This again.... 4bbl on a 318 with a 2bbl

-
A

abcdefghii

Well-Known Member
Joined
Nov 14, 2024
Messages
105
Reaction score
97
Location
Northwest VA
Lurking over here because there's a good bit more information about 318's than I can find on any D150 forum.

I've read a bunch of threads here that putting a 4bbl on a 318 is entirely doable, despite having read on ram forums that it'll make my truck run like crap. However, the discussions here seem way more involved than simply "it won't work"

If I were to put a 4bbl intake and carb on my truck today, what's a readily available combo that would work well? Edelbrock LD4B looked to be recommended a lot on older threads, but I can't find any for sale. Is a factory 340/360 a solid option? Then we get into carbs, I'm not trying to convince myself the truck is a racer, but I'd also like some more power without spending a fortune.

The truck has factory AC which I plan to keep, EGR is blocked off on the current intake, I had a new exhaust installed a few weeks ago, it's a dual system with mandrel bends and 2.25" piping, it's got a billet Pertronix distributor and all new timing gear.

I'm sure when I figure out and buy a 4bbl set up, I'll then be looking at the linkages with a wtf look on my face, but that's something others have figured out countless times before.

Thanks.
 
4bbl will help the power on your truck, both part throttle and full throttle. I like 600 cfm's, dual plane intake that supports your accessories. You can use your current 2bbl linkage, with a small amount of creativity. I've done it a bunch.
 
factory cast iron 4bbl is a great manifold. edelbrock performer (just the plain ol' performer) is a fantastic upgrade.

both are plentiful and affordable and you can retain all of your factory things and stuffs.

carb keep it small, 500~625 carter/edelbrock afb or AVS2, or a small holley with vacuum secondaries.

the linkage and kick down stuff is important, search around and you'll see many threads on how to convert.
 
The LD4B would be a great choice, if you can find one, but they aren't cheap. There were some years of Diplomat/Gran Fury that came with a 4 bbl setup, but also not common. An Edelbrock 318/360 performer intake is a good choice, and much more common. What you need to be aware of is potential port mismatch, where the intake manifold ports are far larger than the cylinder head ports, this situation would somewhat defeat the purpose of adding a 4 bbl. What year is your truck and what heads are currently on it?
Linkages are a separate issue and there are solutions for this, including modifying the existing linkage, a Lokar cable for the transmission throttle pressure, or sourcing original pieces from later 360 4 bbl equipped trucks.
More information about your current combination will help answer your questions.
 
abcdefghii said:
Lurking over here because there's a good bit more information about 318's than I can find on any D150 forum.

I've read a bunch of threads here that putting a 4bbl on a 318 is entirely doable, despite having read on ram forums that it'll make my truck run like crap. However, the discussions here seem way more involved than simply "it won't work"

If I were to put a 4bbl intake and carb on my truck today, what's a readily available combo that would work well? Edelbrock LD4B looked to be recommended a lot on older threads, but I can't find any for sale. Is a factory 340/360 a solid option? Then we get into carbs, I'm not trying to convince myself the truck is a racer, but I'd also like some more power without spending a fortune.

The truck has factory AC which I plan to keep, EGR is blocked off on the current intake, I had a new exhaust installed a few weeks ago, it's a dual system with mandrel bends and 2.25" piping, it's got a billet Pertronix distributor and all new timing gear.

I'm sure when I figure out and buy a 4bbl set up, I'll then be looking at the linkages with a wtf look on my face, but that's something others have figured out countless times before.

Thanks.
Click to expand...
The LD4B is a great 318 intake and will work with AC. (many older aluminum intakes don't have provisions for the A/C compressor brackets) a 600 or 650 carb should work well. So would a spread bore/ Thermoquad type carb would be great.
 
if going for a cast iron, there are a couple thermostat locations (centered/offset)
depending upon the config of your truck, the offset one may clear the A/C better

and I have had great luck with the 600 vac sec Holley.
also did 2 - 4 adapter plates (for SB fords) because 4bbl intakes were unobtanium, and the holley was the only carb that would work. super forgiving to poor tuning, too
 
Putting a 4 barrel on a stock 318 will probably decrease gas mileage it isnt so much that it wont work theres just no gain with a stock cam and heads. Just my $ .02
 
IMG_20250109_041304_646.jpg


Stock intake manifold and camshaft.

