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| − | '''There are numerous sources of information to assist the untrained individual in the rebuilding or repairing of specific components of a vehicle, but there needs to be a place where he/she can learn what to do and what not to do in the modification of their vehicle(s). This article will attempt to fill in the blank spaces in their understanding concerning these modifications.
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| + | Have a nice day Crosley. |
| − | ==The first modifications to be made to your vehicle==
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| − | It is usually cheaper and easier to begin making mods to the motor and that's where most everybody starts in their quest to make the vehicle faster/quicker.
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| − | The problem with this approach is that you're starting at the wrong end of the vehicle. Unless you're starting with a scratch build, you're probably modifying an OEM vehicle which was engineered at the factory to provide good gas mileage (numerically low ring and pinion, (probably something in the 2.70 to 3.00 range) and a tight torque converter (maybe somewhere around 1,200-1,400 rpm stall).
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| − | This vehicle was designed for all sorts of people, the vast majority of whom expect good fuel mileage and quiet operation. The cam, intake manifold and other parts that came stock in the vehicle were matched to the ring and pinion gears in the rearend and the stall characteristics of the torque converter to accomplish this goal. When you begin changing parts on/in the motor, you are upsetting this balance of parts and operational characteristics that were built into the vehicle at the factory.
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| − | The first things that a newbie usually changes are the cam, intake manifold and carburetor (if working on a pre-efi motor) in an effort to make the ol' hoss a world beater.
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| − | First things first. The cam must be matched to the static compression ratio of the motor. The most important timing event on a camshaft is considered by most knowledgable people to be the intake valve closing point. The intake valve begins to open at some point before the piston gets to top dead center on the exhaust stroke. The piston decends in the bore with the intake valve open and the cylinder is filled with air/fuel mixture. After the piston gets to bottom dead center and starts back up on the compression stroke, the intake valve closes and compression begins. If we are beginning with a stock motor on which the static compression ratio is somewhere around 8.5:1 and put a cam in that has more duration and closes the intake valve later than was designed for at the factory, the piston will push some of the air/fuel mixture back through the still-open intake valve and cylinder pressure will be lower than it was with the stock cam that closed the intake valve at exactly the right point to work with the stock static compression ratio. This is the #1 mistake made by rookies, believing that changing the camshaft alone will make more horsepower. If you're going with more cam, then raise the static compression ratio also, so that the cam and static compression ratio are matched. The OEM's have super computers that tell them exactly the timing points to be ground into the cam to match the s.c.r. and make power at the rpm's the general public expects. This is usually idle to around 4,000 rpm's or a little higher. Any cam that you bolt into the motor will have an operating range of roughly 3,500 rpm's. In other words, it will be efficient from idle to 4,000 or 1,000 to 4,500 or 2,000 to 5,500 or 3,500 to 7,000 or whatever, depending on the valve opening and closing points ground into the cam when it is manufactured. It will also have a wide Lobe Separation Angle (max lift intake point after top dead center added to max lift exhaust point before top dead center and divided by 2) for good manifold vacuum to properly operate power brakes and other vacuum operated accessories and contribute to a smooth idle (Grandma doesn't want the motor going RUMPETY-RUMP when she's on the way to bingo and there are a lot more little old ladies buying cars than there are hot rodders). An OEM cam might be measured at 114 to 118 degrees lobe separtation angle (LSA) for instance. You can figure the Lobe Separation Angle yourself. Let's say that the intake centerline is 106 degrees after top dead center and the exhaust centerline is 114 degrees before top dead center. Add 106 to 114 and divide by 2 to find a Lobe Separation Angle of 110 degrees. You might also see LSA expressed as lobe displacement angle. This is not to be confused with lobe center. Lobe center is the point of maximum lift of the lobe, after top dead center for the intake lobe and before top dead center for the exhaust lobe.
