Camshaft install tips and tricks
(→Engine RPM for break in) |
(→Pre-lube) |
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Do not use any abrasive materials such as Scotch-Brite pads or sandpaper of any kind to accomplish these solvent and soap cleaning operations. Use only soft, clean rags. The camshaft is cleaned so that rust-preventative oils and greases can be completely removed. If left on the camshaft, such substances might hinder the penetration of an extreme pressure lubricant such as molybdenum disulphide. | Do not use any abrasive materials such as Scotch-Brite pads or sandpaper of any kind to accomplish these solvent and soap cleaning operations. Use only soft, clean rags. The camshaft is cleaned so that rust-preventative oils and greases can be completely removed. If left on the camshaft, such substances might hinder the penetration of an extreme pressure lubricant such as molybdenum disulphide. | ||
| − | ===Pre-lube=== | + | ===Installation and Pre-lube=== |
| − | '''3. | + | '''3. Actual installation of the camshaft into the block.''' |
| − | + | On a complete engine assembly, it is often helpful to install the camshaft BEFORE the crankshaft; in many cases the cam would be the first part to be installed by the assembler after "final cleaning" of the block. (The cam bearings are likely to be installed by the machine shop.) If this is the case, it is very helpful to--if possible--set the block on the floor bellhousing-side DOWN, so the block is vertical. The camshaft then can be lowered into the block straight down, and there's minimal effort needed to assure that the cam lobes and cam journals DO NOT nick the bearings. If the cam MUST be installed horizontally, it is almost mandatory to use a "handle" on the front of the cam, and to take particular care that the cam doesn't bang into, or scrape across the bearings. Whether vertical or horizontal, if the crankshaft isn't in the way, it's easy to guide the cam through the bearings with one hand while supporting the front end of the cam with the other. | |
| − | '''4. Failure to use an extreme pressure lubricant additive in the engine oil for camshaft break-in.''' | + | |
| + | '''4. Failure to properly massage an extreme pressure lubricant such as molybdenum disulphide into the pores of the metal on all lobes and lifter faces.''' | ||
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| + | Molybdenum disulphide will actually bond with the metal and give maximum protection to the lifter crown/lobe. Use the 'moly' lube on the distributor gear, cam lobes and the lifter foot that contacts the lobe only- '''not''' the bearing journals, and '''not''' the sides of the lifters. Engine oil or ATF can be used on the lifter bores or lifter sides, and the pushrod cups. | ||
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| + | '''5. Failure to verify "lifter spin" on flat-tappet lifters.''' | ||
| + | With the camshaft and lifters installed, but before the timing chain is attached or the pushrods are installed, mark each lifter and lifter bore with a "Sharpie" or other marker. A simple stripe on the lifter bore aligned with a dot on the visible part of the top of the lifter is fine. Rotate the camshaft several revolutions, and assure that the lifters spin in the bores, as noted by the increasing mis-alignment of the dot on the lifter relative to the stripe on the lifter bore. The lifters may not all spin the same amount--some will spin more than others--but they must all show some rotational movement as the cam spins. The only exception to this that I'm aware of is Buick "Nailhead" V-8s, which (at least in OEM form) have no crown on the lifter foot, no taper on the cam lobe, and no offset between lifter bore and cam lobe. The Nailhead lifters are NOT intended to spin. | ||
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| + | '''6. Failure to use an extreme pressure lubricant additive in the engine oil for camshaft break-in.''' | ||
There are many different products for facilitating valid cam break-in.Each cam grinder has his own specific product to facilitate valid cam break-in. The aftermarket has also come to our rescue with many different formulations of Zinc dialkyldithiophosphates (ZDDP). | There are many different products for facilitating valid cam break-in.Each cam grinder has his own specific product to facilitate valid cam break-in. The aftermarket has also come to our rescue with many different formulations of Zinc dialkyldithiophosphates (ZDDP). | ||
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====Valve springs==== | ====Valve springs==== | ||
| − | ''' | + | '''7. 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 (if those springs will accept the amount of valve lift and the retainers will clear the valve seals/valve guides) to break in the cam, then use one of the many tools available to change the springs with the heads on the motor. Those without shop air to hold the valves up through this operation can feed some clothesline cord through the spark plug hole and then bring the piston up to smash the rope and hold the valves up. 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. Although expensive, these are available from [http://crower.com/ 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. Of course, you would have to elongate the pushrod holes to accommodate the longer pushrod cup to pivot dimension and maybe alter the slots in your guide plates as well. | 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 (if those springs will accept the amount of valve lift and the retainers will clear the valve seals/valve guides) to break in the cam, then use one of the many tools available to change the springs with the heads on the motor. Those without shop air to hold the valves up through this operation can feed some clothesline cord through the spark plug hole and then bring the piston up to smash the rope and hold the valves up. 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. Although expensive, these are available from [http://crower.com/ 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. Of course, you would have to elongate the pushrod holes to accommodate the longer pushrod cup to pivot dimension and maybe alter the slots in your guide plates as well. | ||
| − | ''' | + | '''8. Failure to check for valve spring coil bind at max lift.''' |
If you cannot tell by eye, verify by inserting a .010" feeler gauge between the coils. A .010" between five coils would give a total of .050" safety margin before stacking the spring solid. If you cannot pass the feeler gauge between the coils, the spring is either coil bound or dangerously close to this condition, and you have probably over shimmed the spring (the fitted dimension is too short). | If you cannot tell by eye, verify by inserting a .010" feeler gauge between the coils. A .010" between five coils would give a total of .050" safety margin before stacking the spring solid. If you cannot pass the feeler gauge between the coils, the spring is either coil bound or dangerously close to this condition, and you have probably over shimmed the spring (the fitted dimension is too short). | ||
| − | ''' | + | '''9. Failure to check for retainer to valve guide/seal clearance.''' |
1/16"-1/8" clearance at full valve lift is considered sufficient. This is the limiting lift factor with the stock L31 Vortec heads. Most uninformed people will say they can run a 0.500" lift cam with them stock. That leaves ZERO clearance between the retainer and the seal. Not good. GM says the limit is about 0.420" with the stock pieces. GM engineers say 0.420" lift allows 0.030" retainer-to-seal clearance. | 1/16"-1/8" clearance at full valve lift is considered sufficient. This is the limiting lift factor with the stock L31 Vortec heads. Most uninformed people will say they can run a 0.500" lift cam with them stock. That leaves ZERO clearance between the retainer and the seal. Not good. GM says the limit is about 0.420" with the stock pieces. GM engineers say 0.420" lift allows 0.030" retainer-to-seal clearance. | ||
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