Some thoughts on cam and lifter wear
By Charles Reichard
There has been a lot of discussion regarding the increase in flat tappet cam failure the last few years. Much finger pointing goes toward our only domestic flat lifter supplier, Stanadyne. We started using Stanadyne lifters about a year and a half before the lifter shortage hit. We had NO increase in lifter failures when we changed over. The lifters look different so there was no old stock involved or anything like that. One order we got Eaton’s and the next Stanadyne’s. The primary visible difference was the Eaton lifters were Parkerized on the bottom and the Stanadynes were not. The metering system is also different. The Parkerizing is a protective coating used on cams and sometimes lifters that disappears a few seconds after startup. This coating is deposited in an acid solution that slightly degrades the finish on the lifter foot. According to Stanadyne, they have made no change in their lifter manufacturing procedures or materials.
Chrysler Corp. stopped Parkerizing all their cams many years ago when they discovered this degradation of the surface finish actually contributed to cam failures in their 2.2L OHC engines.
Almost all domestic camshaft castings come from the CWC foundry in Muskegon, MI. The heat-treating is done at the foundry. While there can be several different casting patterns used for each engine, the material is usually identical except for the P55 castings. The heat-treating is also identical. There have been no changes at CWC or at their customers supplying semi-finished castings to the performance market other than some increased automation. About the only significant difference in the castings is the lobe width, with wider lobes offering greater load carrying ability.
Why then are we seeing an increase in cam failure? There are several contributing factors. The first and likely primary factor is the lack of zinc additive in most of today’s oils. As I understand it, all oils for highway use have NO ZINC. Zinc has, for many years, been one of the primary antiwear additives in motor oils. Due to factors involving contamination of catalytic converters, zinc has been outlawed in motor oils for highway use. There has been a decrease in zinc content for several years but as of January 1, 2004, it is eliminated in all oils for highway use. If an oil contains zinc, it must be labeled “ for off road use only” or “Not for highway use”. Diesel oils may be an exception. Several of our racing customers have switched to 15W40 diesel oil with good results. (6/1/2007 Word is out that zinc has now been removed or substantially reduced in the diesel oils)
A very useful web site with lots of oil related information is www.bobistheoilguy.com. I had only a few minutes to peruse the site but it had lots of very useful information. Check it out!
Another significant factor is the increased use of synthetic oil. While some synthetic oil works ok with flat tappet cams, many do not. Never break in a fresh engine with synthetic oil. There are no cam grinders that I know of that recommend the use of any synthetic oil with flat tappet cams. The use of synthetics is primarily needed in very high temperature or low temperature applications. If you properly control the oil temperature you have less need for synthetics. Several of our customers add 2 quarts of conventional oil to their synthetic oil with good results.
An excellent additive with high zinc content is General Motors EOS. I haven’t seen a new bottle yet but I have heard that the label has been changed from engine oil supplement to engine assembly lubricant so it won’t be used as an oil additive regularly. I have heard on good authority that EOS is not compatible with Mobile 1 synthetic oil. That doesn’t necessarily mean anything as to compatibility with other synthetic oils. Other companies such as Prolong, have similar additives.
Another significant factor continues to be lack of proper break in procedure. While many engine builders remove the inner spring for break in, often this is not enough. Higher rocker ratios popular today mean increased spring pressures and very significantly higher stress across the nose of the lobe. Often the open pressure with outer springs only is still too high for proper break in with these higher ratio rockers. We like to see open pressures less than 275 lbs for break in.
The best break in involves 1.2 or 1.3 rockers with the inner springs removed. After 30 minutes at 1500-2500 rpm install the inner springs and run with the break in rockers. Next run with 1.5 rockers, and then with the final rocker ratio to be used. This is time consuming to say the least but not nearly as time consuming as disassembling the engine to clean out several ground up lobes and buying gaskets, rings and bearings at the least. Our customers that follow this procedure have far fewer cam failures than the ones who don’t.
It is very important that the engine fire immediately. Excessive cranking will wipe the assembly lube from the cam and lifters. Be sure the timing is set and the carb full of fuel. The engine should run between 1500 and 2500 rpm for about 30 minutes. Vary the speed a bit during the break in.