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| − | Now, the newbie comes along and decides that the motor needs more cam. In most cases, he has no idea what the static compression ratio of the motor is or the piston deck height or the squish clearance or anything else about the interior of the motor. All he knows is that he wants the RUMPETY-RUMP that he heard coming from the Super Comp motor he heard at the drag strip or the hot rod down at the Sonic Drive In. What he may not know is that the motor in that Super Comp car has upwards of fifteen to twenty thousand dollars invested in it and is maximized for racing. It idles like that because the cam has to be very aggressive to work with the 12.0:1 to 16.0:1 static compression ratio that is built into the motor. It may have been designed to make power from 4,500 to 8,000 rpm's for instance and will be coupled to a very loose torque converter that stalls at around 5,000 rpm's for instance. As far as the hot rod down at the Sonic, that owner may have used a cam such as a Thumpr to get that sound and the car may not be as fast as it sounds.
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| − | I'm just throwing these numbers around to show you that the cam in the Super Comp motor will not work in your street-driven 350 Chevy. The Thumpr cam may work, but you may be able to make more horsepower and torque by matching the other motor characteristics to the proper camshaft and still have your rump-rump.
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| − | I've gotten a little off track with my explanation. We need to go back to what a newbie should do to his vehicle FIRST.
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| − | The very first modification done to an otherwise stock auto/truck should be a different ring and pinion gear. A good compromise between mileage and acceleration in a street car is somewhere around 3.70:1 ratio and should be complemented with new shocks and new bushings in the spring/suspension link mountings. If the owner intends to change this vehicle into a semi-serious street/drag car, then additional aftermarket traction devices such as anti-wheel hop products and tires with different rubber compound should be considered. Even more serious competitors should consider mini-tubs or full tubs in the car to accommodate wide racing slicks. A large number of racers who show up at my track mount slicks on separate wheels (wide steel wheels will work just fine) to be bolted to the car after they drive it in off the street.
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| − | See this article I wrote to understand why and how a shorter rear gear will accelerate the car quicker with no changes to the motor, transmission or torque converter.
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| − | http://www.crankshaftcoalition.com/wiki/Why_a_shorter_rear_gear_will_accelerate_the_car_quicker
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| − | Of course, when it comes to traction, some type of slip-limiting device like the Chevrolet Posi-Traction or aftermarket Detroit Locker or Auburn units or similar units will do an excellent job of hooking up both tires. However, these are not mandatory to get both tires to pull and not spin the passenger side tire.
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| − | With a front-motor, rear-drive vehicle, the chassis twists diagonally upon application of power. The left front gets lighter and the right rear gets lighter. The right front and the left rear get heavier. This is why you will see the right rear tire spin while the left rear hooks up on a car with a "one-legger" or "open" type differential. The right rear is light and needs additional weight applied to it. This can be accomplished cheaply and easily by installing an air shock on the RIGHT REAR ONLY to replace the conventional shock absorber on that side. Experimenting with the air pressure in the shock will allow you to equalize the weight applied to both rear tires on acceleration and "hook up" both tires without going to the expense of installing a locking device in the differential. Just keep adding air pressure to the shock until you have two equal-length black tire stripes on the pavement when accelerating from a stand-still. I've done this many times and have seen other racers do it with equal success. An additional benefit is that the car will be easier to drive at the strip with an open differential that has been "weight equalized".
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| − | Now, with the rear end nailed down and operating, it's time to move on to the middle of the car and take a look at the transmission and torque converter, assuming an automatic transmission will be used. If the transmission is a manual shift, then overlook the following information and go stiffer on the rear gear (4.10, 4.44, etc.)
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| − | If the car is very light (under 2,800 lbs with driver aboard), then a 2-speed automatic will work fine on the drag strip and should work on the street as well. Heavier cars should use a 3 or 4-speed auto. If fuel mileage is a concern in your world-beater, then a 4-speed overdrive auto is probably the better choice. I'll leave it to someone else to go into detail about the choices here, but the GM 700R4 has shown to be a good choice for non-computer applications. They can be beefed up to take considerable abuse.
