There was a thread back a while where OldMiniBikes member misfit build a big valve head If I remember correctly it was a 32/28 valve size and he sent it to me to flow. It was the highest flowing head I have seen and the port runner was stock! I did not remove the valves to see what he had done in the bowl and SST but I should have. I will see if I still have the data but if my memory serves me it would coil bind at around .380 as he put weak springs on it for me. Anyway it was in the mid 90's and still climbing when it hit coil bind. The next best head is a MDB head I have it came with bad guides that were cut to the roof of the port (not sticking into the port. I flowed it the way it came and max flow was arount 81CFM, after replacing guides which were full length but tapered in the port and seat work it got to 85CFM. If you send me your email I can send you some excel spreadsheets of some of the results of various heads I have done, I have some in my photos but I don't think the print is big enough to read, I put one in this post.
There was a thread back a while where OldMiniBikes member misfit build a big valve head If I remember correctly it was a 32/28 valve size and he sent it to me to flow. It was the highest flowing head I have seen and the port runner was stock! I did not remove the valves to see what he had done in the bowl and SST but I should have. I will see if I still have the data but if my memory serves me it would coil bind at around .380 as he put weak springs on it for me. Anyway it was in the mid 90's and still climbing when it hit coil bind. The next best head is a MDB head I have it came with bad guides that were cut to the roof of the port (not sticking into the port. I flowed it the way it came and max flow was arount 81CFM, after replacing guides which were full length but tapered in the port and seat work it got to 85CFM. If you send me your email I can send you some excel spreadsheets of some of the results of various heads I have done, I have some in my photos but I don't think the print is big enough to read, I put one in this post.
Thank you sir. I have found more flow since I got the proper equipment. I was using a Simmons Carb comparator before..and it helped too, but I wanted a real CFM number, as I sell heads and carbs pretty regularly. A stock Ruxing carb showed 44cfm, and Huayi showed 43.. a 390 showed in the 80's ( I don't have that info in front of me now).
Thank you, sir. I have improved my numbers after getting better equipment to work with. I was using a Simmons carb comparator, which helped as well, but I wanted actual CFM numbers,. as I sell a fair amount of carbs and heads. A stock Ruxing showed 44cfm, and my SA carbs flow around 60cfm. ( I will be working on the carbs as well now). I have made fixtures to flow the small block carbs and the gx390 carbs as well..will be making one for a tillotson soon too.
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Barry HP books has a book by Harold Bettes that I have found very helpful, called Engine Airflow. shows some simple tools you can make to check for stagnant air and show swirl. I am also making a new head holder with sliding acrylic tubes to let me adjust to bore size. My bench is almost 30 years old and a pitot tube design which has some drawbacks over a orfice plate design. At the .050 lift point the scale reading is very small and it is hard to get a accurate number, I may convert it to a orifice plate and add switches to shut off some of the vacuum motors.
I have flowed the intake side of two stock hemis, and one rtc6.
Hemi:
.100-35
.150-43
.200-45
.250-45
.300-45
.350-44.5
.400- (coil bind before making it)
Hemi #2
.100-33
.150-43
.200-48
.250-49
.300-50
.350-51
RTC6
.100-35
.150-48
.200-53
.250-55
.300-56
.350-58
.400-59
I will test the exhaust when I get time.
Hemi:
.100-35
.150-43
.200-45
.250-45
.300-45
.350-44.5
.400- (coil bind before making it)
Hemi #2
.100-33
.150-43
.200-48
.250-49
.300-50
.350-51
RTC6
.100-35
.150-48
.200-53
.250-55
.300-56
.350-58
.400-59
I will test the exhaust when I get time.
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