“Siamese” exhaust ports

[Beaus67]

Hey David (CZLN6) I’m curious about the “Siamese” exhaust ports, is it known that Ford built some I6 heads with the 3rd and 4th exhaust ports separated? And if they did it in 67 why didn’t they continue to separate them from that point forward? Maybe I’m totally off base but as I was getting ready to dispose of my old head (original 1967 head) and I noticed that the #3 and #4 exhaust ports are divided by what I believe is a cast into the head port divider. Is this unusual? I thought I would ask the guy that wrote the book on these engines. This is the same head that had the unusual combustion chamber shape. Maybe I have a proto type? Or maybe it’s just as common as they get. It did stop me from junking the head, at least for now. What are your thoughts should I keep this thing for induction into the Ford Inline 6 Museum?
Bill

 

[vssman]

My original '68 head looked exactly like that too...

 

[MPGmustang]

what are the exact casting numbers on the head... that looks cool!!!

 

[Beaus67]

Here’s a pic of the casting numbers. I kind of thought the “ribs” in the Siamese ports kept the exhaust directed straight out of the head rather than swimming around in the chamber but this head has the ribs as well and they seem to be even more pronounced and come all the way out to the end of the chambers. Still hoping David weighs in on this, I’ve always thought that “weld in divider” was a gimmick but now I’m thinking there must be something to it because if Ford did it they there must have been some engineering/benefit, but then they abandoned the concept so ???

Bill

 

[thesameguy]

I'm gonna go out on a limb and say in the '60s (and '70s, and some of the '80s) the exact behavior of exhaust and its effect on engine performance wasn't really understood. Exhaust resonance tuning is a relatively recently perfected art form, and back in the day manufacturers were trying all sorts of things to optimize flow into and out of the engine and balance that against manufacturing costs. You really didn't start seeing consistent exhaust (or intake, for that matter) characteristics in engines until the '80s - up until that point lots of engines went through repeated minor revisions to get things just so.

 

[MPGmustang]

IMO, I would keep the head, then put a 3x1 bbl setup on it and run it... I wonder if the log is bigger or the same... the exhaust port is little different so what else is changed.

could you post a pick of one of the combustion chambers one with valves and one without?

 

[Beaus67]

Here is some pics I posted in an earlier thread, I had also measured 3 combustion chambers - 1, 5, 6 and I got 52cc, 52cc, 52cc. If I get time I may go over this head with a little more detail. Does anyone know if you can cc the log in the same manner as the combustion chambers i.e. with a known quantity of liquid? And what the procedure might be. Might be fun to see if the log is unique as well.

Bill

 

[bubba22349]

Sure you could CC it with the head off.

 

[turbo2256b]

I have a 3 1 bbl set up for sale its like new. Had it on the car for years but never drove the car since 80 or so. It s for the round log head.

 

[MustangSix]

Here’s a pic of the casting numbers. I kind of thought the “ribs” in the Siamese ports kept the exhaust directed straight out of the head rather than swimming around in the chamber but this head has the ribs as well and they seem to be even more pronounced and come all the way out to the end of the chambers. Still hoping David weighs in on this, I’ve always thought that “weld in divider” was a gimmick but now I’m thinking there must be something to it because if Ford did it they there must have been some engineering/benefit, but then they abandoned the concept so ???

Bill

The ribs are there to capture heat under the carburetor to keep the intake floor hot. It aids vaporization and helps cold driveability and economy.

 

[JackFish]

Perhaps Clifford started making the port dividers to emulate this pattern.

 

[MustangSix]

I noticed that the chambers also seem to be more relieved than the usual log wedge. The chamber walls are laid back away from the valves, not shrouding them as much as usual.

You may have stumbled on a "hi-po" casting number! I'd be interested to see what that head flows versus other castings.

 

[CZLN6]

Howdy back Beau and all:

Sorry to be so late in responding. We're down south for the winter and I don't have regular access to the internet. I also don't have my reference material so this is off the top of my head. So take it for what it's worth.

This is the third head that I've seen photos of that had a port divider. All were mid "C" castings with what appears to be an as cast from the factory divider. One was from a casting from a Canadian 170 engine. Unfortunately no one I have been able to talk with can tell me any details of the when, what, or why. My guess as to why it was eliminated was due to the "thin wall" sand casting process that was being utilized with these engines. It probably saved some time, complexity and money to eliminate the divider. However, this is just guessing on my part. Your head is not super valuable because of it, but it is interesting and raises questions.

Jack gave you the only explanation I've ever heard as to why the ribs. But this is not likely the Hi-Po kit head that FoMoCo marketed. It was based on the 170 casting referred to as having "Kidney" shaped chambers, which were slightly smaller in volume too. The hi-po head photos I've seen did not have a port divider. But, I try very hard to never say never or always when in comes to FoMoCo in the mid to late sixties. I keep hoping that someday someone will come along to answer all the mysteries.

Sorry, I'm not much help.

Adios, David

 

[wsa111]

David & Jack, i wonder if the cc's of the log is the same size as a stock 67??
I need to take a closer look at the intake valve size.
I wonder if some left over prototypes were just put on the assembly line to use them up.
Typical of Ford to empty the parts bin of old parts then move on. Bill

 

[Beaus67]

Thanks for the information and theory, I guess my dreams of having a one-off highly sought after and very valuable FoMoCo hi-tech (for the 60’s) proto type are out the window, but I do think that its unique enough to keep since it really doesn’t take up much space. I thought MustangSix was just having a little fun with me on the Hi-Po comment. There was actually a Hi-Po kit for the I6? I would love to see the specs on that, probably ends up being some or all the things you guys have been doing for years. It’s not difficult to see why so many people like this little engine; it can be as basic or complex as you want, time and money being your only real limits. My boys coming home for Spring break and he’ll take it when he goes back; that will be this builds real test, can it survive Oregon State University?

Bill

 

[MustangSix]

I was pulling your leg with the hi-po comment, but the reason for the ribs really is for heat retention. The length of the log requires some help with vaporization and the hot floor helps considerably.

The water heated carb spacer helps prevent icing in the carb, but it also actually helps keep the carb at coolant temps to help prevent that excess heat from reaching the carburetor. The intake floor under the carb could be several hundred degrees hotter than the coolant in the spacer, that's why removing the heater hoses can cause an increase in carb temps - the opposite of what you might expect on most engines.

 

[MPGmustang]

Your head is not super valuable because of it

noteing the cost that it takes to put one it properly it's aleast worth that much more... that's my opinion tho... just think of the time and money put into cast heads that don't have that port divider. that's a chunk of change at least...