This idea was pioneered by Dave York. He wrote an article for the old Slant Six News. Here is what he did:



The pictures weren't really clear, and I wanted to try this myself and put the throttle bores in the factory location so I tried this experiment myself.

I used many power tools for this project: a sawzall, a 4 inch grinder, a drill press, a tap and die set, a pair of vise grips, and a dremel tool. The grinder and a drill are the only really necessary tools, but a dremel and a sawzall REALLY make life easier.

First you cut the carb mounting pad off and grind the manifold roughly flat:



Then you use an old two barrel carb base gasket to trace the outline of the throttle bores where you want them, and drill a series of small holes on the perimeter of the bores:

Fortunately cast iron is brittle and you can give the intake a good whack with a hammer and the drilled out portion will break right off.

At this point in the project a problem became very apparent to me. The Super Six intake manifold has a slightly different shape to the "box" the carb sits on. This minor design change allowed for the wider bolt pattern of the two barrel carb. Also on the two barrel intake the outboard boss is gone for the one barrel carb so the area for the throttle bore is much wider. On the one barrel intake the is not enough space between the outboard one barrel carb bolt boss and the boss for the inboard intake to exhaust manifold bolt boss to mount a two barrel carb. The picture below shows the exhaust bolt boss protruding into the new two barrel throttle bore:


This a picture down into the intake showing that the boss for the intake to exhaust manifold bolt is to big to be ground down or drilled out:

I will address how I compensated for this later.

I used a Dremel tool to grind the intake to as close to the two barrel outline as possible:

This helps a little with the boss blocking the bore, but not much.

This is where my method differs somewhat from Dave York's. Instead of buying a pre-fab aluminium carb adapter and bolting/JB Welding it to the intake, I fabricated my own carb mounting pad out of flat steel I bought at my local home improvement store. This allowed me to compensate for the boss sticking into the bore by making the mounting pad hole oversize and cheating it towards the driver's side of the intake. It is not an elegant or even pretty solution, and it doesn't completely eliminate the blockage by the boss, but it helps and is much better than not doing it. (Note 1- See Below)

The next step is to carefully coat the mating surface on the intake manifold with JB Weld or some other similar epoxy:

This is an important step since this acts both as a gasket between the carb mounting pad/flange/adapter and it is how your carb mounting device is secured to the intake (Note 2- see below)

Here is a picture of my end result next to my cracked factory aluminium Super Six (if you look close you can see the crack):


Thats it! This whole project too me three nights working with power tools, so you could probably get it done in an ambitious weekend with or without power tools. Dave York says he cut his carb mounting pad off with a hacksaw. Well, he must have arms and a back like a bodybuilder since I had a hard time doing it with my sawzall. I highly recommend using power tools for this project.

Dave York's method was actually easier in two respects, both due to the throttle bore orientation. Making the throttle bores run parallel to the engine give you more room to drill the new bores and you aren't going to run into any bolt bosses. This also allows you to use the aftermarket carb adapter like Mr. York did rather than fabricate your own like I did. Unfortunately this means people with automatics are going to have to fabricate some other sort of kickdown linkage and you won't be able to use the factory choke provisions.

If you know you are never going to use a Holley 2280 or Carter BBD carb, you CAN use the small to large two barrel carb adapter made by Mr. Gasket to mount the carb in the same direction as the factory did without building your own carb mount from scratch. I wanted to be able to run both stock carbs as well as mount aftermarket adapters so I made my own carb mounting plate and tapped the holes so I can remove the studs later.

At the end of the day I think it is much simpler and more practical to just go buy an aftermarket or factory Super Six intake. The only advantage I see to doing this project the way I did it is if you ae using some really weird carb or throttle body and can't find an adapter for it or you don't have clearance to run adapters or just want to have the carb or throttle body bolt right to the intake.

I only recommend doing this project if you absolutely cannot find a factory two barrel piece or do not have the money for a factory or aftermarket manifold. Seing as how used manifolds can be bought for $30-150 depending, I really think it is better to just buy one pre-made. However, if you like to tinker with stuff and want to create your own custom intake, then this method should work for you. Its ugly, but it will work.

So there you have it. It IS possible to turn a one barrel intake into a two barrel, but it is really a paint in the butt. My intake is ugly because I was building it mostly to see if it could be done. Someone with better metalworking skills and more desire to build a nicer looking manifold could do a much better job. This manifold also has numerous problem which make it not a very good choice for racing applications (but hey, if you have the money to go racing just buy a real manifold!).

Note 1- I used three inch wide steel that was either 1/8 or 3/16 thick (I can't remember) I cut two plates roughly four inches long, welded them together, and drilled out the throttle bore like I did on the intake manifold and drilled and tapped the holes for the carb studs. Steel is not easy to drill and tap, nor is it easy to drill a throttle bore into. I was using a drill press and I still broke several bits, including one instance where the bit froze in the piece and the piece spun madly before breaking the bit and flying across the room. Fortunately I was uninjured and nothing was broken. Point is, be careful. In making this plate I had to do a lot of grinding work to clear the intake to exhaust manifold nut and bolts. Keep that in mind if you decide to try this. Making my own mounting plate did allow me to cheat the throttle bore to the driver's side slightly. This combined with grinding the bolt boss down as much as I could reach really helped to eliminate much of the boss' interference with the throttle bore.

