Meanwhile, back to the original subject...
My 848 head's intake ports have been opened up and ported just as it was detailed in the hop up article written by Frank McGurk and published in the May, 1955 issue of "Hot Rod" magazine.
This head was ported in the early 60's and has not been used since the previous owner switched to the later engines when thay became available in 1963.
I purchased the head for my 261, and had it 'freshened' up, (cleaned, new large powerglide valves, springs, etc.) by a very reputable speed shop in my area.
While he was at it, I had three cylinders flowed on his 'SuperFlow' flow bench when he was done. I thought you might be interested in the results.
As freshened, the intakes flowed 200 cfm at .500 valve lift at 28" depression. At that point, the flow 'stalled', indicating port saturation. In other words, increasing the valve lift had no further affect.
Surprisingly, the exhaust was far more restrictive than the intake. As originally tested, the three exhaust ports chosen 'stalled' at 100 cfm, again at .500 valve lift. The graph generated showed a very large dip in the flow at .300 valve lift. All ports tested were very consistant with these results!
Looking closely at the exhaust valve and the combustion chamber, it was noticed that the combustion chamber wall bulges in towards the edge of the valve, before receding away as the valve opened further! The chamber wall shrouds the exhaust valve at exactly .300 lift! This was clearly indicated by the exhaust flow graph.
The speedshop machinist piloted a small boring bar in the exhaust valve guide, and opened up the chamber wall to unshroud the valve, and the ports were retested. Now, the exhaust flow increased to 120 cfm, again at .500 lift, and the large dip in the flow was gone!
The results were 200 cfm intake, 120 cfm exhaust, all at 28" depression, .500 lift, and a smooth flow curve.
I hope that some of you may find this interesting. Toolman
