vacuum type spark advance apparatus for an internal combustion engine comprising vacuum actuated spark advance mechanism, a vacuum line for connecting the spark advance mechanism to the venturi of the air and fuel intake passage of an engine and means in parallel with the vacuum line to connect the spark advance mechanism to the manifold of the air and fuel intake passage including a spark control valve and throttle controlled valve operable to regulate the Vacuum applied to the spark advance mechanism to provide optimum spark advance at all engine speeds.

Another object is to provide vacuum type spark advance apparatus as set forth above wherein the spark control valve comprises a vacuum line having a restriction therein and a vacuum operated valve in series with said restriction operable on manifold vacuum reaching a predetermined value with said throttle operated valve actuated a predetermined amount to connect the spark advance mechanism through said restriction and throttle operated valve to a vacuum line opening into the manifold of the fuel intake passage of the engine.

Another object is to provide vacuum type spark ad- I vance. apparatus as set forth above wherein the throttle operated valve comprises a housing having a cylindrical recess therein into which vacuum lines extending to the engine manifold, the spark valve, and the spark advance mechanism open, and means within the throttle operated valve operable during opening of the throttle of the internal combustion engine with which the vacuum type spark advance apparatus is associated to, connect. the.

3,152,168 Patented Nov. 17., 1964 spark advance mechanism with the spark valve and the manifold vacuum line.

Another object is to provide vacuum type spark advance apparatus as set forth above wherein the last mentioned means includes an arcuate slot providing first for communication between the spark advance mechanism and the spark valve and then between the spark advance mechanism, the spark valve and the manifold vacuum line on rotation of the throttle associated with the throttle operated valve, and a restricted passage is provided between the spark valve and manifold vacuum line.

Another object is to provide vacuum type spark advance apparatus as set forth above wherein a variable or contoured restriction is first provided between the spark advance mechanism and spark valve during the initial rotation of the throttle to provide communication between the spark advance mechanism and spark valve.

Another object is to provide an improved vacuum type spark advance apparatus which is simple in structure, economical to manufacture and efficient in use.

Other objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawings, illustrating a preferred embodiment of the invention, wherein:

FIGURE 1 is a diagrammatic representation of vacuum type spark advance apparatus for an internal combustion engine according to the invention.

FIGURE 2 is an elevation view of the throttle operated valve of the spark advance apparatus illustrated in FIG- URE 1.

FIGURE 3 is a partial section of the throttle operated valve shown in FIGURE 2 taken on the line 33 in FIGURE 2.

FIGURE 4 is a graphic representation of spark advance in engine degrees plotted against engine speed in revolutions per minute showing the spark advance obtained by the usual two-hole vacuum type spark advance apparatus and optimum spark advance requirements at Various engine speeds, and different constant manifold vacuums.

FIGURE 5 is a diagrammatic representation of a modification of the vacuum type spark advance apparatus illustrated in FIGURE 1.

With reference to the figures, a particular embodiment of the invention will now be disclosed.

In accordance with the invention spark advance mech anism generally indicated lit, throttle operated valve 12 and spark valve 14 are connected together with vacuum lines i6, 113, 20, 22 and 2d and to the venturi 26 and manifold 28 of the fuel and air intake passage 39 of an internal combustion engine, as shown in EGURE 1 to provide optimum spark advance for the internal combustion engine with which they are associated at substantially all en ine speeds.

The apparatus shown in FIGURE 1 operates to combine venturi and manifold vacuum to provide optimum spark advance for the associated internal combustion engine. Thus as the throttle operated valve rotates during opening or closing of the throttle 32, manifold vacuum controlled by the restriction 3d at the venturi end of vacuum line In and by restriction 3-6 in vacuum line 18 acts to position rod 38 of the spark advance mechanism to provide optimum sparkadvance; On further opening of throttle 32 the manifold vacuum line 24 is connected directly to the spark advance mechanism 1% through vacuum line 2% and the vacuum applied to the spark' 2060 rpm.

3 degrees of rotation of the engine is plotted against engine speed in revolutions per minute at difl'erent constant manifold vacuums. The spark advance provided by the usual two-hole vacuum type spark advance systems is shown in solid lines at different constant manifold pressures. The spark advance required by the engine for optimum operation is shown in dashed lines at similar constant manifold vacuums.

It can be seen'for example by comparing the solid line indicated 2 with the dashed line indicated 2" that the spark advance provided by the usual two-hole vacuum type spark advance apparatus for internal combustion engines is much greater than the optimum spark advance required by the engine for engine speeds below The same is true of the spark advance with respect to advance requirements at other constant manifold pressures as indicated by the other sets of dashed and solid lines shown in FIGURE 4.

