Cylinder Head Information
Here is the Data for a Hesco head as measured by McCabe Motorsports:
Intake valve: 2.00"
Intake Port Volume: 138 cc
Intake Valve I/H: 1.610"
Spring pressure on seat: 95lbs
Spring pressure open at .400" lift 215lbs
Coil binds at 1.050"
Spring Diameter: top 1.205" bottom 1.330"
Retainer material: stee
Chamber volume: 59.6cc
Exhaust valve size: 1.550"
Exhaust port volume 76.4cc
Exhaust Valve I/H: 1.615"
Head flow data @ 28"
Lift Intake/Exhaust
.100 74.5/55.4
.200 134/92.8
.300 183.3/116.8
.400 226.5/131.2
.500 255/142.4
The shop was impressed with the intake flow numbers and said that the exhaust needed the most improvement. He said if they could have raised the exhaust port .25" there would have been significant flow improvement. He could not flow the head any higher due to the coil bind at .500" lift. He speculated that the intake would have continued to increase in flow. He also noted that there were signs of possible coil bind with some of the valve guide seals having the wire spring messed up. He said that new spring would be needed to take advantage of a custom cam or any cam that would approach .500" of valve lift. He also said that the valve guides would need to be machined down some to accommodate a larger lift cam.
The stroker motor that this head came from went through 3 camshafts. I asked him to speculate what could have caused it with what info he had. He said possible factors could have been: improper cam break in, coil bind, lack of zinc in oil, or possible rocker arm geometry. He said that the current spring pressure would not have been a factor.
I will most likely work with them with the rest of my stroker motor. Another interesting problem he ran into when doing a Stroker motor was that there are 4.0L blocks that had different cylinder bore lengths. He said that the shorter cylinder bore block had a problem with 258 rods and cast pistons. The shorter bore caused too much piston rock at the bottom of the bore. He is also capable of ordering custom pistons much like Hesco's.
My next step is to get these flow figures to my custom cam grinder (Jay Allen at
www.camshaftinnovations.com) and see what he says. I suspect that I will need to get some port work done on the exhaust side to maximize the power of a custom cam. I will keep everyone posted on my discussions with the cam grinder and McCabe Motorsports.
