In the last issue of Engine Masters, we set out to start a series of articles that gets right to the core of engine building by showing the tricks, techniques and tools required to successfully build an engine. The aim is to arm the reader who dreams about putting together a high performance powerplant with the information needed to get it done. How? The goal is to answer the question of "How to do it" as much as "What to do." We covered what goes into building a short-block, and how it is done, in the last issue. This time around, we turn our attention to the cam, valvetrain, and top-end.
Really, this is a pretty broad subject, and the details vary depending upon the caliber of the build, and the equipment being used. The idea is to focus on the ideas that are universal to any engine buildup. Some of the detail may be more than you need to know for a very basic assembly, but knowing more is never a bad thing. We encourage feedback from our readers, so if you have an area of engine building you'd like explored in detail, contact me at steve.dulcich@sorc.com.
Install and Degree the Cam
At the most basic level, only a few things need to be ensured while installing a camshaft. The camshaft must be clean and properly lubed, and once in, it must spin freely in the block. The lube used will depend on the type of cam. Flat-tappet camshafts require a special high-load break-in lube on the lobes, which is usually packaged with the camshaft. The bearing journals should be lubed with an assembly oil or regular motor oil. Roller camshafts, either mechanical or hydraulic, normally do not need special cam lube on the lobes, and can be installed with oil on the lobes and journals.
Installing the camshaft can be as simple as sliding the stick into the bore, and making sure the timing dots are in alignment at TDC when the timing set is bolted in place. Most mild to stock rebuilds, and a surprising number of high performance engines, are put together this way. Taking such an approach is like flying blind, since the camshaft's installed centerline will not be known unless it is actually checked by the process commonly referred to as "degreeing-in." Unfortunately, inaccurately degreeing-in the camshaft is one of the most common engine assembly blunders, often making matters worse than just lining up the dots. If the cam is going to be degreed-in, it has to be done with the utmost in accuracy. Tools for degreeing a cam are relatively inexpensive; degree wheels can be purchased from most cam manufacturers, while some such as COMP Cams offer kits with everything you'll need.
Degreeing-in begins with accurately...
Degreeing-in begins with accurately finding TDC, which serves as the key reference point for the cam phasing. TDC can be found with a piston stop, a deck bridge and dial indicator, or an indicator on a stand. Start by setting up a degree wheel and pointer at the crank, and set it up to indicate zero degrees at an eyeballed TDC. Next, use the dial indicator to fine tune the pointer. Since the exact TDC point is difficult to distinguish on the indicator, a checking height in the vicinity of TDC is used before and after TDC (the actual checking height isn't critical; I use both 0.025 and 0.050 inch). Zero the indicator at TDC, and then rotate the crank to the checking height before and after TDC, recording the degree wheel readings. Adjust the pointer so that the readings are the same value before and after TDC at the checking height. When the values are the same, the zero mark will be centered at TDC. When making the checks, the crank should be rotated in the normal direction of rotation.
Proper lube upon installation...
Proper lube upon installation is vital to a cam's survival, especially with a flat tappet. Apply the manufacturer's lube to the lobes, such as the moly-based paste supplied with this Lunati Voodoo cam, and apply oil to the journals. When installing the cam, use a cam handle tool, and guide the 'shaft carefully into the tunnel without banging-up the delicate cam bearings. The cam should slide into place easily and should rotate freely in the bore. If the cam binds, there is a problem that needs to be corrected before moving on. Possible causes of cam binding can be improperly machined or sized journals, a bent cam (run-out), as well as misaligned or damaged cam bearings. The bearings will show witness marks were the cam is binding.
Now that the degree wheel...
Now that the degree wheel and pointer are set up to read exactly TDCNow that the degree wheel and pointer are set up to read exactly TDC, a lifter is installed on the No. 1 intake lobe, and a dial indicator or a special checking tool is set up to record the tappet rise. The object is to read from the degree wheel exactly how many degrees past TDC peak intake lift occurs. Begin by rotating the crank and zeroing the indicator at peak lift. Since the exact point of peak lift is difficult to distinguish, a checking height is used when reading the degree wheel. I use both 0.025 and 0.050 inch, recording the degree wheel readings at these points before and after the indicator goes over the nose of the lobe. The installed centerline is determined by averaging the degree wheel reading at a given checking height before and after peak lift. When making the checks, always rotate through the checking positions in the normal direction of engine rotation.
Lifters Logistics
Lifters basically come in four types: flat-tappet and roller, available in solid or hydraulic versions depending on the camshaft type and design. Always use the appropriate lifters for the type of camshaft being used. Flat-tappet lifters must rotate in the bores, while rollers must maintain their alignment to keep the roller wheel in line with the lobe and avoid destruction. Typically, solid rollers and retrofit hydraulic rollers use a link bar arrangement to pair up the lifters and hold them in alignment. OEM hydraulic rollers will typically use alignment yokes and a spring-steel spider for alignment. The essentials for lifter installation are cleanliness, proper lubrication and free movement.
Solid roller lifters are often...
Solid roller lifters are often shipped with protective grease in the bearings, and require cleaning and soaking in synthetic oil to properly prepare them for use.
When installing the link bars...
When installing the link bars for a roller set-up, makes sure that the link bar is orientated properly. For some applications, a link bar installed in the wrong orientation will cause failure--typically the manufacturer will provide markings and instructions on the correct orientation. When the lifters are installed, set the cam at the base circle for that pair and work the lifters through their range of motion to feel for any binding.
In contrast to a roller, a...
In contrast to a roller, a flat tappet must rotate in the lifter bore for survival. Lube a flat tappet with cam lube on the base and engine oil on its sides and oil the lifter bores. The lifter must slide easily in the bore, without any binding or tight spots. Some block cleaning procedures using shot tumblers can create a burr at the top of the lifter bores, causing binding. Always prep and check the lifter bores during the mock-up stage of engine assembly.
With hydraulics, either flat-tappet...
With hydraulics, either flat-tappet or roller, the lifters should never be pre-filled or primed in their hydraulic mechanism. The lifters will fill with oil and self-adjust when the engine is pre-lubed and fired.