The automotive world has totally embraced the notion of hydraulic roller lifers. Yes, rollers reduce friction and present the opportunity to employ a more aggressive lift profile compared to a flat tappet cam. But there’s still room in this world for performance flat tappet camshafts.

There’s still a strong demand for a flat tappet cam and lifter package—whether it be mechanical or hydraulic. While you can save some coin by choosing a flat tappet cam, there are a couple of important technical details that must be checked off the list before you spin that flat tappet-cammed engine for the first time.

Ironically, the cause for all the problems for flat tappet cams had nothing to do with camshafts and lifters. Instead the tipping point was a significant change in engine oil.

In 2005, the American Petroleum Institute introduced API SM category oil, which radically lowered the zinc and phosphorous levels from 1,500 to roughly 800 parts-per-million (ppm). You’ve probably seen the abbreviation for zinc and phosphorous as ZDDP. This acronym stands for zinc dialkyl dithiophosphate. This is a high-pressure lubricant that, until 2005, was found in generally high concentrations in all off-the-shelf oils. But in that year with API SM oil, ZDDP levels plummeted by almost 50 percent—and that’s when flat tappet camshaft-equipped engines began suffering failures.

ZDDP is an anti-wear additive that drastically improves oil’s ability to reduce wear in extreme pressure situations (like the interface between the camshaft lobe and the lifter). This is important because there are two main contributors to failed flat tappet cam lobes during new camshaft break-in: low ZDDP concentrations in oil and/or excessive valve spring pressure.

This story will reveal a proven procedure for breaking-in your flat tappet camshaft when combined with the right components that include quality break-in oil along with the proper selection of valve springs. There are no shortcuts in this procedure. Ignoring or failing to follow through with these recommendations may lead to a failed cam lobe.

If that happens, the engine really should be completely disassembled so that all the oil passages can be thoroughly cleaned. Otherwise, some of that metal may end up right back in the oil the next time the engine is started. Considering how much effort it is to perform the job, its time well spent to perform this procedure correctly the first time.

We’ll use a small-block Chevy as our test subject, but these same steps apply to any four-stroke, pushrod internal combustion engine. For this story, our small block Chevy was equipped with a new Summit Racing flat tappet hydraulic camshaft pushing on a set of Melling hydraulic lifters. Once everything is clean and ready for assembly, the first step is to ensure that each lifter can easily travel inside its lifter bore. Carefully inspect each lifter bore for burrs or perhaps a light ridge on the bore that might prevent the lifter from moving freely within the bore. Flat tappet cam lobes are designed with a slight taper that induces the lifter to spin. This improves lifter wear characteristics and also offsets forward cam movement.

Next you can fully coat all the lobes with the break-in lube supplied with the camshaft. A full but light coating is all that’s necessary on each lobe and should be followed with that same lube on the face of each lifter. There’s no need to coat the sides of the lifters with the moly paste, break-in oil will perform that task.

With the camshaft and lifters in place and the timing chain and gears properly installed, the rest of the valvetrain can be reassembled. This leads us to valve spring selection. The best way to ensure the lifters and cam survive the initial wearing in process is to reduce the valve spring load. For this small-block, we chose a set of standard 1.25-inch diameter single springs with a damper. Our springs came from Trick Flow and we’ve listed the specs in the chart at the bottom of this story, along with Comp specs for their recommended springs for big-block Chevy, and small- and big-block Fords.

The key is to avoid high spring pressure that increase load on the lifter and cam during the break-in procedure. We know of an engine builder who recently lost a flat tappet cam in a big-block Chevy during the break-in process. He was using quality break-in oil but two lobes failed because they were working against a stiff spring. His chose a high quality spring, but its specs placed the seat load (valve closed) at 155 pounds and an open (full valve lift) load of 340 pounds at 0.500-inch valve lift. The failure of several lobes points out that this was likely too much spring pressure during break-in. Once the cam has achieved its proper break-in, this spring would probably work. But for the break-in procedure, it was just too much.

