Camshaft install tips and tricks

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).

Most ZDDP additives recommend a specific quantity in the oil for break-in, and then half that amount for each subsequent oil change. Yes, it is possible to get too much ZDDP in the oil and generate spalling of the cam lobes. So, do your research, or use roller lifters where this stuff is not required.

'''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.  

'''Note:''' More info on checking clearances at [[Valve train points to check]].

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.

 

Lifter clearance should be 0.0012" to 0.002", with 0.0015" (one and one half thousandths) considered close to ideal. Too loose can be 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 Comp Cams p/n 5003 [http://www.summitracing.com/parts/CCA-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. But having that hole is no guarantee...

[[File:Bad cam and lifter edm.jpg|thumb|left|500px|Bad cam and EDM hole-equipped lifter]] <br style="clear:both"/>

'''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.

==Roller cams are not immune==

While the move has been made by the OEMs to stop using flat tappet cams and lifters, replaced by hydraulic roller cams and lifters, they are not immune to failure.

The same type of oil additives should be used, however do not use the heavy moly cam break in lube on a roller cam or lifter- it will cause much more problems than it will cure. Instead, follow the manufacturer's instructions. If those are not available for some unknown reason (all are online), use straight motor oil or a roller lifter-specific lube for the roller lifters and cam.