Why the changes to the LD4B?

[Hyper_pak]

Does anyone know why the changes were made to the LD4B intakes? Which one was cast first, no MOPAR part number, or the MOPAR number. The differences I see for sure are the CARB Flange area and of course the MOPAR PN. Also I have 2 different versions, were there even more variations? Maybe it has been discussed before, I couldn't find a thread on it.

 

[MrJLR]

Duel plane and single plane....?

EDIT.....yes - I get it....I was wrong.....lol

Jeff

 

[brian6pac]

Someone milled out the divider, they came with a notched out divider in the rear for a holley 3 bbl.

 

[RustyRatRod]

Duel plane and single plane....

Jeff

Those are both dual plane, sir.

 

[toolmanmike]

The non Mopar part number intake was sold at parts stores and speed shops as well as mail order. The Mopar part number was sold through Mopar parts departments at dealerships. FYI, I just heard the LD340 was banned in NHRA.

 

[xLURKxDOGx]

The non Mopar part number intake was sold at parts stores and speed shops as well as mail order. The Mopar part number was sold through Mopar parts departments at dealerships. FYI, I just heard, and don't know if it's true that NHRA had banned the LD4B in stock classes.

I thought it was only the ld340?

Jake

 

[toolmanmike]

I thought it was only the ld340?

Jake

I heard that scuddlebutt from a couple avid racers but they were Chevy guys. Lol

 

[toolmanmike]

I thought it was only the ld340?

Jake

Yes it was the LD340. NHRARacer.com - NHRA Tech Department makes changes to the engine blue print specifications

 

[d55dave]

While most LD4B have 318 port sizes I recall reading that some bad the 340/360 port size and were very similar to the LD340. Do both of those intakes have the same port size?

 

[6pk2goDemon]

Interesting...My LD4B has the carb flanges like the pic on the right with the Mopar parts #s

 

[RustyRatRod]

Interesting...My LD4B has the carb flanges like the pic on the right with the Mopar parts #s

View attachment 1715168105

The one on the right in the above picture has been modified by removing the center divider. Yours has not. This means there are at least two different styles of the LD4B. I have seen a few people say there was a spread bore (Thermoquad) version made of both the LD4B and LD340. Although I have seen several modified, I have never seen what I could confirm as a factory spread bore version of either intake. IMO, the carburetor flange like the one you have, C, was probably the early style and they went to the later style, like the picture on the left above, to improve carburetor sealing.....but that's just a guess, as these were made such a long time ago. It's anybody's guess.

 

[67 gt]

I didn’t know there was 2 carburettor base types so I went out and took a couple of flicks of mine , no Mopar numbers . Worked great on the 273 ! No use at the moment as I’m building the stroker but I do have a lot of hop up parts for that little 273 if I ever get another project.

 

[d1970]

I was told years ago they milled the center divider of a dual plane intake to help balance the air signal to the carburetor for the air/fuel mixture at higher rpms.

 

[MrJLR]

Those are both dual plane, sir.

I guess ive been misinformed. ....lol.....
Now i need to read up on that......

Jeff

 

[MrJLR]

Those are both dual plane, sir.

Dang.....even Google has misleading information on this.....

"A dual-plane manifold has a split opening in the plenum area directly below the carburetor mounting pad. ... Single-plane manifolds have a single intake opening into the plenum and feeds all 8 cylinders directly."

So.....please help educate me?!!!

Jeff

 

[toolmanmike]

A single plane has a open plenum to the runners. A dual plane has 2 different plenum floors. One side feeding 4 cylinders and the other the remaining 4.

 

[toolmanmike]

This link might explain it differently and has some good pics. Intake Manifolds: Single Plane or Dual Plane?

 

[diymirage]

Looks to me like the pennie pinches found a way to save some material of the carb pad on the right hand manifold

Same reason they put smaller heads on bolts nowadays, less raw material = higher profits

Dang.....even Google has misleading information on this.....

"A dual-plane manifold has a split opening in the plenum area directly below the carburetor mounting pad. ... Single-plane manifolds have a single intake opening into the plenum and feeds all 8 cylinders directly."

So.....please help educate me?!!!