Many customers like to point the finger to soft lobes or defective castings. Having a soft lobe is as likely as putting your hand in a bucket of water and having 1 finger come out dry. A single soft casting is unlikely as well. We buy Small Block Chevy castings 65 to 150 at a time. If there is a defective batch of castings then we are going to see a huge number of failures in the space of a few days from several different customers. If you have 1 or 2 worn lobes and the rest look fine then there is nothing wrong with the cam. About the only issue that the cam grinder controls is the taper on the lobe. Even this can vary a bit with no ill consequences. Another less obvious factor is the lobe lift for a given duration and rocker ratio. A lobe design that has too much lift for the duration will have a sharper nose radius. This has a detrimental effect on wear and is greatly aggravated by high rocker ratios. Sometimes it is advantageous to use a little less lobe lift to still take advantage of the faster valve opening offered by the higher rocker ratio.
Then there are the failures that we can only file under “stuff happens”. We see strange things, like obvious indications that the lifter was not rotating for a short time but with no major failure. This is often indicated by a thin line the width of the lobe on the bottom of the lifter. It can be seen and felt easily. We have seen this several times in cams with 6 or more races and significant dyno time that have virtually no cam wear. After replacing the lifters there were no further problems. Obviously the lifter had started rotating again at some point. Lifters frequently don’t rotate much if at all at idle or low rpm. Some engine builders cut a slot on the inner side of an old valve cover so they can observe pushrod rotation at higher engine speed without getting an oil bath.
It is critical to make sure race engines do not idle at low rpm for prolonged periods. The cam and lifters depend largely on splash lubrication for survival and there isn’t much splash going on at idle. Also the lifters will rotate less at low rpm.
Another less obvious thing is using a heavy cam lube on the sides of the lifter. This can temporally inhibit lifter rotation. Use only light motor oil on the lifter body and the heavy lube on the bottom of the lifter and the lobe. Don’t forget to lube the distributor drive gear and fuel pump lobe as well. Be sure to check the actual lifter clearance in the lifter bore
I am a great believer in preheating the oil and water in any performance engine. It can be difficult to heat the oil for some but anyone can put hot water in the radiator for initial startup. A small torpedo heater can be used to warm up the oil if you don’t want to spring for a little heat pad that sticks on the oil pan. Some people use a heat lamp near the pan for an hour or so. It is also important to initially break in the engine with lighter oil so it can get circulating more quickly. We don’t have to worry about heavy loads or high temperatures during break in.
Sometimes, despite your best efforts, you still wipe out a cam occasionally. If the proper procedures were not followed then you know why. Often people say, “I never did all that stuff before and never had a problem. Why should I do it now? Today’s cam profiles are very different from those of a decade ago. They impose a higher load more quickly than older designs due to higher acceleration rates and frequently have higher lift. Also valve springs are significantly improved and often have higher open pressure. If you don’t follow proper break in procedure then you will experience cam failure sooner or later.
Another frequently overlooked item is truing the lifter bores. Lifter bores are frequently not located properly even in brand new blocks. Even if they are not tilted fore and aft, which would create excessive wear, they can be mislocated axially which would change the cam timing on those cylinders causing a loss in power. Even brand new blocks should get lifter bores trued, bushed and precision bored and honed. The lifter bore clearance is different for different types and diameter lifters. Check with the lifter manufacturer for proper clearance.
When you use 1.2 or 1.3 rockers for break in, be sure to trial fit them before final assembly of the head. They frequently require elongation of the rocker arm slot or hole away from the rocker stud. This is the opposite of the work required for high ratio rockers that require machining the slot toward the stud.
Following all the proper procedures for cam and lifter break in doesn’t necessarily guarantee you will never wipe out a cam but it increases your chances for success 10 fold. We have several NASCAR Late Model Stock customers that get 2 or even 3 seasons out of a cam and lifters. They typically race 75-150 laps every week + practice and qualifying. That represents a lot of laps.
Everyone should be evaluating their break in procedures. You can spend a little extra time initially or much more time and money doing it over later. Be sure to evaluate your oil and be certain it contains zinc. It is a good idea to use an oil additive high in zinc content. Flat tappet cams can provide long life and very good power output if they are properly installed and broken in carefully.