One way to avoid this for a big-block Chevy would be to choose a light spring for the initial break-in and then switch to the final spring after break-in. If using a dual valve spring, its common practice to remove the inner spring to reduce the load and then re-install the inner spring after the cam is fully broken in. Yes, this is extra work, but still less effort than having to completely disassemble and clean the engine, then purchase and install a new cam and lifters.

Another option is to create a taller installed height. It’s not uncommon for heads to require as much as 0.060-inch shim under the valve spring to reduce the installed height, which is the distance from the spring seat to the underside of the valve spring retainer. Omitting this shim can reduce the seat load by as much as 20 pounds. Once the cam is broken in, the spring could then be removed and the appropriate shims added to bring the installed height to its recommended spec.

Another option would be to go with a stock replacement spring such as the Sealed Power spring for a small-block Chevy we’ve listed in the chart at the bottom of this article. This spring barely has 75 pounds of load at the installed height and at 0.450-inch valve lift is well below 200 pounds of open load. This would allow the cam to break in easily. Then you could change to a more performance-oriented spring. Be sure to check that the lighter spring can handle the total valve lift your cam generates. This particular spring can handle 0.500-inch valve lift with sufficient clearance to coil bind. Another good point is that these stock springs are very inexpensive. For our engine, we decided on the Trick Flow-style springs with a slightly taller installed height.

Here is the place where choosing the correct break-in oil is critical. Our experience has revealed several companies offering quality break-in oil including Comp, Driven Racing, Edelbrock, Lucas, and a few others including a recent Break-In oil from Summit Racing.

The key to choosing quality break-in oil involves more than just finding higher ZDDP levels. The best break-in oil will generally be either a low- or non-detergent oil. This may appear to be counter-intuitive, but there’s a reason why this works. Detergents are used in normal engine oil to help carry away contaminants. But chemically, these detergents also strip away the layer of zinc and phosphorous placed in the high-load areas. So the best break-in oil will have both a higher concentration of ZDDP as well as minimal detergents (such as calcium).

We decided to use Summit Racing’s new break-in oil for this small block Chevy engine. We added five quarts of the SAE 30 oil and will use this for the first 50 to 100 miles of engine operation. After that point, we plan to drain the break-in oil and replace it with Summit Racing’s 10w30 high performance oil that also contains higher ZDDP numbers that are more in line with older engine oils.

With the new cam in place, we were ready to pressure lube the engine. There are several tools available through Summit Racing that can accomplish this task. Here’s another example where choosing the right tool can make a difference. The Summit Racing pressure lube tool includes a channel or cutout that connects the left and right side lifter galleries in both the small- and big-block Chevys.

If you merely use a shaft to drive the oil pump or a tool that does not include this crossover channel, turning the oil pump (clockwise for the Chevys) will only push oil through the left (driver) side oil gallery and up to the rockers but not the right side. This is because all Chevy V8 engines use a cross-over channel in the distributor body to direct oil to the right side lifter gallery. If the pressure lube tool does not include this channel (or the channel is too narrow) then only half the lifters will receive oil. This is not necessarily a deal-breaker since the rest of the engine will receive oil including the mains and rods. But excluding the entire right side lifter gallery is certainly not ideal. The Summit Racing pre-oiler tool includes this cross-over channel and produces the desired results.

We used a similar tool when we assembled this small block but you could also just use an old small block distributor and shaft. We connected our pre-oiler to a 1/2-inch electric drill motor as the load can often be excessive for smaller 3/8-inch drive drill motors. We prefer to remove the valve covers and spin the oil pump to make sure oil is pumped to all 16 rocker arms.

Next, it’s important to install the distributor accurately to ensure that the engine will start on the first couple of rotations. We’ve written a story that details how to install the distributor correctly the first time. The emphasis here is to avoid long cranking sessions on the starter motor that tends to wipe the lube off the cam lobes.

The ideal procedure is to accurately place the distributor with 12 to 15 degrees of initial timing Before Top Dead Center (BTDC) so the engine fires quickly and will run properly. The other portion of this plan is to pre-fill the carburetor float bowls with fuel and make sure the accelerator pump squirts fuel into the intake manifold. If your car is equipped with an electric fuel pump, this is a simple process. If your engine has a mechanical pump, don’t crank the engine to pump the fuel. Instead, use a small funnel to pour some fuel down the vent tube. This will place fuel in the float bowl and allow the accelerator pump to shoot some fuel into the engine. Combined with the pre-set initial timing, this ensures the engine will start immediately.

