Hi,
I'm back here overcomplicating things so instead of trial and error that can't easily be undone I'm hoping to find some experience. I'm building a hodgepodge 57 ranchero, manual trans 292"+ with cam (of inappropriate design), cleaned up b intake manifold (or something stupid made from aluminum), g heads mildly ported, making a set of long tube (fender exit, 180° tri y, 8:1 depending how the tubes fall). Porting on the exhaust side should I port match to gasket shape, leave the one angled corner (should header port try to match that shape), braze in that portion to level the floor (could be a chance to raise the roof). For the headers should the flange be matched to the port or slightly oversized (supposedly reduces reversion to valve), 1 5/8 primaries seem appropriate (although unable to find any good calculators on length, tube sizes after Y's, collector sizes) Would using an appropriate size and length collector extension dumping into a larger exhaust significantly hurt the power over just running the open extension or transitioning into dual 2" full length exhaust.  It seems to be held that larger exhaust does add some base to exhaust note and ive got 3" exhaust sitting in the garage. thanks
Seth

There are a couple of things in your post that I don't quite understand, such as "cam (of inappropriate design"); "(...8:1 depending on how the tubes fall)'.                             

I would not use 3-inch exhaust pipe, unless you plan to run single exhaust. I recommend that you read Ted Eaton's article Ford Y-Block Exhaust Testing (eatonbalancing.com). 

I recently asked Ted why all Y-block heads (excluding Mummert's aluminum heads ) have the same size exhaust valve, even though not all Y-block heads have the same size intake valve. Ted said that the exhaust side flows well enough that there was no need to increase the valve size. Unless you're looking to extract every horsepower possible, and don't intend to run on the street, I would not attempt to re-design the exhaust ports in the manner that you've suggested. Hopefully, one of the forum members who has done some serious head porting will chime in.   

It is difficult to explain porting to someone who is a beginner, but don't remove the metal on the upper port between the guide and the exit of the port.  You will find water very quickly there.  Squaring up the exit is not necessary, either.  Leave the angle corner alone and just clean up the slag in the port and blend the valve job above and below the seats.  Less is more with this head.  Joe-JDC

JDC

Here’s the link to the Ford Y-Blk header test as published in The Y-Block Magazine.
Ford Y-Block Exhaust Testing – Eaton Balancing

And here’s the link to some of the posts made on this site during the testing.  Be forwarned that this particular thread is about eleven pages long.
Exhaust test to end all tests? 

Lorena, Texas (South of Waco)

Cam I'm thinking of a comp thumper style cam. Not the greatest but compromise sound and street abilities. 8:1 is single collector with all 8 tubes in sequence. Gives some interesting results, similar to 180° headers, without changing the idle sound.

I've read Ted's articles and also pretty sure the 11 page post recommended more than once. My comcern is im not using as stout of a setup so not sure how to compare is setup to a lesser built engine. I was looking into the 1 1/2 or 1 5/8 fender headers from the test because of style and fitment before getting side tracked with 8:1. Figure ive got 12 feet of 3d printed snap together pie cuts to mock up let's see how far it can go.

I am not a fan of CCams for the Y due to a fiasco I had with a custom grind from them that was a total failure.  They do not understand the lifter angle of the Y block vs the lifter angle of the SBC, or other make of engines.  They are different, and if you need to advance or retard the camshaft, the lobes will be completely off their respective degrees needed for the advance or retard.  The only way the CC would degree was installed straight up(what many folks call dot to dot) which is at the 3 o'clock position on the Y block gear set and 12 pins between.  Isky makes several different grinds for the Y that can be had from mild to wild.  Check with Ted for a possible performance Isky upgrade.  I know camshaft blanks are difficult to find right now, so CC may not even be able to grind you a cam.  Joe-JDC

JDC

Joe, although necessary, I wish you hadn't posted the photo; now I'm worried. Is there a way to test the heads for leaks before they are installed and put into service?

Sorry to cause you to worry.  I have ported dozens of Y block heads, and I have only made holes in about 3 heads over the last 14 years working on the Ys. I was trying to get every cfm possible out of the -G heads when that hole happened.  That head was for the EMC competition, and was welded, sealed, and went on to make 467hp before being removed for another set of heads.  Most any competent machine shop should be able to pressure test the heads for you at a charge.  Joe-JDC

JDC

I was pretty conservative with the porting-took my time, looked at lots of photos (including John Mummert's cutaway views), and did a lot of reading as well. However, I'm a long-time believer in Murphy's Law. I'll be celebrating my 70th birthday (maybe "celebrating" isn't the best choice of words) next month. It's a little late in life to start being optimistic.  

I was actually thinking of trying to pick profiles and have a cam and lifters reground by oregon. They can do 108 lc looking under .480-.500 valve lift And the shortest duration that nets
Good overlap. Im curious about shorter exhaust duration as read some positives on lower rpm