The structure of the invention provides means by which the actual spark advance maybe caused to closely approximate the required spark advance over the entire range of operation of the engine associated with the spark advance apparatus.

As shown best in FIGURE 1, the spark advance mechanism ltl comprises a housing 42 having secured between the parts thereof a flexible diaphragm d4. Diaphragm 44 has secured thereto by-means of clamping plates 46 and the rod 33. Spring 59 is positioned in housing 4-2 to urge the diaphragm 44 toward the right in FIGURE 1.

On the creating of a vacuum in chamber 52 form-ed by a part of housing 42 and the diaphragm through vacuum line lid connected thereto as shown, the rod 38 will be caused to move to the left as shown in FIGURE 1 whereby the ignition contacts 55 and the disc 54 pivoted about the distributor timing cam 56 will be caused to rotate in a direction indicated by the arrowdS to advance the spark of the internal combustion engine associated therewith by an amount dependent upon the vacuum in chamber 52. The spark advance mechanism it is well known in the art.

Vacuum line 16, as illustrated in FIGURE 1 is connected through a restriction 34 to the venturi 26 of the air and fuel intake passage of the internal combustion engine with which the spark advance apparatus is associated. The fuel and air intake passage 36 as shown includes the fuel feed means 69, throttle 32 and a manifold vacuum passage 62 to which one end of the vacuum line 24 is connected.

Spark valve 14 is connected to vacuum line 16 through vacuum line 18 having restriction 36 therein, as shown in FIGURE 1. The spark valve comprises a housing 64 having a partition 66 with an annular opening 68 therein extending transverse thereof, as shown in FTGURE l. A flexible diaphragm is also provided within housing 64 and extends parallel to partition 65 to provide a vacuum chamber 72 within housing 64. Valve structure 74 is secured to diaphragm 70 by clamping plates 76 and 78 and is urged by spring till into seating engagement around the periphery of the opening 63 in partition do.

On sufiicient vacuum being drawn in chamber 72 through

vacuum conduits

62, 24 and 22 as by means of arcuate slot 98 and line 2?. connected to housing 64, as shown, the valve '74 is caused to move in opposition to spring 80 to permit a vacuum to be drawn through vacuum line 18, restriction 3d and vacuum line 16 to cause rod 38 to move to the left and advance the spark of the associated engine as previously indicated.

The throttle operated valve 12' comprises a body member 32 having a cylindrical recess 84 in one side thereof and a through opening 8-5 extending transversely therethrough, as shown best in FTGURE 3. Vacuum lines 20, 22 and 2.4 are connected to passages 83, t and 92 in body member 32 which passages terminate in the cylindrical recess in the body member 82 in arcuate relation to each other, as shown best in FIGURES 1 and 2.

A cylindrical valve 94 having shaft 96 secured thereto and having an arcuate recess as in the inner surface thereof is positioned in the recess 84 in body member 32, as shown best in FEGURE 3, with the shaft 96 extending through the opening 86 in body member 82. Valve 94 is held in position against the bottom of the recess 34 by means of spring 1% and cover Th2 which is secured to body member 32 by convenient means such as screws A seal 105 with appropriate passages is provided between valve 34 and body member 82 as shown.

Actuating means for rotating valve 94 in conjunction with operation of the throttle 32; is provided in the form of connecting link 106 which is secured to shaft 96 by means of set screw 168.

As the throttle 32 is rotated toward the open position, shown in broken lines in FIGURE 1, link 1% which is mechanically connected thereto is caused to move so that valve 94 is rotated in the direction of arrow 112 in FIC- URE l. Rotation of valve 94 in the direction of arrow 312 causes passages 8d and to first be connected through arcuate slot 8. On further rotation of valve 94 passage 2 is also connected by means of the arcuate slot 9% to

passages

88 and 90.

Thus in over-all operation as the throttle 32 is rotated to produce an engine speed above idling speed the throttle operated valve 12 operates to connect vacuum lines 22 and 24 whereby full manifold vacuum is applied to the spark valve 14 to cause the valve '7 thereof to open and manifold vacuum, a part of which is bled off through the venturi restriction 34, is applied to the spark advance mechanism it to produce spark advance as required by the engine wi h which the spark advance apparatus shown in FIGURE 1 is associated. As the valve 94 operates to fully connect

passages

88 and 98 on rotation-of throttle 32, the manifold vacuum applied to the spark advance mechanism 39 is further regulated by the restriction 36 in vacuum line 18.

