[Stan Weiss]

Originally Posted by johnta1

Here's a link to the test (Part I & II)


Ultimate Pontiac Head Flow


What Paul said does sound familiar.

John,
Thanks for the link. Looking at the article it says "All testing was done at 12 inches Hg" I am sure we can all agree that is not the case. 12 inches of water does also not seem to work. Now 1.2 inches of Hg which is 16.3 inches of water might be close. Remember Holley 4 bbl are rated at 1.5 inches of Hg.

Stan

[steve25]

The 4 bbl rating of 1.5”hg is equal to 20.5 H2O.
This seems to me to work best with those numbers.

[steve25]

Hey folks please note that in the second part of that flow test shootout that a 5C head does not have a 1.77” exh valve .

Those tall flow numbers must be from that 1.77” valve size being used along with some level of porting.

[steve25]

John here’s some info for you for the 455.

To the best of my ability without making molds yet here’s the intake and exh centerline length’s I come up with.

Int. 4.565”
Exh. 5.040”

I also made a centerline arc of the exh short turn from the chamber floor to the crown of the short turn.

[johnta1]

Thanks, Steve.

[steve25]

Here are two intake flow test and a revised exh flow test.

I will post the exh test first.

The reason for this second exh test on the same port is because I forgot that the SD head uses Tulip valves and although the owner gave me a used exh valve, it was not the original one.

Some general info.
The casting date on this head I have been doing the testing on is F163, the other head is G073.

The barometer today was 29.65
Humidity was 64%
Temp in the shop was a cool 55

Column one here was the first exh flow test I did with the non stock valve, the second column is todays test with the stock Tulip valve.

The (T) means there was turbulence at that lift point and the mt means there was minor turbulence seen.

Exh tested @ 28”

.050”///// 25.2 //// 26

.100”///// 56 //// 52.3

.150”///// 84.7 //// 85.3 mt

.200”///// 112T T //// 110 T

.250”///// 134.2T //// 134.7 T

.300”///// 144T+ //// 151.7 mt

.350”///// 154.5T //// 159.7 T


.400”///// 160.4T //// 160 T

.450”///// 165.4 //// 163.9

.500”///// 167.4 //// 168.9

.550”///// 169.9 //// 171.8

.600”///// 173.8 //// 176.8

.650”///// 179 //// 178.8

.700”///// 181 //// 180.8

Here are the two stock intake port test done with the stock Tulip intake valve.

Flow test where done with
1) the rocker stud hole blocked off.
2) the Correct spark plug screwed in
3) my flow bench adapter screws into the valve cover bolt hole so that eliminates the potential intake leak source there.

Column 1 is a test of a left hand port/ port with the push rod on the left.

Column 2 is a right hand intake port.

.050”///// 31.7 ///// 35.4

.100”//// 66.6 ///// 70.5

.150”///// 102.7///// 106.6

.200”///// 137.5 ///// 142.8

.250” //// 169///// 172.9

.300”///// 193.2 ///// 196.6

.350”///// 208.1///// 211.6

.400”///// 217.3///// 219.6

.450”///// 224.2///// 226.5

.500”///// 234///// 235.5

.550”///// 237///// 240

.600”///// 241.6///// 244.7

.650”///// 243///// 246.2

.700”///// 247.7///// 246.6

I did not have the time to compare the dimensions of both ports to each other, but I will.

[Jack Gifford]

Up to .300" the intake flow is impressive. And not shabby at .500".

[Skip Fix]

Steve we need to compare flow with a tulip as well as flat valve on the intake side. I know my RAIVs picked up over 5% on the intake with a flat valve and I reproduced that on a friend's virgin RAIV head with his stock valves and a "plain D port" flat valve.

If I remember correctly didn't 455 HO heads in 71 and 72 use a flat valve?

[steve25]

Skip, the new valves the owner of these heads has are flat non tulip types, but they do have under cut stems.

The next two flow test I do will be these same two intake ports tested with these new valves.

