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460jimbob the first thing you need to do ( and this is for any type/ brand of head) is to access what you have now which will tell you how you might improve the ports.
To do this you need to know how a port is basically geometrically designed.
This will then allow you to take simple measurements and make simple templates number1) see how your port(s) shake out now and number2) these templates will guide you in any porting work you may undertake.
Here is a geometric drawing of a known port.

in this diagram note the two circles, one Big and one smaller one on its center.
This port uses a 2.11” valve, the minimum diameter of the valve bowl throat as you can see is 1.60”.
This is small for this 2.11” valve and is well under the 85% minimum that would be a good start to using this 2.11” valve.
The maximum that a throat should be for any head, and yes even flat out race heads is 91.5%
Back to this diagram note that the small inner circle I talked about before is a radius of .800”, this then is the same diameter as the throat which is 1.60”.
Also note that the bigger circle is that .800” plus the 1.60” throat for a total of 2.400”.
From my discription here I hope you can see that any increase in throat size will make for these circles to get bigger .
Here are two more pictures of a throat template set on this geometric drawing and a throat template made with a machine screw for a handle.
These templates can be made to help you find where the main restriction is in your ports .
The usage of inside snap gauges will be of great help to you also, so plan on getting a set along with a cheap plastic dial caliper if you do not have such.

I gotta run now, but I bet you will now have further questions to ask.


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32 Posts
Hi again JimBob and Stude.
I posted yesterday what I did in a rush and there’s much more detail I can give then what I put up in terms of these heads and any head in general.
First let me say this, the last time I ported a set of iron marine heads was 2 years ago and my arms are still sore from flipping them around to port them and then hump them onto the flow bench!
If your building one of these motors I would pick up a part time job so I could get a set of aftermarket aluminum heads just for the darn weight savings, no less for the added flow they have out of the box, Dam these heads may even weight more then iron BBC heads do!

jim these heads intake ports in stock form flow more then enough to make 425 hp, this only takes about 225 cfm out of the 260 cfm that these heads flow, it’s the exh side that truly sucks on these heads as you may or may not know.
With the ok exh ports that the iron 351 4bbl heads have I can’t believe Ford ever approved these to go into production with there stunted 128 cfm of exh flow which makes for a pitiful 50% exh to intake ratio and a engine that runs hot, especially if it’s under 9.5 to 1 compression.
Here’s some photos and info of the 460 marine mule head I used to develop the ports I reworked those years ago.
I increase the exh valve size to 1.75”.
The average throat diameter got taken out to 1.456”, which still makes for a small 83% throat to valve ratio.
I did this deliberately so I could pick up a nice fat amount of low lift flow and a good amount of high lift flow.
The exh port in these heads are so choked off with the size of the valve guide boss no less the huge air injection boss that in total it took me 3 hours of very hard grinding to get the port to how you see it in these photos.
The result was a peak flow gain at only .500” lift of 185 cfm, which is a 53 cfm gain over stock.
In fact the reworked exh port is already flowing more at at .225” lift then the stock port did at .550” lift.
The proper use of the 1.750” valve made for a 20 cfm flow gain even way down at .100” lift even.
The real good 3 angle valve job that I was able to put in by means of the larger valve had a lot to do with these flow gains, and the bigger valves help out in the compression department also.
Note that I did not even gasket match the exh port, as there is no need to do such .
Even a novist home porter with the right cutting burrs and pan cake type cutting stones can replicate what I did here as time input should not be a issue.
If need be for flat out racing purposes along with enough compression I am sure that these exh ports could be reworked to produce over 225 cfm, it’s just that some of the low lift flow numbers would have to be given up.

I am out of time again, but I will post more this afternoon about how to make and use the templates that I have shown here, as I think you folks might have questions about the details of there usage.