With all those parameters set, the engine should start on the first or second revolution. Once the engine starts, immediately bring the engine speed up to a minimum of 1,500 rpm. It’s best to double-check the oil pressure and monitor the engine for any leaks. Assuming there are no gushers, constantly vary the engine speed between 1,500 and 1,900 rpm. This is important because all V8 domestic pushrod engines lube the cam and lifter interface with splash oiling from the crankshaft. It’s also important to vary the engine speed as much as possible to alter the splash pattern to ensure all 16 lobes and lifters receive adequate lubrication.

If the engine is a complete rebuild with fresh rings, keep the cam break-in time to no more than 10 minutes. Assuming the engine is in the vehicle and the initial break-in procedure has progressed with no issues, drive the car immediately and mildly load the engine multiple times. This places cylinder pressure behind the rings which will ensure a proper break-in. This cannot be accomplished with the engine merely running at 1,500 rpm with no load as on a test stand. However, if the engine has time on it (as ours did), then the cam break-in can be accomplished in the driveway or on a test stand with no load.

To ensure proper piston ring break-in, we prefer to drive the engine as soon as possible with light load while monitoring oil pressure and water temperature. It’s best to put 100 or so miles on the engine and then drain the break-in oil and filter and replace it with high-zinc performance oil from the same companies mentioned earlier. Be sure to use a high-zinc performance oil (but not a break-in oil) for the rest of this engine’s life as these performance oils use a higher level of ZDDP which will ensure the camshaft will live a long happy life.

Now armed with the proper procedure, you’re ready to dive into that flat tappet camshaft upgrade you’ve been considering. Don’t be intimidated by all the negative talk you may have heard. This procedure will offer the best chance of making your flat tappet performance cam live a long and happy life.

Valve Spring Specs for Eccentric Ways: Camshaft Break-In

Small Block ChevySealed Power VS6771.238"76 lbs.
at 1.700"
194 lbs.
at 0.450" lift
Small Block

Trick Flow 16324-161.250"110 lbs.
at 1.78"
279 lbs.
at 0.445" lift
Big Block

Comp 911-161.524"
122 lbs.
at 1.900"
309 lbs.
at 0.500" lift
Small Block

Comp 942-161.350"110 lbs.
at 1.78"
284 lbs.
at 0.500" lift
Big Block

Comp 940-161.464"93 lbs.
at 1.900"
237 lbs.
at 0.600" lift
241 lbs./in.

