Newman Cams

NewmanCompany History
In 1966 DAVID NEWMAN commenced grinding performance camshafts on a Churchill cam grinder that he modified for non-production camshaft manufacture. One of the first camshafts that he ground was for the Competition Department of the Rootes Motor Company, now Peugeot, grinding Hillman Hunter and Imp competition camshafts.

By the early 1990'sthe company had increased the manufacturing plant to 5 CNC Turning Centres, 4 CNC Milling Centres, 1 CNC Cylindrical Grinder, 6 Rocker Arm Grinders and 6 Camshaft Grinders, together with a fully equipped Inspection Department.

From 1998 the company moved into the production of performance camshafts in steel and chilled iron, manufacturing cams for F1, F3, BTCC, ETCC, DTM, FIA, GT Le Mans, MOTO GP etc.

The Four Cycle Engine
First of all let's make sure you have a good understanding of the cam's function in the four cycle engine. You probably already know the four basic strokes of the four cycle engine: INTAKE, COMPRESSION, POWER, and EXHAUST. Each stroke represents one-half of a revolution of the crankshaft or 180 crank degrees. 4 cycles x 180° = 720° or two revolutions of the crankshaft. Two revolutions complete one sequence of the four strokes. The camshaft is connected via the timing chain or beltand sprockets at a 1:2 ratio to the crankshaft and therefore revolves once for every two turns of the crank. It's purpose is to operate the intake and exhaust valves in the correct timing with the piston as it sequences thru the four strokes.

Engine operation
The engine opeation during the four cycle procedure is as follows:Intake valve opens at Top Dead Center (T.D.C.), and as the piston lowers, it draws in the fuel/air mixture; the intake valve then closes at Bottom Dead Center (B.D.C.) completing the intake stroke. The piston rises, with both valves closed to compress the fuel/air mixture completing the compression stroke. The spark plug ignites the fuel/air mixture which drives the piston down to B.D.C. with the valves still closed completing the power stroke.The burnt gases due to their high pressure virtually expel themselves and the piston drives the last of the gases out the cylinder.The exhaust valve closes at T.D.C. completing the exhaust stroke. All the above arevalid forengineswith 0o overlap or no overlap.The engineers of the 1910's and 1920's discovered that the midrange and high-speed power could be greatly improved by lengthened valve timing.The stretching of the intake valve timing allowed the engine to breathe deeper and take in greater amounts of air and fuel, thus creating a more powerful explosion in the combustion chamber. An important advantage gained from lengthened valve timing is that the greatly expanded gases are eliminated more efficiently and virtually by their own pressure. Lengthening of valve timing allowed the engineers to create in effect a fifth cycle in the four cycle engine and to produce more horsepower.

Camshaft profiles
Select the camshaft that meets your requirements in regard with the use of your vehicle.

Road camshaft - PH1
This is a camshaft that would be used for road use and will normally run with standard carb or injection system and can be fitted without additional tuning equipment. It is meant for town use and will have a smooth tick-over and will give it's increase in power in the low mid-range. Other modifications to the engine will increase the performance of this cam.

Fast Road camshaft - PH2
This is a camshaft for increasing mid-range of the engines and is meant for mild competition use and where the driver requires an increase of power in the mid-range without suffering too much loss of power in the low-range. The tick-over will be heavier than a stan­dard engine. The fuel system may have to be modified and the cam will work to its optimum with modifications to the cylinder head, inlet/exhaust system and possibly the management system.

Fast Road/Rally camshaft - PH3
This type of camshaft is really the limit for normal road use. It will require fuel system and management modifications. It will have a noticeable loss of low-down power and the tick-over will be heavy. For competition use, where mid-range power is important and road use where the maximum power is required.

Tarmac/Rally/Sprint/Race camshaft - PH4
This camshaft is for competition use only and can be considered as a  race cam. It could be used on the road, but would not be suit­able for use in traffic. It will have a very heavy tick-over and there will be a noticeable loss of power below 3500 rpm. Its main use is for a torque race cam, giving a strong surge of power in the upper range power, yet still having the ability to floor the throttle below 5000 RPM and pull cleanly away. It will require modifications to the carb/injection system, cylinder head and induction exhaust system.

