Trying to understand Manifold choices

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AZ-Nick

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I purchased a 69 swinger 340.
I hope that this doesn’t sound too stupid to you but I am trying to drive myself crazy sometimes when I should leave everything as it is…..

I am trying to read as much information about the 340 so I have a better understanding on what works and what doesn’t work.

I have read over and over again that the stock manifold was or is a very good manifold and the only downside to it is the weight it has.

The next best option was the LD3(spelling?) and the RPM Air Gap, both flowed just as good or just bit better, and definitely much lighter.

So I am trying to understand why would someone install a plain Performer intake over the stock intake, it has to be only because of the weight and or cost. I don’t believe that it flows as well as the original intake!

Nick
 
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AZ-Nick said:
The next best option was the L3d (spelling?) and the RPM Air Gap, both flowed just as good or just bit better, and definitely much lighter.
So I am trying to understand why would someone install a plain Performer intake over the stock intake, it has to be only because of the weight and or cost. I don’t believe that it flows as well as the original intake!
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Weight savings over the iron. Plenum style. We are about to put a Performer on a Barracuda's 340. That was chosen over the Air Gap due to the climate being more temperate and the car is driven when it's pretty cold out.

I love my LD340. Great for a cruiser or mild street/strip.
 
the stock manifold was and remains a very good manifold. the LD340 is slightly better in the upper RPM range, but on an otherwise stock or warmed over motor isn't worth much more over a stock intake.

a performer would likely be used if somebody wanted to run a different carb and didn't want to modify an LD340, or couldn't find/afford one.

the RPM is bascially the next generation of the LD340.

all are good choices, as are the offerings of weiand and to some degree offy.
 
Thank you everyone, for your answers, I can see that there could have been different reasons.
 
The base Performer (not talking the Performer RPM/Air Gaps here) probably would get beaten by a factory intake on the dyno- their ports are kind of a compromise between the 273/318 size and the 340/360 size, so Eddy could offer a "One size fits all" manifold for the SBM. It was intended as a replacement for the LD340 (and the D4B/LD4B), but doesn't really live up to either of them, in my humble and somewhat biased opinion. The only reason I would run one is if I didn't already have a 4 bbl. manifold, and just wanted a nice street 4 bbl., which they are. Although I'd be hard pressed to pick one of those over, say, a Weiand Stealth. Just personal preference there, though. The Performer AG would be a different matter entirely.
 
Professor Fate said:
The base Performer (not talking the Performer RPM/Air Gaps here) probably would get beaten by a factory intake on the dyno- their ports are kind of a compromise between the 273/318 size and the 340/360 size, so Eddy could offer a "One size fits all" manifold for the SBM. It was intended as a replacement for the LD340 (and the D4B/LD4B), but doesn't really live up to either of them, in my humble and somewhat biased opinion. The only reason I would run one is if I didn't already have a 4 bbl. manifold, and just wanted a nice street 4 bbl., which they are. Although I'd be hard pressed to pick one of those over, say, a Weiand Stealth. Just personal preference there, though. The Performer AG would be a different matter entirely.
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I can understand that.
I have an original 340 manifold sitting on the shelf and I am tempted to install it on the 340 if it is compatible with a Edelbrock carb which is currently on the Performer manifold or purchase a different brand carb
 
AZ-Nick said:
I purchased a 69 swinger 340.
I hope that this doesn’t sound too stupid to you but I am trying to drive myself crazy sometimes when I should leave everything as it is…..

I am trying to read as much information about the 340 so I have a better understanding on what works and what doesn’t work.

I have read over and over again that the stock manifold was or is a very good manifold and the only downside to it is the weight it has.

The next best option was the LD3(spelling?) and the RPM Air Gap, both flowed just as good or just bit better, and definitely much lighter.

So I am trying to understand why would someone install a plain Performer intake over the stock intake, it has to be only because of the weight and or cost. I don’t believe that it flows as well as the original intake!

