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16 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.


16 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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