Please be aware that the process described below is for camshaft break-in and not engine break-in which is a whole different subject altogether. This article assumes that the engine is already bedded in.
Proper flat tappet camshaft set-up and break-in, as any engine builder knows, are keys to the life of a camshaft, both short and long term. The correct procedure allows the lifters to establish rotation and develop a good wear pattern.
The most critical time in the life of a flat tappet camshaft is the first 20 minutes of break-in during which the bottoms of the tappets “mate-in” with the cam lobes.
The start-up should be as close to the assembly as possible. Not more than a day at most.
- Remove the camshaft from the box, and clean it with mineral spirits or a parts washing solvent. Remove the rust preventative that is placed on the cam before shipping. Always thoroughly clean any part before installing it in an engine. Never “assume” that the parts are cleaned before packaging. During shipping, packaging material can rub into the component surface and must be removed!
- Perform a visual inspection immediately. Look carefully for dings, dents, deep scratches, or any other defect that may be detrimental to the break-in or long-term life of the camshaft. Pay special attention to the lobe and journal contact surfaces and distributor gear.
- Before installing the camshaft apply an ample amount of the supplied camshaft and lifter installation lube (COMP Cams® Part #153 or similar) to the cam lobes, journals, distributor gear, and coat the bottom of the lifters.
- It is not recommended to use any type of oil restrictors to the lifter galley, or use windage trays, baffles, or plug any oil return holes in the valley. Oil has a two-fold purpose, not only to lubricate, but to draw the heat away from whatever it comes into contact with. The cam needs oil splash from the crankcase, and oil run-back from the top of the engine to help draw the heat away. Without this oil flow, all the heat generated at the cam is transferred to the lifter, which can contribute to its early demise.
- Always use new lifters on a new flat tappet cam. If you are removing a good used flat tappet cam and lifters and are planning to use them again in the same (or another) engine, you must keep the lifters in order as to what lobe of the cam they were on. The lifter breaks-in to the specific lobe it is mated with and it can’t be changed. If the used lifters get mixed up, you should discard them and install a new set of lifters and break the cam in again as you would on a new cam and lifters. Also, you may use new lifters on a good used cam, but never try to use used lifters on a new cam.
- Make certain your spring pressures are correct. Normal recommended spring seat pressure for most mild street-type flat tappet cams is between 85 to 105 lbs. For extended camshaft life, flat-tappet cams should not be run with more than the recommended open valve spring pressure. Racing applications will often need to run more spring pressure at the expense of reduced camshaft life. In order to break-in a camshaft with high open pressures, the inner springs should be removed to reduce break-in load. The inner springs can then be reinstalled after initial break-in is complete.
- DO NOT “pump-up” hydraulic lifters before use. This can cause the lifters to hold a valve open during engine cranking, which will cause low compression. The low compression will delay engine start-up and is very detrimental to proper camshaft break-in.
- If possible, prime the oiling system. When priming, rotate the engine at least one complete revolution to assure oil gets to all valve train components. Valve covers should be off to assure that all rockers are oiling.
Big Block Chevrolet’s have an oil-priming idiosyncrasy. When priming a Big Block Chevy with a drill motor and priming tool, it is often necessary to prime for as much as 20 minutes (while rotating the engine) to get oil to all of the lifters and rockers. It is advisable to prime these engines with the valve covers removed so you can check to see oil coming out of all of the rocker arms before firing the engine. This last step is advisable on all engines, but particularly on Big Block Chevrolet’s.
Always remove the inner spring during break-in when using dual valve springs, or if you have a high load single spring, use a lighter spring. An alternative solution that addresses this same concern is using a set of low-ratio break-in rocker arms. Both of these solutions provide your best chance of proper camshaft break-in and long term durability. While these tips may be a slight inconvenience, a little time and effort on the front-end is much better than destroying your new engine.
Fill the engine with the correct oil for the break-in
Mechanical camshaft engines require oils containing higher concentrations of anti-wear additives phosphorous and zinc (1200-1300ppm vs. less than l000 for conventional oils). Do not use synthetic oil during the break-in period. Along with the high ZDDP content of the break in additive discussed in point 3 above, use only Total Quartz Diesel SAE 15w/40 oil for the initial 30 minute break-in period.
Pre-set the ignition timing to start the engine at a fast idle. It is important that the static ignition timing is as close as possible and if the engine has a carburettor, it should be filled with fuel. The engine needs to start quickly without excessive cranking to insure immediate lubrication to the cam lobes. If the engine will not start, don’t continue to crank for long periods, as that is very detrimental to the life of the cam. Check for the cause and correct. Cranking for long periods can displace the break-in lubricant from the lobes and lifters.
Start the engine and immediately bring the rpm to 3,000 rpm. Immediately the engine is running maintain the engine speed between 1500 to 3000 rpm during the first 30 minutes of operation. Get the engine running fairly smoothly and vary the engine speed from 1500-3000 rpm in a slow, to moderate, acceleration/deceleration cycle. During this time, be sure to check for any leaks and check out any unusual noises. If something doesn’t sound right, shut the engine off and check out the source of the noise. Upon restart, resume the high idle speed cycling. Continue the varying break-in speed for 20 – 30 minutes. This is necessary to provide proper lifter rotation to properly mate each lifter to its lobe. Should the engine need to be shut down for any reason, upon re-start it should be immediately brought back to 3000 rpm and the break-in continued for a total run time of 20 – 30 minutes.
Do not let the engine idle. Slower engine speeds will not supply the camshaft with an adequate amount of oil for the break-in period. The engine rpm may be varied periodically from 2000 to 3000 to direct oil splash to different areas of the camshaft. It is very important to vary the rpm up and down in this rpm range during the first 15 to 20 minutes. Do not run the engine at a steady rpm.
During this break-in period, verify that the pushrods are rotating, as this will show that the lifters are also rotating. If the lifters don’t rotate, the cam lobe and lifter will fail. Sometimes you may need to help spin the pushrod to start the rotation process during this break-in procedure. Flat tappet cams (both hydraulic and mechanical) have the lobes ground on a slight taper and the lifter appears to sit offset from the lobe centreline. This will induce a rotation of the lifter on the lobe. This rotation draws oil to the mating surface between the lifter and the lobe. If it is possible to view the pushrods during break-in, they should be spinning as an indication that the lifter is spinning. If you don’t see a pushrod spinning, immediately stop the engine and find the cause.
After the 30 minute break-in period, CHANGE THE OIL AND FILTER to be sure all contaminants and break-in lube are removed from the engine. The inner valve springs should now be replaced and the correct rocker arms installed. Let the engine cool, and then drain the crankcase and properly dispose of the oil and oil filter. Refill the crankcase with Ravenol RSS 10W/60. Do not use off-the-shelf synthetic oils, only racing oils with high ZDDP levels, usually API SL specification. At this point the initial break-in is complete. I recommend changing the oil and oil filter after the first practice and race meeting are over. There is no reason why the oil will not last for at least half a season of racing.