Instruction manuals

Valve Timing for Max Output

A technical paper by Ed Iskenderian on camshaft selection, installation and tuning.
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  00   ã   ZC >  . a a >  . 00 a   Z  C - 1I  M  a z   -  M   Foreword III placing Valve ming for aximum Outp u in th e h ands of Top TlIllers, Ed lskenderiall is passing on a digest of his 25 \ cars hard WOll experiellc.c in th e Hop Up and En gine Mo dific ation s hcld. l\lan y of the tips in this hook arc not generally knowll and oth e  ~ ; ne of t e ll m'Cl'looked or not corrcct ly Ilmlcrstood . \ Vhcn properly applied th ese tip s w ill sa ve many h our s of w~ s e \\'ork and mo ney. Years ago Ed bccalllc convinced that the cams haft \ v .I s the back bonc of tllc ra cing cng in e and t-lwt: greater power wOllld conic frolll better ca mshaft design and rcfinement. v\ : ith thi s Olle th ought i ll mind he clccidcd to conce ntr ate his knowledge in th e manufact l1l e of fin er CllllShaft s, cach ans\\'ering the spcc ih c Il eells of the en and ty pe of raee e nt ered. Fo r 15 years speciali 7a tion in the design :1ll c1 refi nernent of th e world's fincst racing cams has been his onc tllollg ht. Toda y, the Isk en derian organi 7a ti on pmsesses th e world's largest faciliti cs for th e designing, tcsting and prodllctioll of racing Gllns , 1Ilt l valve gear co mponcnt s. A new modern building providin g a 4000 incrcase in working space will help continue this leader s hip in the ca mshaft field. Ed works closely w ith America' s Top TUllers-R acing Drivers alld Mecha llics. Fr om associated tests and th e interchange of ex pcrienc es v, : ith tllesc mcn eOIlle the pra ctica l d<l ta which are incorporated ill hi s lat es t desig ll s. Bv this me th od of specia li z. ation, Ed Iskenderian has dcveloped an illlp;'essi\'e list of first s - Thc Track Grind - The Mushroom Track Grilld-The Radius Tappet Constant Acceleration 404 Grillcl Thc OI- IV BiglolV Grillcl- T he CrossRo l Grin d as well as th e Exclusive lIardface Overlay Process th e Parabolic OHV, 5 ycl e Polydyne Profile Roller and Flat Tappet Grinds and most rec ently - the RPM Series and High Lift 505 Mag num Grinds. III preparing Valve Timing for aximum Output for publication , Eel lske nd eria ll wishes to thank ll a nk Elfrink , a ut omotive wTiter, for his lIlanuscr ipt assista nc e, and Ian Ca mer on, publi cations consultant. for the overall de sign an d produ cti on of the finished b oo k. Copyri g ht 1962 by Ed Iskenderian All rights reserved, including th   right to reprodu ce this book or port ions the r of in any form. Printed in U.S.A. CONTENTS Page V L VE TIMING FOR MAXIMUM OUTPUT .. _.... ....... ....... ...... ....... 3 Stock car ca mshaft, Ba sic ca m design, Overlap, Valve Opening Diagram THE C MS HA FT 5 Types of Cams, Type of Valve Trains, Cam Contours, Purpose of Reground Cams TY PES OF C M FOLLO W ERS .. ..... ..   ................ .... . .. ................. . 8 Types of Followers, The Isky 404 Cam, The Isky Roller Cam R CING VA LVE SP RI N GS . . .. 11 Valve Float, Types of Va lve Springs, Valve Spring Surge, Com· pound Valve Springs, Damper Coils, Installing and Measuring Spring Tension, Measuring Valve Lift, Checking for Fatigue, Measuring Push Rods, Checking for Interferences, Correct Method for Accurately Measuring Valve Spring Length, Avoid Surge an d Excessive Compression, Adjusting Tension with Washers CYLINDER HE D DESi GN .................... .... .. ...... ..... :.... ....... ...... ..... 20 Hemispheri ca l L·Head, F·Head, Overhead Valves, Overhead Cam· shafts, Wedge Shape Combustion Chamber, Improving Engine Breathing BETTER VO LU METRIC EFFiCiEN Cy .............. ..... . ........ ....... .. .. ......... 25 HOW TO DE TER MINE POR T SI ZES (Chart).... .... ........   .................. 26 PORTING ......................... .. .. .. .......................... .. .. .. ...... ....... ...... .. . 26 Porting and Carburetion, Porting and Relieving, Drawing), Isken· derian Cross· Flow Camshaft F ORCE D INDUCTION DRiVES ..... ...... .. ... .. ...... . ....... ... ........ ..... ...... 30 THE PO P PET VALVE.. . .... ........ .... ..... ......... ..... ......... .................. ...... 31 Valve Operating Conditions, Valve Materials , Austentic Steels, Valve Seating for Racing, Seat Grinding , Valve Stem Clearance in Guide, The Fuel Mixtures , Effect on Valve Life, Maximum Valve Efficiency TORQU E, H ORS EP OW ER ND DY NAM OMETER TESTING .. ... .. .... 34 Torque and Horsepower, Torque and Horsepower Formula, Dyna · mometer Testing Torque and RPM, Torque Curve, GM Test 20, 1956 Torque Curve Standard and EI Dorado) ....    Pa ge THE FIELD OF CAM DESIGN - WORKING UP TO T HE POLYDYNL ................. _   ................... 38 TOP TUNE RS TIPS HOW TO DETERMINE TOP DEAD CENTER ACC UR ATELY ...... _ ...... 45 Po si.tive Stop Method PROCEDURE FOR CHECKING VALVE OVERLAP WITHOUT DIAL INDICATOR OR DEGREE PLATE ........................ 47 POSITIVE METHOD FOR FINDING TOP DEAD CEN TER ............ _.... 48 KNOW YOUR SPARK L EAD ........ .. . 49 CHECKING A CAM IN THE ENGINE . 5 Eliminating Sl ac k in Camshaft Drive, Check Opening and Clo si ng of Valves, Dr aw ing the Va l ve Lift Curve and Graph, Valve L as h and Val ve Timing , Maximum Pe rform ance R eq uires a High Speed Camshaft, Select the o rr ec t Rear En d Ra tio JUGG LI NG TAPPET CLEARANCE .... .... .. .. .. 53 Effects of Altering Valve L as h, In creasing Tappet Clearance Short· ens The T imin g Working Procedure FEATU RE ARTICLES VALVE TIMING FOR TOP PERFO RMANCE by Don Francisco ... ... SS CORRECT SPARK LEAD by Ted Frye .... 63 EN GINEERED SPRING ASSEMBLIES ... 7 Chrysler, Mopar , Chevrolet, V8, Ford V8, Oldsmobile V8 NEW PRODUCT DEVELOPMENT.. .... 76 Chevrolet Forged Aluminum Offset o nnec tin g Rod, Chevrolet Du al Spring (New Intereference Design), Ford Special Alloy Va lve Springs, New Anti·Pump Up Hydraulic Racing Tappets, High Qu a lity Ove rsize Exhaust Valve for Chevrolet V8), Screw·in Ro cker Arm Studs (Exclusive Jam Nut D es ign), Li ghtweig ht Aluminum Spring Retainers, Heavy Duty Split Valve Locks Valve Timing for Maximum Output THE STOCK CAR CAMSHAFT Th e camshaft dcsign of the Americ an Pa sse nger Car Engine stresses lo w speed performance and sm oo th idlin g. To bring out the sc char· acte ri s ti cs I  ; to 2 ' o of the horsepower is sacrificed. This O l tpll t can be in creased fr om 20 to as high as 1 00 % with the usc of our reground ra ci ng camshafts tcamed with hi gher compr es sIon ratios and multi· ea rburetion. T OP CENTER TOP C ENTER INTAKE CLO SE S EXH U ST OPENS BO   OM CEN TER BOTTOM C ENTER BASIC CAM DESIGN Th e id ea l calli w01lkl open the intake valve in stantly to full lift at approxilllately top dead ce nt er, dwell in the full open position until approximately 40 degrees after bottom center and then close instantly. Natura ll y, such abrupt ac tion wou ld cr ea te terrific m ec hani ca l stress and many other compli ca tion s. Con se qu en tl y cams must be co ntour ed to open a nd close th e valves in a more ge ntle manner. OVERlAP It is now understood that in actuating the valves we a r limited to ce rtain rates of valve acccleration and deceleration. Since it is n eceSS<Iry that we maintain a r ea sonable alilOunt of va l ve lift over the greater portion of the intake a nd exhaust stro ke s we havc 110 alternative but to lead and l ag the valve opening p er i od s to such an ex tent that thc intake and ex haust eycles actua ll y overlap. From first glan ce this valve o\'erlap wou ld se em rather detrimental, which it is at sl ow speed s. Howcver, at higher engine speeds this deficiency diminishes and becomes a s li ght as set, as expl ai ned later on under Exhaust Closes:' Page 3  INTAKE OPENS In the timing di agram one not es that the intake va lv e begins opening 20 de grees before top d ea d center or hefore the pi ston starts on the suc ti on strok c. Thi s is done to gi vc the \ al ve a head start on the piston a11d we find that at top center the valve w ill he wc ll o ff its