US3858289A

US3858289A - Method and means for automatically marking timing indicia on vehicle engines

Info

Publication number: US3858289A
Application number: US414802A
Authority: US
Inventors: James T Westervelt; Philip E Swis; Glenn M Brown
Original assignee: Cross Co
Current assignee: Cross Co
Priority date: 1973-11-12
Filing date: 1973-11-12
Publication date: 1975-01-07
Anticipated expiration: 1992-01-07
Also published as: IT1021281B; DE2453569A1; DE2453569B2; JPS5078704A; DE7437679U; GB1444852A; DE2453569C3

Abstract

An engine has preformed timing numerals on the block end wall but without the radial line indicia which are to correspond to the numerals and be read with respect to a pulley mark during manual timing. The radial indicia are marked on the engine in the manner which reduces the probability of error with respect to top dead center of Cylinder No. 1 (TDC) as follows: A notch is formed in the pulley at a known angle with respect to the timing mark. A notch sensor and an engine block marking tool are mounted on a common carriage, spaced apart by the same angle so that when the sensor is opposite the notch, the zero line in the marker is opposite the pulley mark. The crankshaft is rotated at a measured speed by an external source and a sensor picks up each arrival of TDC while at the same time the notch sensor picks up each arrival of the pulley notch. The angle between these two impulses causes the carriage to be angularly adjusted until the impulses coincide, at which time the tool marks the radial indicia adjacent the numerals.

Description

United States Patent Westervelt et al.

Jan. 7, 1975 METHOD AND MEANS FOR Primary Examiner-C. W. Lanham AUTOMATICALLY MARKING TIMING Assistant Examiner-Dan C. Crane INDICIA 0 VEHICLE ENGINES Attorney, Agent, or Firm-l-larness, Dickey & Pierce [75] Inventors: James T. Westervelt, Rochester;

Philip E. Swis, Mt. Clemens; Glenn 57 ABSTRACT M. Brown, Royal Oak, all of Mich. An engine has preformed timing numerals on the [731 Asslgneei The Cross Company, Fraser, MlchblOCk end wall but without the radial line indicia [22 Filed; 12 1973 which are to correspond to the numerals and be read with respect to a pulley mark during manual timing. [21] Appl' 4141802 The radial indicia are marked on the engine in the manner which reduces the probability of error with 52 s 1. U 29 15 4 R, 29 407 29 33 R, respect to top dead center of Cylinder No. l (TDC) as 73/118, 33/181 AT, 33/19 13, 33/1310. 15, follows:

324/16 R A notch is formed in the pulley at a known angle with [Si] lnt. Ci B23p 15/00, 823p 23/00 respect to the timing mark A notch sensor and an Field Of Search 2 R, 407, 33 engine block marking tool are mounted on a common 73/118, 119 R; 324/1 R, 16 T; 33/181 AT, carriage, spaced apart by the same angle so that when 180 180 B, 19 B, DIG. 15 the sensor is opposite the notch, the zero line in the marker is opposite the pulley mark. The crankshaft is 1 References Cited rotated at a measured speed by an external source and UNITED STATES PATENTS a sensor picks up each arrival of TDC while at the 2,043,931 6/1936 Morgan 33/181 AT Same time Mich Sensor Picks up each arrival of 2,072,984 3/1937 Haskins 324/16 R the P y notch- The angle between these two 3,527,087 9/1970 Converse, 1116161. 73/1173 mpu causes the i g to be a g y adjusted 3,691,641 9/1971 Bell et al. 33/181 AT until the impulses coincide, at which time the tool 3,697,865 10/1972 Smith et a1 73/118 marks the radial indicia adjacent the numerals, 3,820,386 6/1974 Grikscheit et al 33/180 B 14 Claims, 5 Drawing Figures j Wh /77 wry/'07 J i 1 M M I l l l [WWI/41% I I [pk/i171? [I Mdf/(ll/ I 21 l /%14 171 5] //1 r 3mm fi/ry/rfizf m/r fwd/12f)?" 7 Jam [7/1101 l 99; 1 Mm 7am; 22/32/3372; fffm fl /rmwr/ #747774 i flfij 7'27! 4/ d Cami/7w 99:7 5% l M 7 72m? f/m/rz 7 1; I M t M1,, 727 1! 17,

firm 2/1242 l flfi/rfl! i7 fi/M/Z;