As the throttle is opened manifold vacuum drops permitting valve 74 to close and venturi vacuum increases to control the spark advance. On continued opening of the throttle 32 vacuum line 20 is connected to vacuum line 24 through the arcuate recess 98 whereby venturi vacuum is bled to the engine manifold and controlled by means of restriction 40.

The modification of the vacuum actuated spark advance apparatus of the invention illustrated in FIGURE 5 is similar in structure to the spark advance apparatus of FIGURES 1-4. Therefore, the same reference numerals followed by the suifix a will be used in designating similar elements of the modified spark advance apparatus. The spark advance mechanism ltla, spark control valve 14a and the venturi 26a and manifold 23a. of the air intake passage 3% are the same as those illustrated in FIGURES 1-4 and described above. They will therefore not be considered in detail.

The restriction 49:; previously in the vacuum line 20 has been transferred to the vacuum line 24a in the modified apparatus and the spark valve 14a is connected directly to the manifold vacuum line 24a and the passage Qtla, as shown in FIGURE 5. Also, the cylindrical valve 94a of the tnrottle controlled valve 12a is connected to rotate counterclockwise as shown in FIGURE 5 as the throttle 32a is rotated in an open direction.

In addition in the modified apparatus the passage Ztla terminates in a contoured end 118 to provide a variable orifice registering with the arcuate slot 9E6! of the throttle vance at low engine speeds may be provided for particular conditions by properly contouring the opening 118.

Further in the modified apparatus it will be seen that there is a restricted passage 114 extending between the passages 90a and 88a of the throttle operated valve 12a. The passage 114 having the restriction 116 therein is positioned in parallel with the spark valve 14a and serves to connect the spark advance mechanism a directly to the manifold vacuum line 24a simultaneously with the connecting of the spark valve 14a between the spark advance mechanism and the vacuum line 24a. Thus even at very low engine speeds and before the sparkrvalve 14a is actuated some spark advance due to manifold vacuum is provided. Thus due to the provision of the restricted passage 114 further control of the spark advance mechanism at low engine speeds is accomplished.

In operation of the spark advance apparatus illustrated in FIGURE 5 the cylindrical valve 94a. of the throttle operated valve 12a is caused to rotate in a counterclockwise direction on counterclockwise rotation of the throttle plate 32a toward an open position. On initial counterclockwise rotation of the cylindrical valve 9411 the contoured end 118 of the passage 96a is opened to the arcuate slot 98a over five or ten degrees of rotation of the valve 94a. The spark valve 14a. is thus connected between the spark advance mechanism 16a and the manifold vacuum line 24a through a variable restriction as by means of the coaction of contoured opening 118 and slot fia. Due to the contouring of the opening 118 the vacuum felt at the spark advance mechanism is maintained at an optimum desirable amount during the initial opening of the throttle 32a. When the opening 112 is fully open and the spark valve 14:: actuated the flow through the spark valve 141; will be controlled by the restriction 36a in conduit 18a as before.

Further it will be noted that as the passage 90a is connected to the vacuum advance mechanism 10a that the vacuum advance mechanism 10a is also simultaneously directly connected to the manifold vacuum line 24a through the passage 114 having the restriction 116 therein. Thus a small manifold vacuum will be felt on the vacuum advance mechanism before the spark valve 14a is actuated providing further control of the vacuum advance mechanism 10a at low engine speeds.

On subsequent counterclockwise rotation of the cylindrical valve 94a the arcuate slot 98a connects the passages 88a and 92a. At this time the venturi vacuum applied to the spark advance mechanism 10d is primarily controlled by the orifices 34a and 40a as before.

Thus in accordance with the invention vacuum type spark advance apparatus is provided whereby the actual spark advance produced thereby may be shaped to provide optimum spark advance for the internal combustion engine associated therewith over the normal range of operation thereof. Further, the spark advance apparatus as disclosed is simple in construction, economical to manufacture and efficient in use.

The drawings and the foregoing specification constitute a description of the improved vacuum type spark advance apparatus for ignition distributors in such full, clear,

concise and exact terms as to enable any person skilledmanifold vacuum, comprising vacuum actuated spark advance mechanism, means connecting said spark advance mechanism through a restriction directly to the source of venturi vacuum, a vacuum controlled spark valve located between the spark advance mechanism and the source of manifold vacuum, and means for first connecting said spark advance mechanism to the source of mani-' it) fold vacuum through said spark valve and subsequently separately connecting said spark advance mechanism through a restriction to the source of manifold vacuum directly.