se at , so as to o ff er little r es istan ce to the in co ming c kn ge. INTAKE CLOSES Now 0te that thc intake va l ve rema in s opened so me 64 degre es a ftcr bottom cellter which is long after the piston h as cha ng ed dir ec tion and is co ming up on the co mpr ess ion strok e. Thi s is b es t explained by the f ac t that the intake char gc having been in motion builds up kille ti e e   e rg y and tends to c 011tinu e to fl ow long a ft er thc pi ston chan ges direc ti on, should the intake va l ve have hecn cl osed at bo tt om ce nt er here would be a cons id erable throttling e ff ect on the intake ch a rge . EXHAUST OPE NS Looking at the ex haust valv e, it is see ll that the val ve begins opening so me 64 d eg rees before bottom ce nt cr or beforc the power stroke ha s ac tu a ll y becn completed, Thi s slight l oss of u sef ul power is off se t by t~e f ac t that the hot ex haust gasses leave the cy linder partia ll y und er their o wn pr ess ure, thereby rcduc in g the c ff ort on the eng in c's part to c xpel th e burnt g asses on the upwa rd stroke of the piston, eXH A UST CLOSES Notiec that thc ex ha llSt va lv e remains open for so me time a ft er top ccntcr, here again kine ti c energy co m es into play in that thc hurnt gases co ntinue to fl ow out and se a ve   ge thc ey lillder. It might he added that on so me inclined ove rh c ad va lv e cng ill es wh en definitc diameter and length of ex haust st ac ks arc u sc d a mild super cha rge is e ff ec ted by the ex haust gasses. Actua ll y dr aw in g the intake charge in during the short ove rl ap pe ri od, THE VALVE OPENING DIAGRAM From the forcgo in g it is obvious that it is of no L se to co mpare the cam d cs igns with r es pect o nl y to actual points of valve opening and clos ing, Th e importa nt fa ctors are lift and rate of lift and o nl y wh en a graph is drawn by pl otting val ve lift with r es p ec t to cranksha ft ro ta -tion ca n a good study be mad e. Th e necess ar y tools arc a . )00 minimum range dial t es t indi ca tor to r ea d val ve lift in thousandths of an in ch and a timing disk to be att ac hed to the crankshaft. Valv e Lift is then checked every 5 d eg rees of crank rotation and reco rd ed on graph paper giv in g the v alve opening diagram. Page 4 The Camshaft TYPES OF CAMS Ther e ar c a 11\  types of cams, such as face cams, cylinder ca m s, the familiar auto Ill otive tvpe of C IIl a nd manv others which we w ill not go II1t o n ov,. It is safe to say that during thc d evel opme nt period of the l uto II H ti ve eng II1 e pra c ti GIl   ~ evcry ki nd of cam in onc shape or anoth er has becn usc d to operate the va l vcs or cvcn to convert the reciprocaliIlg IIl o tioII of the pi ston in to a ro ta ti o Il at the cr: l l k, wh ic h is jlI st the oppos it e arraIlgc lll ent of thc valve ca m w hi ch co m'erts a ro tat ion IIlt o a r eCI p roca tmg m ovc mcnt. r Iowcvcr, our 1l];lII1 husin ess is co n cc rn ed with making mo dified ~.lll d sp ec ia li zed vcrS Ions of the cO II ve ntional cam to he found on the ev er yc  a\' ~ IIIt   o bile CamJi n ri s(JIl of 1'1111-'1' Irain for I)usllrl)fi 1)1.'1'1' h,'arlz',, ' ('n~i ll'   (Jilt! an [, l eorl ,'n;::illl', T Il! ' aIm 1'lIg;IiI' II i S 1,,'II,'r bu 'n lh 17>; onrl I'om l) us ·, I ion 11 1/171 )('r (l/Or  J I  l{'ri s l; I's /;/1 1 ils l a ll l' {. I 1 1I' is fl!ore j7 . r l,' Ih an II/{, L- I/ ,'arl  PUSHROD OVERHEAD { ' I FLA 7 1-1E AD VA LVE 71?4 tlt./ VA LVE TRAIN ;;lnr. D IFFERE NT TYPES OF VALVE TRAIN There are of C() lIf Se I1l~II1y typcs of engincs but fr om thc va lv e an g le , cn g iIlc t~p es , Ill lJc rou g hl y cll\ ,ic c:d iIlto t wo hpe s: the side valv e or L-head en gine an d the ove rhe ad valve engine , Thc L- h ea cl en g ill c is fa st b CCOII1iIlg CX tiIl ct O l thc Ame ri can automotive pro clu c-tion scene but in competition it is still used in special classes and certa in associations where eng in e spec in en tions are limited to o ld er engin es, Page 5
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