The Rules of Successful Camshaft Installation
Research indicates that most cams that wear out start to fail during the first few moments of operation. Many cams are irreparably damaged, even before the engine is started, because the basic rules of camshaft break-in have not been followed.
The cause of premature cam and tappet failure is metal to metal contact between the tappet and cam lobe. Should this contact occur due to lack of proper lubrication or excessively high pressure due to valve train interference shearing the oil film, then ‘galling’ will take place. When this happens, metal is transferred from the tappet to the cam or vice versa in a process comparable to welding. Microscopic high spots, which are present on all machined parts, become overheated due to friction and pressure and bond together, tearing sections loose from the tappet or lobe. These pieces of metal remain attached and create further local overheating during the following revolutions of the camshaft and lead to ultimate failure of the affected components. Listed below are steps to ensure long and trouble free life from the camshaft and associated components.
- New Piper cam followers and springs are recommended. Piper springs must be used when stated.
- Coat camshaft lobes and followers generously with Piper Cam Lube or a high grade engine oil.
- Camshaft retaining cap bolts typically have a low torque wrench setting, therefore when fitting camshaft retaining caps it is important to observe the following rules. 1. Never use any power tools to tighten retaining cap bolts. This includes pneumatic or cordless impact wrenches, cordless impact drivers and drills, pneumatic or cordless ratchets. 2. Torque retaining cap bolts to the manufacturers torque wrench settings. 3. Follow the manufacturer’s recommended tightening sequences and stages. Camshafts are prone to snap when these rules are ignored and may render your warranty void. If you are unsure of the correct torque wrench settings, tightening sequences and stages for your engine; consult an official workshop manual or ask the workshop of your local dealer for advice. Do not rely on online forums.
- Check entire valve train for interference before starting the engine, i.e. valve to piston contact, for twin-cam engines, valve to valve possible contact and spring boxing. Valve springs should show .030″ clearance between centre coils. Valve should have minimum .060″ clearance from piston/block. Engines that utilise hydraulic tappets should have at least one inlet and one exhaust tappet temporarily replaced with mechanical tappets set with zero clearance. This allows accurate figures to be obtained from the above checks. When all checks are complete, ensure original hydraulic tappets are refitted.
- It is essential you check your new Piper camshaft is identical to the camshaft you are replacing (except for lobe forms). In the unlikely event you notice any manufacturing defects, stop installation and contact Piper after sales for advice. Failure to check may invalidate your warranty.
- Ensure coolant level is correct. The engine must start instantly and must not be subjected to a long grind on the starter motor.
- When installing camshafts in classic cars, before attempting to start the engine for the first time, fill the carburettor with petrol, prime the oil system by manually turning the oil pump and ensure the ignition timing is correct.
- Do not idle engine during the first twenty minutes of operation; rpm should be kept at 2500 or above. In pushrod engines oil throw-off from the crank may not be sufficient to lubricate the cam followers. Also contact stresses at the nose of the cam are very high at low speed. If adjustments need to be made during the twenty minutes break-in period, shut the engine down. DO NOT IDLE.
- In some OHC engines where re-profiled cams are used, you may need larger than standard adjustment shims.
- When modifying engines that utilise finger followers, e.g. Ford Pinto SOHC engine, it is imperative that you ensure the followers sit in a horizontal position. Failure to do so will alter the rocker geometry. Increasing or decreasing the valve lift can result in failure.
- If the lobes of your new Piper camshaft(s) are coated with a black or grey phosphorus coating, this must not be removed. All camshafts are coated with a protective oil coating which must be removed with a suitable solvent prior to installation.
- If your new Piper camshaft(s) came supplied with any of the following, please ensure to fit these after the protective oil coating has been removed. 1. Grub Screw. 2 Core Plug. 3. Ball Bearing (see note below). 4 Woodruff Key. 5 Bissell Pin / Dowel. Piper strongly recommends using a retaining compound when fitting core plugs, and a thread locking compound when fitting grub screws.
Note: With the following Vauxhall / Opel camshafts, only fit the supplied ball bearing if the camshaft being replaced has a ball bearing fitted. Astra / Nova 1.3 / 1.4 / 1.6 GTE. Astra 1.8 J series. Astra C20XE 16v exhaust camshaft.
A Guide to Correct Timing
To check your cam timing, you will need a 360° protractor and dial gauge. The engine must be set at TDC and the protractor bolted to the crank pulley. Attach the dial gauge so that the foot is resting on the valve spring cap (or follower on OHC engine). Attach a pointer to the engine and zero the protractor. The engine is now at TDC with the protractor reading zero.
Turn the engine until full lift is first shown on dial gauge. Note number of degrees (e.g. 106 degrees ATDC), continue to turn the engine and note when lift starts to reduce (e.g. 110 degrees ATDC). True full lift position will, in this case, be 108 degrees. Your figures will differ but true full lift is at midway point.
The correct full lift position for your cam is shown on attached information sheet.