[tazdevil]

Lots of aftermarket manifolds out there. Trouble is, your engine is not cammed nor does it have higher compression for it to handle a four barrel. It would definitely give you poorer fuel mileage, too.
I assume that you have a small block. You did not tell us that info.

 

[dana44]

This is a 318, right? You need a 318 4bbl intake, not a 340 or 360. They fit, but the port size is different and tend to leak, so an aftermarket 318 intake is needed. Take tazdevil's comments into account, too.

 

[TWX]

There's also the throttle linkage assembly which needs to move the throttle linkage further toward the side, and the throttle pressure linkage that ties back to the transmission, which is a different part on a 4bbl car. The latter can be modified to work (taking one's current one out and bending it in bench vise essentially) but the former must be replaced. Not massively expensive, but an extra cost none the less.

I did the swap on my 360. Before I did the cam swap the lower RPM performance was not affected. Upper RPM performance was, but not something that I saw much of in daily driving. Once the cam was done it was better. Admittedly the 360's 2bbl carb was probably bigger than the 2bbl on the 318, but I still wonder how much bang you'll get.

I suppose that if you do want to do this, you should look for a mid-eighties M-body (5th Ave or New Yorker or Diplomat or Fury) that was a 4bbl 318 car, that would be the best source for factory linkages and intake. You'll still probably want an aftermarket carb as those were probably feedback-carbs for use with the fancier ignition control, but at least the metal parts could come from there.

In all honesty, for the work you're talking you may just want to do an engine swap if you can find a good 4bbl 360 vehicle as a source.

 

[cle73satellite]

Well wut if I went with an aftermarket 318 intake and 4 barrel? Would that eliminate the problem with the throttle linkage? I kinda thought that would be my best bet anyway, and its not overly expensive.

 

[dana44]

No, throttle linkage is a different cable between 2 and 4bbl cars (thanks Tannon, forgot that one), the difference is a couple inches in length. Also, the ports on the newer roller cammed 4bbl 318 is different than the early 318s, which never were offered in a 4bbl, unless you find a 273 intake and it has the correct bolt pattern (straight or angle available if not mistaken), so an aluminum 318 specific intake is the best item available. Some people have gotten the 360 intakes to work, but the proneness to intake gasket leaking is not worth the effort to do this swap, the ports are more than a quarter inch taller, gasket failure is inevitable.

 

[cle73satellite]

Well I've found a 4 barrel intake made specifically for that year 318. How could it be specific for that, and still have the throttle linkage issue? It seems that would make it work.

 

[TWX]

The linkage is a separate part to the intake, that's the problem.

 

[cle73satellite]

Oh I understand that. Wut I'm wondering is if because its specific, its made to fit the original linkage. Idk maybe I'm just thinking too hard lol. I gotta look more into it though.

 

[TWX]

The linkage has to align to the side of the carburetor, and different types of carburetors have different widths and positioning fore/aft.

The linkage has to clear the intake ports, on a center-dump 2bbl they're lower than on a split-level manifold like many 4bbls have. Also 4bbl manifolds usually have larger ports to have to clear.

 

[dana44]

That's right, The linkage location for a 4bbl is in a physical location than the 2bbl, but the bracket to hold the two will work.