BUILDING AND TUNING

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GETTING THE MOST FROM YOUR MOTOR, POWER AND LONG LIFE.

"When the results disagree with the theory, believe the results and invent a new theory"

"As you read this material that I've published remember that our main business is racing, not engine building. I've built a grand total of 7 racing racing engines in my 50 years of life. I have done a lot of research and did build engines that worked a long time ago that I wouldn't call racing engines. I have found that building the short block is really quite straight forward. The real test is the upper assembly, and more importantly, tuning. It only takes a few mistakes to turn good parts into trash very quickly. If you're building your first race motor get as much information as you can. Build slow and build clean. To be competitive and win races, don't hesitate to consult a professional builder." Thad

"Very little knowledge is original. If anyone thinks I've copied their work without acknowledgment, let me know. I'll be happy to give credit where credit is due" Thad

"I want to give a lot of credit for the correct knowledge that I have to Danny Tonagel owner of DANNY'S AUTOMOTIVE in Abita Springs, Louisiana. A very successful Drag Racer and the sharpest motor guy I know." Thad.

"BUILDING THE BOTTOM TO LAST"

I will be posting information on engine building below. Including the bare essential tools required to properly blue print an engine. Here is a quick outline: Get it clean; use good quality parts; keep it clean; have the rotating assembly properly balanced; keep it clean; record everything on a build sheet; keep it clean; know the torque specs for your hardware; keep it clean; know your clearance limits; keep it clean; have a calibrated torque wrench; keep it clean; use good assembly lubes, something better than moly; keep it clean; be prepared to spend a lot of time checking and re-checking; and lastly, keep it clean.

I highly recommend reading through all the tech info. at the Reher-Morrison and Barry Grant sites. These sites can't answer every question but they give you some direction on optimizing your own combination.

Also, the upper and lower engine assembly books by Reher-Morrison are very good.

LIST OF TOOLS NEEDED: DIAL CALIPER; DIAL INDICATOR & BASE; TELESCOPING GAUGE SET; MICROMETER SET; DIAL BORE GAUGE; ROD STRETCH GUAGE; RING FILING TOOL; RING SEATING TOOL; RING INSTALLER; COMPRESSION TESTER; AND A LEAKDOWN TEST GAUGE. YOU DON'T HAVE TO BUY THE MOST EXPENSIVE, BUT DON'T BUY THE CHEAPEST EITHER. TAKE GOOD CARE OF THESE TOOLS AND THEY WILL OUTLAST YOU.

THERE ARE MANY GOOD SOURCES BUT A PLACE TO START IS POWERHOUSE PRODUCTS.

I DON'T WANT TO LIST A LOT OF TORQUE SPECS SINCE THERE ARE SO MANY AFTERMARKET FASTENERS BEING USED NOW. IF YOU'RE USING ARP HARDWARE CONTACT THEM AND USE THEIR SPECS.

BIG BLOCK CHEVY CLEARANCE SPECS

BEARING CLEARANCES ARE A FUNCTION OF JOURNAL DIAMETER AND APPLICATION. THESE WILL BE FOR A RACE APPLICATION WITH CAST IRON BLOCK, ALUMINUM HEADS, STEEL RODS, NO-NITROS, NON-SUPERCHARGED, USING RACE GAS.

MAIN BEARINGS .0030 - .0040

ROD BEARINGS .0030 - .0040

(FOR A 600-700 HP BBC .0028 - .0035 IS OK FOR BOTH)

CRANK END PLAY .0050 - .0080

ROD SIDE CLR. .015 - .020

PISTON TO BORE .0060 - .0090 (CHECK MANUFACTURER'S SPECS)

FLOATING PISTON PIN .0005 - .0008 (IN PISTON)

.0005 - .0007 (IN ROD)

.0 - .0005 END PLAY (PIN TO RETAINER)

RING VERTICAL CLR. .001 - .004 (IN GROOVE)

RING GROOVE DEPTH (RING GROOVE DEPTH SHOULD BE EQUAL OR .001 - .003 > RING WIDTH)

COMPRESSION RING GAP .0045 - .0050 PER INCH CYL. DIA.

(CHECK MANUFACTURER'S SPECS)

PISTON TO HEAD CLR. .035 - .040

PISTON TO VALVE CLR. .060 - .065 INTAKE

.115 - .120 EXHAUST

.050 - .060 RADIAL (DOME POCKET)

CLEVITE HAS SOME GOOD TECH READING ON BEARINGS.

IN ORDER TO GET THE DESIRED BEARING CLEARANCE YOU CAN BUY ADDITIONAL MAIN AND ROD BEARINGS IN A +/- .0001 SIZE. MIX AND MATCH THESE WITH THE STANDARD SIZE TO GET THE CLEARANCE YOU NEED. REMEMBER THAT IN A RACE MOTOR IF A CLEARANCE FALLS OUT OF THE RECOMMENDED RANGE, HAVE IT FALL IN THE LARGER DIRECTION. A RACE MOTOR WILL NOT LAST WITH A CLEARANCE THAT IS TOO TIGHT.