252 ,7234 j i 7261mm 1 4.7 jfiw 44 NW I'r/ 7; i174 fir/4 O O 2,? ,f/mw' 7; 70/217211! Z l 5%; '1 mt 74 Jamar a l] 1 flrw I Patented Jan. 7, 1975 3 Sheets-Sheet l Patented Jan. 7, 1975 3,858,289

3 Sheets-Sheet 2 25 Sheets-sheaf 3 v Pat ented Jan. 7, 1975 METHOD AND MEANS FOR AUTOMATICALLY MARKING TIMING INDICIA ON VEHICLE ENGINES BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a method and means for providing indicia used during the life of a vehicle engine for manually adjusting the ignition timing.

In the conventional method for manually adjusting ignition timing of a vehicle engine, a timing light is illuminated each time the spark plug of Cylinder No. l fires and note is made of where a mark on a crankshaft pulley is with respect to a scale on the engine block. The distributor may then be adjusted until the mark is illuminated in the proper position with respect to the top dead center (TDC) point on the scale.

Various factors adversely affect the accuracy of location of the engine block scale indicia with respect to the pulley mark. These indicia are normally short radial lines and have reference to numerals immediately outwardly of the lines, the numerals being zero representing true TDC and approximately or l5 on either side of TDC.

The conventional method of casting the radial lines and numerals into the engine block, the tolerances of dowel holes used during engine assembly, and further tolerances in the key connection between the flywheel and shaft all contribute to the possibility of an absolute error in the scale reading. That is, instead of the flywheel mark being at the zero radial line when Cylinder No. l is at true TDC, the mark could be a considerable angular distance to one side or the other of the zero mark. This error, which could be as much as three degrees in some cases, can be critical for certain timing functions such as emission control.

2. Description of the Prior Art Although various methods have been attempted in the past to overcome the above-described difficulties, these arrangements do not have the benefits and advantages of the present invention.

The following U.S. patents were discovered as the result of a novelty search on the subject matter of this invention:

No. 2,072,984 Haskins No. 3,474,667 Fuchs No. 3,527,087 Converse III, et al.

No. 3,538,759 Schrom No. 3,552,196 Schrom No. 3,572,103 Marino No. 3,697,865 Smith et al. BRIEF SUMMARY OF THE INVENTION It is an object of the present invention to overcome the disadvantages described above and to provide a novel method and means for applying timing indicia to an engine which greatly reduces the error and renders a highly accurate relationship between the timing indicia and TDC.

It is a further object to provide an improved method and means of this character which is well suited for high production techniques and can be carried out simultaneously with the automatic adjustment of the distributor timing.

Briefly, the method of this invention includes the steps of preforming the timing pulley mark on the engine, providing means on the pulley a first known angular distance from the mark for actuating a sensor, mounting said sensor and an engine marking tool on a common carriage spaced apart by a second known angular distance, whereby the pulley mark is at the zero 0 line of said marking tool when said actuating means is spaced from said sensor by the difference between said known angles, rotating the crankshaft, measuring the angular distance between the arrival of said actuating means at the sensor and TDC of Cylinder No. l, angularly adjusting the carriage until said measured angular distance is equal to said difference between the known angles, and then causing the marking tool to form radially extending indicia corresponding to numerals on the engine block.

The marking means of the invention, as illustrated, comprises sensor actuating means on the engine pulley spaced from the pulley timing mark by a first known angular distance, an engine block marking tool for marking radial timing indicia and a sensor mounted on a common carriage and spaced apart by a second known angle, whereby the pulley mark is opposite the zero line on said tool when the actuating means is spaced from said sensor by the difference between said known angles, means for rotating the engine crankshaft and measuring the angular distance between TDC of Cylinder No. l and the arrival of said actuating means at the sensor, means for angularly adjusting the carriage until said measured angular distance is equal to said difference between the known angles, and means for then causing the marking tool to mark said radial indicia on the engine block.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall perspective view of a machine used for carrying out the method of this invention.

FIG. 2 is a side elevational view of the marking slide unit.

FIG. 3 is a cross-sectional view taken along the line 3-3 of FIG. 4 and showing details of the marking slide unit.

FIG. 4 is a schematic partial front elevational view of the marking slide unit, engine block, pulley and associated parts taken in the direcrion of the arrow 4 of FIG. 2 for the purpose of showing the relative positions of operative elements of the invention.

