Windsor Super Victor – plenums, port forms & finishes Vs flow
Posted: Sat Jul 22, 2017 7:00 pm
I am not sure who started the ball rolling here – maybe Chad or Larry but the subject of surface finish sure pull in a sizable response. I did not contribute anything at the time because I was in the depths of a head and intake porting rush. Now the bulk of that is done here is my ten cents worth on the subject on porting intake, the flow bench techniques, runner forms and surface finishes that I currently favour.
First lets deal with the preferred methods for flowing a 1 x 4 single plane intake.
There are many ways of putting the air through the induction system but the method I use is about the simplest as far as a bench installation is concerned. The flow test setup starts by placing a carb up-side-down into the five inch hole that is usual for most commercial flow benches. This is clamped in place so when the bench starts blowing air through the system it does not take off.
Next, if one is to be used, the spacer is positioned and finally the intake placed on to and the assembly bolted together.
With the butterflies wired in the open position we are ready to start masking of all the ports that are not going to be flow tested at this moment. This is how 99.99% of manifolds are flow tested. In fact when I did the intake manifold for Buick's factory shot at the land speed record for under 4 litre V6 production sedans this is how I did the intake. I suppose the results were OK as it out-powered Smokey’s intake and the car did beat the existing record by quite a big margin but was it the best? Who knows?
A few years later Roger ‘Dr. Air’ Helgesen came into my life and taught me a bunch more about 1 x 4 SP intakes than I already knew.
And here is how that came about. I had been friends with Roger for a couple of years and at one drag race event I bumped into a couple of his customers. Both were running Victor Jnr’s on their SB Fords (289 & 302). Both had originally used ported and matched versions of this popular intake but when they installed Rogers modified version of the Victor Jnr. their cars dumped a bunch off the ET (I am trying hard to remember here but I think it was in the region of 2.5 – 3 tenths for both cars) and the trap speed went up by about 3 MPH.
About a year or so later I am building a flat tappet, iron headed magazine project 5.0 and am just about a week from having it dyno ready. Roger spots the build and asks if he can test his intake against mine. This engine was not intended to be a max effort deal but more of a ‘build it at home with your Sears tools’ type of project. My Victor Jnr was port matched and the casting roughly cleaned up with 60 grit emery rolls. In short it was nothing you could not do in your shed with an electric drill. Only a couple of hours went into it. Stock shapes but with casting flash mostly removed. And for what it is worth these intakes work well in this almost out-of-the-box form.
I pull the intake from the test engine and Roger passes me the replacement. I am almost horrified. There is not a sign of any emery work within the intake. All surfaces were finished with course tooth carbide leaving a scalloped surface. Still the test went ahead because of the results those two guys at the strip had reported. After about 30 minutes of timing and mixture tests the results seen at the strip repeated on the dyno. 453 hp before and 474 after.
OK - what gives here RH?
Here is the inside story on this.
First the flow testing method. There is always 2 ports drawing at the same time with a SP V8 intake. When the piston is 90 degrees down the bore on the intake stroke a second cylinder is in the overlap period where the exhaust is pulling hard on the chamber and on through into the intake runner. This means that to simulate how the air is moving in the plenum you need to not only have the port under test open but also the following port to draw a certain amount open so as to simulate what is actually happening in reality. A figure of about 20% of the area of the port at the manifold face for the second cylinder seems to get the job done.
Let’s consider 351 Windsor’s cylinders 6&5 because that is what I am currently working on. When 6 is pretty much on a max draw cylinder 5 opens up and sends a pretty fierce pressure wave up to the plenum and this partially robs cylinder 6 of it’s full draw.
The lead-in to most runners is in the form of a radius but when adjoining cylinders are in a robbing mode it is better to have a sharp divider biased as in the sketch below. The first cylinder to draw has a large radius leading into it. This big radius takes it’s curve from the adjoining cylinder which should have no radius on it – i.e. a sharp edge. Because both cylinders are drawing jointly for a substantial period the sharp edge helps flow on both cylinders and has some measure toward reducing inter cylinder robbing. If the manifold is flowed just one cylinder at a time the flow tests will not reveal the effect of this sharp edge move on adjacent drawing cylinders thus compromising it’s performance.