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| − | The next component to be addressed is the torque converter. It is mandatory that the converter is matched to the camshaft you'll be using. As was stated earlier in this article, stock converters will stall at around 1,200 to 1,400 rpm's, depending on the amount of torque produced by the motor among other things and that's fine when you are using a stock-type cam that begins making power at idle. But when you change the cam out for a longer duration/higher lift model, you're no longer making power from idle and the car will be a dog until the rpm's increase to the point where the motor is making power. One way around this is to install a converter that stalls higher than stock so that the motor comes up on the cam quicker and the car accelerates faster. Any cam you install in the motor will have an operating range of about 3,500 rpm's. In other words, it might make power from idle to around 4,200 rpm's (stock cam) or from 1,500 to 5,000 rpm's or 2,000 to 5,500 or 2,500 to 6,000 or 3,000 to 6,500 or 3,500 to 7,000. I'm sure you get the idea. It works in a certain "window" of operation and is inefficient below and above those rpm's. So, if you install a cam that operates between 3,500 and 7,000 rpm's and use a converter that stalls at 1,200, you can see that the motor will not be producing enough torque from 1,200 to 3,500 to move the car efficiently. The car will be a D-O-G. On the other hand, if you use the 3,500-7,000 cam with a converter that stalls at around 3,500, then when you nail the loud pedal, the motor will rev up close to the stall speed of the converter and you'll be making power and applying torque to the rear tires sooner. (PLEASE NOTE THAT EACH APPLICATION IS DIFFERENT AND THAT A PROFESSIONAL TORQUE CONVERTER MANUFACTURER SHOULD BE CONSULTED FOR THE EXACT CONVERTER FOR YOUR APPLICATION). If I could get a little plug in here, I know Jim Hughes personally and have for many years and I can, without question, recommend Hughes Converters. Jim is a man of honesty and integrity, both personally and professionally.
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| − | MISTAKES THAT COULD FRAG YOUR FLAT TAPPET CAM AND LIFTERS.
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| − | DISCLAIMER: THE FOLLOWING INFORMATION WAS GLEANED FROM MANY DIFFERENT SOURCES. SOME OF IT MAKES SENSE TO ME AND SOME OF IT DOESN'T. USE WHAT YOU THINK IS REAL AND THROW OUT THE REST OF IT. I HAVE NOT USED ALL OF THE SUGGESTIONS LISTED HERE. THROUGH THE YEARS, I HAVE ACCOMPLISHED MANY SUCCESSFUL FLAT TAPPET CAMSHAFT BREAK-INS, BUT I HAVE ALSO ROACHED A FEW. USE THIS LIST AS A GUIDELINE SO THAT YOU REMEMBER TO CHECK ALL THESE THINGS WHEN INSTALLING A NEW FLAT TAPPET CAMSHAFT. DO NOT TAKE EVERYTHING POSTED HERE AS GOSPEL. IF THE MANUFACTURER OF THE CAMSHAFT YOU'RE USING RECOMMENDS PROCEDURES THAT DIFFER FROM WHAT IS SHOWN HERE, USE THE MANUFACTURER'S RECOMMENDATIONS TO THE LETTER AND DISREGARD THIS INFORMATION.
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| − | *1. Failure to remove all [[rust]]-preventative from cam and lifters with solvent once you get them home. (This advice does not include removing coatings applied at the factory such as phosphates. It is only suggesting to remove rust-preventative grease that may or may not have been applied to the cam/lifters to prevent rust in storage. This grease will not have the extreme pressure characteristics that Molybdenum Disulphide has and should be removed so that MD can be applied properly. MD is the black, tar-like extreme-pressure grease that is recommended by some camshaft manufacturers to be applied to the lifter crowns/cam lobes for initial camshaft break-in).
