Page 1 of 1
Posted:
Thu Feb 12, 2009 8:48 pmby GNNOVA
I started using my pitot tube tonight and I had readings of 28.5'' on the short side of the turn at the valve seat. The outside and center was in the 8" to 12" area. This is on a small flat head. I believe this is telling me that I need to open up this area. I was thinking of making this area into a "D" shape with the wide part of the "D" in the short turn area. Am I correct with my assumption and could my idea improve the condition?
Ken
Posted:
Thu Feb 12, 2009 11:41 pmby 200cfm
Is there shrouding or unshrouding in the 8 to 12 area? Something is biasing the high speed flow toward the 28" area IMO. You are measuring the air existing the valve seat, right.
Bruce deals with flathead valves.
Posted:
Fri Feb 13, 2009 7:21 amby GNNOVA
This measurement was taken on the intake before the valve. I was about an inch into the port, just into the raduis and about a 1/4" before the valve. The port is presently round throught, from the inlet through the turn and to the seat. It measures close to the same diameter from beginning to just before the area below the seat where it gets larger.
Ken
Posted:
Fri Feb 13, 2009 8:35 amby bruce
Funny thing is everyone that ports flatheads without a flowbench swears that the flow is line-of-sight into the chamber! And you can't tell them any different.
Widen/flatten, while trying not to remove the turn on the short side a tad and measure again . . . repeat as necessary. Might find you have to lengthen the short turn also. Not sure how much of a radius you have on the short side?
Posted:
Fri Feb 13, 2009 12:38 pmby GNNOVA
Thanks Bruce. I was hoping you would have some idea on the issue. I did my port and opened up the area around the valve in the head, but was not seeing the improvement from the head work this year that I had seen with the same work as last year (The port this year has a better entry into the seat area). So I thought I would try using the pitot tube to look at the port. Looks like I have more port work. Also thanks for the input 200cfm, I didn't say that it was a intake port the first post which I think mislead you. I'll post later to let you know how it worked out.
Ken
Posted:
Wed Feb 18, 2009 7:54 pmby GNNOVA
Well I tried widening the short turn by not touching the center part and just working on the outside edges. This caused my flow numbers to go down by a couple cfm. I then tried to take a little off the area opposite the area of high pressure I measured with the pitot tube and that made no difference. The short turn radius has a radius of about 1/4" just below the valve seat. Bruce would you happen to have any time to take a look at it and give me any ideas. I could make it worth you'll time.
Ken
Posted:
Wed Feb 18, 2009 8:04 pmby bruce
Ken, Give me a shout and I'll see what I can "see" . . .