SEVEN PILLARS OF CYLINDER HEAD MODIFICATION
1. Porting or increasing the diameter of the intake and exhaust ports - generally not required in most Volvo engines;
2. Polishing or smoothing intake/exhaust passages and combustion chambers;
3. Matching or carefully adjusting the fit of the intake and exhaust manifolds to the cylinder head so that the respective orifices line-up with extreme accuracy;
4. Precision valve seat grinding where the valve seats are precisely ground to a nearly continuous curve (5-angle job) or continuous curve (radiuses) to allow air to more smoothly enter the combustion chamber;
5. Big Valve Kits where larger intake and exhaust valves are fitted to improve airflow. This modification does, however, reduce intake and exhaust velocities at low rpm, making the engine less responsive in stop-and-go city driving;
6. Valve stem and guide modification where special stainless steel valves featuring narrower stems are fitted to a cylinder head. Since the narrower stems block less airflow, engine output is increased; and
7. Fitting a higher lift, longer duration camshaft -- an easy and extremely desirable modification as most Volvo engines are "under-cammed".
STAGES ONE & TWO
The first (and most cost-effective) modification to be made is fitting a more aggressive camshaft. Although finding the correct cam for your car can be difficult, the Volvo Performance Handbook lists the designations for most high-performance camshafts stocked by AB Volvo. While not all Volvo dealers stock these items, registered owners of The Volvo performance Handbook can be introduced to the factory sources that are eager to meet the needs of the power-hungry!
There are a total of 8, 11, 2 and 2 available grinds for B18/20, B21/23/200/230, B5254, and B6304 engines respectively.
After fitting a performance camshaft, some recalibration of the fuel delivery system may be required. Engines fitted with Bosch LH fuel injection can, however, easily recalibrate themselves using the feedback loop provided by the Mass Airflow (MAF) and O2 sensors.
STAGE THREE
The next step is to polish the intake manifold. This can be done manually or outsourced through companies listed in The Volvo Performance Handbook. This is followed by port matching and fitting a big valve kit. Apart from selecting the correct parts and sources, this stage demands the services of a specialist equipped to conduct professional modifications. If a tuner does not have a flow bench, they are not capable of taking-on Stage Three work. Period.
STAGE FOUR
Finally, there remains the task of polishing and re-working the shape of the combustion chamber and moving to a slightly higher compression piston to preserve the correct compression ratio. This is best conducted by a professional tuner well-versed in preparing professional racing engines. There probably only one or two shops in each state or province capable of such work -- and they don't advertise in the Yellow Pages! By the time you've made it past Stages One through Three, however, you'll probably know the best local source for this kind of work.
CONCLUSION
Stage One & Two modifications can increase the power of a well-functioning engine by up to 20%. Stage Three will add another 20-25%, and Stage Four an additional 15%. Translates into the following gains:
B18/B20 ~ 180 Bhp
B21 ~ 160 Bhp
B23/230 ~ 185 Bhp
Other engines may achieve more or less, but the overall output will be dependent on how effectively the engine management systems are calibrated. OBD II cars are considerably more difficult to tune and may not react well to camshaft changes.
When it comes to cylinder head modification, one rule holds true:
Read thrice, plan twice, modify once and win forever!
The only thing i 've changed to the engine is a K&N replacement air filter.I would very much appreciate it if you could shed some light on this subject,as here in greece VOLVO isn't that much known and i wouldn't want to take the car to someone with no experience.Thank you.