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| − | *2. Failure to wash the cam and lifters with hot soapy water to remove the remainder of rust-preventative not removed with solvent. CAUTION; WASH ONLY THE CROWN OF THE LIFTERS. (THE VERY BOTTOM OF THE LIFTER WHERE IT CONTACTS THE CAMSHAFT LOBE). DO NOT ALLOW WATER TO GET INTO THE INTERIOR OF THE LIFTER BODY. BE VERY CAREFUL HERE IF THE LIFTER HAS AN OILING HOLE THAT HAS BEEN EDM'D INTO THE CROWN TO PROVIDE OIL FROM THE INTERIOR OF THE LIFTER BODY TO THE CAMSHAFT LOBE. Dry the cam and lifter crowns thoroughly with hot air from a hot air gun or hair dryer to remove all traces of moisture before applying Molybdenum Disulfide.
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| − | WARNING: DO NOT USE ANY ABRASIVE MATERIALS SUCH AS SCOTCHBRITE PADS OR SANDPAPER OF ANY KIND TO ACCOMPLISH THESE SOLVENT AND SOAP CLEANING OPERATIONS. USE ONLY SOFT, CLEAN RAGS. THE WHOLE INTENT OF CLEANING THE CAMSHAFT IS SO THAT WE CAN REMOVE RUST-PREVENTATIVE OILS AND GREASES THAT MIGHT HINDER GETTING DOWN TO THE BASE METAL IN ORDER TO PERFORM OPERATION #3 SHOWN HERE.
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| − | *3. Failure to properly massage an extreme pressure lubricant such as Molybdenum Disulfide into the pores of the metal on all lobes and lifter faces. Moly will actually bond with the metal and give maximum protection to the lifter crown/lobe.
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| − | *4. Failure to use an extreme pressure lubricant additive to the engine oil for camshaft break-in.
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| − | *5. Failure to use the proper valve springs for cam break-in. You can't use the 300 lb over-the-nose springs that you'll eventually use in the motor and expect the cam to live at break-in. Assemble the heads with stock or weak single springs to break in the cam, then use one of the many tools available to change the springs with the heads on the motor. Alternately, assemble the heads with the springs you will run and use reduced-ratio break-in rockers, then change out the rockers after break-in. These rockers are available from Crower in different ratios for different motors. A popular ratio for a small block Chevy would be a 1.3:1 rocker. In other words, let's say the lift at the cam is 0.350" and the theoretical lift at the valve with 1.5:1 rockers is 0.525". Using the 1.3:1 rockers would result in lift at the valve of only 0.455", thus reducing stress at the camshaft/lifter interface during the crucial break-in period.
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| − | *6. Failure to check for valve spring coil bind at max lift.
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| − | *7. Failure to check for retainer to valve guide/seal clearance.
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| − | *8. Failure to check for binding at the rocker/stud interface.
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| − | *9. Failure to check for piston/valve clearance..... 0.080" on the intake and 0.100" on the exhaust is considered by many to be the minimum clearance acceptable. You will probably find the closest near-miss at the exhaust valve on overlap, when the piston is chasing the exhaust valve back onto its seat.
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| − | *10. Failure to run the motor at high rpms (2500 or higher, alternating 1000 rpm's up and/or down to allow the crank to throw oil in different places at different revs) for the first 40-45 minutes of its life. NO IDLING. NO IDLING. NO IDLING. The motor should not be run at less than 2500 rpm's for a minimum of 40 minutes. If a problem develops, shut the motor down and fix it, then resume break-in. The main source of camshaft lubrication is oil thrown off the crankshaft at speed, drainback from the oil rings and oil vapors circulating in the crankcase. At idle, the crank isn't spinning fast enough to provide sufficient oil splash to the camshaft/lifters for proper break-in protection.
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| − | *11. Failure to clearance lifters in their bores so that they spin freely. Lifter clearance should be 0.0012" to 0.002", with 0.0015" (one and one/half thousandths) considered close to ideal. Too loose is as bad as too tight.
