Intro to a port job
EXHAUST.
No before numbers, they all flow 132-145cfm stock anyway.
I'm in the middle of testing and touching up the exhaust. Some were short 10 cfm from what i was looking for so i did a little blending of the lower angle to short turn, left the angle alone around the bowl. They dont need to be pretty to work good, not polished, smoothed, but no sand rolls or shine.
It flowed w/no pipe and prior to touch up..as follows..
@28" 4" BORE 1.60 valve
Lift-cfm
.2-110
.3-144
.4-160
.5-166
.6-171
New numbers after touch up.
@28" 4" bore no/pipe
no pipe-
Lift....cfm
.200-110
.300-144
.400-160
.500-179
.600-186
And w/1 3/4 x 10" pipe.
Lift....cfm
.200-109
.300-150
.400-170
.500-190
.600-197
At really low lifts the pipe doesn't do much, as you can see from the numbers, but after the valve opens... the pipe carries the velocity 'just like your header tube does' and the numbers jump. Without it...the front of the air stream expands out of the port window ,slows and then the rest of the stream crashes into it. Fwiw. This is an end port, like .1,2,7,8 exh port. Pics sucks, sorry.
EXHAUST.
No before numbers, they all flow 132-145cfm stock anyway.
I'm in the middle of testing and touching up the exhaust. Some were short 10 cfm from what i was looking for so i did a little blending of the lower angle to short turn, left the angle alone around the bowl. They dont need to be pretty to work good, not polished, smoothed, but no sand rolls or shine.
It flowed w/no pipe and prior to touch up..as follows..
@28" 4" BORE 1.60 valve
Lift-cfm
.2-110
.3-144
.4-160
.5-166
.6-171
New numbers after touch up.
@28" 4" bore no/pipe
no pipe-
Lift....cfm
.200-110
.300-144
.400-160
.500-179
.600-186
And w/1 3/4 x 10" pipe.
Lift....cfm
.200-109
.300-150
.400-170
.500-190
.600-197
At really low lifts the pipe doesn't do much, as you can see from the numbers, but after the valve opens... the pipe carries the velocity 'just like your header tube does' and the numbers jump. Without it...the front of the air stream expands out of the port window ,slows and then the rest of the stream crashes into it. Fwiw. This is an end port, like .1,2,7,8 exh port. Pics sucks, sorry.