"The difference between luck and skill is measured by its duration"

Frank Hawley

" All men dream, but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find that it was vanity. But the dreamers of the day are dangerous men, for they may act their dreams with open eyes, to make it possible."
T. E. Lawrence

"IGNITION TIMING AND THE HIGH COMPRESSION RACE MOTOR"

I'LL BE TALKING BASICS HERE THAT WILL DEPEND ON YOUR OWN COMBINATION AND TRACK TESTING. IGNITION TIMING IS A FUNCTION OF HEAD CHAMBER DESIGN, SIZE, PISTON DOME SIZE, COMPRESSION RATIO, CAM PROFILE, AND RPM. THE GREATER THE EFFICIENCY OF THE HEADS, THE LESS TOTAL TIMING REQUIRED. THE SMALLER THE C.C. OF THE HEADS, THE LESS TOTAL TIMING REQUIRED. THE HIGHER THE RPM, THE MORE TOTAL TIMING REQUIRED. A TIGHT FIT, HIGH DOME PISTON WILL NEED MORE TOTAL TIMING THAN A FLAT TOP PISTON BECAUSE OF THE NEED FOR INCREASED FLAME TRAVEL AROUND THE DOME. FOR EXAMPLE: A BBC WITH 121CC HEADS MAY NEED 38-40 DEGREES TOTAL ADVANCE TO ACHIEVE MAX PERFORMANCE. A SBC WITH 49CC HEADS MAY PERFORM BEST WITH 32-36 DEGREES TOTAL TIMING. RETARDING THE TIMING AT HIGH RPM CAN HELP THE TORQUE CURVE, BUT THIS NEEDS TO BE A TIMED EVENT (TIME DELAY) AND NOT SET WITH A RPM CHIP. I HAVE FOUND THAT FOR A BRACKET/DRAG RACE MOTOR, LOCKED OUT TIMING IS BEST. MAYBE USE A STARTER SAVER MODULE TO HELP THE START WHEN HOT; BUT SET YOUR TOTAL TIMING AND BE PREPARED TO CRANK FOR A SECOND OR TWO. THEN HIT THE IGNITION SWITCH ON. REMEMBER THAT ADVANCED TIMING HELPS ACCELERATION. HOWEVER, AS LOAD AND RPM INCREASE, YOU'RE NOT ONLY FIGHTING THE UPWARD PISTON MOVEMENT BUT DETONATION WILL OCCUR AS WELL IF THE OCTANE LEVEL OF YOUR FUEL IS TO LOW FOR THE COMPRESSION OF YOUR ENGINE. TRACK/AIR TEMPERATURE WILL ALSO AFFECT ULTIMATE TIMING. YOU'LL BE ABLE TO INCREASE TOTAL TIMING A DEGREE OR 2 ON A 65 DEGREE DAY COMPARED TO 90 DEGREE DAY. ENGINE TEMPERATURE HAS THE SAME AFFECT. ALSO, DON'T FORGET YOUR CARB JETS. ADVANCING THE TIMING ACTS TO LEAN THE FUEL MIXTURE AND RETARDING TIMING WILL ENRICH THE FUEL MIXTURE. 36 DEGREES IS GOOD PLACE TO START WITH A HIGH COMPRESSION RACE MOTOR. MAKE SURE YOU'VE GOT THE RIGHT OCTANE GAS FOR YOUR COMPRESSION AND GO UP OR DOWN FROM THERE. PLAY WITH THE PLUG GAP AND MAKE SURE YOU HAVE THE CORRECT HEAT RANGE PLUG. FOR A GAS, NON-SUPERCHARGED MOTOR, TRY .040-.045 FOR MSD TYPE. FOR DUAL POINTS TRY .030-.035. FOR A MAGNETO TRY .018-.020.

Don't get too carried away with jet and bleed changes to the carb. Holley and Barry Grant have a lot more resources than you and I do. They do a very good job out of the box. ( other than idle speed, idle mixture, and float level) If you are doing the initial tuning at the track without a dyno (most of us), then this is when you will make your big changes.

Once your getting your best ET's and MPH's stop. A properly tuned motor will be very consistent under most seasonal changes. Watch your plugs and your time card if you think your running under some extreme temp or pressure change. To be extra safe, have your fuel setup SLIGHTLY rich. You may not get max performance, but you won't burn anything either. Just don't go overboard.

Keeping a detailed logbook is very important for bracket racing. The 1/100 & 1/1000 changes that moderate temp and pressure changes make can be anticipated with good records.