Nick
Click to expand...
IF the rest of the 340 is stock, the stock manifold is about as good as it gets. Even if it's just had a couple of mods, like a mild cam and headers, the stock manifold is hard to beat.
 
Sometimes there is no rhyme or reason to why people do their own "upgrades" over stock setups that work well..

Sometimes it's just shiny and new.
 
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AZ-Nick said:
Thank you everyone, for your answers, I can see that there could have been different reasons.
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Oh yea. When it comes to performance, the OEM intake is very good but that is for what it is and when it was made and why they made it that way. Everything in context and with the understanding of when it was made and the reasoning behind the design. The OEM has to be rock solid for decades, pass all laws of the time, etc…

The after market is free from this constraint. Only one goal in mind, more power. Leaving the constraints of the OEM allows for more rpm potential. Larger ports, raised carb heights, etc…

Edelbrocks LD-340 was there first and best dual plane of yesteryear. The rpm is now the crown owner. Ether are very good. It’s just a little hard to find the older one. Best with a new RPM.

The RPM is good to the mid 11’s for n the light weight car with all the supporting goodies. A cam up to around the 255@050 is about as large as the rpm likes, after that, you should be looking at a single plane intake manifold.

I’d only use a performer if I didn’t have an intake (and just did!) for the job the oem would do. While the weight savings is something everyone screams “It will net you a better at and more speed at the track!” ,which I can not argue, are you really at the strip enough to warrant the expenditure? It’s not really justifiable to me. Even more so when I see fellas running low 10’s and 9’s in the 1/4 mile, but that’s another and different story I’ll not dive into.

The oem intake is still good to use with small cams. Under 230@050 cam duration. While a rpm will make more power, does the expense warrant it for me? For you? Maybe down the line the rpm comes in. IMO, it would be a good idea, but on the cheap, you’re good with the iron. Consider it a $$$ savings for now.

Carb

The Edelbrock carb can be used with the oem intake, TQ intake as well. A 600 is fine enough for general street usage. A 750 would be better. There’s not a lot of power difference but there is a nice little gain in throttle power and pedal feel difference .

Holley or another Edelbrock is up to you. I really like the Edelbrock in the street, Holley at the track.
 
318willrun said:
IF the rest of the 340 is stock, the stock manifold is about as good as it gets. Even if it's just had a couple of mods, like a mild cam and headers, the stock manifold is hard to beat.
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That’s exactly what I am told it has, a mild cam, and yes it does have headers.
I think I will leave it alone for now and if I need to get into refreshing the motor then I will go one way or the other.
 
I’m
rumblefish360 said:
Oh yea. When it comes to performance, the OEM intake is very good but that is for what it is and when it was made and why they made it that way. Everything in context and with the understanding of when it was made and the reasoning behind the design. The OEM has to be rock solid for decades, pass all laws of the time, etc…

The after market is free from this constraint. Only one goal in mind, more power. Leaving the constraints of the OEM allows for more rpm potential. Larger ports, raised carb heights, etc…

Edelbrocks LD-340 was there first and best dual plane of yesteryear. The rpm is now the crown owner. Ether are very good. It’s just a little hard to find the older one. Best with a new RPM.

The RPM is good to the mid 11’s for n the light weight car with all the supporting goodies. A cam up to around the 255@050 is about as large as the rpm likes, after that, you should be looking at a single plane intake manifold.

I’d only use a performer if I didn’t have an intake (and just did!) for the job the oem would do. While the weight savings is something everyone screams “It will net you a better at and more speed at the track!” ,which I can not argue, are you really at the strip enough to warrant the expenditure? It’s not really justifiable to me. Even more so when I see fellas running low 10’s and 9’s in the 1/4 mile, but that’s another and different story I’ll not dive into.

