Flow Difference ... exhaust seat angle

Last week while porting some D0VE heads I had a chance to do a few tests along the way.
Still using the stock valve size, 1.656" and changing the seat angle.
I say "along the way" because I did these flow tests after simply removing the thermactor boss in the exhaust port and just rounding the short side radius ... along with changing the valve jobs to accomodate the different angles.
45 degree seat angle valve job used a 35 degree topping and a 12mm radius bottom from 55 degrees to 75 degrees, (a NWN003 cutter).
52 degree seat angle valve job used a 38 degree topping and a 25mm radius bottom from 62 degrees to 80 degrees, ( a NWN60100 cutter).

45 degree valve job
.100" = 62.6
.200" = 112.6
.300" = 141.4
.400" = 160.8
.500" = 167.7
.600" = 169.9
.700" = 168.7

52 degree valve job
.100" = 59.5
.200" = 108.1
.300" = 141.0
.400" = 161.2
.500" = 169.3
.600" = 174.0
.700" = 177.8

BOTH seats were 1.5mm wide and to near the outside edge of the valve; maybe .010" inboard.

This pretty much shows what simply changing the valve job will do to the airflow with a crude "quicky" clean-up on the D0VE exhaust port.

Very interesting comparison there. If Columbus wouldn't have decided to go on a boat ride, we would still be thinking the earth was flat. We never find anything out unless we try. Thanks for the info Randy.

very interesting thanks for sharing!

It really "in the details".

How much more HP would 5 CFM of exhaust flow make possible? At .600" for example. I'm not trying to be an ass, just curious.

Jess

Mustang-junky wrote:How much more HP would 5 CFM of exhaust flow make possible? At .600" for example. I'm not trying to be an ass, just curious.

Jess

It is not so much the added air flow as it is the CHANGE in the flow curve which now allows a larger cam lobe to be used on that port for more horsepower, without costing torque.
This test was done to show the TENDENCIES between the valve jobs, not about the airflow increase or decrease seen with a D0VE head at a specified valve lift.

AND this is nowhere near the amount difference of a good flowing head ... although it is not 5 cfm but, 7.9 cfm, which is 4.5% increase.

Some people are just not gonna comprehend seeing the trees when looking at the forest.

rmcomprandy wrote:

Mustang-junky wrote:How much more HP would 5 CFM of exhaust flow make possible? At .600" for example. I'm not trying to be an ass, just curious.

Jess

It is not so much the added air flow as it is the CHANGE in the flow curve which now allows a larger cam lobe to be used on that port for more horsepower, without costing torque.
This test was done to show the TENDENCIES between the valve jobs, not about the airflow increase or decrease seen with a D0VE head at a specified valve lift.

AND this is nowhere near the amount difference of a good flowing head ... although it is not 5 cfm but, 7.9 cfm, which is 4.5% increase.

Some people are just not gonna comprehend seeing the trees when looking at the forest.

Great info Randy ------------. Thank you

Randy, I know you said stock valve size, were they stock style valves as well? Or were they a tulip style?

Diggindeeper wrote:Randy, I know you said stock valve size, were they stock style valves as well? Or were they a tulip style?

Stock OEM production valves ...

Thank you