"VALVE TRAIN TECH"

GO TO AS MANY PRODUCT SITES AS YOU CAN AND READ THEIR TECH ARTICLES. THEN TALK TO YOUR BUDDIES AND YOUR MACHINE SHOP. THEN YOU WILL REALLY HAVE ABOUT 60% CONFLICTING INFORMATION. I'LL STATE A FEW TRUTHS THAT I'M COMFORTABLE WITH. GO WITH A MECH. ROLLER CAM THAT MATCHES YOUR COMPRESSION RATIO AND THE BREATHING ABILITY OF YOUR HEADS. MAKE SURE YOUR VALVE SPRINGS ARE OF THE BEST QUALITY AND ARE CORRECTLY MATCHED TO YOUR SETUP. CHECK FOR CORRECT INSTALLED HEIGHT AND SEAT PRESSURE. DON'T GO CHEAP ON PUSH RODS. THESE WILL BE ABOUT THE LAST THING YOU BUY. WHEN THE LONG BLOCK IS ASSEMBLED DO THE CORRECT LENGTH AND GEOMETREY CHECKS TO GET THE CORRECT ROD LENGTH. REMEMBER THAT A THICKER/MORE RIGID ROD IS BETTER IN MOST CASES. FOLLOW ALL THE MANUFACTURER'S BREAK IN SPECS FOR THE SPRINGS. PROPERLY CLEAN AND OIL SOAK YOUR ROLLER LIFTERS. SET YOUR COLD LASH AS REQUIRED AND RESET/CHECK HOT.

ONE THING THAT COST ME MONEY YEARS AGO WAS WHEN I USED SPRING LOADED ROLLER LIFTERS THE FIRST TIME. THESE ARE GREAT IF YOU WANT TO MAKE CAM CHANGES QUICKLY. HOWEVER, WHEN SETTING THE VALVE LASH YOU MUST DEPRESS THE BACK OF THE ROCKER ARM TO TAKE OUT THE SPRING TENSION. IF YOU DON'T, YOU'LL GET A NORMAL FEELER GUAGE DRAG AT A VERY INCORRECT LASH SETTING. ONCE EVERYTHING IS SET CORRECTLY IT IS VERY IMPORTANT TO CHECK YOUR LASH AND SPRINGS REGULARLY. AS LONG AS EVERYTHING IS OK NOTHING WILL CHANGE. IT'S WHEN THINGS CHANGE THAT A PROBLEM IS BREWING AND THE SOONER YOU CATCH IT, THE CHEAPER IT WILL BE TO FIX.

"VALVE LASH ADJUSTMENT"

I USE THE EXHAUST OPENING / INTAKE CLOSING METHOD. THERE SEVERAL SLIGHTLY DIFFERENT WAYS OF DOING THIS. UNLESS YOU'VE GOT SOME WILD CAM DURATION AND OVERLAP THE FOLLOWING WORKS FINE.

HAND TURN THE CRANK IN THE NORMAL ROTATION DIRECTION. WORK ON ONE CYL. AT A TIME. AS THE EXHAUST VALVE STARTS TO OPEN (@ 1/5 OPEN) SET THE INTAKE LASH. TURN THE CRANK AND WHEN THE INTAKE VALVE HAS OPENED AND IS STARTING TO CLOSE (@ 1/3 CLOSED) SET THE EXHAUST LASH. COMPLETE EACH CYL. AND RE-CHECK AFTER YOU TIGHTEN THE STUD GIRDLE.

FOR COLD ADJUSTMENT SUBTRACT .006 FROM THE HOT LASH FOR AN IRON BLOCK WITH ALUMINUM HEADS.

ADD .002 TO THE HOT LASH SETTING FOR AN IRON BLOCK WITH IRON HEADS.

RE-CHECK AND ADJUST WITH MOTOR WARMED UP. 130 - 160 DEGREES IS FINE.

YOU CAN MAKE SLIGHT POWER CHANGES WITH DIFFERENT LASH ADJUSTMENTS. I DON'T BELIEVE IN INCREASING VALVE LASH. YOU COULD ADD SOME BOTTOM END POWER BY OPENING THE LASH UP .002 - .004. TOO MUCH OF THIS AND YOUR VALVE TRAIN WILL BEAT ITSELF TO DEATH.

I DO LIKE TO TIGHTEN THE LASH A LITTLE. IF YOUR NORMAL HOT LASH SETTING WAS SAY .028, YOU CAN SUBTRACT .004 - .008 AND SEE SOME TOP END GAIN. DON'T GET TOO CARRIED AWAY, ESPECIALLY WITH THE EXHAUST LASH. THAT TINY AMOUNT OF TIME IT GETS TO REST ON ITS SEAT IS WHEN IT COOLS. COMBINE THERMAL EXPANSION AND A TIGHT LASH AND YOU GET A BURNED EXHAUST VALVE.

YOU CAN ALSO ALTER YOUR POWER BAND UP OR DOWN A FEW 100 RPMS BY CHANGING THE CAM TIMING. ADVANCE THE CAM FOR MORE BOTTOM END POWER. RETARD THE CAM FOR MORE TOP END POWER. I DON'T EVER PLAY WITH THE CAM TIMING. IT DOES WORK, I'M JUST TOO LAZY TO FOOL WITH IT.

TO READ MORE ABOUT THE THEORY OF WHY ALL OF THE ABOVE HAPPENS GO TO THE CAM COMPANY LINKS SHOWN.

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"More on the valve train to come"

Keep your race car combination balanced. It's so easy to build power these days that creating a weak link is easy too. Think about how each of the major components work together. The carb; heads; cam; compression; converter/clutch pack; axle ratio; and tire diameter all need to work together.

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