Parts List for Eccentric Ways: Camshaft Break-In

DescriptionPart NumberQuantity
Summit Racing ZDDP Performance Motor Oil, SAE 30SUM-1-SAE305 Quarts
Summit Racing ZDDP Performance Motor Oil, 10w30SUM-1-10W305 Quarts
Summit Racing Oil Pump PrimerSUM-9010151
Trick Flow Valve Springs for Small Block Chevy TFS- 16324-161 (Set of 16)
COMP Cams Valve Springs for Big Block ChevyCCA-911-161 (Set of 16)
COMP Cams Valve Springs for Small Block FordCCA-942-161 (Set of 16)
COMP Cams Valve Springs for Big Block FordCCA-940-161 (Set of 16)
This is what happens when you try to shortcut a flat tappet cam break-in procedure. There’s generally no warning until the engine begins to run poorly as one or more lobes go round. (Image/Jeff Smith)
Coating the cam lobes and the bottom of the lifters with a suitable moly lube will ensure that the first few moments of engine operation are properly lubed. Just coat the bottom of the lifters with the moly lube and use engine oil on the lifter bodies and the cam journals. (Image/Jeff Smith)
We chose these 1.250-inch diameter single wound springs with a damper for our small-block Chevy. These Comp springs check out at 105 pounds on the seat and 273 pounds at max open valve lift. Or, you could also go with a stock replacement small-block spring that generally comes in around 75-80 pounds on the seat. (Image/Jeff Smith)
If you have a Rat motor with dual springs, it’s a good idea to remove the inner spring and just run the outer for the first half-hour to hour of break-in time. Then you can re-install the inners after the cam has survived the initial break-in. Yes it’s more work but better than having the cam go flat! (Image/Jeff Smith)
Another way to increase spring pressure after the cam is broken in is to purposely set a taller installed height and then re-install the shims to establish the proper seat and open loads. (Image/Jeff Smith)
With all the lifters, pushrods, and rockers in place it was time to set the preload or lash. Since this was a hydraulic lifter cam, we set the preload at 1/2-turn past zero lash. The process is not difficult once you master the EO-IC sequence as mentioned in the body copy. Note we’re using poly locks on this engine as our personal preference is to avoid stock self-locking nuts because they don’t retain their original adjustments. (Image/Jeff Smith)
Small and big block Chevys use a channel in the distributor body to direct oil from the main oil passage at the rear of the block to the right side lifter gallery. The arrows point to this channel in the stock distributor body (top) and in the other tool (bottom). Note that the middle tool offers only a very small channel. That tool minimizes oil to the right side lifter gallery. The lower tool in this photo is nearly identical to the Summit Racing version that includes this important feature. The Summit Racing tool part number is listed in the Parts List included in this post. (Image/Jeff Smith)
Quality break-In oil is critical to give the cam and lifters a fighting chance to survive. Summit Racing’s break-In oil has a high 1,400 ppm ZDDP level that helps the lifters establish a proper wear-in pattern. After a few miles in the car, we will drain this oil and replace it with Summit Racing’s high-zinc 10w30. (Image/Jeff Smith)
Current off-the-shelf motor oils all feature an American Petroleum Institute (API) donut certifying that this oil can be used in newer engines. SN or newer rated oil should not be used in flat tappet camshaft engines as the ZDDP numbers are roughly half what they should be and the oil also contains high detergent concentrations that work against the ZDDP.
We spun our pressure lube tool with a ½-inch corded drill motor until oil exited all 16 pushrods. Sometimes you have to turn the engine over a revolution or two to get the oil up to all 16 rockers. (Image/Jeff Smith)
When installing the distributor, make sure the Number One cylinder is on the compression stroke and set the initial timing at around 12-14 degrees initial. This will help the engine start and run immediately. (Image/Jeff Smith)
It’s important to pre-fill the carburetor float bowls with gas so the engine will start as soon as the starter motor begins to crank. This is easy with a separate electric fuel pump. If the engine uses a mechanical pump, pour about six ounces of fuel into the primary vent tube. Two or three shots of fuel from the accelerator pump should be enough fuel to start the engine. (Image/Jeff Smith)
As part of this story, we installed a Summit Racing hydraulic flat tappet cam in this small block following the above procedure. This engine had plenty of miles on it so we didn’t have to worry about breaking in the rings so we bolted our engine to a Summit Racing test stand to break in the cam. The engine started on the first turn of the starter and within 20 minutes of running at part throttle the initial break-in was complete and the engine was running great. (Image/Jeff Smith)
Once you have at least 15 minutes of running time on the engine, it’s best to drive the car for a short distance keeping a close watch on oil pressure and coolant temperature. This is especially important if the engine has new rings as the rings need load to properly seat. If the engine is not new, then the final break-in on the cam can be accomplished in the driveway. Assume once the engine has 20 to 30 miles under its belt that the cam is fully broken in and you can change the break-in oil and filter to remove contaminants after 100 miles. (Image/Jeff Smith)

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Author: Jeff Smith

Jeff Smith has had a passion for cars since he began working at his grandfather's gas station at the age 10. After graduating from Iowa State University with a journalism degree in 1978, he combined his two passions: cars and writing. Smith began writing for Car Craft magazine in 1979 and became editor in 1984. In 1987, he assumed the role of editor for Hot Rod magazine before returning to his first love of writing technical stories. Since 2003, Jeff has held various positions at Car Craft (including editor), has written books on small block Chevy performance, and even cultivated an impressive collection of 1965 and 1966 Chevelles. Now he serves as a regular contributor to OnAllCylinders.