Full Race camshaft - PH5
For race use only. Not suitable for road or rally use,. Little power below 5000 RPM . Will have virtually no idle and will require carb/injection, exhaust/induction., cylinder head and engine management modifications.

Camshaft characteristics

Nose
The nose is the section of the profile where maximum lift occurs and is positioned each side of the opening and closing flanks. Due to differing cam design requirements and engine designs, the nose radius of performance cams can vary. The nose is also the section of the profile that reverses the direction of the valve. The cam lobe controls the opening and closing of the valve, but at some point the valve has to stop before it can reverse its direction. The length of time the valve remains at its maximum heightis called dwell angle and is very important when setting up the cam.

Lift
When selecting a performance cam it is important to know how much lift will impart to the valve. The more lift a cam produces the more radical the profile. When tuning an enginewe increase the compression ratio, which means reducing the combustion chamber vol­ume in relation to swept volume. This is often achieved by skimming the face of the cylinder head, thus reducing the clearances between piston and valves. Obviously if we increase the valve lift, we need to do some careful calculations to ensure that the valves do not contact the piston. It may be necessary to machine pockets in the piston crown or to use domed forged pistons with pockets in order to ensure the rquired clearence between the piston and the valve. Cam lift can be calculated by deducting the base circle diameter from the overall lobe height.

Base Circle
The base circlerefers to the portion of the lobe that does not impart any valve motion as the cam rotates. It controls the part of the four stroke cycle where we require the valve to be closed.

Ramp
This is the section of the profile that prepares the cam follower to contact the cam lobe. Ramps are found on both the opening and closing side of the profile. The ideal situation in a per­formance engine is to get the valve open as quickly as possible, and frequently these ramps are heavily modified, often making performance cams less quiet in operation. The closing ramp is usually less modified than the inlet on performance cams, as it is important to close the valve gently back on its seat. If this is not the case, the valve will tend to crash back on its seat, and excessive damage to both valve and seat will result.

Flank
The lobe flank is the section of the profile that extends from the ramp to the nose and it is this section of the profile that accelerates the cam follower to the full lift position. As the cam continues to rotate it allows the now compressed valve spring to close the valve in a controlled manner, until it rests back on its seat.The flank is a very important part of the performance profile as it controls the rate or acceleration of the valve.

Overlap
Overlap is the lobe centre angle and is measured from the centre line of the inlet and exhaust lobes. The closer the lobe centres are together the greater the overlap. By altering this angle we will alter the position of the inlet and exhaust valves relative to each other, and increase or decrease the amount of time both valves are open together.To determine the overlap, add the opening before T.D.C. of the inlet valve to the exhaust closing after T.D.C. i.e. inlet valve opens 40 degrees before T.D.C, exhaust valve doses 50 degrees after T.D.C overlap = 90 degrees.Overlap is employed to allow the burnt gases escaping through the exhaust valve, to help induce the incoming charge of fuel/air mix­ture. This incoming charge in turn helps force out the remaining exhaust gases.

Cam Followers
In order for the cam lobe to impart motion to the valve it must run on a cam follower. The follower converts the rotary motion of the lobe into linear motion.Cam follower configurations vary, however , in all new engines the most common followers are the hydraulic followers. They adjust the valve clear­ances automatically by the use of hydraulic pres­sure.The advantageis that as they are self adjusting, should remain silent and mainte­nance free under normal conditions. Also be­cause they are under hydraulic pressure they are in constant contact with the cam lobeit is much easier to predict exactly when a valve opens and closes, and reduce emissions.However the use of hydraulic followers in performance engines is limited and while they are suitable for most fast road applications, the demands made by the more radical profiles and higher engine speeds, bring their use into ques­tion. In this case we can change into mechanic followers.

Duration
The term duration refers to the amount of time the valve is off its seat. The more duration the cam has the more radical the profile, and the rougher the engine will run at low speeds. The subject of duration is a big confusion.To quote a duration figure without quoting the checking height at which it was measured is quite meaningless.Only by using a common checking height of the duration between different profiles, ispractical to say if a profile is radical or not.