Screenshot_20250407-182605_Gallery.jpg



Simple is Good...


.
 
missing linc said:
What you need to be aware of is potential port mismatch, where the intake manifold ports are far larger than the cylinder head ports, this situation would somewhat defeat the purpose of adding a 4 bbl. What year is your truck and what heads are currently on it?
Click to expand...

Duh... Completely neglected to write that it's an 81. The port mismatch is what I have read about a bunch saying it won't work due to the difference in size.

It's currently got what I assume to be the original factory heads on there. Long term, those might get swapped out, for for now that's what it has.

dr dodge said:
depending upon the config of your truck, the offset one may clear the A/C better
Click to expand...

Good point, it's currently got an offset thermostat. Something I'll have to keep an eye on when looking at intakes.

Dartswinger70 said:
Putting a 4 barrel on a stock 318 will probably decrease gas mileage it isnt so much that it wont work theres just no gain with a stock cam and heads. Just my $ .02
Click to expand...

I figured it'll decrease fuel mileage, but it's not a daily driver, so not the end of the world. I just don't want to end up with a crappy running truck.

George Jets said:
Simple is Good...
Click to expand...

Sorry, what am I looking at? Is it the factory 2bbl intake with an adapter and a 4bbl?
 
Dartswinger70 said:
Putting a 4 barrel on a stock 318 will probably decrease gas mileage it isnt so much that it wont work theres just no gain with a stock cam and heads. Just my $ .02
Click to expand...
A stock B&B 2 barrel is only 255-270 cfm. The Primary cfm of a 600 Edelbrock is 250-300. Keep your foot out of it and it might be ok. But then, why switch? Unless you need more. :thumbsup:
 
abcdefghii said:
Duh... Completely neglected to write that it's an 81. The port mismatch is what I have read about a bunch saying it won't work due to the difference in size.

It's currently got what I assume to be the original factory heads on there. Long term, those might get swapped out, for for now that's what it has.



Good point, it's currently got an offset thermostat. Something I'll have to keep an eye on when looking at intakes.



I figured it'll decrease fuel mileage, but it's not a daily driver, so not the end of the world. I just don't want to end up with a crappy running truck.



Sorry, what am I looking at? Is it the factory 2bbl intake with an adapter and a 4bbl?
Click to expand...
Take the port mismatch and throw it to the uttermost part of your mind, never to be remembered again on installing a 4bbl on the 318. And if you keep your foot out of the 4bbl's, I bet you pick up a tad of MPG. Your ability to tune it will determine how happy you are with the performance and gas mileage.
 

Every small V8 that I stuck on a 4 barrel ran better and got better mpg too. Now if you drive it like you stole it because of the increase in pep, then yeah, your mpg will suffer. I also went with an aluminum intake and headers on them.
 
For those interested in keeping their stock intake manifold and camshaft.

20260127_105153.jpg


Mr Gasket 2 to 4 Barrel adapter.
#1933

Available at Autozone, Advanceautoparts, and Summit Racing

Around $30

Runs and starts better than stock 2 bbl setup. No change in gas mileage. Added power from the secondaries when you want to use them.

Edelbrock 1406 600 cfm carbs are a good bolt on match for the 318s.

Keeps the stock head to intake manifold port match. Saves opening up the lifter valley to change intakes.

Works great for the daily drivers.

To each their own...


.
 
George Jets said:
Mr Gasket 2 to 4 Barrel adapter.
#1933

Available at Autozone, Advanceautoparts, and Summit Racing

Around $30

Runs and starts better than stock 2 bbl setup. No change in gas mileage. Added power from the secondaries when you want to use them
Click to expand...

This isn't the worst idea, at least initially.... I can put a 4bbl on there, figure out the linkage, figure out tuning a 4bbl and enjoy that for a while.

