Carburetor from 2 to 4bbl


is it posible to Change the small caruretor to to big one ?
what is to make to Change it to the 4bbl carburetor.
my Mercury cougar conv has an 2 bbl Carb with 178 HP , the 4 bbl has 250 HP .
if the effort is not to much i´d like to Change it.

greetings from Germany, tom

On a 351 Cleveland engine? It isn’t that simple.
Factory 4V engines had different cylinder heads, exhaust manifolds, along with the intake and carburetor. Hi octane fuel, cam and dual exhaust also helped increase the HP to that advertised number.

Tom, if you are looking to easily get more power from your 2 bbl engine, you may want to consider removing the original carburetor and replacing it with a 500 cfm 2 bbl from Holley - model 4412C. If you do this swap and go from single exhaust to dual exhaust, you will add about 25-30 hp from what I’m told. I’ve done this on a 70 cougar with 351 2 bbl Windsor and a 72 mustang with 351 2 bbl Cleveland. In both cases I was very happy with the results. John

You could go with the Edelbrock Performer 351c 2v intake, or the 351c Performer RPM air gap for the 2v engine. Both are for the 2bbl Cleveland heads. From there, a 600 cfm four barrel, and dual exhaust would be a good upgrade. The Holley would net you the auto trans kickdown. The 500 cfm two barrel is a good upgrade on the cheap, but you will find more with a decent intake, small four barrel, and dual exhaust. If it were me, I would upgrade to a mild performance cam while I had the intake off, since you would already have the intake off. For a mild engine, even the performer plus cam would be decent, but a mild comp XE grind like the 256, or 262 would be a good one for an other wise stock car and higher rear end gears 2.70-3.25. The comp 268H is another good one, and responds well to other upgrades. Remember, the 2bbl heads are designed more for velocity (torque) than total airflow, so don’t go wild if you DO decide to upgrade the cam. Recurving the distributor is a great way to find horsepower. If you decide to go that route, let me know and I can help you with that as far as procedures go.

I just put a performer 289, summit dual feed 600cfm carb, and already had installed a comp XE256 along with 1 5/8" full length headers, as well as a Flamethrower Distributor. I can tell you that the intake and carb really woke my engine up. It now pulls to where the cam does, and added a LOT more torque off the line as well. Keep in mind that I recurved the distributor to work with the rest of the combo.

You can do a carb and intake swap pretty quickly and still do a nice clean job so don’t get intimidated. It’s not a lot of work. Oh yeah, the Summit carb works well and also has the auto trans kickdown.

So two options:Quick and super easy? Holley 500 two barrel. A tad more involved, but still easy? Edelbrock Performer and 600 carb. Just be sure that if you go this route, the 4 BBL intake you select is for the 2 BBl heads. I believe that Offenhauser still makes a 4 BBl intake for 2 BBL heads as well.

Here are a few suggestions:, www.summit,

They will allow you to search by engine so you can search 351 Cleveland 2BBl and find a four barrel intake for your 2 BBL heads. You can also do an eBay search and find a ton of 2 BBl Cleveland four barrel intakes. Even though the 2 BBl heads are no match for the 4 BBl heads, they still breathe pretty well and will handle a a decent size cam, and respond well to a good intake and carb. I had a 400 Cleveland, another 2 BBl engine, that ran like a scalded dog with a performer 400 intake, 600 Holley, crane 278 energizer cam, and milled heads (to up the compression). It also ran good with nothing more than a 500 Holley 2 BBl
And dual exhaust.