Thumper's Thoughts On Porting, Valve Size & Head Flow
Performance is the name of the game!
ALL engine types are welcome... MCS or 'Just-a-Cooper'!
Why buy? Modify! Thinking of needing more power? Thinking of upgrading your Head?
Porting cylinder heads has been the way to more power since there were engines!
It has shown that MOST heads, aftermarket or stock, WILL increase power potential when massaged, ported, and a performance valve job added!! If your head is an "out of the box unit", the power output can be increased with port work! How much power? Anywhere from 18 to 35 WHP on the MINI S with STOCK Tune and ECU settings like most of us have. Or 58 to 65 WHP with ECU Tune and our stock size valve Head.(TPR1)|
- SO, after making all those mods, do you feel you still could use more power?
- Don’t want to purchase a “Racing Head” when you don’t race?
- Want more power for the aggressive drives and weekend track day, and don’t want to sacrifice most of the low to mid-range power for the daily drives to work?
- Want better MPG for the freeway drives?
- Just want more power?
I get lots of inquiries about the "valve size" in the Thumper Ported Heads... I have to answer that question this way:
The Flow Number is the amount of air the ports will flow, at a certain cam or valve lift. The larger the Flow Numbers, the more RPM is needed to get the power from the heads. That upper RPM will hurt the lower torque numbers and throttle response, for the daily commute and drives in traffic when off boost!
Two things make a good head! Flow volume AND velocity! The velocity of the air is what fills the chambers, which allows the engine to build power. The faster the air speed, the quicker the power is made! And this is where the low to mid range power is critical. The flow volume will allow power through the mid to top end.
There are a number of ways to build flow. The first is to port, as you know. The second is to install larger valves (+ 1.0mm or +1.8mm), which is also good. However, if the ports and valve size are too big air will become "lazy" or slow moving, which causes slow, sluggish low speed response and loss of good MPG!
The way to increase the air flow is to run a higher engine RPM, to build up the flow speed (velocity). Try this... an MCS with big-valve head! Runs killer on the top end. But... under 4000-4500 rpm… it is a dog.Lazy air movement at the lower RPMs kill the daily drive fun as the low to mid-range power is sacrificed for the higher RPM power needed for track racing.
Most of my heads are on cars that are used with dual purpose (spirited street and occasional track.) I want crisp, fast, throttle response, snap off the line on a mildly modified engine (pulley, CAI and exhaust.) I want a head that will pull hard and strong to 6800-7200 rpm! So... I want VELOCITY and Flow Numbers! I do this by keeping the stock valve size and doing a 5-angle performance valve job with a “flow cut” on the valve! The 5 angles act as a boost to the air flow as the valve just leaves the seat, and also when the valve is just about closed! This increased low-lift flow allows the air to fill the chamber faster! The faster the chamber is filled the faster and more power the engine will make! Then when coupled with my PORT/throat/bowl work the Head will keep making power till you lift off the gas!
We do also make a Thumper Performance Upgrades ( TPR2 and TPR2r ) for those that want to Track Race with the RPM levels in the 4500-8000 rpm ranges. As now the rage seems to TURBO the r53, we now even offer a Ported BVH with the Inconel Exhaust valves. No one head fits all applications.
(Note: for all other Cylinder Head modification SEE: www.thumperoforangepark.com )
Thumper Performance Ported Heads are made to your application, NO "one size fits all!"
We do the head for the N/A Cooper as well as the Supercharged!