Head flow #'s
08-21-2015, 06:51 AM
#1
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Thread Starter
Head flow #'s I have been looking at a lot of different Cathedral port heads. I noticed most are pretty close in the intake flow #'s but Tony Mamo and Ai seem to have way higher exhaust flow #'s. I was just curious why that is?
08-21-2015, 07:08 AM
#2
LS heads don't have that great of exhaust flow and these heads could use extra help in that department. Thats why a lot of LS cams have bigger duration numbers for the exhaust side. In the "old days" I remember that head porters tried to get the exhaust to flow 85% as much as the intake. Now, too many people just look at intake flow when buying heads, just looking for that "big number".
08-21-2015, 09:31 AM
#4
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LS heads don't have that great of exhaust flow and these heads could use extra help in that department. Thats why a lot of LS cams have bigger duration numbers for the exhaust side. In the "old days" I remember that head porters tried to get the exhaust to flow 85% as much as the intake. Now, too many people just look at intake flow when buying heads, just looking for that "big number".
OP, what you've also pointed out is one of the benefits to aftermarket castings. They can be designed to accommodate different things - line more direct port designs, larger exhaust ports, different angles. There are limits to the stock castings.
And there's a reason Tony gets such crazy numbers on his heads
08-21-2015, 09:53 AM
#5
Most ported cathedral heads will flow in the 220's-230's at .600" depending on what head you are looking at and what version.
When you add a 1-3/4" pipe the port flows another 20-40cfm again version dependent.
You need to pay attention to many factors when looking at flow numbers
What bench were they flowed on
last time bench was calibrated
bore size head was flowed in
was a pipe used in testing(before and after;what size)
flowed @28?
it's tough to do apples to apples without having the heads you are looking at being tested at the same independent qualified facility.
Flow numbers do not always tell the tale it's another piece if data to base the rest of your parts selection on.
The bottom line is how repeatable a cylinder heads shops work is on vehicle after vehicle.
When you add a 1-3/4" pipe the port flows another 20-40cfm again version dependent.
You need to pay attention to many factors when looking at flow numbers
What bench were they flowed on
last time bench was calibrated
bore size head was flowed in
was a pipe used in testing(before and after;what size)
flowed @28?
it's tough to do apples to apples without having the heads you are looking at being tested at the same independent qualified facility.
Flow numbers do not always tell the tale it's another piece if data to base the rest of your parts selection on.
The bottom line is how repeatable a cylinder heads shops work is on vehicle after vehicle.
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08-23-2015, 02:16 PM
#8
TECH Addict
Thread Starter
Most ported cathedral heads will flow in the 220's-230's at .600" depending on what head you are looking at and what version.
When you add a 1-3/4" pipe the port flows another 20-40cfm again version dependent.
You need to pay attention to many factors when looking at flow numbers
What bench were they flowed on
last time bench was calibrated
bore size head was flowed in
was a pipe used in testing(before and after;what size)
flowed @28?
it's tough to do apples to apples without having the heads you are looking at being tested at the same independent qualified facility.
Flow numbers do not always tell the tale it's another piece if data to base the rest of your parts selection on.
The bottom line is how repeatable a cylinder heads shops work is on vehicle after vehicle.
When you add a 1-3/4" pipe the port flows another 20-40cfm again version dependent.
You need to pay attention to many factors when looking at flow numbers
What bench were they flowed on
last time bench was calibrated
bore size head was flowed in
was a pipe used in testing(before and after;what size)
flowed @28?
it's tough to do apples to apples without having the heads you are looking at being tested at the same independent qualified facility.
Flow numbers do not always tell the tale it's another piece if data to base the rest of your parts selection on.
The bottom line is how repeatable a cylinder heads shops work is on vehicle after vehicle.