Crane Cams advises that IT IS NOT advisable to run mechanical lifters on a hydraulic camshaft. Although certain racing applications could benefit from the additional RPM potential of the mechanical lifters (and some racers do so), the ramp design of the hydraulic lobes is not designed for use with valve lash. The resulting harshness (as evidenced by valve train noise) will rapidly shorten the life of the camshaft and the lifters, and also the rest of the valvetrain components. Never run hydraulic lifters on a mechancial camshaft, as immediate lifter pump-up will occur, leading to a lack of performance and possible engine failure.
Archive for Camshaft
When it comes to picking a cam and a converter, there are a number of decisions to be made. Is the car really a racecar, or is it driven on the street 90% of the time? How hard do you want it to launch, what are the rear gears, engine cubic inch, weight of the car? All of these things directly relate to the stall and the cam(s) that you pick for your vehicle. The question really is: Where does the engine start making torque with the cam you have picked? Now, if you have already run your setup on the dyno, that would be the best indication as to what stall converter to run. If you already have a modified stall converter and now need a cam, you really want to know where that stall comes in, so you can get a cam that best matches that starting RPM range of your setup. Article courtesy of Crane Cams
Something that many people take for granted is checking the camshaft end play (especially on flat-faced lifter camshafts) when assembling their engine. In most instances, the lifters will bear against the taper that is ground into each lobe, locating the camshaft to the rear of the engine, as intended. However, there are a number of other factors that must be considered and should always be checked for good performance and longevity.
When building a fresh engine with new cam bearings, the cam end plug has been removed, and a new one should have been installed. If the end plug is now located too far forward in the block, the end of the cam may now be bottoming out on the plug, causing the lobes to be improperly aligned with the lifters. It will also cause the timing sprockets to be out of line. This will cause premature cam and lifter wear, and will damage the timing chain and sprockets. Make sure that the cam sprocket is able to ride against its correct thrust surface and that the cam and crank sprocket are in alignment when installed on your camshaft. On engines that may have a cam thrust plate (Ford FE, Chrysler LA 273-360, etc.), clearance to the end plug must also be checked. If the plug is too far forward when the plate is tightened, the back of the cam could now be forced against the rear plug. Galling will occur, heat will be generated, and unhappy metal particles may be passing through your powerplant. Also, camshafts from different manufacturers may have slightly different lengths, so don’t assume that if one cam fits properly, others will as well.
On thrust plate equipped engines, plates may vary slightly in thickness, and the steps on the cam and cam sprocket can also vary. Make sure that you don’t have a stack-up of tolerances that could prevent the cam from rotating freely. Install the cam, thrust plate, and sprockets without the timing chain to verify that nothing is in a bind. You should have approximately .003-.005″ of end play to allow for thermal changes and to promote proper lubrication in the thrust area. Engines that have roller camshafts installed (that didn’t originally have them) may require an aftermarket cam button spacer or some other type of device to keep the cam from moving forward (roller camshafts have no lobe taper). A slight amount of end play is also required for proper function. If possible, leave the cam end plug out until final assembly. This way, you can check end play once the front cover has been installed, its gasket crushed, and all tolerances taken up. With a dial indicator riding against the rear of the cam, reach through the lifter bores and move the cam back and forth. The .003-.005″ end play dimension should be maintained. When installing the cam end plug, be careful not to drive it in too far, undoing all of the work you’ve done up to this point.
There are many configurations and methods that manufacturers have used to locate their camshafts properly. It would be impossible to list all of them here. Just be sure to check the basics of proper cam alignment, end play, and free rotation. If you aren’t sure that what you have is correct, consult a shop manual, or someone familiar with your type of engine and application.
