2 BBL to 4 BBL, any advantages?

[1981CJ5]

I am toying with the idea of changing my 2 BBL carb to a 4 BBL carb, what would I need to do and what would I need to get as far as parts? I know I will need the carb, but what other mods will be needed?

Will this increase my power?

Thanks

 

[Tug-n-pull]

What kind of motor are you talking about? tug

 

[Bounty__Hunter]

And what carb do you currently have?

 

[Joopin]

if you upgrade from a 2BBL to a 4BBL on any engine it will have an increase in horsepower. How much will depend on the engine and its condition and componets. One thing you absolutly need for the upgrade is a new intake manifold and since you are replacing that, it would be a good idea to get a spacer to go inbetween the carb and manifold. This will give you an increase in power as well... the air has a longer distance to travel into the manifold creating a "ram air" kinda thing. Don't go too big or you wont be able to close the hood!
One thing I have always been told is when adding stuff to an engine is to do the top and bottom at the same time, especially on an older engine. If you put a new carb and stuff on top, it may increase strain on the bottom of the engine... crankshaft etc...
If you do go through with this another good idea is to get a better camshaft and timing chain... this will really boost your power when paired with tthe new carb and manifold!

 

[1981CJ5]

have the stock 258 I6, with the Carter BBD. The Carter has been running well, no problems with stalling, good idle. Just looking for something to add a little more power.

 

[Bounty__Hunter]

Most 4barrels likely move too much CFM for the 4.2L in stock trim. I'd install a Motorcraft or Weber. Clifford Performance offers the 4bbl intake for the 4.2L, but it's usually intended for use with a high performance package such as head work, larger cam, perf. exhaust, etc.

 

[far_right]

I would try a weber, or simular (sp) first... a 4bbl is a little too much cfm for a stock 258 like bounty said

 

[Tug-n-pull]

Just installed the Motor Craft 2150 2 BBL in place of the Carter and Wow I love the change. I now have all the carb I feel I will ever need and it was half the price of the webber. Great on angles and the rpm range is much higher thus more hp. Go to changing all the manifold and other stuff you will need it is going to get a little very costly. Tug

 

[skyjeeper]

i've got an offenhauser 4bbl intake and eddlebrock 600cfm performer carb on my 258. it was quite a bit too much untill i put really small jets and large needles with stiffer springs. it runs decent now (idle). it does have a noticeable increase in power (i put headers and a cat back exhaust in at the same time).

there is a calculation:


(max RPM) X (CID)
3456


so... a 258 with a max rpm of say 5k...


(5000 RPM) (258)
3456



which comes out to 373.something CFM