[jamaca85]

are these right? besides the outside hole for the exhaust. these big valve 7K3 heads seem to outflow almost all other pontiac heads by alot. are these numbers right?

[25stevem]

Yes, those number are right for the 7K3 heads and that chart makes them look a notch above the round port 7F6 HO heads because those numbers are way too low, and the numbers for the 7M5 heads are a tad off from / low from what they should be.

Here’s my stock numbers for a 7K3 and a 7F6 casting tested at 28”done on my flow bench.

7K3 intake, stock casting 62

.050”. 39.5
.100”. 75.8. 77.2
.200”. 135.3. 144

.300”. 177.4. 176.6
.400”. 198.8. 198.2
.450”. 203.7. 201.7
.500”. 206. 202.8
.550”. 208.4. 204

.600”. 209.8. 205.5

7K3 exh , a end port

.100”. 53.5
.200”. 95
.300”. 128
.400”. 148.4
.450”. 152.9
.500”. 161
.550”. 163.7
.600”. 166.4
.650”. 168.2

Retest @.650” with a 1 3/4” ID tube.= 176.5, or 5% more.


Stock 7F6 intake

.100”. 76.9
.200”. 152.2
.300”. 201
.400”. 218.4
.450”. 227
.500”. 231

[Half-Inch Stud]

Danged pushrod bulge. I wonder if the inhale flow improves for a 2" clay inlet angled to shoot smoothly over the bulge, like 4 of the Intake runners.

[Stan Weiss]

Originally Posted by jamaca85

are these right? besides the outside hole for the exhaust. these big valve 7K3 heads seem to outflow almost all other pontiac heads by alot. are these numbers right?

These number (like mine) came from a number of different sources. What they did not do is correct them all to the same depression.

Stan

[25stevem]

Here’s what a stock 670 casting flows with just a good valve job freshen up that takes the valve seat OD out to 2.10.

This rework mainly effects the flow numbers above .200”


.050”. 40.2
.100”. 82
.150”. 119.9
.200”. 150, this is a killer number that only the 670 casting can produce.

All the next fat flow numbers are due to the details of the valve job tweak.
.250” 178.3
.300”. 198
.350”. 210.4
.400”. 212.7
.450”. 213.9

I have to try and dig out my truly stock 670 intake flow numbers for you.

[Half-Inch Stud]

Flow stalling at 210-214 tells me the port went turbulent, noisey as all heck. Need the bulge reduced. Maybe the short-turn cheeked.

He k, all the inhlae flows appear to have gone turbulent to me. I'm spoiled to see flow breakaway to the 230+ range from 0.35" - 0.55"

[25stevem]

Number 1 ) Air flow thru a port is always turbulent once the valve D x .18 lift point is reached!

At a certain flow volume when the piston has hit peak velocity traveling down the bore there is always a big spiral of air going down around the bore and a water fall of air coming off the short turn trying to mesh / merge its way into that spiral.

Number 2) when it gets turbulent enough that the air volume pitching over the short turn can no long mesh into the spiral air mass then port gets loud and the peak air flow number that was had will regress.

When this condition takes place and if the push rod pinch was the port choke then opening that up more would allow more air into the port which has already lost control of the air volume trying to make its way out the valve and into the chamber.

The result of this would be that flow regression would now take place at even a lower lift point then before.