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BEFORE YOU START:
Use an engine rebuild manual for specifications and more detailed information about your particular engine.
CHECK the lifter bores for excessive egg shape wear. If the bores are worn the block will require machining or replacement.
CHECK your pushrods for wear and straightness.
CHECK your rocker arms for cracks and wear. If you are installing a cam with higher lift than before, check the tips of the rocker arms more carefully for wear. Uneven wear at the rocker tip will not allow smooth valve operation and cause rapid wear.
CHECK your valve springs for the correct pressure. If any one valve spring is below 75# seat pressure, or is more than 10% below the average, replace the whole set. Here is a guide to the correct spring pressures for street performance cams:
INT. DUR. @ .050 SEAT PRESSURE OPEN PRESSURE
---------------- ------------- -------------
180 to 200 90 to 100 225 to 250
200 to 220 100 to 110 250 to 275
220 to 240 110 to 120 275 to 300
240 to 260 120 to 130 300 to 325
NEVER EXCEED 375 POUNDS PRESSURE WITH THE VALVES OPEN.
If you are replacing a failed camshaft, determine why it failed before installing a new one. There may be a cause of failure that will present the same problem for a new cam.
After removing the old camshaft from your engine, thoroughly clean the engine, removing all dirty oil and impurities. Even the slightest amount of impurities can ruin a new cam.
INSTALLING YOUR CAMSHAFT:
Prior to installing the new camshaft, inspect the cam lobes, oil holes and bearing journal surfaces for any damage which may have occured in shipping. Use a mild solvent to remove any metal shavings, corrosion etc. Do not scrub or use any type of abrasive cleaning agent. Dry the camshaft with a lint-free towel or compressed air.
Attach the cam sprocket (or 3" to 4" long bolts) to serve as a handle when installing the new cam. Lubricate your camshaft with the special prelube provided. Gently insert the camshaft into the engine block with a rotating motion, being carefull not to dislodge or damage the cam bearings (Note: The cam bearings are easily damaged if the side of the cam journal is scraped across the edge of the cam bearing). Once the camshaft is in place, make sure it rotates freely.
Rhoads variable lifters are the only type of lifter that need to be filled with oil before installation. To fill Rhoads lifters with oil, completely submerge each lifter upright into a container of oil and compress the innerplunger with a pushrod until it hits bottom. Hold several seconds and release slowly. Repeat several times until the lifter is completely filled. Soaking the lifters alone will NOT fill them. DO NOT PRE-FILL ANY OTHER TYPE OF HYDRAULIC LIFTER.
Coat the lifters with prelube, especially on the bottoms, and place them into the bores. Rotate the camshaft to make sure the lifters move up and down freely.
Install the timing set. Install the valve train for #1 cylinder, adjust and Check for interference at maximum lift:
CHECK valve to piston clearance: you must have .090" for intake and .100" for exhaust minimum. Valve to block clearance should be checked if larger than stock valves are used.
CHECK valve spring retainer to valve guide or valve seal for clearance: you must have .060" minimum, .120" prefered.
CHECK rocker arms for bottoming out on the studs at full lift.
CHECK springs for coil bind (if dual springs are used, check the inner spring before installing and checking the outer spring): Use a .012" feeler gauge to check the full circumference between coils, as coil binding usually occurs on one side of the spring only. Total clearance between all coils must be .050" minimum, .060" is prefered.
IF ANY OF THESE CLEARANCES IS QUESTIONABLE, FIX IT.
"GOOD ENOUGH" PROBABLY ISN'T.
DEGREEING YOUR CAM:
Mount a degree wheel to the crankshaft and a pointer to the engne block. Remove the rocker arm and pushrod from #1 cylinder. Install a TDC stop in the spark plug hole of #1 cylinder.
To locate top dead center, rotate the engine until the piston contacts the TDC stop. Mark the degree wheel at the pointer. Now rotate the engine in the opposite direction until the piston stops. Make another mark on the degree wheel at the pointer. If the degree wheel is properly located, there will be an equal number of degrees on on both sides of TDC on the degree wheel. If an unequal number of degrees exists, the degree wheel will have to be relocated. For example, if you come up with 34 degrees on one side and 30 degrees on the other side, the wheel will have to be moved 2 degrees to correct the misalignment. Once the degree wheel is aligned, remove the marks that you made and remove the TDC stop.
