performer RPM air gap v.s ported LD4B

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Dart360Custom

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Ive got a LD4b on my 360 that has been port matched for 4 brl ports and was wondering if it would be worth swapping to an rpm airgap in terms of power and function.

here is the specs.

74 ish 360

.030 trw flattops

block zero decked

mid 70's heads that have been ported to 4 brl intake sizes and the exhaust took as far as i felt safe.

mopar purple shaft "assuming"(.509 lift)

700 double pumper


car has 3.55's and a reverse manual 727

would it be worth swapping intakes?
 
If you were running 340 or 360 heads, you had the big ports already. Isnt the LD4B the 340 intake? It would have those ports anyway. In terms of back to back testing, I havent done it. But as I recall, a few guys did, and the RPM and RPM air gap (same basic designs) were tops for dual plane intakes. The LD4B was very good for it's day, and still a good choice for sneaky stock-type looking intakes, but the RPM will beat it all across the board.
 
moper said:
If you were running 340 or 360 heads, you had the big ports already. Isnt the LD4B the 340 intake? It would have those ports anyway. In terms of back to back testing, I havent done it. But as I recall, a few guys did, and the RPM and RPM air gap (same basic designs) were tops for dual plane intakes. The LD4B was very good for it's day, and still a good choice for sneaky stock-type looking intakes, but the RPM will beat it all across the board.
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I think the LD4B is for late 273 & 318 heads. Still has the smaller ports. The LD340 is the one with the larger ports.
 
The ports of the LD4B are smaller than the LD340 or the Performer. Gasket matching at the intake/head interface will not change the restriction - so I would say yes, you will see/feel a noticeable improvement with your combo.

I had the LD340 on a fairly stout 340 and changed to an Airgap and found no appreciable difference. In your case I believe you will. You might also think about going with the RPM Performer if you do much driving in cooler weather as the Airgap takes ±10 minutes to warm up enough to let some heat to the carb.
 
I cant remember where I read it. But if you flip both intakes, you can see that the RPMS runners are more individualized towards each cylinder, whereas the LD4B's are not. Apparently, this makes a difference too. I would take the RPM. But if you a nostalgia kinda guy, thats when I would get the LD4B.
 
mikedevore said:
Lets see here, 30 year old tech vs modern tech. HMMM
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Are you insinuating parts over 30 yrs old are useless? worn out? past there prime? etc. I :protest: that insinuation .
 
Theres a difference in power between the LD-340 and the RPM. It's just that you really do not feel it the drivers seat, but you gotta see it on the dyno.
 
Thanks for the clarification...I can never remember aboutt he small port versions...lol.
 
Nah, there's two of them. There is the 318/360 which is the small port, and theres the 340/360, which is the large port.
 
Ive only seen the 318/360 one. The stock 340 intake is better then the performer any ways.
 
some folks on this thread are indicating that there's "no appreciable difference" in performance from the ld340 to the rpm air gap. i made this swap on my 340 (10.5 comp., mp .557 cam, 750 holley), and i can tell you the air gap made a HUGE difference.
get it, you won't be disappointed.
my 2 bits
 
moper said:
Nah, there's two of them. There is the 318/360 which is the small port, and theres the 340/360, which is the large port.
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What intake is this Moper?
 
Hi Bloke's,
As I understand the Edelbrock Performer manifolds!

#1. Edelbrock Performer (small port) for 273/318.
#2. Edelbrock Performer RPM (large port) for 340/360.
#3. Eledbrock Performer AirGap (larger port) for 340/360.

I think that covers the current Edelbrock Performer offerings at least in Australia.

The Edelbrock LD4b is again small port for 273/318.
the LD340 is larger port and the runner layout is totally different to the LD340.

my 2cents
 
318ute got it right. performer is small port for 318 and everything else is large port.At least in eddy flavors.
 
I up graded to the air gap and it was like day and night. There is a little less in the low rpm than the stock but then it's on with more pull longer and higher without fading. The more you give it, the more it wants and I run a 650 holley on my s/b with it. I love it, a good investment.
 
moper said:
Rumble, I was talking about the Edelbrock performers...
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Theres a small port and large port performer?
 
Yup. However, I think they may have eliminated one. I was just surfinga round...I can see the small port Performer, p/n 2176 (non EGR) and p/n3176 (EGR), both are listed as "318/360" with the smaller ports. No other larger port Performers are listed. The next step up is the RPM. That has the larger 340/360 sized ports. So I'm thinking they may have streamlined things. But I'm sure I've had small and big port Performers in my possesion at the same time...lol. I do know the port castings were identical, they just machined them to the larger port size. I havent bought one in a while.
 
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