LD340 vs LD4B Differences?

[AlaskaJeff]

IF you were getting one of these manifolds which one would you choose and why? Both are the older castings with the CHRYSLER number stamped on them. They look Very similar, but I'm sure someone who
has used them both knows the differences and which is better for certain applications.

 

[Locomotion]

Basically, the LD4B is designed for smaller, milder LA engines -273-318 - and has smaller ports while the LD340 is for bigger and more modified LA engines - 340-360. But there is no reason why someone can't use either one if whatever size LA being used has the appropriate mods for the particular application. (i.e.: LD4B on a 340/360 for a mild street build and/or fuel mileage for everyday driving or LD340 on a 273/318 with matching larger ports and higher rpm use.) You just gotta keep the overall combo right so everything works together.

The ones in the photo are both modified for use with a Thermoquad. They originally came with a square bore carb pad.

 

[AlaskaJeff]

Basically, the LD4B is designed for smaller, milder LA engines -273-318 - and has smaller ports while the LD340 is for bigger and more modified LA engines - 340-360. But there is no reason why someone can't use either one if whatever size LA being used has the appropriate mods for the particular application. (i.e.: LD4B on a 340/360 for a mild street build and/or fuel mileage for everyday driving or LD340 on a 273/318 with matching larger ports and higher rpm use.) You just gotta keep the overall combo right so everything works together.

The ones in the photo are both modified for use with a Thermoquad. They originally came with a square bore carb pad.

Good info, thanks. I currently have the pictured LD340 on my mildly built 360. At least the porting job on mine is cleaner that the LD4B I guess it's where it's supposed to be.

 

[pittsburghracer]

I put an LD4B on the 360 I built for my 1976 dodge van that I towed with. I had a smallish cam, J or X heads, headers, and a 650 Holley and ran great. But knowing what I know today it would be an LD340.

 

[gzig5]

My 340 had a LD4B on it when I bought it. Car ran well with it. Butt dyno did detect a slight pickup when an Air Gap was installed with the same carb, but it wasn't a huge difference due to stock cam.

 

[crackedback]

Ports are reversed on the LD4B and no coil mount bosses.

Either works fine on a SB. 4b's are usually a bit less expensive than the 340.

 

[toolmanmike]

Yep LD4B is made for 66 and newer 273 and 318's. Smaller ports and of course it will work on 340-360.

 

[toolmanmike]

Ports are reversed on the LD4B and no coil mount bosses.

Either works fine on a SB. 4b's are usually a bit less expensive than the 340.

Why do you think they did the port reversal thing?

 

[1WildRT]

Back in the day I owned four LD340's, one was stock, one just had the divider wall cut down, one was modified to accept a Thermoquad & one was hogged out by a local racer.. It had a Chrysler pt# so it must have been "stock".....

They all worked pretty well, I actually ran the one with the Thermoquad mod more that all the others combined... I had a Tquad that just worked... It spanked a few stout big blocks & pulled decent fuel mileage..

I also had one LD4B... Probably should have tried that one but I was more into going fast than the best low RPM torque..

I swapped more cams, carbs & intakes on that car than all the other cars I owned...

Funny thing, Edelbrock flipped the upper & lower planes between the two manifolds... Always wondered what they were thinking...

 

[George Jets]

LD4B

 

[cudamark]

IF you were getting one of these manifolds which one would you choose and why? Both are the older castings with the CHRYSLER number stamped on them. They look Very similar, but I'm sure someone who
has used them both knows the differences and which is better for certain applications.



View attachment 1716019338

View attachment 1716019339

Your 4B has been modified. Stock it would have two oval ports for a square bore carb. The LD340 is made for a spread bore carb. As mentioned, the port sizes are different with the 4B being smaller. Coil mount and choke pad are two other differences. The best choice would depend on which heads you're using and performance level you desire.

 

[toolmanmike]

This one doesn't have a choke provision.

This one with the Mopar part number does.

 

[crackedback]

Both of those intakes in the first post have been modified.

LD340's were square bore.

That OEM notch in the plenum separator is for a 3 barrel Holley, secondary throttle plate clearance.

 

[JDMopar]

Edelbrock never made an LD4B or an LD340 in spreadbore configuration. If you see one like that, it has been modified. Nothing wrong with that, but they never came that way.