Lobe separation is the distance in camshaft degrees that the intake and exhaust lobe centerlines are spread apart. This separation changes cylinder pressure and determines where peak torque will occur within the engine’s RPM and power range. Tight lobe separations, such as 106°/108° or shorter, will increase cylinder pressure, causing peak torque to build earlier in the RPM range and peak-out in a short amount of time. This is great for dirt track racing, so the car comes out of the corner hard. The shorter lobe separation will also give that rough idle everyone loves to hear. A broader lobe separation, such as 112°/114° or wider, will reduce cylinder pressure. This causes the torque peak to come in later in the RPM range, but also allows the torque to build over a wider RPM range, giving you more mid-range and top-end power. This type of lobe separation is needed in many applications, such as fuel injected, nitrous and blower applications.
Due to the EPA’s mandate for zinc removal from most motor oils, proper flat tappet camshaft break-in procedure is more critical than ever before. This is true for both hydraulic and mechanical flat tappet camshafts. As a point of interest, 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 lobe.
There are some oils with additive packages that are better for camshaft “break-in”. These include: Shell Rotella T oil; Chevron Delo 400; and Mobil DELVAC oil. These oils are listed as diesel oils, but work great for flat camshaft “break-in”. We also recommend the use of Crane Cams # 99003-1 Break-in lube or GM “E.O.S.” (Engine Oil Supplement) Assembly Lubricant # 1052367. These should be poured over the lifters and camshaft prior to start up.
CAUTION: We do not recommend the use of synthetic oils for “break-in” because they are too slippery. This characteristic reduces the tendency of the lifter to rotate on the camshaft lobe and mate properly. Prior to installing the camshaft and lifters, it is recommended that the crankcase be drained and filled with new, clean oil. The oil filter should also be changed at this time.
Proper flat tappet camshaft break-in starts with the cam installation and includes the following steps:
1. Before installing the camshaft and lifters, wash them thoroughly in clean mineral spirits to remove the rust preventative that is placed on the cam before shipping. NOTE: As a “rule of thumb”, 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!
2. 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”.
3. Lube the bottom of the lifters with the moly paste provided with the cam. Lube the sides of the lifters with oil. Lube the camshaft lobes with the moly paste supplied with the cam.
4. Install the camshaft, lifters and timing set. Lubricate the tips of the pushrods with Crane Engine Assembly Lube (99008-1) or motor oil before installation.
5. Set your valve lash or lifter preload.
6. 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.
Preset the ignition to start the engine at a fast idle. Keep in mind that with many engines, when the timing chain sprockets have their marks at 6 o’clock on the cam sprocket and 12 o’clock on the crank sprocket that the number 1 cylinder is at TDC at the end of the exhaust stroke. For the ignition to fire the number 1 cylinder on start up, the number 1 cylinder must be at TDC at the end of the COMPRESSION stroke. That frequently requires rolling the engine through 1 additional revolution and putting the timing marks at 12 o’clock on both sprockets. Check you service manual or watch the action of your rockers to determine which stroke you are on. Both valves will be seated at the end of the compression stroke. The exhaust will be just closing at the end of the exhaust stroke.
7. Fire up the engine and bring the engine to a fast idle between 1500 and 3000 RPM. Do not worry about getting the ignition timing set perfectly at this time. 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 the lifter to the lobe.
8. Let the engine cool, and then drain the crankcase and properly dispose of the oil filter. Refill the crankcase with the proper viscosity and API service index recommended by the engine manufacturer. This should be a mineral oil not a synthetic oil.
At this point the initial “break-in” is complete. You can drive the vehicle in your normal manner avoid prolonged idling. We recommend changing the oil and filter after 500 miles. We strongly recommend mineral oils with flat tappet camshafts to help assure proper lifter rotation.. You might want to put another 5000 miles on the cam before switching to synthetic if that is your preference.
Spring Pressures: For extended camshaft life, flat-tappet cams should not be run with more than 330# of 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 so that the open “break-in” load does not exceed 330#. The inner springs can then be reinstalled after initial “break-in” is complete.
Lifter Rotation: 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 centerline. 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.
Never use old flat tappet lifters on a new cam. On flat tappet cams, the lobes and lifter bottoms mate together and if the lifters are removed from the engine, they must go back on the same lobe from which they were removed.
