340 Intake Manifold Casting# 2531915 - Upgrade

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PROSTOCKTOM

PROSTOCKTOM

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I'll be the first to admit I know very little about OEM SBM intakes. That said I need some input from the small block crowd.

I have a older friend that has a 385" (360) stroker in a 67 Valiant Signet, Purple Strip cam, ported heads, AVS carb, and a ported iron 1969 #2531915 intake.

He's told me for years that it's a great intake once ported, but I tend to think there has to be a better option in aluminum that will still fit under the hood with a OEM air cleaner.

The other issue is he tends to be very frugal and uses what he has rather than spend on the latest and greatest. I've driven this car several times and you better make sure you have it

pointing straight before you stab it to the floor. This car can be a real handful to drive. After 15 years of use it's time for a refresh this summer and I thought I would by him an aluminum

intake to go back on it. So what aluminum intake would you replace it with that would be an improvement in port volume and yet still fit under the hood?

Thanks.
Tom
 
That 915 manifold does a really good job especially
when modified (Not that we would do that on a Stock
Eliminator car) and when tested at the track it ran just
as well as a LD340 when the weight was adjusted to be equal
in the car.
That being said we run a Victor in our higher HP 408 68 Valiant
and it fits fine even with a tall Air Cleaner under the stock hood and it
made the best ET over the 5 intakes we tested (10s thru the mufflers
@ 3000+ Ft.).
 
The '71 "2100" iron intake with a good thermoquad still is one of the best original set ups....
 
GTX JOHN said:
That 915 manifold does a really good job especially
when modified (Not that we would do that on a Stock
Eliminator car) and when tested at the track it ran just
as well as a LD340 when the weight was adjusted to be equal
in the car.
That being said we run a Victor in our higher HP 408 68 Valiant
and it fits fine even with a tall Air Cleaner under the stock hood and it
made the best ET over the 5 intakes we tested (10s thru the mufflers
@ 3000+ Ft.).
Click to expand...

Thanks John, This is just a street car still running 14" rims, mild torque convertor, and 3.21 gears out back. Thinking a Victor might be to much intake for that application.

However if a Victor will fit under the hood then any other intake would as well. What do you think it needs? Or is fine like it is?

Thanks,
Tom
 
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First picture,This would be a replacement for the factory intake. Exactly the same but aluminum. I have it bolted on a plastic mock up engine in the second picture because its light and is the same dimensions as a factory cast iron intake. It has all the same hose and sending unit outlets and even the choke tub.
The LD340 would be the same but it does not have the choke tub built in.

Second intake choice A Wieand is another good intake seen in the third picture on the engine painted orange.

An Air gap seen on the forth and fifth picture we had to cut the hood braces for the factory air cleaner. seen in the forth picture

Sixth picture is a holley strip dominator. This also needs hood trim for the factory air cleaner.

You can get away with the taller intake if you use a low profile aftermarket air filter base. That is what we use to make the air cleaner on the seventh and eighth pictures for the Indy intake which is the highest . And it still sealed tight against the hood after trimming the braces.

Last picture is another Air Gap on a 67 Barracuda. It fit under the hood using the 69 and earlier air cleaner but tight. The car has steel motor mounts. If they were rubber it would bounce off the hood

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The Mopar intake in your first photo is very close to the original cast iron one, but, not exact. It takes a different carb base gasket as the original 915 intake is a 4 hole, whereas the Mopar aluminum one has the two oval slots.
 
cudamark said:
The Mopar intake in your first photo is very close to the original cast iron one, but, not exact. It takes a different carb base gasket as the original 915 intake is a 4 hole, whereas the Mopar aluminum one has the two oval slots.
Click to expand...
I use the same open gasket for them all . The insulated gasket that is used is also open. I haven't used a 4 hole gasket in a long time.

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PROSTOCKTOM said:
This is an interesting article I just ran across. Mopar Small-Block Intake Manifold Flow Test

They claim a Performer RPM doesn't flow as well as the LD340, but that it actually makes more power from better distribution.

Tom
Click to expand...
The thing I found that really helped the LD340 was the equalizer slot cut into the divider. I tried that on some other intakes and it seamed to work. The direct connection manual wants you to cut out more for race applications. I found just the 1/2 inch by 1 1/2 works great on all dual plain intakes

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PROSTOCKTOM said:
So what aluminum intake would you replace it with that would be an improvement in port volume and yet still fit under the hood?
Click to expand...
So you are talking about the 385 equipped 67 Signet right?, with 3.21s, skinny14s, and a "mild" TC, right?
Well IDK anything about port-volume being an improvement.
But, IMO, in that 385Combo, as described, that factory iron intake is not the thing to change.
Ok sure, on the dyno, yur gonna see changes, but, that 385 is already overkill just as it sits, for the Signet chassis..... and
obviously, at the track, the difference will come out, with the appropriate gearing and TrapRpm.
But as a streeter;
I have a hard time imaging that at WOT, you could ever, on the street, notice any WOT-power change at all, from any change in any popular street-intake. I mean, top of First gear is like 50@5700 (if not spinning the tires), and on the shift, the Rs will fall down...down.....down; to where no aftermarket intake will make much of a difference. At 3500rpm they are all gonna be pretty close.