FIG. 5 is a schematic diagram showing the operation of the marking system as well as its relationship with equipment for setting the ignition timing;

DESCRIPTION OF THE PREFERRED EMBODIMENT The apparatus generally indicated at 11 in FIG. 1 is for the purpose of marking timing indicia on a vehicle engine generally indicated at 12, and also for setting ignition timing by adjustment of the distributor, although the latter feature by itself is not part of the present invention. Conveyor means 13 carries each engine 12 to apparatus 1 l, the engine being mounted on a pallet 14. The pallet and engine are moved sideways off conveyor 13 over a supporting plate 15 upwardly movable by a reciprocable fluid motor 16 to hold opposite marginal edges of the pallet against overlying locating stops I7 and 18. Supporting plate carries locating pins engageable with the pallet to accurately position the pallet and engine horizontally, stops l7 and 18 being used for vertical positioning. Oil supply means (not shown) may be provided on the side of the engine not visible in FIG. 1 with pallet 14 acting as an oil drain, no oil pan being mounted on the engine.

Proper location of engine 12 may close a sequence switch (not shown) which not only operates suitable automatic means for introducing lubricant into the engine preparatory to the test but also advances a drive slide 19 carried by tracks 20 and shiftable by a reciprocable fluid motor 21. Drive slide 19 has means (not shown) engageable with complementary means on flywheel 22 to rotate the engine and means 23 (FIG. 5) for accurately measuring the engine speed. Simultaneously, a distributor timing adjusting slide 24 which may be of a conventional type is advanced into operative engagement with the distributor, a top dead center (TDC) sensor 25 with a transducer proximity device is introduced into the Cylinder No. l spark plug hole 26, and a marking slide unit generally indicated at 27 is moved into operative engagement with a pulley 28 (FIG. 3) connected to the drive shaft by means of a reciprocable fluid motor indicated schematically at 29 in FIG. 2.

The block of engine 12, or an attachment thereto such as the timing chain cover, has an end wall partially indicated at 30 in FIG. 4 which may have preformed thereon an inclined boss 31 with digits or numerals 32 representing the number of degrees before and after TDC. However, at least the radial markings indicated at 33 in FIG. 4 are not preformed on the engine at this point. It is an object of the present invention to form these radial markings so as to correspond with the numerals but in a manner which will accurately reflect the fact that when a timing mark 34 on pulley 28 is opposite the radial mark corresponding to the zero numeral, the piston of Cylinder No. l, (spark plug hole 26) will truly be at top dead center.

For this purpose, marking slide unit 27 is mounted on fixed track 35 and carries an L-shaped bracket 36 the upright portion 37 of which supports a plate 38. The plate is secured to bracket portion 37 by means which permits limited floating movement of the plate in a plane, perpendicular to the engine crankshaft, this means being shown in the form of bolts 39 passing through resilient bushings 41 carried by bracket portion 37 (FIG. 3).

A carriage trunnion 42 is secured to and extends horizontally from plate 38. A carriage locating ring 43 is rotatably carried by trunnion 42, the ring carrying a shaft 44 supported by

bearings

45 and 46 within bore 47 of the trunnion. Ring 43 has a flared guide surface 48 at its outer end which is engageable with the periphery of pulley 28 carried by the engine crankshaft. Thus, as unit 27 is advanced by its reciprocable fluid motor 29 trunnion 42 will be centered precisely with respect to the engine crankshaft.

An annular carriage 49 surrounds and is mounted for rotation on trunnion 42. The outer end of the carriage carries a magnetic notch sensor 50 adjacent pulley 28. This is a proximity device responsive to the absence of metal at a notch 51 in the rim of pulley 28, or to other suitable sensor actuating means carried by the pulley. Notch 51 is spaced from mark 34 by a first known angle a. In the illustrated embodiment this angle is 90 but other suitable angles could be chosen. In some cases notch 51 could coincide with and even act as mark 34, in which'case angle a would equal 0.

Marking tool 52 is also carried by carriage 49. The marking tool is actuatable by a reciprocable fluid motor 53 and is angularly positioned so that when the tool is extended, it will stamp radial indicia or graduation lines 33 on inclined boss 31 adjacent numerals 32, or stamp the numerals as well. Tool 52 is carried by a member 54 mounted on carriage 49, and the tool and sensor 50 are spaced by a second known angle b. In this case, b a. Thus, when notch 51 is opposite sensor 50 mark 34 will be opposite the zero graduation line on tool 52, which represents TDC.