Note 2- I am also going to weld my pad to the intake as soon as the JB Weld sets up. I don't want to leave any possibility of a vacuum leak. Bear this in mind if you make your own carb mounting pad- you either need to have absolute faith in JB Weld or have access to a welder.

cool reed, I guess I should have saved my boat anchor to have a little fun. I like projects that you do "just cause you can."

I've got about 3-4 1 barrel intakes in my shed that are...'boat anchors'...

Sounds like it might be worth it to pull them out, make some mods and see how good they turn out for kicks...

good job Reed.

-D.Idiot

Thanks guys. Honestly, the only reason I would recommend anyone doing this is if the really wanted to or if they wanted to build a completely custom intake. One option I could see would be worth doing would be modifying the intake to run a side draft carb since Cortez motor homes and Lynx manifolds are rare. That could be done by cutting the EGR area off and just welding the steel plate into a carb box. If you were careful you could avoid blocking the intake to exhaust manifold bolts too.

Otherwise just buy a decent looking ready made intake instead of killing yourself making an ugly frankenstein one.

Another interesting thought would be to cut the straight portion of the runners off of one manifold and weld then to another making a really heavy cast-iron pseudo-Hyper-Pak one barrel intake.

All true, but its the thought process that is interesting to look at. I saw a set of triple SUs go with a lynx intake several times in ebay.au, so its interesting to see how you could modify a stocker. Besides, if they're lying around, why not have some fun and learn a bit as you go. Better to mess up one of those than a nice expensive intake

MJ

Just a question on the go : can anyone think of a 2bl. carb that should work well on a slant 6? With a machined manifold i mean...
Would weber (side or downdraft) or any european carbs do the work?
Why and why not? Do they differ from a Carter BBD in the fundamental working?

Marc

Since a stock 225 slant six flows about 210 CFM, anything bigger than a BBD (280 CFM) is unnecessary. Once the cam is changed and bigger valves are installed then a larger carb may be justified. Other carb options include staged two barrels (the Holley 5200/Weber carbs), four barrels, Ford two barrels (more flow than a BBD), side drafts etc... Any carb can be made to work on any engine, but for a stock motor I would stick with a BBD. Anything more exotic and you are getting into racing or high performance applications.

Staged two barrel carbs are interesting because they offer the potential for better fuel economy and more power.

Side draft carbs and other more exotic webers or Solexes are interesting but only if you want to spend the time sting them up. The are generally too much of a hassle for a daily driver unmodified slant six.

Hey, Reed! On the mounting plate you made, if you had angled the drill a bit when drilling all those holes, you could have made your own Tornado!
Seriously, I love to see this kind of writeup. Hands-on shadetree grassroots wrenching!

_________________
"When you find a big kettle of crazy, it's best not to stir it." - Pointy-haired Boss

1964 Valiant V200, 225/Pushbutton 904
BBD, CAI, HEI, LBP, AC, AM/FM/USB, EIEIO

...

Great!, now put it on the van!

How much difference do you figure it makes to turn the carb 90 degrees?
And, what difference?

Looks like Reed did it one way, and the article he posted did it the other..........

So I'd say you can do it whatever way you want depending on the way you want to hook up the throttle and kickdown (or what throttle and kickdown linkage you already have)

BTW, My 64 would have to have it turned 90degrees from Reeds to work with the existing throttle linkage and kickdown linkage

_________________
Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

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emsitil nailed it-From a performance standpoint, turning the bores 90 degrees will give a more even fuel distribution across all the cylinders. From a daily drier standpoint the main difference is throttle and kickdown linkage attachment. If you are running a manual transmission car or if you are running a cable style kicdown linkage on an automatic, or if you are good adapting a one barrel kickdown linkage to a different carb, I would recommend you make the throttle bores 90 degrees different from what I did. If you are running an automatic transmission and want to use factory kickdown pieces than you pretty much have to make it like I did. As was pointed out, if you have a car with the early style rod throttle linkage, the turning the carb 90 degrees makes it possible (with some creative cutting and welding) to run a two barrel with your factory throttle linkage.

Blue- Go for it!

Reed, for the carb question, my point is that i live in Europe and Carter BBD's are not the kind of things you find very easily...
I've got two downdraft weber carbs. They come from a 1.6L mild racing motor (or 1.5?...). We discussed that some time ago with dan and he told me not to mount them (i'll make my own intake of course) cause they'll be far too small.
The thing is : even one carb seem to be bigger (in throttle bore) than the stock carter bbs or holley 1920 i currently have.
Moreover, these motors used to get less than 20mpg which i assume is already anough for a 170 /6.
What do you think about it?
Thanks for your help

Marc

What downdraft webers?, or from what car?