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32 Posts
Before I get deeper into how to make and use templates and measuring gadgets I would like to help you guys out by taking a step back from what I was going to post and reinforce the info and the kinda direction that Scotty was going for.
This once again can help you access things and where you need/ want to go with the work.
There is a very simple carved in stone formula that is this Dx.18.
D is just valve diameter and working the formula gives us a important lift number.
So let’s say we are dealing with a 2.06” intake valve.
We then multiply this by .18 for a result of .370”.
Ok, so why is this so important, well this is the amount of lift and in turn flow that is controlled by the area and shapes on each side of the seat to the tune of up to 3/4s of a inch or so.
Up to this lift point the amount of air passing into the chamber is taking the path of least resistance and is really not yet following the basic size and shape of the port that you have going on back to the flange.
This is called the change over point and can clearly be seen on the flow bench because the vertical manometer fluid column will start to lightly bounce around.
The fluid is bouncing around because right at .370” lift the air mass can not decide what to do.
Now with this info you should see how important the valve job used is and the valve bowl shape and the shape that the chamber is in this .370” lift range.
Another good way to look at this would be if let’s say you where running a lift at the valve of .500”, well .370” is 74% of that .500” so where talking about a big chuck of the total amount of air ingested into the cylinder!
It should be clear from this how important the valve job is because for example a 3 angle valve job can in compass 3/8” of a inch out of that total 3/4” on the back side of the valve that I talked about a few paragraphs ago.
Here in this simple drawing I made of the cutaway of a short turn is a example to keep in mind of what parts of a short turn control what lift range to a large degree, so this info is pretty well cut in stone also.
In my drawing here divided up the short turn into 3 sections, top, middle and lower.
The top or crown section has the most effect on high lift flow numbers, the lower section which includes the valve job and sometimes even the chamber lip as in some Heart shaped chambers controls to a great extent the amount of low lift flow.
And the middle section has a effect on both low lift and high lift flow.
That’s enough for now.


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32 Posts
Air just like water will always first try to take the path of least resistance.
I river once it’s forced to move more volume then can be done by means of least resistance will start to carve out its banks to move that added volume, air can not carve out metal!
Another big point to always keep in mind when reworking any part of a head is velocity.
The more air you move thru a given size area the more the velocity will go up.
The detail to this is that once a certain velocity level is reached air will not follow around anything greater then a 15 degree bend / change in direction.
To make it do so the air mass needs to be expanded which in terms of head ports means slowed down back to a non critical velocity point.
Hence in terms of a intake port the expansion from a port runner into the valve bowl and then again thru the valve job and out onto the chamber.

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32 Posts
I have the time now to explain the making and usage of the templates I have been talking about.
Just to review and use a modified phrase, the throat of the valve bowl is the tail that wags the Dog so to speak.
For any given valve size to start to be effective in the amount of air that it can pass the throat needs to be a minimum of 85% of the valve size.
For a novist porter with no flow bench at home I would suggest not to exceed a maximum throat size of 88%.
There are a bunch of reasons for this, but first and foremost it will keep you out of trouble.

I make my throat bowl templates out of .060” sheet plastic from a hobby shop and also from old valves that are big enough to be ground down on a bench grinder to the throat size I am in need of.
The first step if your going to enlarge your current throat size is to use a old valve of the stem size your heads use.
This is because when you make the throat bigger it must be done so in a concentric manor, at least for a good amount of the bowl size increase.
Whatever size template your making needs to have a flat side equal to 94% of its diameter
So for example a 1.66” throat template will have flat that is 1.560” wide.
Also transition from round to each end of the flat needs to be softened a bit .
What you end up with is like what’s in one of my pictures here, and another picture shows a 1.66” template being sunk into the valve bowl of this pair of Buick nail heads that I am currently porting.
The new throat diameter needs to at least go in deep enough into the valve bowl until any cutting that was having to take place on the short turn has stopped.
This is because some heads / ports have deep bowl and you can go in much deeper and some bowls are shallow.
If you stop cutting just when you clear the short turn, then this will help to keep you from cutting thru a port wall possibly.
I have adjustable seat cutters that I use to open up the bowls and this saves a heck of a lot of what would be tuff grinding .

I would suggest that if your shooting for more then a .040” increase in throat diameter that you have a machine shop open the bowl up for you.
In one of my pictures you will see the lip from the start of my rework of making a throat bigger.
One you have a good start on the bowl size increase the new needed arc of the short turn needs to be put in because the roof and port side walls will need be cut to compliment the new throat size.
You can make a short turn template out of plastic or sheet brass or aluminum.
I would suggest that you make a series of 3 progressively larger templates to help guide your porting .

there is a bunch more detail I need to get into about the correct usage of these templates, and I will post up more this evening.


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32 Posts
I must apologize for not posting back more info last night.
I went out to the food store yesterday evening and the fuel pump in my vehicle gave up the ghost!

I will do the info post later today.