In more general terms, mark 34 will be opposite the zero line on tool 52 when notch 51 is spaced from sensor 50 by the difference between said two known angles a and b. For example, if notch 51 were acting as mark 34 (angle a 0) and angle b between sensor 50 and tool 52 were 270 (measured clockwise) in FIG. 4, then notch-mark 34, 51 would be opposite the zero mark on tool 52 when it had traveled clockwise exactly 270 past sensor 50.

Carriage 49 is rotatably carried by bearings 55 and has a racksegment 56 meshing with a pinion 57, the pinion being driven by a servo motor 58 mounted on bracket portion 37. As is described below, motor 58 will rotate carriage 49 in response to error signals until tool 52 is so positioned that the radial graduation line corresponding to zero" is opposite pulley mark 34 at the precise instant of TDC in Cylinder No. 1.

FIG. 5 shows schematically the manner in which the method and means of this invention operates. The figure has two sections labeled Timing" and Marking, indicating that both setting of the distributor timing and marking of the engine block may be accomplished simultaneously in the apparatus.

TDC sensor 25, notch sensor 50, and speed sensor 23 associated with engine drive slide 19 send signals to a comparator 59, these signals providing input to the comparator for measuring the angle between the notch sensor pulse and TDC.This measured angle will be compared by a servo command 61 with the known difference 62 between angles a and b. The comparison will result in an error signal output of a magnitude depending upon how far off said measured angle is from said known difference.

Upon a command signal 63 given when the engine and other parts are properly positioned and the engine is rotating at a desired speed, the error signal output from the servo command is delivered to a servo driver 64 which instructs servo motor 58 to rotate carriage 49 until the measured angle between the notch sensor and TDC pulses is equal to said known difference between angles a and b. In FIG. 4, this known difference would be 0. Since the angle between TDC and pulley mark 34 is fixed, this will mean that each time TDC is reached, pulley mark 34 is at a point opposite boss 31 at which the radial graduation mark 62 representing 0 should be formed. Upon the error signal from servo command 61 becoming zero, and on target" signal 65 will be sent to tool operating motor 53, marking boss 31 with the radial mark 62 and all the other graduations 33 which correspond with numerals 32. Accuracy of the timing indicia on engine 12 will thus be assured for future manual timing of the engine.

At the same time that this is taking place, the conven tional distributor adjusting apparatus 24 may be utilized. As shown in FIG. 5, TDC sensor 25, a point closure sensor 66 for distributor 67 and speed sensor 23 will send signals to a comparator 68. Upon the comparator receiving a command input 69 similar to command 63 the measurement of angular distance between point closure and TDC will be fed to a servo command 71. This unit also receives an input 72 of a desired angle between point closure and TDC, and responsive to the comparison between its two inputs will send an error signal to a servo driver 73 and hence to a servo motor 74 whichwill adjust the distributor timing until the actual angle equals the desired value.

After this operation takes place, engine 12 will be returned to conveyor 13.

We claim:

1. A method for marking radial timing indicia on vehicle engine blocks comprising the steps of preforming a timing mark on the engine pulley, providing means on the pulley a first known angular distance a from said mark for actuating a sensor, mounting said sensor and an engine block marking tool on a common carriage spaced apart by a second known angular distance b, rotating the crankshaft, measuring the angular distance between the arrival of said actuating means at said sensor and TDC of Cylinder No. l, angularly adjusting said carriage until said angular distance is equal to the difference between angles a and b, and then causing the marking tool to form radial indicia on the engine block.

. 2. The method according to claim 1, further provided with the step of causing the center of rotation of said carriage to coincide accurately with the crankshaft axis.

3. The method according to claim 1, said step of mea suring the angular distance between the arrival of said pulley actuating means at the sensor and TDC of Cylinder No. 1 including the steps of sensing arrival of TDC through the No. 1 Cylinder spark plug hole, and also sensing the rotational speed of the crankshaft.

4. The method according to claim 1, further provided with the steps of measuring the angular distance between distributor point closure and TDC simultaneously with said first-mentioned angular distance measurement, and adjusting said point closure to achieve a desired angular distance between point closure and TDC.