Position a dial indicator securely above the intake lifter. The stem from the indicator should be aligned with the lifter as close as possible. Rotate the engine at least two revolutions. Make sure that the dial indicator is working freely and the lifter is not sticking in the bore.
Rotate the engine clockwise until maximum lift is reached. Zero the dial indicator and continue rotation until a -.050" reading is reached. Mark the degree wheel at this point. Rotate the engine counter-clockwise until maximum lift is reached again. Continue counter-clockwise until a reading of -.070" is indicated. Now rotate the engine clockwise until -.050" is shown on the dial indicator. Mark the degree wheel again. Halfway between the two marks is the center of the intake lobe. An example of this might be 180 degrees on one side of the degree wheel and 36 on the other side. By adding these two figures you get a sum of 216 degrees. This number is divided by two (108 degrees) is your lobe center. If your cam is ground with 108 degree lobe center seperation, then the cam is installed at split overlap or "straight up". If the number is smaller than the cam's lobe center seperation, such as 106 degrees, then the cam is advanced. If the lobe center comes up larger, such as 110 degrees, then the cam is retarded. If you aren't sure of the lobe center seperation, repeat the process for the exhaust lobe. Adjustments can be made with the use of degree bushings, offset keys, or a multi-position crank gear.
INSTALL THE REST OF THE VALVE TRAIN AND ADJUST:
With the piston at top dead center of the compression stroke, hold the pushrod with the thumb and index finger of one hand and tighten the rocker nut with the other while moving the pushrod up and down. The lash is adjusted to zero when you can no longer move the pushrod up and down.
HYDRAULIC LIFTERS: For stock type and Rhoads lifters tighten an additional one turn for proper preload. With non-adjustable rocker arms torque to the proper setting and check the lifter preload. Stock type and Rhoads lifters require a minimum of .010" between the plunger and the retaining clip (preload). High Rev lifters require .000" to .002" clearance (lash) in the valve train. In many cases using a higher lift camshaft will require longer (or adjustable) pushrods.
SOLID LIFTERS: Adjust the valves .004" tighter than recommended to compensate for the loosening that takes place during break-in.
Finish assembling the engine except for the valve covers. Install a new oil filter and oil. Before initial start-up, prime the engine oiling system by using an electric drill to drive the oil pump. This will help ensure that you have proper lubrication to all parts on start-up.
START-UP:
Avoid prolnged cranking of the engine on initial start-up. Once your engine has been started, keep the engine speed between 1800 rpm and 2000 rpm for about 20 minutes. DO NOT ALLOW THE ENGINE SPEED TO DROP BELOW 1200 RPM. This high rpm break-in is critical, as low rpms put more load on the cam lobes and reduce valve lifter rotation. With the valve covers off you will be able to see if the pushrods are rotating. Pushrods not rotating indicate that the lifters are not rotating. IF THIS OCCURES, STOP THE ENGINE IMMEDIATELY AND DETERMINE THE CAUSE. DO NOT RESTART THE ENGINE UNTIL THE CAUSE IS CORRECTED. When the lifters are not rotating, the cam lobes and lifters will self-destruct, sometimes in a matter of seconds, or create damage that will greatly reduce the life of the camshaft.
IF YOUR ENGINE IS RUNNING QUIETLY
AFTER THE FIRST 20 MINUTES,
CONGRATULATIONS!
YOU HAVE CORRECTLY INSTALLED
YOUR NEW CAMSHAFT.
After the engine has been run-in, you should check and adjust the lash or preload to the proper hot specs.
RHOADS LIFTERS can be adjusted by ear when the engine is hot. With the engine running, back the adjustment off until a very loud "clacking" is heard. There is clearance in the valve train at this point. Tighten the adjustment back down until the clacking stops and then tighten an additional one turn. The ticking that the Rhoads lifter makes is much quieter than the "clacking" that you heard when there was clearance in the valve train.
