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Frequently Asked Questions - Cylinder Head/Camshafts & Associated Components
 
Cam profile suitability for standard pistons
Reason for having different inlet and exhaust camshafts
Dos & Don'ts of Uprating your Camshafts
Performance gains from new cams
Should I have cylinder head work or cam change for more power?
MBE Management System installation instead of upgrading cam profiles
Do I need to make Cam timing changes when fitting throttle bodies?
Autograss cam change to increase power
 
Cam profile suitability for standard pistons
Question: I have a 2.0L Duratec and my plan is to change the cams to get more power from 3000 - 8000 rpm without any internal engine modifications to support this. I am willing to change valve springs to support a higher lift Cam within the stock piston clearance range.  I understand the limitations at this point.   I have researched a number of possibilities, but cannot evaluate them well as I am not a cam engineer, although I am a mechanical engineer and understand the basics. Please could you give me some advice?

Answer: Unfortunately, there are no short cuts when it comes to designing a cam profile but to give you a simple explanation.  A cam profile needs to be a smooth transition to control the valve train so control is not lost, so if you wish to add lift, the overall duration has to increase to allow a smooth transition to occur.  If you simply produce a profile that draws a straight line between fully closed to fully open, the mechanical components will simply disintegrate.  There is a theoretical limit which is based on the weight of the components and the speed at which they can be moved at, some companies attempt to get to close to the edge of this limit and in some cases exceed it.  Failures may not be instantly obvious in many cases and it may take time for your engine to destroy itself.  

On your own engine the limitation is the valve pocket depth, so when you wish to increase the lift of the cam profile, the duration will increase so the proximity to the valve pockets will get ever closer.  When we have produced cam profiles, we do this in conjunction with Kent Cams and spend a huge amount of time and money insuring it will mechanically fit as well as insuring it is a safe profile.  It is then extensively dyno tested to ensure gains.  Many competitors simply look at the standard profile and look at what they can expand it by and do none of the testing, when you look at the profiles available the information will tell you only a limited amount as to what the cam profile actually is and without a cam plot would you begin to understand what the potential benefits are.  At which point you will then need to test them to see what results you get.

Therefore it is impossible for me to comment on other profiles and even valve springs, we can only advise you on our own product and in many cases, our figures may appear to be lower than that of our competitors and we prefer to advise you of figures we have seen when producing our products.

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Reason for having different inlet and exhaust camshafts
Question: I see you sell camshaft kits when inlet and exhaust is different, please can you explain why?

Answer: Choosing different camshafts for the inlet and exhaust is quite common, it allows the engine designer to produce different characteristics from an engine.  Competition engines have a different set of requirements to road engines, road engines are all about emissions first where competition engines are about power and performance. 

There are no hard and fast rules, but a basic guide is that the milder the exhaust cam in relation to the inlet cam, the earlier in the rpm range the engine will produce torque.  The more aggressive the inlet cam, the higher up the rpm range, the engine will be able to carry on producing power but there always has to be a compromise.  You cannot just fit a very small exhaust cam and a very big inlet cam. 

The only way to discover where the cams should be timed to, to tune them to optimal performance is to start at some safe values and then swing the inlet cam and the exhaust cam through the range settings (obviously safe to ensure no mechanical contact) on a rolling road noting the results from every setting and every combination to see which produces the best overall performance to suit your requirements.  Unfortunately you will need to experiment with not only cam profiles and combinations but you could then go further with the exhaust design optimising for each setting.  This, as you can imagine, is a very time consuming and expensive task, not only are you wearing the engine out but with the cost of the dyno, fuel and the person mapping the engine, this can very easily cost many thousands of pounds. 

This is why we sell many produces not only to the retail customer but to the trade customers as well as we have developed and tested our components and evolved packages over time. 

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Cylinder head work or Cam change
Question: I have a Formula 27 Clubman with a C20XE, 45DHLA's & Lucas electronic dizzy, dyno'd at 131bhp at the wheels. Another F27 owner with an XE engine is getting 180bhp at the wheels using 45DCOE's and the same ignition. His only other mod is extensive head work. I would like more power for road & limited track use. Should I have head work done or would a cam change be better? I have £500 to spend.

Answer: We do two specifications of cylinder head. The first one uses standard valve size, wasted stem valves, bronze guides and is fully ported with combustion chambers matched (price approx. £1,000). The second head we do, normally only fitted to engines of 280bhp and above, is approx £2,500. We believe from the test results we have seen, the first head will produce approx. a 10 - 20bhp increase. This is dependant on the rest of the specification of the engine. We only recommend this kind of modification on carburettor engines over 220bhp and fuel injected ones over 235bhp. The second cylinder head would produce approx. 20 - 30 bhp more and again only worth using over 280bhp.

I would think there must be some other reason why your friend’s car produces so much bhp. Possible variables are ram pipe length, exhaust manifold design, even rolling roads vary dramatically from day to day and rolling road to rolling road. We have seen in excess of a 50bhp loss from the worst to the best exhaust manifold and system. So before you start spending money, I would suggest that you get your friends car to a rolling road at the same time as yours and do a back to back test. If you have a picture of the exhaust manifold and intake system fitted to your car, I may be able to give you a better idea of where your friend’s engine has been achieving more horsepower.