Back in ~1975, I put a 340 under the hood of a V200 wagon......... with a 2-bbl 318 top end on it from a 69 Satellite. I'll take a wild guess that your friend's Signet and my wagon weighed about the same. She was a high-compression tire-frying, screaming demon. And I imagine, so is a 385/Signet.
My current combo runs an AirGap, and I highly recommend it. But the engine has also run an X-cellerator, an AVS/iron, and a TQ/iron. All of them spun the tires thru two gears (A833) at least; so I mean, on the street,
it's like hunting squirrels with a shotgun.......
IMO; pretty much any intake on a 385 will do, cuz in a Signet, the gun is already way big enough.
But if you just want to buy your "older friend" an intake, well, don't let my testimony stop you, lol; there's plenty of choices out there, that will spin the tires all the same.
 
I would leave well enough alone!

Our Valiant has 3:91 gearing and a 10
inch converter.
It will be at Mopars at the Strip (Muscle Cars)
defending the street legal eliminator title it won last year.
 
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sor
AJ/FormS said:
So you are talking about the 385 equipped 67 Signet right?, with 3.21s, skinny14s, and a "mild" TC, right?
Well IDK anything about port-volume being an improvement.
But, IMO, in that 385Combo, as described, that factory iron intake is not the thing to change.
Ok sure, on the dyno, yur gonna see changes, but, that 385 is already overkill just as it sits, for the Signet chassis..... and
obviously, at the track, the difference will come out, with the appropriate gearing and TrapRpm.
But as a streeter;
I have a hard time imaging that at WOT, you could ever, on the street, notice any WOT-power change at all, from any change in any popular street-intake. I mean, top of First gear is like 50@5700 (if not spinning the tires), and on the shift, the Rs will fall down...down.....down; to where no aftermarket intake will make much of a difference. At 3500rpm they are all gonna be pretty close.

Back in ~1975, I put a 340 under the hood of a V200 wagon......... with a 2-bbl 318 top end on it from a 69 Satellite. I'll take a wild guess that your friend's Signet and my wagon weighed about the same. She was a high-compression tire-frying, screaming demon. And I imagine, so is a 385/Signet.
My current combo runs an AirGap, and I highly recommend it. But the engine has also run an X-cellerator, an AVS/iron, and a TQ/iron. All of them spun the tires thru two gears (A833) at least; so I mean, on the street,
it's like hunting squirrels with a shotgun.......
IMO; pretty much any intake on a 385 will do, cuz in a Signet, the gun is already way big enough.
But if you just want to buy your "older friend" an intake, well, don't let my testimony stop you, lol; there's plenty of choices out there, that will spin the tires all the same.
Click to expand...
like hunting squirrels with a shotgun.......:rofl:
 
I believe just the weight off the nose of the car will make a big difference. My choice would be a factory style dual plane in aluminum. Yes the old factory iron intakes were great, But they are so darn heavy.
 
I am leaning toward buying a Performer RPM, non air gap at the moment after reading the article were Dave Hughes tested a bunch of intakes.

Should knock at least 25 pounds off the nose and like previously mentioned it will roast the tires with whatever intake it has on it.

I liked the fact that the Performer RPM only has 16 cfm difference from best to worst runner where other intakes were as much as 40 cfm difference.
 
This is my 68-69 340 stock intake, race car, but runs fine on the street.

116A20F7-418A-4673-B8FC-3E8F3DC6F1A0.jpeg
 
I really wanted to go with a Performer RPM, but he doesn't want to change his choke setup on the AVS he runs.

So I guess that leaves me looking for a Mopar aluminum dual plane. No good deed goes unpunished.

Tom
 
i just watched a video ...i think it was that Holdner guy. He replaced a stock cast iron intake with an airgap and there was no change in hp on the dyno. Also watched a video where they replaced an airgap with the edelbrock rpm and no change on dyno hp. I think it was a chev small block producing 450 plus rpm. There are lots of 10 second 340's running cast iron intakes.
I don't know what it is about aluminum intakes but for some reason guys can't change out the stock intake fast enough.
 
The majority of the 340 Stock Eliminator cars anymore are capable of running
well into the 10's with stock manifolds with either AVS or Thermoquads.
A few have been in high 9's running the production Carbs and stock compression
ratio and stock lift camshafts (.462/.473).
 
PROSTOCKTOM said:
I've driven this car several times and you better make sure you have it
pointing straight before you stab it to the floor. This car can be a real handful to drive.

Thanks.
Tom
Click to expand...
If it runs that good I see no reason for improvement.
 
It's just the idea to knock 27 pounds off the frontend and since it's time for an engine refresh I figured I would buy him an intake.

Tom
 
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