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32 Posts
Hi all.
I have been thinking about doing a series of short videos to instruct on how to use these templates I have been posting about since I think doing such will help more .
I will have time to do this over the weekend.
Is it possible to post short videos on this site, or do I have to link to them?

thanks in advance!

· Registered
32 Posts
Hi to everyone again.
I am truly sorry for taking so long to get back to post up into by means of doing a video, but my buddy who was going to help me with that end of it literally had to go back out to Sea.

So here I am doing it with photos and hoping to detail what work needs to be done so that most any one can make the same good results happen.

while the exh side on these iron 460 heads leaves much to be desired, the int side is near already ported for you from the factory.

in these heads the throat of the valve bowl is the main restriction or choke point.

Also as is the case with any iron head from any brand the full size of these heads 2.19” valve is not being used.

The OD of the stock valve job used ends at a OD of 2.065”.
The stock intake throat diameter is 1.83”, or 83.5%.

This is well under the 85% minimum.
The throat size should be taken up to a minimum of 1,88” which will then be 85.8%,
or even better up to 1.90”which would be 86.7%.

let me just stop right here and say that with even just a 1.88” throat a novist porter even without the aid of a flow bench should get 290 CFM @28” at .650” lift out of these pretty darn easy!

This is because other then the valve bowl throat the rest of the intake port is comprised of basically the needed area to do so.
Your porting work should start off by incerting a 1.88” valve in the guide and then by carful grinding sinking it into the valve bowl.

You should sink it down deep enough such that your cutting action on the short turn has stopped because the arc of the short turn is pulling away from the valve bowl area.

More work will need to be done in the bowl but now you should focus on reducing the thickness of the valve guide and also Boat tailing it down a whole bunch as it approaches the seat area.

the mass of the guide is another major restriction which needs to be improved on.

If your heads are in need of new guides or liners then these should be installed before taking a grinder to the guides.

if you are doing this work on the bowl and have seats that are good and intend to reuse then cut some thin strips of duct tape long enough to cover the main seat area twice so if you slip with the cutting Burr you will be safe.

By the way if you are in the process of rebuilding these heads from top to bottom I would not think twice about going up to a 2.250” valve even if I was only planning on using a 1.88” throat size!

Photo 2)
is a 1.83” template just barely hanging in the stock throat.

The 1.83” template now freely down deeper in the bowl which shows the throat restriction.
A 1.88” valve .
A 1.90” valve.
A 1.780” valve / template in the guide and resting on the very top of the guide.
I will post more on Friday.


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32 Posts
I had some time to day to get back to this head and I am making a report on it for you folks.

I flowed it stock but I only had a stock 2.19” valve with a slight 29 degree back cut to it.
This increase the low lift flow numbers up to about .150” a little bit more over true stock.
Also in consideration of the flow numbers here at .500” and up, note that my biggest flow bench test cylinder is only 4.250”.
This was limiting the port peak flow numbers some.

I will list 3 columns of flow numbers [email protected] 28”.
First are the stock numbers, then the ported and then the difference in flow.
I spent 35 minutes in reworking the number 3 intake port to get these numbers.
The first thing I did was to heavily boat tail the valve guide as you can see in my photos, but note that it could still use a bit more work to narrow its profile where it joins the roof.
The second thing I did was to work the valve bowl so I could sink a 1.88” valve down a little bit.
For this first flow test I only sunk it in .210” down from the level / flat cut made in the chamber around the valve, not from the cast chamber floor itself.

you should be able to see from my photos I hope just where I confined my rework to in the valve bowl.
The photo of the pile of grindings next to the 2.19” valve is how much came out just to boat tail that massive valve guide.
flow @28”
.050”/////37/////36.2///-.8 cfm
.100”/////73.5/////77.4///+3.9 cfm
.150”/////112/////121///+9 cfm
.200”/////142.8/////157.5///+14.7 cfm
.250”/////169/////188.2///+19.2 cfm
.300”////191.2/////210.4///+19.2 cfm
.350”/////217.6/////224.2///+6.6 cfm
.400”/////234.6/////238.6///+4 cfm
.450”/////242//////249.2////+7.2 cfm
.500”/////251.2/////261.4///+ 10 cfm
.550”/////257.3/////270.5///+ 13.2 cfm
.600”/////257.3/////275//// + 17.7 cfm
.650”/////257.3/////280.6////+ 23.3 cfm


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