I don't recommend camshafts unless you have at least pocketed pistons. You would again, be simply throwing money away. If you look at the section on our web site called 'dos and don'ts' this should give you all the reasons why.

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Performance gains from new cams
Question: I would like to change the camshafts in my engine and I was wondering if it was possible to do this without making any other changes to the engine and what performance gains I would see?

Answer: It really depends on the engine you have, for example the 1.4L, 1.6L & 2.0L Vauxhall engines have only minimal valve to piston clearance in standard form and if you replace the camshafts, they either have to be so mild that a minimum safe clearance is maintained or that they are retarded so as to avoid valve to piston contact.  In both cases, any gains are minimal if at all.  When using a larger duration camshaft that is timed in a retarded state normally there will be a reduction in bottom end torque and only a slight gain in peak bhp and the overall result normally makes the car slower.  So with these particular engines, it is not worth the money.

Some engines such as the 2.0L Duratec and the Hayabusa engine, have slightly more valve to piston clearance in standard form and therefore allow the use of a mild camshaft and will see reasonable gains, but to see any substantial gains in performance, additional components that give increased compression, clearance and strength will be required.

Your intake system and management system are equally important in any improvement.  In any engine using a single throttle body, these are particularly restrictive and have been designed by the manufacturer for a specific purpose.  Engines such as the Hayabusa, which have 4 individual throttle bodies allow for a reasonable improvement in performance, but the management system fitted to most engines limits what can be done with your engine.  If you read the kits and look at the components on our website, we will normally recommend suitable combinations and if your engine is unsuitable for a basic camshaft change, there will not be one listed.

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MBE Management System installation instead of upgrading cam profiles
Question: I have bought a 2.0 16v engine with the following work done, Coscast 2.0 16v skimmed, polished & ported head, new lifters, Schrick 268 cams, 2.1 bottom end using 88mm forged Omega pistons, compression ratio of 11.8:1, knife-edged lightened & balanced crank, new shells, ARP bolts & new oil and water pumps. I’m looking to up the cam profiles. What would you suggest?
Would your basic MBE unit be sufficient? Can it be supplied with a 'map' to get me started?

Answer: I would think the cam profiles you are currently running are about the most aggressive you can safely use on the standard intake and management system. If you were to fit the MBE management system, this would give you the ability to tune the engine still further without the problems that you would get from the air flow meter on the standard system. But if you were to pick a too aggressive cam profile, lets say over 290 degrees and still retain the original intake manifold with a single butterfly, the engine would become difficult and unpleasant to drive. The effect would be similar to what was achieved on group A engines, in the early to mid 90s. You would have to set your idling speed higher and higher and the engine would pull much later up the rev range. If you intend on achieving over 200bhp, I would suggest you add throttle bodies to the MBE management system in the very near future. As the four individual butterflies would overcome the problems mentioned.

By adding the management system now, at the very minimum you would be able to optimize what you have currently got. This would make the engine far more driveable and should give you good improvement in torque and bhp. I would then suggest you went for throttle bodies, followed by a larger camshaft at that point.

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Cam timing changes when fitting throttle bodies
Question: Do you advance the inlet cam when stock engine is equipped with throttle body? I ask, because the bigger inlet manifold section requires advanced timing on inlet to achieve max power due to changed (duct section/raised valve flow/area) ratio.

Answer: Normally when we are fitting throttle bodies to a standard engine, for example the latest Ford Duratec, we leave the cam timing in its standard positions. There are several reasons for this. The first being, that when we supply a kit, we try and design the system to be as simple to fit as the end user. If we were to specify retiming the inlet cam, especially on the standard production engine where tolerances are very tight, there is a possibility that the inlet valves could come in contact with the pistons. Although advancing the inlet cam is almost certainly going to improve the performance of the engine, in our opinion the main reason why the inlet cam is fitted in a retarded position is for emission purposes on a production engine. If the cam were to be advanced on a standard intake system, it would be much harder to pass current emission standards and due to the restrictive nature of most standard intake systems, which are designed to produce as much torque as possible, advancing the inlet cam without improving the intake system is most likely to upset idle and in many cases reduces bottom end performance.
If your engine is of an earlier design (pre tighter emission control), such as a 2.0L XE engine, advancing the standard cam is likely to have little if any effect, since when the engine was designed the emission controls weren't as tight and therefore the cam was reasonably advanced to begin with.

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Autograss cam change to increase power
Question: I want to change the cams because I have not got enough power - 202bhp at the flywheel. Can you tell me the best cams to use? I have an autograss 20 Nova 2.1L 16v with slipper pistons, steel rods, solid lifters, piper cams, Omex management and a pair of 45 Webers.

Answer: The fact that you are using the car for grass track is always a tricky situation. If you produce too much power, quite often when the engine is off cam it will bog down and when it comes on cam, it will come on with a bit of a bang and break traction too easy. The camshafts I would probably suggest you run, are our SBD 295 profiles on both inlet and exhaust. These should give you a nice increase in peak power without sacrificing too much lower to mid range, making the car still driveable. Anything bigger than that, is likely to cause the problems I have mentioned.

Links: Camshafts

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Please check our customer cars section which may help answer your questions
 
2.0L Vauxhall Components | 1.4L & 1.6L Vauxhall Components | Duratec Components | Hayabusa Components

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