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| − | *12. Failure to initially adjust the valves properly. Using the "spin the pushrod until it feels tight" method will normally result in valves too tight. With both valves closed and the piston at TDC on the compression/firing stroke for that cylinder, hold the tip of one rocker arm down tightly against the valve stem with one hand and jiggle the pushrod up and down with the thumb/forefinger of your other hand until all play between the pushrod and the other end of the rocker arm is removed, then turn the rocker nut 1/2 to 3/4 turn to set the preload. Now, do the same thing on the other rocker arm/pushrod for that cylinder. The bulletproof way to adjust valves is this method just described. Beginning on the #1 cylinder and following the firing order, you can adjust the intake and exhaust rockers for each cylinder as you turn the crank 1/4 turn at a time. In other words, on a Chevy, bring the piston of #1 cylinder (front, driver's side) up to top dead center on the compression/firing stroke. Both valves will be closed and the intake and exhaust lifters will be on the heel of the camshaft at that point, so you can adjust both the intake and exhaust rockers for that particular cylinder at the same time. Turn the crankshaft 1/4 turn clockwise and adjust the intake and exhaust rockers on #8 cylinder (rear, passenger side). It is the next cylinder in the firing order after #1. After you have adjusted both the intake and exhaust rockers for #8 cylinder, turn the crankshaft clockwise another 1/4 turn. That will put the piston of #4 cylinder (second from front, passenger side) at top dead center and you can adjust both intake and exhaust rockers for that cylinder. Following this, turn the crankshaft another 1/4 turn and adjust intake and exhaust rockers on cylinder #3 (second from front, driver's side). Another 1/4 turn and adjust both on cylinder #6 (third from front, passenger side), another 1/4 turn and adjust both on cylinder #5 (third from front, driver's side), another 1/4 turn and adjust both on cylinder # 7 (rear, driver's side) and finally, another 1/4 turn and adjust both on cylinder #2 (front, passenger's side). This routine will work on any motor if you start out on #1 and follow the firing order, turning the crank 1/4 turn in between adjustments to move on to the next cylinder in the firing order. Be careful on Fords, they have a different cylinder numbering system and several different firing orders, depending on the engine family.
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| − | *13. Failure to inspect the distributor drive gear for wear. Too much wear can allow the cam to walk in its cam bore and allow a lobe to contact an adjacent lifter.
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| − | *14. Failure to have everything ready for the motor to fire on the first few turns. Fully charged battery, good starter, known-good carburetor with full fuel bowl, source of fuel to the carburetor to allow minimum 40 minutes of uninterrupted running. Ignition timing set. NO GRINDING ON THE STARTER. NO GRINDING ON THE STARTER. NO GRINDING ON THE STARTER.
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| − | *15. Failure to prime the oiling system prior to firing the motor. Prime until you get oil out of the top of each and every pushrod. Observe the oil pressure gauge to be sure pressure is registering. Priming will aid lubing the valvetrain at initial startup. It's the last area of the motor to get lubed on dry start.
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| − | *16. Failure to use new lifters on a used cam. Used lifters should only be used on the very same cam, in the very same block and in the very same positions they were removed from. Chances that the lifter bores will be machined on the very same angles on a different block as the block the lifters came out of are about equal to you hitting the lottery.
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| − | *Now, this last bit of advice comes from Racer Brown, world-renowned camshaft manufacturer/engineer who ground the hot cams for Chrysler Corporation during the horsepower wars of the 60's.
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| − | "Overfill the crankcase by at least 4 or 5 quarts of oil so that the oil level comes to within an inch of the top of the oil pan. Install a set of fairly hot spark plugs with a gap of 0.050" to 0.060" to prevent oil-fouling of the plugs, which is otherwise inevitable under no-load conditions with all the extra oil aboard. During this operation, we want near-maximum oil flow, together with a maximum of oil vapors and liquid oil thrashing about in the crankcase so that the cam lobe and lifter interface lubrication is considerably better than marginal."
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| − | *This advice from Racer is too scary for me, but I included it so that you know someone, somewhere has done it.
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| − | *Just a note to make you aware of the loading between the camshaft lobe and lifter crown. That pencil-point of contact, if carried out to a square inch, would be somewhere between 250,000 and 300,000 POUNDS PER SQUARE INCH.
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| − | So, it is incumbent on the engine builder to do everything in his/her power to assure that all precautions have been taken to protect parts with this much pressure between them.
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| − | [[Category:General hotrodding]]
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