OK that’s it for today. Will discuss surface finishes and what the bench showed in terms of CFM in the next day or so. (does that carbide finish actually help flow?)
DV
First lets deal with the preferred methods for flowing a 1 x 4 single plane intake.
There are many ways of putting the air through the induction system but the method I use is about the simplest as far as a bench installation is concerned. The flow test setup starts by placing a carb up-side-down into the five inch hole that is usual for most commercial flow benches. This is clamped in place so when the bench starts blowing air through the system it does not take off.
Next, if one is to be used, the spacer is positioned and finally the intake placed on to and the assembly bolted together.
With the butterflies wired in the open position we are ready to start masking of all the ports that are not going to be flow tested at this moment. This is how 99.99% of manifolds are flow tested. In fact when I did the intake manifold for Buick's factory shot at the land speed record for under 4 litre V6 production sedans this is how I did the intake. I suppose the results were OK as it out-powered Smokey’s intake and the car did beat the existing record by quite a big margin but was it the best? Who knows?
A few years later Roger ‘Dr. Air’ Helgesen came into my life and taught me a bunch more about 1 x 4 SP intakes than I already knew.
And here is how that came about. I had been friends with Roger for a couple of years and at one drag race event I bumped into a couple of his customers. Both were running Victor Jnr’s on their SB Fords (289 & 302). Both had originally used ported and matched versions of this popular intake but when they installed Rogers modified version of the Victor Jnr. their cars dumped a bunch off the ET (I am trying hard to remember here but I think it was in the region of 2.5 – 3 tenths for both cars) and the trap speed went up by about 3 MPH.
About a year or so later I am building a flat tappet, iron headed magazine project 5.0 and am just about a week from having it dyno ready. Roger spots the build and asks if he can test his intake against mine. This engine was not intended to be a max effort deal but more of a ‘build it at home with your Sears tools’ type of project. My Victor Jnr was port matched and the casting roughly cleaned up with 60 grit emery rolls. In short it was nothing you could not do in your shed with an electric drill. Only a couple of hours went into it. Stock shapes but with casting flash mostly removed. And for what it is worth these intakes work well in this almost out-of-the-box form.
I pull the intake from the test engine and Roger passes me the replacement. I am almost horrified. There is not a sign of any emery work within the intake. All surfaces were finished with course tooth carbide leaving a scalloped surface. Still the test went ahead because of the results those two guys at the strip had reported. After about 30 minutes of timing and mixture tests the results seen at the strip repeated on the dyno. 453 hp before and 474 after.
OK - what gives here RH?
Here is the inside story on this.
First the flow testing method. There is always 2 ports drawing at the same time with a SP V8 intake. When the piston is 90 degrees down the bore on the intake stroke a second cylinder is in the overlap period where the exhaust is pulling hard on the chamber and on through into the intake runner. This means that to simulate how the air is moving in the plenum you need to not only have the port under test open but also the following port to draw a certain amount open so as to simulate what is actually happening in reality. A figure of about 20% of the area of the port at the manifold face for the second cylinder seems to get the job done.
Let’s consider 351 Windsor’s cylinders 6&5 because that is what I am currently working on. When 6 is pretty much on a max draw cylinder 5 opens up and sends a pretty fierce pressure wave up to the plenum and this partially robs cylinder 6 of it’s full draw.
The lead-in to most runners is in the form of a radius but when adjoining cylinders are in a robbing mode it is better to have a sharp divider biased as in the sketch below. The first cylinder to draw has a large radius leading into it. This big radius takes it’s curve from the adjoining cylinder which should have no radius on it – i.e. a sharp edge. Because both cylinders are drawing jointly for a substantial period the sharp edge helps flow on both cylinders and has some measure toward reducing inter cylinder robbing. If the manifold is flowed just one cylinder at a time the flow tests will not reveal the effect of this sharp edge move on adjacent drawing cylinders thus compromising it’s performance.
OK that’s it for today. Will discuss surface finishes and what the bench showed in terms of CFM in the next day or so. (does that carbide finish actually help flow?)
DV