Camshaft install tips and tricks
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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. | 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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| + | '''12. Failure to clearance lifters in their bores so that they spin freely.''' | ||
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| + | 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. One way to provide a flat tappet cam and lifters with additional lubrication is to groove the lifter bores. One tool for doing this operation is the [http://www.summitracing.com/parts/CCA-5003/ Comp Cams p/n 5003] lifter bore grooving tool sold by Summit. Solid lifter flat tappet lifters are available with a small machined hole in the lifter foot that feeds pressurized oil to the interface between the cam and lifter. | ||
Note: More info on checking clearances at [[Valve train points to check]]. | Note: More info on checking clearances at [[Valve train points to check]]. | ||
===Engine RPM for break in=== | ===Engine RPM for break in=== | ||
| − | ''' | + | '''13. Failure to run the motor at high rpm (2500 or higher, alternating 500/1000 rpm up and/or down to allow the crank to throw oil in different places at different revs) for a minimum of 20 minutes. |
No idling! The motor should not be run at less than 2500 rpm for a minimum of 20 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 of the crankshaft at speed, drain back 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. | No idling! The motor should not be run at less than 2500 rpm for a minimum of 20 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 of the crankshaft at speed, drain back 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. | ||
| − | ''' | + | '''14. Failure to initially adjust the valves properly.''' |
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Using the "spin the pushrod until it feels tight" method may result in valves too tight. Holding the rocker arm tip down against the valve stem tip with one hand, jiggle the pushrod up and down with your thumb/forefinger of your other hand until all play is removed, then turn the rocker nut the number of times specified by the lifter manufacturer to set the preload. (Another good reason to buy lifters from someone you can talk with about them on the phone instead of buying them in a white cardboard box with no name on it). Builders who have done hundreds of engine builds may have the "feel" to do the "twist" method, but those who are doing their first few builds lack the experience to do this and will have better results with the "jiggle the pushrod up and down" method. | Using the "spin the pushrod until it feels tight" method may result in valves too tight. Holding the rocker arm tip down against the valve stem tip with one hand, jiggle the pushrod up and down with your thumb/forefinger of your other hand until all play is removed, then turn the rocker nut the number of times specified by the lifter manufacturer to set the preload. (Another good reason to buy lifters from someone you can talk with about them on the phone instead of buying them in a white cardboard box with no name on it). Builders who have done hundreds of engine builds may have the "feel" to do the "twist" method, but those who are doing their first few builds lack the experience to do this and will have better results with the "jiggle the pushrod up and down" method. | ||
| − | ''' | + | '''15. Failure to inspect the distributor drive gear for wear.''' Too much wear can allow the cam to walk in its cam bore and contact an adjacent lifter. The builder is also responsible for using a distributor gear that is compatible with the camshaft gear material. Coordinate this with the cam grinder before you ever begin assembling the motor. Hardly anything will make you feel more stupid than finding one or the other of the gears eaten up, necessitating an engine tear-down to clean out all the shrapnel. |
| − | ''' | + | '''16. 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 20 minutes of uninterrupted running. Ignition timing set. Warning: no grinding on the starter! | Fully charged battery, good starter, known-good carburetor with full fuel bowl, source of fuel to the carburetor to allow minimum 20 minutes of uninterrupted running. Ignition timing set. Warning: no grinding on the starter! | ||
| − | ''' | + | '''17. 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 certain that pressure is registering. Priming will aid lubing the valve train at initial start up. It's the last area of the motor to get lubed on dry start. You can make a tool by disassembling an old distributor and removing the gear, or just grinding off the gear teeth so that the teeth don't engage the cam teeth. Or, you can spring for 20 bucks and get a very nice priming tool that will be a nice addition to your tool chest. In either case, you will NOT get oil to the passenger side rockers of a Chevrolet-designed V-8 unless you use either the distributor or the tool to block off the oil galley under where the distributor bolts down. Here is an example of a tool for use with a Chevrolet engine: [http://paceperformance.com/index.asp?PageAction=VIEWPROD&ProdID=25140 Proform oil pump prime tool].That sort of tool is not needed on, for example, Oldsmobile- or Pontiac-designed V-8s. | Prime until you get oil out of the top of each and every pushrod. Observe the oil pressure gauge to be certain that pressure is registering. Priming will aid lubing the valve train at initial start up. It's the last area of the motor to get lubed on dry start. You can make a tool by disassembling an old distributor and removing the gear, or just grinding off the gear teeth so that the teeth don't engage the cam teeth. Or, you can spring for 20 bucks and get a very nice priming tool that will be a nice addition to your tool chest. In either case, you will NOT get oil to the passenger side rockers of a Chevrolet-designed V-8 unless you use either the distributor or the tool to block off the oil galley under where the distributor bolts down. Here is an example of a tool for use with a Chevrolet engine: [http://paceperformance.com/index.asp?PageAction=VIEWPROD&ProdID=25140 Proform oil pump prime tool].That sort of tool is not needed on, for example, Oldsmobile- or Pontiac-designed V-8s. | ||
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| − | ''' | + | '''18. 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. If you purchase a used flat tappet cam from a swap meet or yard sale, plan on using it for a doorstop. | 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. If you purchase a used flat tappet cam from a swap meet or yard sale, plan on using it for a doorstop. | ||
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