5. A method for marking radial timing indicia on the vehicle blocks of vehicle engines and simultaneously setting the distributor timing on a production basis, comprising the steps of preforming a pulley timing mark on the engine, forming means on the pulley a first known angle a from the pulley mark for actuating a sensor, moving engines in succession along an assembly line, diverting each engine laterally off said assembly line as it reaches a timing station, accurately positioning the engine both vertically and horizontally, driving the engine by engagement with the flywheel end of the crankshaft, placing a TDC sensor in the No. 1 cylinder spark plug hole, advancing a distributor timing adjusting slide into operative engagement with the distributor, providing a pulley sensor and a marking tool spaced apart by a second known angle b on a common carriage, centering said carriage with respect to the crankshaft axis, measuring the angular distance between positioning of said pulley actuating means opposite the pulley sensor and TDC during rotation of the crankshaft, causing said measurement of angular distance to rotatably shift said carriage until the angular distance is equal to the difference between angles a and b, causing said tool to mark the engine block in response to achieving of said angular distance, sensing the angular distance between distributor point closure and TDC simultaneously with the sensing of said aforementioned angular distance, causing said measurement of point closure-TDC angular distance to adjust the points until the angular distance is at a desired value, retracting said drive means, timing adjusting slide, TDC sensor and carriage, and returning said engine to said conveyor.

6. Means for marking radial graduation lines corresponding to timing numerals on the block of an engine having a pulley with a timing mark, comprising sensor actuating means carried by the pulley a first known angular distance a from said mark, a carriage supporting a marking tool and a pulley sensor spaced apart by a second known angular distance b, means for rotating the engine crankshaft and measuring the angular distance between TDC of cylinder No. l and the arrival of said actuating means at the sensor, means for angularly adjusting said carriage until said measured angular distance is equal to the difference between angles a and b, and means responsive to said angular adjustment for causing said marking tool to mark radial graduation lines on the engine block.

7. The combination according to claim 6, said carriage being of annular shape and rotatably supported by a trunnion, means for advancing and retracting said trunnion axially with respect to said pulley, and means carried by the trunnion and engageable with said pulley for centering the trunnion with respect to the crankshaft axis when it is advanced toward the pulley.

8. The combination according to claim 7, said centering means comprising a shaft rotatably supported within the trunnion and carrying an outer portion engageable with the periphery of the pulley, said means for angularly adjusting the carriage comprising a servo motor having a pinion and rack segment connection with the carriage.

9. The combination according to claim 8, said centering means further comprising resilient supporting means for said trunnion permitting it to shift in a plane perpendicular to the crankshaft axis.

10. The combination according to claim 8, said pulley sensor being carried by the outer end of said carriage, the means for actuating said tool comprising a reciprocable fluid motor.

11. The combination according to claim 6, said sensor actuating means on the pulley comprising a notch, said pulley sensor being a proximity device, said angular distance measuring means comprising a comparator connected to a TDC proximity sensor in the No. l spark plug hole and said notch sensor, and an engine speed sensor connected to said comparator.

12. The combination according to claim 6, further provided with a servo driver connected to the output of said comparator and a servo motor connected to the output of said servo driver, said servo motor operating a pinion and gear segment connection to said carriage.

13. The combination according to claim 6, further provided with a point closure sensor connected to the engine distributor, a second comparator, means for delivering pulses to said second comparator from said point closure sensor and in response to arrival of TDC,

engine speed sensing means connected to said comparator, and servo motor means responsive to a signal from said comparator of an angular difference between actual and desired point closure with respect to TDC for adjusting the location of point closure.

14. In production line system for simultaneously setting the ignition timing and marking radial timing indicia on vehicle engines of the type having preformed timing numerals on the engine block and a pulley having a timing mark, means carried by each pulley for actuating a proximity sensor, said means being spaced a first known angular distance a from said pulley mark, a conveyor, means for diverting each engine carried by said conveyor as it arrives at a timing station, means at the timing station for holding said engine in an accurate location both vertically and horizontally, a TDC sensor engageable with said engine, an engine drive slide engageable with the flywheel end of said crankshaft for rotating said engine, said slide carrying an engine speed sensor, a marking slide on the pulley side of said engine, means for advancing said marking slide toward the engine, a trunnion carried by said marking slide, means for centering said trunnion with respect to said pulley, an annular carriage rotatably supported by said trunnion, a marking tool for forming radial lines on the engine block corresponding to said numerals and a pulley sensor, said tool and sensor being mounted on said carriage and spaced apart by a second known angular distance b means for sensing point closure of said engine, a first comparator, means for delivering signals to said comparator corresponding to TDC of cylinder No. l and to actuation of said pulley sensor as well as from said speed sensor, whereby the angular distance between TDC and actuation of said pulley sensor may be measured, a servo motor responsive to the output of said comparator for rotating said carriage until said measured angle is equal to the difference between angles a and b, means responsive to said rotational adjustment for actuating said marking tool, a second comparator receiving signals from said point closure sensor, TDC sensor and speed sensor, and a second servo motor for adjusting said point closure in response to a signal from said second comparator of the angular difference between actual and desired point closures with respect to TDC.