Yes, I have had two sets of the 455 HO 197 castings and there stock valves where standard fare D port types.

[PAUL K]

Steve do those factory intake valves have a back cut angle?

[steve25]

No they do not Paul.

What they do have since I just finished checking is there Tulip face provides 3 CCs of the original chamber volume.

I also need to Cc a intake port with the stock valve and the aftermarket replacement to see how much bigger the volume gets.

I am willing to bet there’s 5 to 6 more CCs of port volume with a non Tulip valve in place.

[Skip Fix]

A few years back I flowed my friend's stock 71 and 72 HO and his RAIV. Just sliding that flat HO valve in the RAIV picked up the intake.

Years ago when I bought my bare RAIV heads there were no factory vales still around so got a set of Childs and Alberts' (made by SI) SS. They had even more thickness in the stem that the factory RAIVs! Why we assembled mine with Sealed Power D port valves.

[steve25]

It’s interesting to note that with these SD455 castings the engineers brought back the air injection boss that had first shown up in 67 and then was done away with in mid to late 1968 due to the cleaner burning open chamber.

I wonder if this was intensional or not by Pontiac engineering?

These SD heads where developed at the same time as the NASCAR 366 motor in 70 and 71.
So maybe they where playing it safe by having the boss there in case air injection was needed to meet emissions standards seeing how the original non production SD motor was to be Cam’ed.

The SD455 motor number of LS2 and the LS5 number used for the 71 and 72 455HO motors show that these 73 and 74 SD motors where in development long before the 71 and 72 Ho motors.

This air injection boss does not show back up until the mid and late 70s with 5C and 6C heads that where cast for emissions usage on CA motors only.

[sdbob]

Interesting info thanks.

[steve25]

Your welcome!

Later today I will get around to CCing a Intake port with a stock valve and then with the aftermarket valve these heads will be run with.

[steve25]

Paul here’s a correction to what I replyed to you.

The stock SD exh valve indeed has a back cut.
I mistakenly assumed the since the intake did not, so would the exh.

So to all following my post here the exh flow test I did back in #16 was with a back cut valve.

Next time I will turn my light on over where I assemble heads for flow testing.

[steve25]

Ok here are the intake port volumes with the stock Tulip valve and the more nail head necked down stem valve.

SD. 186.7

Aftermarket. 188.3

Now it’s on to flow testing the intake manifold in the next few days.

I will also be making some port molds.

[steve25]

I had time to make two port molds today.

Excuse the end of the intake port as I ran low on the mold mixture.
The amount of pictures I have to post will need two separate post .

[steve25]

Here’s the exh port mold.

[steve25]

Ok, back with some rework reports.
Sorry for the wait!

I flow tested the intake intake manifold and lost the info on my darn phone, but I do recall that the worst flowing runner was going 262.

My intent then is to rework the intake ports to flow no more then 260 from the 245 to 247 peak flow that they do now.

I have somewhat bowl ported the exh with 85% of that work being on the short turn after grinding off the big casting nub on the floor of each exh port at the crown area.
Photos will be coming as will a template showing the arc change, but for now here is the before and after flow numbers.

The after numbers where with the new valve that had as of now no back cut, but it does have a nice thick margin and a under cut stem.

Note in the stock flow numbers how the bad turbulence from .350” to .450” lift was just shutting down near any increase in flow.

I will do a flow test with a tube on the end of the port to document the flow gain now with the porting work.



.050”//// 26/////26.3

.100”//// 52.3///// 59.4

.150”//// 85.3///// 88.6

.200”//// 110///// 116

.250”//// 134.7///// 148

.300”//// 151.7///// 157.7

.350”//// 159.7///// 168

.400”//// 160//// 176.6

.450”///// 163.8///// 181.2

.500”//// 168.9///// 188.7

.550”//// 171.7///// 194.6

.600”//// 176.8///// 204

.650”//// 178.7///// 208.4

.700”//// 180.8///// 213.6