Flat Tappet Camshafts & ZDDP
Flat Tappet Camshafts
The Standard flat tappet camshaft has served the small block chevy for over 60 years and in other engines for many more. They are still produced by many aftermarket companies and purchased by many people looking for more power in there engines. The oem including GM have all gone to roller for many reasons.
Roller camshafts take less power to turn and in larger profiles produce more power because of the shape of the lobes. They are more square shaped and allow the valve to stay open at max lift for more time allowing more air into the engine. The OEM also went with roller cams because an additive in oil that helps flat tappet cams live longer has been removed because it causes damage to catalytic converters and is not emissions friendly.
ZDDP Removed from oils
Since ZDDP has been removed its more and more common for hot rod builders to choose roller cams. But for the majority of us the added cost of roller cams is to costly. Since many engines can make good power with flat tappet cams its not needed to run roller cams in most engines.
Any conversation on flat tappet camshafts can not be gone over without talking about camshaft failure on break in. Cam shaft break in can become an issue for many reasons. A camshaft failure can be for many reasons. Most of which get blamed on ZDDP not being in new oils but for break in it is recommended to use a ZDDP heavy break in oil. This oil allows more ZDDP during the critical moments needed to support initial start up. With proper break in lube and procedures they can work without failure for many miles.
ZDDP and the internet
If you read the internet you would think that all flat tappet camshafts fail during break in. But this is not the case most of the camshafts sold go into engines that run fine when proper procedures are followed. Many cams fail because of valve train not being setup correctly. A hanging valve or a rocker arm hitting the spring retainer the cam sees pressures well beyond what the valve spring can apply to the camshaft under normal operation.
With proper break in procedure, use of proper oils and break in lube along with the correct engine assembly lube the camshaft cam be broken in effectively. Even with high lift and heavy spring pressures. Camshafts can last for many years after proper break in.
Ready to fire
Things to check during install: Lifter crown is important if the lifters were flat they would not spin and would wipe almost immediately. Lifter spinning free in the bore. If the lifters can not spin freely when assembling the engine it will fail almost immediately as well. These two things more than any effect camshaft break in. They are not part of break in if they are not done correctly during assembly the engine will not last. This goes for any v8 flat tappet engine. Camshaft also has an angle to the lobe that spins the lifter it is very slight so if the lifter does not spin easily it will not be able to over come the friction the lifter will hang and dig into the camshaft.
Check it all first
With some time and attention to detail these types of cams can be a great alternative to roller camshafts cost and extra weight on the valve train. Higher rpm engines often find benefits over the full roller camshafts. Since the roller lifters and camshaft profiles require much higher spring pressures these things can limit the amount of lift and rpm the engine can produce. Once the engine reaches a certain rpm roller lifters need to be solid not hydraulic and the additional weight of the valve train causes extra wear and shortened life of the lifters. With Flat tappet solid lift camshafts the valve train can be lower with less spring pressures. Allow for more RPM and longer life of these extreme engines.
Racing and flat cams
NASCAR is one of the racing bodies that require flat tappet cams. They use larger .904 lifters to support the large camshafts used in high rpm racing. A long with many other modifications can make these engines live at 10K rpm for a 500 mile race or longer.
There are two basic types of flat tappet camshafts. Solid lifter and hydraulic lifter. All engines need clearance for them to work properly since the engines heat causes metal parts to expand. With solid lifer camshafts the clearance is set by a mechanic when the engine is built and during regular maintenance cycles. The Hydraulic camshafts use the same basic design but have an oil filled section with a one way valve that holds the oil in the lifter to make up for the clearance. With these type of camshafts the clearance is set one time during engine assembly and is maintained by the oil filled lifter and does not need to be set.
Types of flat cams
These come in many different styles. They are the most popular and used by most OEM’s for normal and performance engines. For max performance engines they use solid lifters. They are easy to work with and easy to setup the engine. Because of the limits of RPM range they don’t work well in high RPM engines. For the most part these top out RPM wise around 6000 to 6500 rpm at most. After this RPM you will get valve float that allows the valve to bounce off the seat and come further out than the cam will allow. This can cause the valve to hit the piston and bounce back against the cam and damage the lifters and valves.
Short Travel Hydraulic Lifters:
High RPM hydraulic Lifters have shorter travel than normal OEM style lifters and allow the engine to rev much higher rpm. These are more modern version of the hydraulic lifters. They allow very little travel. At high RPM they can only let the valve get so far out of control. With these lifters RPM’s of 7K and more are possible.
Solid lifters are the lightest and highest reeving of all the flat tappet cam options. There are several types of solid lifters some of the more common ones are below. Chevrolet used these lifters for a lot of there higher performance engines. The famous 302 Z28 and the high output Fuelie 327.
EDM Solid Lifters:
These are solid lifters with a hole in the bottom put there with a laser. Its so small a drill bit would not be able to duplicate it. They allow hugh pressure oil from the lifter to lube the camshaft and help keep high pressure high rpm cams from failure.
Tool Steel Lifters:
Usually the top of the high revving mark with or with out the edm feature. These are made from very strong tool steel. With this steel they can be made thinner and lighter but still remain stronger than normal thick wall lifters. These are best for high RPM engines where they will take large amounts of abuse.
Solid lift camshafts use a longer duration and long slow ramp rates. These keep the lifter from making hard contact with the camshaft. It is common for solid cams to have a sewing machining sound. Its a unique sound that many of the hotrod builders love. They also give a strong mid range power that helps make more average hp than hydraulic camshafts. Since the ramp rates are slower the solid camshafts usually have more duration for the same sized camshaft. It is common for solid cams to advertise longer duration overall. They also have a stronger pull at higher rpm power levels.
Even with the best Camshafts engines require the correct support equipment. To take advantage of there longer duration and higher lift rates.