If you are realistic with what an aftermarket intake is going to provide for the cost, then sure.  In a nutshell, the stock intake probably isn't all that bad, and most of the gains IMO come from raising the carb pad and lengthening the runners, which increases low end torque (what you want in a street engine).  Power wise, you might see 5HP, but if you gain say 5 lbs/ft from just off idle to the midrange its a difference you may feel. 

Thinking about it another way: weight.  An iron intake is heavy, and that's weight over the front end, where you don't want it in a car that already has a less than great F/R weight distribution.  Is it going to make the car faster from being lighter?  Not noticeably.  You have to shed 100 lbs for it to make a real difference.  Dropping 100lbs is basically the same as adding 10HP, or a reduction of 0.10 second in the 1/4 mile.  The intake might shave 20lbs on a SBF, so if you do the math its not a huge difference.

So, is it worth it?  You'd have to tell me.  I swapped mine out a couple years back and have no regrets about doing it, but my expectations were also reasonable from the outset. 
 

TKOPerformance wrote:

If you are realistic with what an aftermarket intake is going to provide for the cost, then sure.  In a nutshell, the stock intake probably isn't all that bad, and most of the gains IMO come from raising the carb pad and lengthening the runners, which increases low end torque (what you want in a street engine).  Power wise, you might see 5HP, but if you gain say 5 lbs/ft from just off idle to the midrange its a difference you may feel. 

Thinking about it another way: weight.  An iron intake is heavy, and that's weight over the front end, where you don't want it in a car that already has a less than great F/R weight distribution.  Is it going to make the car faster from being lighter?  Not noticeably.  You have to shed 100 lbs for it to make a real difference.  Dropping 100lbs is basically the same as adding 10HP, or a reduction of 0.10 second in the 1/4 mile.  The intake might shave 20lbs on a SBF, so if you do the math its not a huge difference.

So, is it worth it?  You'd have to tell me.  I swapped mine out a couple years back and have no regrets about doing it, but my expectations were also reasonable from the outset. 
 

Thanks for the input. I like to think that I'm realistic with expectations also.
With an aftermarket intake manifold, I would he hoping to optimise the engine, with hopefully is what a better engineered intake manifold. Hopefully this translates into a few horses, some torque and just a general improvement over stock.
But if the stock intake manifold is good enough and no real difference is gained, then this is all a waste of time.

It depends on the engine I think.  There's no point putting a Performer RPM on a typical 289 because with a stock cam they simply don't wind high enough.  The RPM is 1,500-6,500 RPM, whereas the Performer is idle-5,500.

Ultimately I don't know how much you can really do with the ports and flow.  You're limited by the stock heads more than anything.  Aluminum will reject heat better, and there's still the weight savings.  Like I said, probably not much gain from the intake alone.  I swapped mine as part of an upgrade which included an Edelbrock 500cfm carb, which was optimized as far as the metering rods and jets went and I dialed in the advance curve, so hard to claim what if any of the improvement was from just the intake. 
 

(Might be a good project for Daze....)
I know ....most of the time just "hog'in out the ports" is not the best way to improve flow in a cylinder head BUTT.....
as restrictive/small the ports are on stock 289........I wonder if it WOULD pick up power because they are sooo tiny.
Especially when you throw a big cam & carb into the mix.
I wonder IF ya can hurt the flow by opening & polishing the ports ???
6sal6

6sally6 wrote:

(Might be a good project for Daze....)
I know ....most of the time just "hog'in out the ports" is not the best way to improve flow in a cylinder head BUTT.....
as restrictive/small the ports are on stock 289........I wonder if it WOULD pick up power because they are sooo tiny.
Especially when you throw a big cam & carb into the mix.
I wonder IF ya can hurt the flow by opening & polishing the ports ???
6sal6

On an old head design from the '60s its pretty hard to make the ports worse.  Where you get into trouble is with modern heads like the GT40s, because the port contours are a lot more sensitive.  On old heads simply look to do the following:

1.) Spend most of your effort immediately behind the valve.  Smooth the transition to the throat cut and work the valve guide into a tear drop shape with the point facing the incoming air (opposite directions for intake and exhaust ports).  Really work to smooth the short side radius.

2.) Gasket match the ports.

3.) Try to work the port into a venturi (wider at the top than right behind the bowl.

4.) You can polish the exhaust ports like a mirror, but leave the intake ports a little rough if you have a carb.  It helps keep the fuel in suspension.

Then the biggest thing is what you must NEVER do.  Don't deepen the port floor.  A little clean up is fine, but do not remove material trying to make the port larger on the bottom.  The idea is to give the air a smooth path with as straight a shot at the valve as possible.

Then its not a bad idea to polish the chambers and cc them. 

Do all that and pick a good cam and you should pick up power up top without hurting it too much down low.
 

I'd say 25HP from an intake is just advertising.  On an FE it might act like 15-20HP with the minor improvement in flow and the 100lb weight savings!

I found this article and would welcome people's thoughts.
From what I read, in the 4,000rpm range, some of the intake manifolds showed around a 10hp increase and possibly a 16hp increase with a high rise manifold. It seems thatmaybe a 10-11hp increase is achievable?
Torque seems to go up too.
Other question I had was with the stock manifold... The article talks about stock dual plane. I thought the stock manifolds were single plane?

http://carbdford.com/fletch/tech/intakes/intakes.htm

Last edited by Toploader (8/23/2023 4:28 AM)

I bought a Chink knock-off  (OK go ahead and stone me! of the Performer RPM a few years back.
Using the thin(est) air cleaner I can find...which was the stock filter in the 60's...it just barely rubs on the bottom of my hood.
WITHOUT any kind of spacer! (so be careful on measurements)

I would still get the Alum intake and a 600 CFM Eddy carb (yeah I know ..stone me again for too bigga carb
The Eddy is super easy to tune AND by trimming the secondarys counter weight you can modify when the back two barrels come in.....instead of waiting on the vacuum control. Make sortuva quasi double pumper-ish carb. EZ to do.
And 4 tube headers! (ouch...may I have another stoning please with turbo/free-flow mufflers AND tail pipes to the rear valance to control resonace.
ALL these changes WILL make a noticeable change in scoot.....IMHO
6sal6

Last edited by 6sally6 (8/23/2023 11:06 AM)

The cam in mine was ground for torque, I have the pertonix set up too, the exhaust manifolds are stock, but the pipes are custom made 2-1/4" and routed pretty straight and the mufflers are Walker Quietflows. The heads are stock, but have all the stainless steel valves and seats in them. The distributor has the lighter advance curve too. The compression is great and the plugs look fantastic.
I'd say the biggest improvements made were the exhaust and the distribution mods.