318 Poly 2bbl to 4bbl advice

Fishfan

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Hi folks, long time no see.

I've decided that I'm finally going to convert my 66 Polara with a 318 Poly engine to a 4bbl carb set-up. My rationale, in case you're interested (though I've made up my mind) is that my mileage already sucks, so a little more fuel consumption isn't going to bother me to get what I perceive to be the benefit. That benefit being a more "tune-able" carb and more consistency. After my questions, below, I'll tell you what my journey has been with the 2bbl set-up.

I already have intake manifold for 4bbl. I bought it on Ebay a few years back and never followed through. It's a cast iron manifold, presumably from a truck. I could not find the discontinued Weiand manifold anywhere.

So, here are the questions. Has anyone here done a similar swap? What are the pitfalls. Anything I should know? Clearance issues with the new carb/air cleaner? Which carb should I get? Why?

The guys at the shop I used to use were hot on FiTech but it seems too rich for my blood and unfortunately I've been down too many rabbit holes with them on this car. My instinct tells me to go basic.

Now, why I don't like my 2bbl set-up. It seems to me that the Stromberg 2bbl carb is a fiddly thing. At one point, a mechanic I used to use swapped it out for a Holley but it was worse, so I had my old Stromberg rebuilt and put it back on. But eventually the fitting where the fuel line connected to it wore out and I ordered a rebuilt Stromberg from Summit Racing. But that one almost immediately came up with a leak. Plus there's the little issue that on the odd occasion I floor it, the car almost always lurches forward then hesitates to the point of almost stalling.
 
I would assume that it has the small bolt pattern mounting flange, like for a carter WCFB. If that is the case, You'll either use the WCFB or early AFB, or use an adapter to use a later model carb, which may limit your air cleaner options, due to height.
 
The Poly 318 block looks like a very strong block with more meat in the main bearing saddles than any small block Chevy ever had, period! Some pretty neat engineering in that motor, too, from what I've seen.

You'll probably need to find a 4bbl with the dual bolt pattern and THEN match the throttle bore holes in the manifold with a suitable carb of similar throttle bore sizes. Might end up with an Edelbrock AFB of 500cfm or so? With the stock cam, 600cfm would probably the completely top end of cfm ratings, I suspect, as the stock 4bbls were not nearly that big back then.

Seems like the Hot Heads people that do the early Hemi stuff might have something for the Poly 318? Just a thought.

For a somewhat period correct look air cleaner, the repro '68 Road Runner air cleaner can work pretty well, I believe. The crinkle paint finish would not be correct, but you might find a used one, put the vintage decals on the side, put some black satin paint on it (before the decals go on), and call it "good".

I understand the desire to not spend a lot of money when you don't really need to! I also know that you can try to make an older carb work when it's really past that point of being "serviceable". Summit and such seem to have carbs on sale right now, if that matters.

CBODY67
 
You need to look up the manifold casting number and find out what year 318 poly the manifold is for and then use the carb book to spec the appropriate carb. Many 318 Poly engines used the Carter WCFB rated at 520 CFM. This is a square bore unit.

Dave
 
You need to look up the manifold casting number and find out what year 318 poly the manifold is for and then use the carb book to spec the appropriate carb. Many 318 Poly engines used the Carter WCFB rated at 520 CFM. This is a square bore unit.

Dave
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Casting number is 2206384. I believe it's an AFB carburetor. Today that's the Edelbrock 1405 (manual choke) or 1406 (electric choke), right?
 
I converted a 68 Polara 383-2 car to a 4-bbl years ago, put dual exhaust on it, and my mileage went up. Nothing negative about doing this Mod.
 
1968 Polara Poly 318????? 1968 USA Polara should have been the LA318. Completely different engines.

CBODY67
 
Casting number is 2206384. I believe it's an AFB carburetor. Today that's the Edelbrock 1405 (manual choke) or 1406 (electric choke), right?
No, today's carters will not bolt to that flange. I know that is WCFB flange and I think that the real early afb's used that small pattern. Read my first post.
 
1968 Polara Poly 318????? 1968 USA Polara should have been the LA318. Completely different engines.

CBODY67

My car is a 66 with a 318(A) engine. Hergfest, the poster I think you're referring to says he has a 68 Polara, but with a 383, he converted from 2bbl to 4bbl.
 
No, today's carters will not bolt to that flange. I know that is WCFB flange and I think that the real early afb's used that small pattern. Read my first post.
So is there a new (not rebuilt) carb I can put on that manifold?
 
Not to my knowledge, unless you use an adapter. What is wrong with a rebuilt carb?
 
Not to my knowledge, unless you use an adapter. What is wrong with a rebuilt carb?
You have any idea which adapter and carb combo I could use? I've been fiddling with rebuilt 2bbl carbs for a while, always with issues. I'd really like to have something like the Edelbrock 1405, new out of the box.
 
You have any idea which adapter and carb combo I could use? I've been fiddling with rebuilt 2bbl carbs for a while, always with issues. I'd really like to have something like the Edelbrock 1405, new out of the box.

Go with a 1406 with the electric choke. It should bolt right on to the square bore manifold.
 
The AFB that came OEM on my '67 Newport 383 was the small pattern with the smaller air cleaner base plate hole. Is that different than the WCFB (Will Carter Four Barrel) pattern? I would have suspected they'd be the same bolt pattern.

CBODY67
 
You have any idea which adapter and carb combo I could use? I've been fiddling with rebuilt 2bbl carbs for a while, always with issues. I'd really like to have something like the Edelbrock 1405, new out of the box.
If I were looking for one of those adapters, I'd check with hot heads down in Carolina. Hothemiheads.com. Very nice fella. I think his name is Bob.
 
The AFB that came OEM on my '67 Newport 383 was the small pattern with the smaller air cleaner base plate hole. Is that different than the WCFB (Will Carter Four Barrel) pattern? I would have suspected they'd be the same bolt pattern.

CBODY67
Different bolt pattern. Sometime in the late fifties or very early sixties it changed. I remember the AFB on my 58' 392 was smaller.
 
I suggest calling Bill Richardson in VA. Google Mopar Mecca. He built my poly stroker and he can will recommend or even supply a carb setup for you.
 
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