Jeff

Google oversimplified it and used generic term to describe it (kinda like saying people with boobies are women, well, Bruce Jenner has boobies and he isn't a woman)

The one on the right has the divider milled down for better performance
It still has 2 planes, each of which feeding 4 cylinders

 

[davescuda]

I believe they made more than 2 variations of the LD4B. The one on the left I believe is one of the last runs.
I also read that the LD4B has the same runners as the LD340. The LD4B just has more material to accommodate the 318 and the 273. You just have to open up the runners size to the LD340 and supposable should flow the same. Has anyone else done this? I wondering if the NHRA guys will be buying these and porting them out.

 

[RustyRatRod]

Dang.....even Google has misleading information on this.....

"A dual-plane manifold has a split opening in the plenum area directly below the carburetor mounting pad. ... Single-plane manifolds have a single intake opening into the plenum and feeds all 8 cylinders directly."

So.....please help educate me?!!!

Jeff

Jeff, look closely at that first picture of the manifold on the RIGHT. Look at the plenum FLOOR. Do you see how the floor on the right side is lower than the floor on the left? That's a dual plane. THAT is the split opening into the runners. It does not matter that someone milled the divider out. That does not change the design of the manifold. If four runners are on a different plane than the opposite four runners, it's a dual plane. If all eight runners are all on the same plane, it's a single plane. There are a few exceptions such as Offenhauser's 360* manifolds.....however they are simply a modified single plane.

 

[MrJLR]

Jeff, look closely at that first picture of the manifold on the RIGHT. Look at the plenum FLOOR. Do you see how the floor on the right side is lower than the floor on the left? That's a dual plane. THAT is the split opening into the runners. It does not matter that someone milled the divider out. That does not change the design of the manifold. If four runners are on a different plane than the opposite four runners, it's a dual plane. If all eight runners are all on the same plane, it's a single plane. There are a few exceptions such as Offenhauser's 360* manifolds.....however they are simply a modified single plane.

Thank you!
That makes sense.....I guess I never truly understood the difference!

Jeff

 

[crackedback]

Looks to me like the pennie pinches found a way to save some material of the carb pad on the right hand manifold

And we have a winner!

Change the design, save a little material. Have enough material after 50 manoflids to make a free one.

 

[toolmanmike]

I believe they made more than 2 variations of the LD4B. The one on the left I believe is one of the last runs.
I also read that the LD4B has the same runners as the LD340. The LD4B just has more material to accommodate the 318 and the 273. You just have to open up the runners size to the LD340 and supposable should flow the same. Has anyone else done this? I wondering if the NHRA guys will be buying these and porting them out.

The LD340 has different runner configurations. I eventually will find pics in threads that compare the port sizes between the two.

 

[RustyRatRod]

And we have a winner!

Change the design, save a little material. Have enough material after 50 manoflids to make a free one.

Free?

 

[rumblefish360]

And we have a winner!

Change the design, save a little material. Have enough material after 50 manoflids to make a free one.

That is super believeable!

Looks to me like the pennie pinches found a way to save some material of the carb pad on the right hand manifold. Same reason they put smaller heads on bolts nowadays, less raw material = higher profits

Google oversimplified it and used generic term to describe it (kinda like saying people with boobies are women, well, Bruce Jenner has boobies and he isn't a woman)

The one on the right has the divider milled down for better performance
It still has 2 planes, each of which feeding 4 cylinders

IMO, I think, key word, think, that the carb flange got thicker as the years went on for better/best carb to intake sealing. I don't think it was made thinner as time went on. Just IMO. But I do think I'm correct.

The non Mopar part number intake was sold at parts stores and speed shops as well as mail order. The Mopar part number was sold through Mopar parts departments at dealerships.

BINGO!!!!

I was told years ago they milled the center divider of a dual plane intake to help balance the air signal to the carburetor for the air/fuel mixture at higher rpms.

Yes, kind of. It isn't exactly the mixture. The intake itself has to be made or modified correctly for a good balance of air flow and the carb has to be tuned correctly for a good air fuel mixture. If the intake design isn't all that good, some cylinders will have a better air fuel mixture than other cylinders. Absoulte runner air flow (CFM) doesn't mean it has a good quality of fuel going into the cylinder with it. Really, the divider modification, was a legal "Cheat" to do. It has balance properties, but it also has the intake act a little more like a single plane intake. This "Trick" is in the DC/MP books. It is also suggested to use with bigger cams. As they state it, (IIRC) .600 lift cams. Which back in the day, when the book was written, would be a ratherly large cam! Duartion @ .050 was normally around 260* and greater. Unlike today, you can get smaller cams with big lift.