Flowbench testing on K series heads
Following the modification work on the K16 and VVC heads, they were thoroughly tested on Dave Walkers Superflow flowbench together with a standard K16 head and a standard VVC/VHPD head to quantify the improvments made.
The results of the flow testing are given below
Head no
Below are the results
Inlet flow
Flow figures are CFM at 10 inches water
Head number |
Valve Lift in mm | 1 | 2 | 3 | 4 | 5 | 6 |
1 | 14.74 | 13.80 | 17.52 | 17.88 | 14.00 | 18.50 |
2 | 28.50 | 27.08 | 34.70 | 35.01 | 29.00 | 37.50 |
3 | 42.92 | 43.44 | 52.92 | 53.51 | 45.50 | 57.50 |
4 | 61.38 | 64.18 | 69.68 | 71.50 | 62.00 | 77.00 |
5 | 70.16 | 79.04 | 79.08 | 82.67 | 71.00 | 91.00 |
6 | 72.94 | 90.44 | 89.04 | 92.60 | 91.00 | 103.50 |
7 | 74.96 | 96.80 | 96.58 | 102.02 | 106.00 | 114.00 |
8 | 77.28 | 97.22 | 97.86 | 107.00 | 113.00 | 123.00 |
9 | 78.42 | 97.80 | 98.74 | 111.00 | 116.00 | 131.00 |
10 | 78.50 | 98.38 | 99.14 | 112.12 | 116.00 | 134.00 |
11 | 78.50 | 98.96 | 99.16 | 112.40 | 116.00 | 136.00 |
As can be seen from the flow figures, very good
results can be obtained from the standard K16 head if it is correctly modifed, this saves
the cost of a VVC/VHPD head. Even the head with the 29.5mm inlet valve (which fits the
standard insert) flows as well as a VVC head even though the valves are 2mm smaller, and
at low lift it flows much better.
A modifed VVC head with big inlet valve flows exceptionally well, the Pro Race head doesn't benefit much from the fitting of such large valves and in fact the low lift flow is no better than a standard K16 head. Some of this poor low lift flow was because of relatively poor attention to detail around the valve seats, some remedial work here picked up the low lift flow by around 20% and the high lift flow by around 5-6%.
Exhaust flow
Flow figures are CFM at 10 inches water
Head number |
Valve lift in mm | 1 | 2 | 3 |
1 | 16.40 | 13.80 | 18.04 |
2 | 25.76 | 29.30 | 32.08 |
3 | 36.32 | 45.76 | 45.58 |
4 | 45.68 | 56.44 | 61.94 |
5 | 52.70 | 67.02 | 72.46 |
6 | 58.56 | 77.60 | 74.78 |
7 | 60.90 | 78.78 | 76.84 |
8 | 64.42 | 79.96 | 76.84 |
9 | 65.60 | 79.96 | 76.84 |
10 | 66.18 | 80.54 | 76.84 |
11 | 66.18 | 80.54 | 76.84 |
The modified K16 head with 26mm valves flows almost as well as the VVC at the higher lifts and flows a lot more at the lower lifts, ultimately the VVC head flows more air because the throat is 2mm larger, but the difference is only 4CFM or so. The modifed exhaust port on Mike Bees VVC head flowed around 108CFM at 10mm of lift, there was insufficient time to take readings for all points in the lift spectrum.
Head number 3 is the head I prepared for Johnty Lyons for his Caterham Superlite using Piper 740 cams and solid lifters, head number 4 is the one prepared for Bernard Scouse for his Elise using Piper 740 cams, Head no 6 is the VVC head prepared for Mike Bees on his stonking 1700 Caterham Superlite.