The oem intake is still good to use with small cams. Under 230@050 cam duration. While a rpm will make more power, does the expense warrant it for me? For you? Maybe down the line the rpm comes in. IMO, it would be a good idea, but on the cheap, you’re good with the iron. Consider it a $$$ savings for now.

Carb

The Edelbrock carb can be used with the oem intake, TQ intake as well. A 600 is fine enough for general street usage. A 750 would be better. There’s not a lot of power difference but there is a nice little gain in throttle power and pedal feel difference .

Holley or another Edelbrock is up to you. I really like the Edelbrock in the street, Holley at the track.
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thanks for the wealth of information, I will make some changes if I need to get inside the motor to refresh it down the line.
 
Nick, you will be hard pressed to find an intake that will be worth the time and labor to swap that's as good as the stock 340 intake on a mild engine like yours. If that car was mine, there's nothing that could get me to change it. Nothing.
 
RustyRatRod said:
Nick, you will be hard pressed to find an intake that will be worth the time and labor to swap that's as good as the stock 340 intake on a mild engine like yours. If that car was mine, there's nothing that could get me to change it. Nothing.
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Not even a 6 pak?
 
RustyRatRod said:
Nick, you will be hard pressed to find an intake that will be worth the time and labor to swap that's as good as the stock 340 intake on a mild engine like yours. If that car was mine, there's nothing that could get me to change it. Nothing.
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Are you saying that you WOULD change it back to the original and keep it that way, right?
 
AZ-Nick said:
Are you saying that you WOULD change it back to the original and keep it that way, right?
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If it was original, yes. I wouldn't change it now though if it runs good. I remember it has headers, but whatever intake it has now, as long as it runs good, I'd leave it alone. Unless of course you want to make a cam change and blah blah blah. But if no blah blah blah, I wouldn't mess with it.
 
I mean, you said it's a non numbers engine, right? Then in my mind, there's really no need to make it original since it really cannot be 100%. If you're happy with it, drive the wheels off of it!
 
I'd leave it alone if you like the way it runs. Weight savings is truly meaningless unless the car overall performs better in a measurable amount!!
 
If it is running fine, there is no reason to add 30 lbs to the car. The stock 340 intake is pretty good. If you look at it and compare it to a newer aftermarket intake. They really only moved the T intersection closer to the plenum to ease the turn. If you like the idea of running the stock intake. Go ahead, I’ve run 11.39 at 119 with one that is smoothed out and the divider cut down. Don’t cut the divider, you are light years from needing that.

878B4ADD-D2B4-4563-88C0-494777FE5D85.jpeg
 
guys, are some year intakes better than other years?
for example is a earlier year better than a later model stock 340 intake?
 
I’m my humble opinion from working on these 340’s for over 35 years, there are a few small items you can do to a stock intake. And yes, the older 340 cast iron intake the better. 68’ is better then a 73’ due to emissions bosses of the 72-73, again- my opinion.
1) remove the intake to gasket match- helps gain better flow than the turbulence if the ports are off a bit. Do this if you really want to get into the engine and now you can say you did!
2) make sure block off the heat cross over. Sadly it will kill drivability on cold days till warmed up. The advantage is less heat on the carb area.
3) use a plastic type carb spacer. The factory one is only 1/4” thick with a paper gasket on either side but that little bit also helps keep the carburetor a tad cooler.
4) pull the distributor and replace the advance springs with some lighter springs. Check it out and oil the pivot points of the weights. 340’s seem to love a quicker advance curve than the stock set up.

Okay- that’s all I got. I agree if you have a mild or completely stock 340, leave the cast intake. But look out for a LD-340 and if you find one at a good price…. Pick it up.
Good luck and enjoy your 340!
Syleng1
 
mad dog said:
guys, are some year intakes better than other years?
for example is a earlier year better than a later model stock 340 intake?
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Yes, but it's splittin hairs, IMO. I think the best is the 1971 TQ intake. 72 has the egr "bumps" and 73 has the EGR jets. Of course the 68-70 intakes are great, too.
 
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