Valve springs

The selection of the Camshaft and the type of profile employed will have an influence upon several other areas within the engine, but one component of prime importance is the valve spring. It is the function of the cam profile to open the valve. The valve spring provides opposing force in order to control this motion whilst the valve is opening, and to push the valve back on to its seat after the cam has moved over the nose. Three factors can influence the type of the valve spring after fitting a new cam profile:

  • The cam lift and theshape of the ramps
  • The use of valves with bigger diameter than the stock that night be also heavier than the stock
  • The use of the car and the maximum rpm range of the engine

The aim is always to achieve a set of harmoni­ously matched components which will help the engine to rev freely and smoothly to high RPM in order to produce good power, without premature wear or failure of compo­nents.

Camshaft timing 

Carrying out modifications alters so many factors within the engine that the original timing marks should be considered redundant and used only as a rough guide. A modified engine needs careful & accurate timing.

The most accurate job will be arrived at with two tools:

A timing disc & a dial test indicator. (D.T.I.)

Firstly set No 1 piston at top dead centre (T.D.C.). The original T.D.C. mark is still relevant although not really accurate enough. The D.T.I probe should be positioned down the spark plug hole to rest on the piston crown. Then by turning the crankshaft backwards and forwards an exact position will be indicated by a change in needle direction on the dial.The timing disc should be fitted to the front of the crankshaft. A bent piece of wire secured under anynear bolt head will act as a zero pointer and should be positioned to align with the 0 degree mark on the disc. The engine is now at T.D.C. on No 1 cylinder and the timing disc zeroed.

The procedure varies here a little depending on whether the engine is single or twin cam.

Single cam engine
In a single cam engine both inlet & exhaust cams are all on one shaft.The inlet lobe is chosen for the timing process. Now rotate the crankshaft clockwise to the full lift position specified for the particular camshaft being fitted (a 280° cam has full lift @ 105 degrees). Full lift of the inlet cam should occur here.Iif a vernier timing pulley is fitted, this is carried out while the pulley is loose and then locked up when correct. Now a check can be made of the opening and closing figures for the profile by rotating the engine and reading off the disc, the point at which the valves (inlet & exhaust) lift off and return to their respective seats.

Twin cam engine
The principle remains exactly the same. However, the inlet & exhaust lobes are separated onto the respective camshafts. This means that unlike the single cam engine there is no fixed relationship between the two, this means that the inlet camshaft is timed in the same manner as described for the single camshaft. Additionally the exhaust camshaft is then timed as a separate entity.Vernier timing pulleys are all the more useful for a twin cam engine and the job should end by checking the opening and closing figures as before.

Clearence checks

The principle areas that should be checked are as follows:

  • Coil binding of valve springs.When the cam is at full lift the gap between the coils should not be less than 1.0mm
  • Spring retainers. The clearance between the bottom of the retainer and the top of the valve guide must be not less than 1.5mm
  • Valve to piston clearance.The clearence should be not less than 1.5mm for the intake valves and 2.0mm for the exhaust valves.This clearence must be retained from 0°-10° after T.D.C. for the intake valves and from 0°-10° before T.D.C for the exhaust valves.

How to select a performance camshaft
When selecting a performance camshaft, consider the use for which the vehicle will be required. We all know the claims: 20 BHP extra. This sounds great - but think! These automotive manufacturers can't be that silly to disregard 20 BHP by changing a camshaft. Ask yourself! Where is this 20 BHP? Probably not where you will ever use it at 7500 rpm. Well, probably we will use it, occasionally; it would be nice to have in reserve. Hold on! In this world there is no such thing as a "free meal". What's the possible trade-off of this 20 BHP? It could be a loss of 10 BHP at 2500 rpm. This means, each time you accelerate through 2500 rpm, you could lose 10 BHP. This to me, doesn't sound too good. Be conservative! Don't over-cam your engine. Choose your cam for the correct application. Consider! Fit a milder cam and increase your power by 10 BHP at 3500 rpm. Remember! You get this 10 HP every time you accelerate through 3500 rpm. Multiply this by 10 HP each time you drive through 3500 rpm then deduct the times you reach 7500 rpm. 

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