Frank, if you want 5/16" guides you would have to provide them.  One of my customers is doing that, but I don't have the details handy.  I should know in a couple weeks when he sends them to me.  Your heads are in the second batch of castings, so we have some time on that.  Send me an email in a month or so and we can figure out how to handle it - Jay

   - The guides have been changed from 3/8" stem to 11/32" stem.

I got a valve job and bowl cleanup done on one chamber in order to get flow numbers, and I was pleasantly surprised by the results.  Especially the exhaust port did better than I thought it would.  I had tweaked the stock design just a little bit, and it seems to have made a significant difference.  Still not as good as my SE heads, but better than a lot of FE exhaust ports that I've seen:



After getting the head back from the shop I checked the chamber volume, and this was also a surprise, it was much lower than I expected at 55 cc!  I will have to make a modification to the chamber machining program to get a little more volume.  The upside there is that it can only help the flow.  Pictures of the chamber and the port cleanup under the valve are below.  Please excuse the yellow grease in the chamber and near the valves; that is left over from cc'ing the chamber:

Quote from: 1967 XR7 GT on September 11, 2023, 11:10:41 PM

Quote from: jayb on September 11, 2023, 10:34:00 PM

Flow numbers and valve details for the exhaust side of the SE head are shown in the link below:

https://fepower.net/simplemachinesforum/index.php?topic=7336.0

Also, no reason that the tunnel ports I'm making wouldn't flow in the 360 cfm range with some porting.  But my info for stock tunnel port heads is that they flow around 330 cfm, and that is what I'd expect mine to do.

I saw where it was said stock Tunnel Ports flow in the  320 to 330 range, and  the ported version in the link I provided in my previous post was ported but had a raised floor to reach the 360 cfm, and I don't think the ports were made larger to achieve that flow.

It showed 360 cfm was reached with a 2,250" valve, I wonder how much more can be achieved with a 2.300" valve, and room restraints may require a 1.675" exh valve, with still 240 cfm @ .600" without porting. I am using the .600" range for my self, I would run a cam around .600 to .650" lift for the street.

Going to a bigger valve doesn't always guarantee that you will see benefits.  Sometimes you don't.  The port and throat have to be in line with the valve size and there has to be no issue with valve shrouding, which means that you really need an aftermarket block to take full advantage of a 2.300" valve or bigger.  A 2.250" intake valve will support well over 700 hp.

Quote from: 1967 XR7 GT on September 05, 2023, 01:27:54 AM

Hi Jay

Some Questions:

What valve sizes will be used ?

With the SE exh port, you mentioned about a 250 cfm flow rate, Question: Is that as cast or will they need to be ported ? And if that flow rate is as cast, about how much more if ported ?

Also, with the SE exh port design, what if any decrease in shock tower clearance would there be in say a Mustang or Cougar, not that there's that much to begin with.


And I read where you said the Tunnel Port valve spacing will be used, thinking out loud, bore dia min would be 4.230". Also, the wider rocker stands will be required.

You can use any valve size up to 2.300" on the intake and 1.75" on the exhaust, based on the valve seat sizes that I'm using.    Common valve sizes are 2.25" on the intake and 1.75" on the exhaust.

The SE exhaust port flows 250 cfm with just a good, 5 angle valve job and a cleanup under the bowl.  No porting or enlarging of the port is required.  I haven't ported a set so I don't know what they are capable of, but that is enough flow on the exhaust to support 900 HP, which is quite a bit more than the intake port can support. 

Shock tower clearance would be the same as for any FE head.

Reducing the valve sizes would allow you to go to a smaller bore size than a stock 427, but the chamber is designed for a 4.25" bore so you would have some overhang at the top of the cylinder if you went smaller than that for bore size.