Questions page 1

The following information is the sole property of P B Blackman Sportcars Ltd. T/A formerly Abbey SportCars Ltd. The information is not to be copied for use elsewhere without prior permission or reference. The pages are written for guidance only, the information contained therein is the view of the writer and should not be taken as the definitive recommendation.

Will fitting a fast road camshaft make my car undrivable around town?

The answer to this is usually “No”. Our recommended cam profiles properly installed will give a marked improvement in mid range and full throttle performance.
However, you can’t have something for nothing!! The trade off is often less than 5% power deficit below 2000RPM which most drivers will fail to notice. The additional power however beyond that particular engine speed is unmistakable. In terms of initial tuning the camshaft and timing gears arguably give the greatest power per pound spent.

Can I fit a race spec cam to my V8 engine?

Race cams are best left to the purpose they were designed for and that is racing. If you look at the camshaft section of our product list you will see the approximate power band range in RPM. Fitting say a cam with a profile that comes in at 4000rpm will result in the car being virtually undrivable in town. The engine will rev, assuming the ignition/fueling are adequate but the engine components are likely to fail since they are beyond their safe working limits.
Bear in mind that horsepower and torque costs a relatively small amount but making the whole plot stay together is the costly part. It is relatively easy to build an engine with a cam that comes in @ 4000rpm and with a static compression of say…..13:1. The engine may produce lots of power (all other things being equal) but it will only be a matter of time before the engine requires another rebuild. And that is if it is rebuildable!!

How can I tell if my Camshaft & Lifters are worn?

​​More often than not and on engines with high mileage, the cam and lifters have worn severely which is evident by a carbon stained/brown discoloration of the cam lobes as well as visible wear/chaffing on the lobes. The lifters (cam followers) contact point with the camshaft are often pitted, concave (dished) and consequently worn beyond useful service.
A new lifter has a slightly convex surface circa. 0.002” to enable the follower to rotate. This is of fundamental importance for engine longevity, performance, economy and to enable correct emission levels to be achieved.
When installing a new camshaft it is imperative to replace the follower/tappets also. Failure to do so will result in premature wear to the cam and replacing the camshaft yet again. Please bear in mind that replacing a worn cam and lifter set with new items will give significant improvement to engine performance.
This is not a marketing ploy - Never replace a new cam without new lifters.
Significantly greater power is achieved by up grading the camshaft to one that has a longer duration, higher lift or both. Longer duration cams enable more fuel/air mixture into the combustion chamber and is allied further by valve openings of greater lift.
On many engines and especially those of more recent design, the respective factory development of cam profiles results in an engine that is often difficult to better for all round general use. However, the Rover V8 engine with its 1960’s design can be improved upon by use of the technological advances in camshaft development.

For simplicity of fitting we recommend cam profiles which fit straight in with minimal fuss, with little or no machining for road use. These purpose designed and carefully engineered items can increase power with or without drastic modification.
Typically an after market camshaft will require different advance settings. We recommend the factory setting of a nominal 6degrees advance static and up to 10 degrees optimum. Unless completely comfortable with ignition and fueling this work should be undertaken only by suitably competent individuals.

Do I need to set the hydraulic lifter preload?

When installing a new cam and lifters it is always advisable to check lifter preload. The preload should be between 0.020” & 0.060” (0.038” = 1mm). There is no proprietary piece of kit for checking this clearance other than a modified feeler gauge or a bent piece of say… 1mm (0.038”) MIG welding wire.
The clearance you will need to check is that between the circlip seat and hydraulic valve within the hydraulic lifter when installed with rocker gear and pushrod in place. Please bear in mind that to check clearances the inlet and exhaust valve will need to be shut. You will probably find that the clearance differ slightly on each cylinder bank. As long as the clearance is between the tolerances quoted above then all is fine. The only sure way to achieve 100 percent accuracy however is to use adjustable pushrods.

Do I need to fit double or triple valve springs?

Some camshaft manufacturers recommend double or triple valve springs with their camshaft profiles. These may not be any stronger than the original single spring items but are used to prevent harmonic interference. When a coil spring operates a valve, it will oscillate about some natural frequency determined by its operational speed and the qualities and dimensions of the materials from which it is made. This frequency depends upon the spring length, the spring diameter, coil thickness and the number of cycles per minute.

Paul Blackman 2019

Lotus Esprit V8 Ketteringham Hall