Mr_Asa GRM+ Memberand New Reader
1/8/20 8:55 a.m.

So, I've got an old Mustang with an inline six.  I like the inline six, I do not like the limitations of the head.

For those that dont know, Ford cast the intake into the head of these.  Probably saved them millions in the 60s due to lack of machining, assembly, extra parts, etc.  Unfortunately that leaves you with a 1bbl carb mounted in a position that gets the center cylinders rich and the outer ones lean and just plain doesn't breathe. 

An example of the head


So I milled two flats in the head, then started designing adapters I'm going to cast (or maybe print in stainless steel filament when I'm done upgrading my printer.)

It is fairly easy for me to modify everything now as I haven't cast a final version, but after it will be an order of magnitude harder to adjust.  To that end, I have two central questions with this: any advantage to separating the venturis at the adapter, like this?

Or just cut out the center and go with something like these?


Second question, I initially planned to have both carbs at the same level as I was thinking of one day doing something silly like the classic Shelby dual carb air cleaner, but I got to thinking about air flow and how that would give the rear cylinders just a slightly longer runner (as pictured below.) 



Edit: I recognize that there are inherent flaws in this approach, and fixing the two things I am asking about may be like fixing a leak in the Hoover Dam with FlexSeal, but it's fairly easy for me to optimize these now, so why wouldn't I? 

zordak Reader
1/8/20 9:04 a.m.

Remember this is the opinion of a random guy. If you are not after maximum performance just a little more even A/F across the cylinders anything you do will help. Just keep in mind longer runners in a wet manifold running near horizontal will give more time for fuel to fall out of the air flow.

Mr_Asa GRM+ Memberand New Reader
1/8/20 9:51 a.m.

In reply to zordak :

It's a fair point.  Been a while since I've looked at this, so I need to remind myself of clearance issues, but I think I can drop each down a significant amount to lessen the length.

jimbbski SuperDork
1/8/20 11:12 a.m.

Back in the day someone made a kit to add two more 1 bbl carbs to that manifold. You drilled two holes at each end of the intake and then you drilled and tapped for studs to hold the carb adaptors to the intake.  So what you're doing has been done before but in sort of a "red neck"fashion and not in the "high tech" way you're doing it. 

What kind of carbs are you planning on using? 


To bad you're not living "down under" as Ford of Aussie developed a number of better cylinder heads to bolt to that block and I believe one of them had OHC's.


Mr_Asa GRM+ Memberand New Reader
1/8/20 12:03 p.m.

In reply to jimbbski :

Yeah, the Offenhauser 3x1bbl setups are still somewhat popular in certain circles.  I wanted to do something different, though.

Weber 32/36 carbs.  Nice aftermarket support so I shouldn't have any issues sourcing parts.

I've actually got an Aussie 250-2V engine in storage.  Every now and then I wonder why I'm screwing around with this when I could drop 50 more cubes in and get access to a removable intake.  Project started off as a way to learn how to cast aluminum and I'm still not great at it, so I guess that and the need to rebuild that engine is why. 

Sergeant82d New Reader
1/9/20 9:06 a.m.

A couple of comments from another random guy. But this one is also building a 200 inline 6 Ford. 

You can still get the Offenhauser 3 carb adapter, depending on what year your head is. 

The velocity through the adapter and then the manifold is being drastically reduced by the additional two carbs, but since it is starved for air, that's probably a good thing. 

I don't think it's going to make a bit of difference whether it is divided or not, so I would suggest whichever one is easier. 

Also, if you don't already, be sure to check out the forums. 

Shameless self-advancing plug:

Sergeant82d's Locost 7/Model A roadster pickup

Mr_Asa GRM+ Memberand New Reader
1/9/20 9:28 a.m.

In reply to Sergeant82d :

I saw your build when I was lurking.  I like what you're planning with it.

Provided I get the clearance correct, there's literally no difference in ease of manufacturing for the divided ports or undivided.  I can always mill out the divider if needed?

Been a member of Fordsix for.... E36 M3, going on 20 years... how the hell did that happen?  They were a big part of me keeping the six, unfortunately I don't spend much time there anymore as the older core members all drifted away and I didn't know anyone anymore.  Still, I visit to keep track of some of the builds I really like.  That guy doing an EFI turbo setup in his wife's '67 Mustang, the yellow one, is an inspiration. 

twentyover Dork
1/9/20 12:48 p.m.

In the wayback times when I was young, Ak Miller did a buildup in HOT ROD (can I say that here?)  of the then new Falcon 6. IIRC, he tried a couple carb variations, including a 2 SU sidedraft variant  (I think there were Jaguar E-tpe carbs) and another variant using 4 Honda 450 motorcycle carbs. 


IMO, the limitations turning a couple corners to get into the cylinder drive the desire for sidedrafts. In the interest of transparency, I bought one of the last of the old Classic Inlines alloy heads (after Mike dies but before Vintage Inlines bought the assets) and have it set up for motorbike carbs. I bought two racks of ZX1000 carbs, hacked one carb off each rack, and the carb spacing is eerily similar to intake port spacing on the Ford. Did Kawasaki secretly steal the blueprints for Ford? Umm, maybe a bit too much of a conspiracy theory even for me.


I suggest you look at making adapters for two or three SU's into the side of the plenum (if the crap intake can be considered one.) The variable venturi feature of the SU will help you wit getting the car running.


Just another point of view from the peenut gallery.


No clue on yur original question

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