Roller cams do not require a “break-in” period like a flat tappet cam, but they should be washed in clean mineral spirits and soaked in oil before installation. Roller lifters do not mate into the lobes and, therefore, can be used on different cams.
Big Block Chevrolets 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 Chevrolets.
As stated above, we do not recommend synthetic oil on flat tappet camshafts because it is so slippery that the lifters do not rotate as well as with mineral oil, and lack of rotation is “death to the camshaft”. Additionally, if a vehicle using synthetic oil is stored for a lengthy period of time, the oil falls off the camshaft and the cam is “dry” during the engine start up. We recommend only regular mineral oil for vehicles that are only started occasionally or stored for prolonged periods.
Source: Crane Cams Newletter Issue No. 24
Cam advance, lobe separation, lobe centerline, intake lobe centerline, etc. are all terms being used for comparing and devising camshaft specifications. With so many similar terms being used, there can be a bit of confusion when folks from different backgrounds start talking about them.Lobe separation is the measurement in CAM degrees between the maximum lift point of the exhaust lobe to the maximum lift point of the intake lobe on any cylinder. Some also refer to this as lobe centerline. This dimension is ground into the camshaft and cannot be changed by advancing or retarding the camshaft (unless it’s an engine with separate intake and exhaust cams).Intake lobe centerline, or intake maximum lift, refers to the distance in crankshaft degrees from the cylinder’s Top Dead Center point to the maximum lift point of the intake lobe. This is usually measured as degrees After Top Dead Center. This figure WILL change when the cam is advanced or retarded. As you advance the cam, this number will get smaller, as you are opening it fewer degrees AFTER Top Dead Center. Retarding the cam will make this number larger, as you are opening it more degrees AFTER Top Dead Center.Exhaust lobe centerline, or exhaust maximum lift, is usually expressed in crankshaft degrees Before Top Dead Center. As you advance the cam, this number will get larger, since you are opening it more degrees BEFORE Top Dead Center. Retarding the cam will make this number smaller.
The average of the intake lobe centerline and the exhaust lobe centerline should equal your lobe separation.
The cam timing figures (as measured at a specific lobe lift: .004″, .020″, .050″, etc.) may show the maximum lift point to be distorted when you’re dealing with non-symmetrical camshaft lobes (the opening side has a different shape than the closing side). If you split the difference between the opening and closing figures at .020″ or .050″ lobe lift, this figure will not coincide with the actual maximum lift point of the lobe. There are instances where a non-symmetrical intake lobe is paired with a symmetrical exhaust lobe (or vice-versa), or lobes with varying amounts of non-symmetry may be used as intake and exhaust. We believe that where the opening and closing events actually occur are the most important figures to pay attention to when degreeing your camshaft. Just finding the maximum lift points doesn’t really tell you anything about the camshaft, or if it’s even the correct camshaft! By documenting the opening and closing numbers as you tune, you will gain more knowledge as to what actually helps or hinders your performance. This is also a good time to emphasize keeping track of your cranking compression whenever you change valve lash, cam timing, rocker arm ratio, and especially when changing camshafts.
You may have noticed that most Crane cams have a certain amount of advance ground into them when you check out the camshaft specification card. This is primarily done to insure that you have adequate torque to establish a good performance baseline. We have also found over the years that the correct camshaft for most applications will run best with some amount of advance in it. We believe that it’s certainly better to begin with too much bottom end and mid-range torque, and tune from there, than to have a shortage of torque, and try to figure out how to compensate for that.
The following is a general rule for how we grind most of our camshafts:
Lobe Separation Degrees Advance
up to 102 0
103 – 104 2
106 – 107 4
108 or more 5
This has certainly not been a complete list of all of the terms and philosophies we use when producing our camshafts, but it will hopefully provide a bit of insight as to some of our methods of camshaft recommendation and production.Source- Crane Cams E-News Issue 216