Then add a 4bbl intake and do it again.

Then add new heads and do it again.

And so on

Time to go scouting some classifieds to see how much a carb and intake might run me.
 
The Weiand stealth manifold is a near direct copy of the LD4B. What year of 318 do you have and what gears do you have in your truck. What are you planning on doing with your truck and how much performance gain are you looking for?
 
I'm a big fan of the stock cast iron intake and a Thermoquad on a factory motor. Use the Stealth intake, 340/360 4bbl cam, a set of 360 heads, and it'll run pretty darn good.
 
Garrett Ellison said:
The Weiand stealth manifold is a near direct copy of the LD4B. What year of 318 do you have and what gears do you have in your truck. What are you planning on doing with your truck and how much performance gain are you looking for?
Click to expand...

It's an 81, need to crawl under there to see if there's a tag on the rear end with the gear info.

As for goals and gains, I'm not looking for a massive increase (otherwise I'd be looking at engine swaps) it's a truck I use to cruise around town with, take to shows, haul stuff, it's not a garage queen by any stretch. Just looking for some improvement over the 120hp that it came from the factory with to give it a little more get up and go.
 
One additional thing to consider when you do a 2 to four barrel swap.
This may or may not apply to your truck, as I have found conflicting information on factory equipment in 1981 on the D150.
You need to determine if your 318 was equipped with the Lean Burn ignition/engine management system. It was in wide use by '81, but some trucks were exempt...
The control box was normally mounted on the air cleaner, although some trucks had it mounted near the inner fenderwell.
If you're not sure, look at the distributor. Does it have a vacuum advance cannister on it? If it does, you should be good. If it doesn't, then you have Lean Burn- and that system will need to be eliminated in order to run an aftermarket four barrel, since the factory used electronic feedback carbs with that system, and aftermarket and earlier four barrels will not work with that system.
A little more investigation is warranted here before you start ordering parts.
 
Right on it, Professor! I’d forgotten it’s not uncommon to see that lean burn ECU mess under hood on 1981 trucks. In this instance, it’s probably going to have 2.94 or (more often than not) 3.21 gears.
 
Garrett Ellison said:
Right on it, Professor! I’d forgotten it’s not uncommon to see that lean burn ECU mess under hood on 1981 trucks. In this instance, it’s probably going to have 2.94 or (more often than not) 3.21 gears.
Click to expand...
Yeah, the whole Lean Burn thing is normally something we like to forget about. But there's still some out there...
 
toolmanmike said:
A stock B&B 2 barrel is only 255-270 cfm. The Primary cfm of a 600 Edelbrock is 250-300. Keep your foot out of it and it might be ok. But then, why switch? Unless you need more. :thumbsup:
Click to expand...
when building dirt cars, did lots of chevies (tuning)
we had a guy that hand enlarged the bores of the stock rottenchester on his drill press and polish them,
they (his carbs) were way stronger out of the corner than 3/4 of the holleys,
and idled better, too

has anyone ever worked over a mopar 2bbl? best choice to start with?

just brainstorming

thinking of trying the carb for the/6
 
No lean burn, the previous factory distributor had a vacuum advance can and the Pertronix also has one.

The prior owner already removed what I believe to be a bunch of smog related stuff from the engine... The vacuum amplifier wasn't hooked up to anything, the carbon canisters in the passenger inner fender were all just there not connected.
 
You must log in or register to reply here.
-

Similar threads

318willrun
D150 with a RV 440, just to see what it will run
17 18 19 20 21
Replies
523
Views
14K
318willrun
318willrun
CudaRay
Swapping '69 273 with '84 318 Into My 1969 Dart
2
Replies
42
Views
2K
CudaRay
CudaRay
Righty
Timing light for Magnetic Module Ignition, settings for stock with a Holley 4BBL.
Replies
8
Views
543
Righty
Righty
C
1968 Dodge D200 with a 318 from who knows where
2 3
Replies
59
Views
2K
volaredon
V
7
318 from Down Under
Replies
20
Views
2K
4spdragtop
4spdragtop
Back
Top Bottom