2. Spark timing control apparatus for an internal combustion engine which engine includes an air induction passage including a venturi providing a source of venturi vacuum and an engine manifold providing a source of manifold vacuum, comprising vacuum actuated spark advance mechanism, means connecting said spark advance mechanism through a restriction directly to the source of venturi vacuum, a vacuum controlled spark valve located between the spark advance mechanism and the source of manifold vacuum, and means for first connecting said spark advance mechanism to the source of manifold vacuum through a restriction and said spark valve and subsequently separately connecting said spark advance mechanism through a restriction to the source of manifold vacuum directly.

3. Spark timing control apparatus for an internal cornbustion engine which engine includes an air induction passage including a venturi providing a source of venturi vacuum, an engine manifold providing a source of manifold vacuum and a throttle valve in the air induction passage, comprising vacuum actuated spark advance mechanism, first means including a first restricted passage having a spark valve and a separate throttle actuated valve connected in series therein for connecting said spark advance mechanism to the source of manifold vacuum, second means for bleeding off a portion of said manifold vacuum and for connecting said spark advance mechanism to said source of venturi vacuum, and third means distinct from said first means for bleeding off a portion of said venturi vacuum.

4. Spark timing control apparatus for an internal combustion engine which engine includes an air induction passage including a venturi providing a source of venturi vacuum, an engine manifold providing a source of manifold vacuum and a throttle valve in the air induction passage, comprising vacuum actuated spark advance mechanism, first means including a first restricted passage having a spark valve and a separate throttle actuated valve connected in series therein for connecting said spark advance mechanism to the source of manifold vacuum, second means including a second restricted passage between said spark advance mechanism and source of venturi vacuum for bleeding off a portion of said manifold vacuum and for connecting said spark advance mechanism to said source of venturi vacuum, and third means distinct from said first means for bleeding off a portion of said venturi vacuum.

5. Spark timing control apparatus for an internal combustion engine which engine includes an air induction passage including a venturi providing a source of venturi vacuum, an engine manfold providing a source of manifold vacuum and a throttle valve in the air induction passage, comprising vacuum actuated spark advance mechanism, first means including a first restricted passage having a spark valve and a separate throttle actuated valve connected in series therein for connecting said spark advance mechanism to the source of manifold vacuum, second means including a second restricted passage between said spark advance mechanism and source of venturi vacuum for bleeding off a'portion of said manifold vacuum and for connecting said spark advance mechanism to said source of venturi vacuum, and third means including a third restricted passage between said spark advance mechanism and the source of manifold vacuum distinct from said first means for bleeding off a portion of said venturi vacuum.

6. Structure as set forth in claim 5 wherein said spark valve comprises a chamber, a transverse partition having an opening therethrough and a flexible diaphragm dividing said chamber into a first part defined by said chamber and partition, a second part defined by said chamber,

a partition and flexible diaphragm, and a third part defined by said flexible diaphragm and chamber, a biased valve carried by said diaphragm and seated within said opening, and means for connecting said first restricted passage to said first and second parts of said chamber.

7. Structure as set forth in claim wherein said throttle actuated valve comprises a body member having a cylindrical recess therein, a eylindircal valve Within said recess having an arcuate recess therein, means for first connecting said spark valve to said source of manifold vacuum through said arcuate recess on initial opening of said throttle valve, and means for subsequently connecting said spark advance mechanism directly to said source of manifold vacuum on further opening of said throttle valve.

8. Structure as set forth in claim 5 wherein said throttle actuated valve comprises a body member having a cylindrical recess therein, a cylindrical valve within said recess having an arcuate recess therein, means for first connecting said spark valve to said spark advance mechanism through said arcuate recess on initial opening of said throttle valve, and means for subsequently connecting said spark advance mechanism directly to said source of manifold vacuum through said arcuate recess on further opening of said throttle valve.

9. Structure as set forth in claim 8 wherein said means for connecting said spark valve to said spark advance mechanism through said arcuate recess comprises a passage connected to said spark valve and having a contoured end registrable with said arcuate recess on opening of said throttle valve providing a variable restriction between the spark advance mechanism and the source of manifold vacuum on opening of the throttle valve.

10. Structure as claimed in claim 5 and further including a restricted passage extending between said restricted passages of said first and third means.

11. Spark timing control apparatus for an internal combustion engine which engine includes an air induction passage including a venturi providing a source of venturi vacuum, an engine manifold providing a source of manifold vacuum and a throttle valve in the air induction passage, comprising vacuum actuated spark advance mechanism, :reans connecting said spark advance mechanism directly to the source of venturi vacuum, a vacuum controlled spark valve located between the spark advance mechanism and the source of manifold vacuum, and means including a restricted passage in parallel with the spark valve for initially connecting said spark advance mechanism to the source of manifold vacuum directly and for subsequently connecting said spark advance mechanism to the source of manifold vacuum directly and through said spark valve simultaneously.