Claims

1. A method for marking radial timing indicia on vehicle engIne blocks comprising the steps of preforming a timing mark on the engine pulley, providing means on the pulley a first known angular distance a from said mark for actuating a sensor, mounting said sensor and an engine block marking tool on a common carriage spaced apart by a second known angular distance b, rotating the crankshaft, measuring the angular distance between the arrival of said actuating means at said sensor and TDC of Cylinder No. 1, angularly adjusting said carriage until said angular distance is equal to the difference between angles a and b, and then causing the marking tool to form radial indicia on the engine block.

2. The method according to claim 1, further provided with the step of causing the center of rotation of said carriage to coincide accurately with the crankshaft axis.

3. The method according to claim 1, said step of measuring the angular distance between the arrival of said pulley actuating means at the sensor and TDC of Cylinder No. 1 including the steps of sensing arrival of TDC through the No. 1 Cylinder spark plug hole, and also sensing the rotational speed of the crankshaft.

6. Means for marking radial graduation lines corresponding to timing numerals on the block of an engine having a pulley with a timing mark, comprising sensor actuating means carried by the pulley a first known angular distance a from said mark, a carriage supporting a marking tool and a pulley sensor spaced apart by a second known angular distance b, means for rotating the engine crankshaft and measuring the angular distance between TDC of cylinder No. 1 and the arrival of said actuating means at the sensor, means for angularly adjusting said carriage until said measured angular distance is equal to the difference between angles a and b, and means responsive to said angular adjustment for causing said marking Tool to mark radial graduation lines on the engine block.

11. The combination according to claim 6, said sensor actuating means on the pulley comprising a notch, said pulley sensor being a proximity device, said angular distance measuring means comprising a comparator connected to a TDC proximity sensor in the No. 1 spark plug hole and said notch sensor, and an engine speed sensor connected to said comparator.

13. The combination according to claim 6, further provided with a point closure sensor connected to the engine distributor, a second comparator, means for delivering pulses to said second comparator from said point closure sensor and in response to arrival of TDC, engine speed sensing means connected to said comparator, and servo motor means responsive to a signal from said comparator of an angular difference between actual and desired point closure with respect to TDC for adjusting the location of point closure.

14. In production line system for simultaneously setting the ignition timing and marking radial timing indicia on vehicle engines of the type having preformed timing numerals on the engine block and a pulley having a timing mark, means carried by each pulley for actuating a proximity sensor, said means being spaced a first known angular distance a from said pulley mark, a conveyor, means for diverting each engine carried by said conveyor as it arrives at a timing station, means at the timing station for holding said engine in an accurate location both vertically and horizontally, a TDC sensor engageable with said engine, an engine drive slide engageable with the flywheel end of said crankshaft for rotating said engine, said slide carrying an engine speed sensor, a marking slide on the pulley side of said engine, means for advancing said marking slide toward the engine, a trunnion carried by said marking slide, means for centering said trunnion with respect to said pulley, an annular carriage rotatably supported by said trunnion, a marking tool for forming radial lines on the engine block corresponding to said numerals and a pulley sensor, said tool and sensor being mounted on said carriage and spaced apart by a second known angular distance b means for sensing point closure of said engine, a first comparator, means for delivering signals to said comparator corresponding to TDC of cylinder No. 1 and to actuation of said pulley sensor as well as from said speed sensor, whereby the angular distance between TDC and actuation of said pulley sensor may be measured, a servo motor responsive to the output of said comparator for rotating said carriage until said measured anGle is equal to the difference between angles a and b, means responsive to said rotational adjustment for actuating said marking tool, a second comparator receiving signals from said point closure sensor, TDC sensor and speed sensor, and a second servo motor for adjusting said point closure in response to a signal from said second comparator of the angular difference between actual and desired point closures with respect to TDC.