84 318, stock Holley 2bbl setup.

Was wondering if I'd notice a good bump in power if I dropped a 4bbl intake and carb onto it or if the heads were too restrictive to bother?

I have the 440 for this thing but it might be a while till it makes it in and I have a friend with the 4 barrel setup cheap.

 

i don't know why you would want to put a 4 bbl on there. sure you gain a bit of horse power but these truck were not designed to go fast they were design to haul. the 2bbls are perfect for the 318 and that is why they came from the factory with a 2bbl.

 

Best bang for the buck is headers. A 4 barrel will give slightly more power if you are putting your foot in it. If you are putting your foot in it you will also notice a plunge in gas mileage with a 4. If you drive like grandma you could notice a slight increase in mileage with a 4 barrel.
Bottom line is it usually takes a 4bbl, headers and a matching cam at a minimum to get a good bump in power from these trucks. They were made for longevity and not performance.

 

I know a mechanic who insists that a 4 barrel only gives you more power at high RPMs. He put a large V8 in a Jeep pickup and put a small 2 barrel carburetor on it. He said at lower RPMs (normal driving as opposed to high RPM racing) you actually get more power from a small carburetor with the throttle open then with a large carburetor pulling more vacuum through a mostly closed throttle.

He also said with a small carburetor you cannot get high RPMs. But face it how often do you want 4000 or more RPMs?

 

Well my truck is awful... it has highway gears so accelleration is painful. My 3.9 V6 in my D100 was WAY faster!

 

sound like what you need to do is find some better gears for your truck. i would keep your old gears for when or if you ever get that 440 in there. 440+highway gears= lots of fun and speeding tickets.

 

I would say spend your time and money on your 440 and get it where you want it.

 

Yah, I'll just wait for the 440 I suppose.

I have no idea what gears a 84 D250 camper special would have (8-lug, HD suspension) but it seems to just keep accellerating (slowly) on the highway!

 

I am not trying to dispell his experience, but a discussion of area under the curve would be critical here. I do not have the answer, but peak numbers are not always a telling statistic. I guess the question would be, does a 4 barrel allow the engine to maintain more or less torque over the intended operating range than a 2 barrel. If it does not do so, then it is unnecessary.

 

It doesn't matter what carb you have on the truck, as long as the settings are correct. If your 2bbl is to small, you will lose power, and vice versa, if your 4bbl is to large, you will lose power. There are 2bbl carbs out there designed for 700cfm, although I wouldnt put them on a 318! I think the magic number for these motors with the stock heads would probably be 600cfm Edelbrock/Holley, whatever you prefer. Might have to mess with the jetting, but thats it, not 2 vs 4, but rather flow vs capability. It was stated earlier that they came from the factory with 2bbl carbs for reliability, thats not true, remember what was going on when these trucks were made, the gas wars! Most consumers avoided the 4bbl, due to the Rumors of lower gas mielage, and Mopar needed to sell trucks just as bad as anybody else, so if they could get more mpgs out of the motors, that made for an easier sell at the dealership. I am a GM guy, slowely being converted to a Mopar guy, and i know for a fact that a quadrajet (4bbl) will get better MPG than a 2bbl, aas long as you keep your foot out of it, something most people cant do! I have driven a 73 Cuda with a 318 in it, that was a damn fun and fast ride, so these motors can be made to perform!