12. In an ignition system for an internal combustion engine which engine includes an air induction passage including a venturi providing a source of venturi vacuum, an engine manifold providing a source of manifold vacuum and a throttle valve in the air induction passage, the combination of an ignition distributor including timing means therein for controlling the timing of ignition, vacuum responsive means for positioning said timing means, a venturi in said induction passage for creating a venturi vacuum in accordance with the velocity of air flow through said induction passage, conduit means for transmitting said venturi vacuum to said vacuum responsive means, first valve means for selectively directing manifold vacuum to said vacuum responsive means, and second valve means operative during periods when said engine is operating under substantially wide open throttle conditions for diminishing the effect of said venturi vacuum on said vacuum responsive means.

13. In an ignition system for an internal combustion engine which engine includes an air induction passage including a venturi providing a source of venturi vacuum, an engine manifold providing a source of manifold vacuum and a throttle valve in the air induction passage, the combination of an ignition distributor including timing means therein for controlling the timing of ignition, vacuum responsive means therein for positioning said timing means, means for transmitting venturi vacuum to said vacuum responsive means, first valve means for selectively directing manifold vacuum to said vacuum responsive means, restricted conduit means bypassing said first valve means, and second valve means operative during periods when said engine is operating under substantially Wide-open throttle conditions for diminishing the effect of said venturi vacuum on said vacuum responsive means.

14. In an ignition system for an internal combustion engine which engine includes an air induction passage including a venturi providing a source of venturi vacuum, an engine manifold providing a source of manifold vacuum and a throttle valve in the air induction passage, the combination of an ignition distributor including timing means therein for controlling the timing of ignition, vacuum responsive means for positioning said timing means, means for transmitting venturi vacuum to said vacuum responsive means, first valve means for selectively directing manifold vacuum to said vacuum responsive means, and second valve means operable only during periods of substantially wide-open throttle engine operation for diminishing the effect of said venturi vacuum on said vacuum responsive means.

15. Spark timing control apparatus for an internal combustion engine which engine includes an air induction passage including a venturi providing a source of venturi vacuum, an engine manifold providing a source of manifold vacuum and a throttle valve in the air induction passage, comprising vacuum actuated spark advance mechanism, means connecting said spark advance mechanism directly to the source of venturi vacuum, a vacuum controlled spark valve connected at one side to the spark advance mechanism, a restricted conduit connected at one end to the spark advance mechanism and a valve responsive to throttle valve position for connecting the other side of said spark valve to said source of manifold vacuum during initial opening of the throttle valve and for subsequently connecting the other end of said restrictal conduit to the source of manifold vacuum with the throttle valve substantially wide open.

References Cited in the file of this patent

Claims

5. SPARK TIMING CONTROL APPARATUS FOR AN INTERNAL COMBUSTION ENGINE WHICH ENGINE INCLUDES AN AIR INDUCTION PASSAGE INCLUDING A VENTURI PROVIDING A SOURCE OF VENTURI VACUUM, AN ENGINE MANIFOLD PROVIDING A SOURCE OF MANIFOLD VACUUM AND A THROTTLE VALVE IN THE AIR INDUCTION PASSAGE, COMPRISING VACUUM ACTUATED SPARK ADVANCE MECHANISM, FIRST MEANS INCLUDING A FIRST RESTRICTED PASSAGE HAVING A SPARK VALVE AND A SEPARATE THROTTLE ACTUATED VALVE CONNECTED IN SERIES THEREIN FOR CONNECTING SAID SPARK ADVANCE MECHANISM TO THE SOURCE OF MANIFOLD VACUUM, SECOND MEANS INCLUDING A SECOND RESTRICTED PASSAGE BETWEEN SAID SPARK ADVANCE MECHANISM AND SOURCE OF VENTURI VACUUM FOR BLEEDING OFF A PORTION OF SAID MANIFOLD VACUUM AND FOR CONNECTING SAID SPARK ADVANCE MECHANISM TO SAID SOURCE OF VENTURI VACUUM, AND THIRD MEANS INCLUDING A THIRD RESTRICTED PASSAGE BETWEEN SAID SPARK ADVANCE MECHANISM AND THE SOURCE OF MANIFOLD VACUUM DISTINCT FROM SAID FIRST MEANS FOR BLEEDING OFF A PORTION OF SAID VENTURI VACUUM.