LD340 intake is it still good after this modification

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davescuda

davescuda

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LD340 intake is it still good after this modification

Is this intake still good after the plenum work was done to it

thanks for the input.
 

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Kinda common for back in the day. Gave more top end RPM from what I remember.Still usable.
 
There should only be a small rectangle cut in to equalize the sides like the one you bought from me. This is as good as a torker in this condition. It can be welded back in. My son does this type of work all the time.
 
I never liked finding them like that.
 
Like stated earlier that plenum mod was only done to create a little higher power band. Manifold will still be fine to use.
Had an identical modded ld340 that was also gasket matched on the 340 in my 65 cuda when first purchased and it worked great.
Regret selling it.

Oldschoolcuda
 
It's usable, but like oldman said, you'll want to have just the one inch or so cut out of the divider.

Regarding the torker comment... I ran a torker 340 for a long time before I had cash to replace it... I don't know if there's ANYTHING you can do to an LD340 to make it as bad as a torker. I honestly felt bad when I sold it to a guy for $100.
 
It will be fine. That mod or a version there of is mentioned in the Mopar Racing manuals and improves RPM performance by another 500-800 RPM.
 
Oldmanmopar said:
There should only be a small rectangle cut in to equalize the sides like the one you bought from me. This is as good as a torker in this condition. It can be welded back in. My son does this type of work all the time.
Click to expand...

...the little rectangle cutout was for the old holley 3 bbl
i had a stock 69 340 dart with a torker and although i never
raced it at the track,that thing would melt tires (245 60's)at
will w / 3.55's....go figure
 
I thought the divider notch was for the old holley 3-barrell carbs? I agree on it still being fine and have also seen the mod mentioned before in the racing manual.
 
The old books say it is a mod for the kit car program designed for high lift cams. I think the lift number was high 5's or 600 lift areas. (AKA Big cams)
 
The small notch in the rear was not for mixing purposes or anything of the like. There was one reason only. So that the Holley 3 barrels of the time could open the secondary barrel.

If you look at any intake that had that notch, it is always an old one that was made when those carburetors were popular.
 
It will work fine especially if your up in the 400Hp + range and you want to spin it to 6k and more.
 
The factory cut is small for those 3-barrel carbs. The modification was to enlarge it to about 100% larger. Removing it in it's entirety is a reason to move on IMO. Unless it's a steal, you're going to pay to have it tig welded to fix that.
 
Moparperf said if U want more top end (and slightly less low end) cut the divider down some, not completely like that thing appears to be. I cut mine down about 5/8" and run a 1/4" gasket-runs strong from idle to 7000 with an old 750 AVS
 
I think it's fine too but wouldn't do it to a nice one...also I pulled an rpm air gap off my duster and replaced it with an old torker 340...went from 8.13 to 7.86....go figure that.
 
Ok Here's you answer. No there is nothing wrong with it! The usual modification is to mill this divider down to 1/2 in tall. What this does is give a better balanced flow at high rpm. It does work. It's an old mod. on this manifold.
 
Coffee&Cars said:
Ok Here's you answer. No there is nothing wrong with it! The usual modification is to mill this divider down to 1/2 in tall. What this does is give a better balanced flow at high rpm. It does work. It's an old mod. on this manifold.
Click to expand...

You say 1/2 inch but it is all the way. Does it take away RPM's or add more?
 
FWIW, the MP book says to mill it down to 3/8ths and round it off on the edges.
When I mention the cam lift, AKA "BIG", of course you should have realized that the duration also goes up, way up. Consider the time of the intake, publication and the cam specs of the day. Often a 1.6 rocker was needed for serious lift. Even with cams at or above 250@.050, lift wasn't as it is today.

Cams of this size don't have a streetable bottom end like the uncut intake is designed for so the low end is largely ignored. From the MP stable of Purple cams, you would be looking at a 296/.557 w/1.6 rockers (.594 lift, lash not included) to take advantage the modded intake the way MP puts it in print.

250@.050 w/.594 lift is at the outer end of a street driven cam for most.
Though Lord knows, far be it from me to tell you what cam is to big for the street.
How did that one member put it in his sig? "The cam isnt to large, you just don't have enough motor!" Or something like that???
LMAO!

Yea yea yea, I know some guys here run a cam similar in spec and a AG intake in there rides.
 
I did this same mod to my 340 duster with .500" lift cam, 9.7 comp with a thermoqaud and it was incredible what a difference it made. Car ran consistent 12.20's at 108 mph. Before this mod the car fell on it's face at about 4800 rpm.
 
duster426ci said:
I did this same mod to my 340 duster with .500" lift cam, 9.7 comp with a thermoqaud and it was incredible what a difference it made. Car ran consistent 12.20's at 108 mph. Before this mod the car fell on it's face at about 4800 rpm.
Click to expand...

Did you cut it all the way down or leave the 3/8 to 1/2 inch that they recommend?
 
I'd buy that intake all day if the price was right. Cutting the divider out doesn't turn it into a pro stock tunnel ram. :)

100 or less yes

More than that... not so much
 
duster426ci said:
I did this same mod to my 340 duster with .500" lift cam, 9.7 comp with a thermoqaud and it was incredible what a difference it made. Car ran consistent 12.20's at 108 mph. Before this mod the car fell on it's face at about 4800 rpm.
Click to expand...
correct now your drawing from all 4 bbl's instead of two.
 
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