General Cylinder Head Flow Numbers discussion

[SSDiv6]

Originally Posted by Glenn Briglio

So how much valve loft are we talking about?

On circle track restricted engines, with a combination of a specific valve guide height and lobe design, I have seen a valve launched as high as 0.160" during Spintron testing. Because of valve to piston clearance, it is a bit of trial and error.

[Stan Weiss]

Originally Posted by SSDiv6

On circle track restricted engines, with a combination of a specific valve guide height and lobe design, I have seen a valve launched as high as 0.160" during Spintron testing. Because of valve to piston clearance, it is a bit of trial and error.

Do you have an idea how much more area under the curve there maybe verses the dwell type setup we ran years ago?

Stan

[SSDiv6]

Originally Posted by Stan Weiss

Do you have an idea how much more area under the curve there maybe verses the dwell type setup we ran years ago?

Stan

Stan,

I will have to look at my notes and I will share the info.

[Glenn Briglio]

Originally Posted by SSDiv6

On circle track restricted engines, with a combination of a specific valve guide height and lobe design, I have seen a valve launched as high as 0.160" during Spintron testing. Because of valve to piston clearance, it is a bit of trial and error.

Got to be pretty destructive application and not for roller lifters.

[SSDiv6]

Originally Posted by Glenn Briglio

Got to be pretty destructive application and not for roller lifters.

Just on restricted travel and solid lifters. As long you have good quality lifters and checked the spring pressure often you are good. Prior to the allowance of aftermarket roller rockers, you needed to have a box of spare OEM rocker arms because the tendency of the pushrod to go thru the rocker arm cup.

[Stan Weiss]

Originally Posted by SSDiv6

Just on restricted travel and solid lifters. As long you have good quality lifters and checked the spring pressure often you are good. Prior to the allowance of aftermarket roller rockers, you needed to have a box of spare OEM rocker arms because the tendency of the pushrod to go thru the rocker arm cup.

Been there done that.


Stan

[Adger Smith]

-Head A stock completly untouched
-Head B has flow characteristics that make me feel like it will be okay (.5 under)
-Head C has flow characteristics the make it a record setter

IMHO
And Head C has correct port volume, but probably has a larger CSA at several key places in the port.

[HawkBrosMav]

Let me add a little more specific question to this:

.444 valve lift cam.

Lift -------- Head A -------------- Head B

.050 -------- 50.8 -------------- 35.1
.100 -------- 81.0 -------------- 57.6
.150 -------- 108 --------------- 88.2
.200 -------- 129.9 ------------ 117.12
.250 -------- 142.3 ------------ 136.6
.300 -------- 157.0 ------------ 158.0
.350 -------- 161.8 ------------ 172.6
.400 -------- 166.8 ------------ 175.6
.450 --------- 166.4 ----------- 175.6
.500---------- 165.8 ----------- 174.5

Which head would you rather have? Head B is a bit better up top but Head A is substantially better down low. I would still say looking at it from an area under curve stand point that Head B would be slightly larger but very small difference.

[Billy Nees]

Low-lift flow is very important in a "restricted" engine.

[SSDiv6]

Originally Posted by HawkBrosMav

Let me add a little more specific question to this:

.444 valve lift cam.

Lift -------- Head A -------------- Head B

.050 -------- 50.8 -------------- 35.1
.100 -------- 81.0 -------------- 57.6
.150 -------- 108 --------------- 88.2
.200 -------- 129.9 ------------ 117.12
.250 -------- 142.3 ------------ 136.6
.300 -------- 157.0 ------------ 158.0
.350 -------- 161.8 ------------ 172.6
.400 -------- 166.8 ------------ 175.6
.450 --------- 166.4 ----------- 175.6
.500---------- 165.8 ----------- 174.5

Which head would you rather have? Head B is a bit better up top but Head A is substantially better down low. I would still say looking at it from an area under curve stand point that Head B would be slightly larger but very small difference.

You need to take into consideration the intake manifold and throttle body flow also. No matter how much air flow you have on the cylinder heads, the intake manifold and throttle body/carburetor, can become a restriction.