Stock intake manifold polishing? Is it worth anything?

[70Challenger R/T S.E. 383]

I would like to keep my stock intake but i want a little more performance. I was wondering if i could put a sand roll on a little hand held grinder and polish the runners on the stock intake and get noticeable results and not just be wasting my time.
thanks

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M....massively
O....over
P....powered
A....and
R....rare

[Fury Boy]

don't know if this is the same thing, but I read in a car craft that it was good for like 4-5 horses through the whole power band(if done properly). Maybe I am thinking of something different, but I thought thats what they did. Does anyone know? I think they were using a 440 edelbrock performer RPM.

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Keep'n it Alive
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'63 Plymouth Fury 2 DrHT
* '71 383 Torker Man.,
Comp 280H cam,
Predator Carb

[rumblefish360]

Try puting a spacer under the carb. MoPar even has them in 1/4 inch sizes.
The sand roll is a lot of work for a little gain. Up to you.

[pishta]

Supposedly, a rough intake passage, like a cast surface, is benificial in keeping the Air-fuel mixture atomized. A smooth polished runner might allow the fuel to fall out of suspension, collecting on the runner walls. I hear Extrude honing is great on port fuel injection applications because it is a "dry" intake, but not so good on "wet" apps. such as carbs or TBI setups. Look at the floor of an aftermarket intake and you might see a highly textured area that helps in breaking the high velocity air fuel mix. One can remove sharp angles in a stock manifold and really perk it up, such as radiusing the bottom of the carb mounting boss. "One guy did a stock Q-Jet intake this way and put a 1 inch spacer on top. It flowed better than ANY aftermarket dual plane intake available on his flow bench." (Vizard, How to build Horsepower, vol. 2)

[Fury Boy]

So Pishta, would you gain more power if you roughened the bottom of your intake? the Idea makes a lot of sense to me.

[rumblefish360]

Fuel will collect on the walls anyway. The smooth wall idea is for the mix to get there faster. The puddling effect it has (when smooth) is an overated event. It has merit, don't get me wrong. But it isn't the end of the world event like some make it out to be. Although it can be.
Best to leave it alone, ruff. Tricks like that have there place. The best thing IMOP, to do is put a spacer under the carb & make sure the intake ports line up with the head.(port match). This should be enuff for the street. If not, an aftermarket intake is what you should be looking at.

[Maxwedge]

There is no seriouse racer who uses a rouch cast intake in ANY form of racing. WHile it is true that they tend to but a waffle pattern right inderneath the carb(on the floor of the intake) for the Rough=suspended reason. NO ONE has rough intake runners. Drag race guys in the upper ranks use intakes made of folded sheet metal because the ports are Perfectly smooth and the ports are also consistant in size and shape..two things casting and porting will never get you.
my .02
Maxwedge

[ehostler]

From what I have read, a polished surface is superior to a rough surface.

You do loose a little power because of the fuel atomization, however, you more than make up for it with the gained air/fuel velocity.


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Ed - MoPower

'96 Dodge Ram 1500 SLT CC 360 4X4
'68 Charger 383-4
'69 Coronet 500 Convertible 440-4

[NitroMethane]

Ican't remember when or where I heard this, but I remember reading that because of the characteristics of air current, smooth walls and exact port matches promote reverse airflow along the walls of the runner. Extreme race guys don't really have to worry about this because of the efficiency of their combustion and flow (I'm assuming.) Does this sound right to you? If it makes no sense or is insignificant, tell me and I'll delete it from memory

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Nitro
69 Coronet 440
90 W250 4x4
00 Avenger ES

[pishta]

With todays carbs giving better atomization, maybe the not polished runners have had their day in the spotlight. Alot of street guys are still running 3310's and 1850's out there. As for top fuel racers, they have alot of blow/velocity to get that mix through their smooth sheet metal intakes, I think keeping atomization and fuel puddling is not really a factor. Most racers agree the air pump principle, more in more out, is key to a good ride. As for a street car that has to idle and pull smoothly, etc. it might still benifit from a not polished intake system. Im shying away from the "rough" word here because even old aftermarket aluminum intakes are not really that "rough" to begin with. Give it a try, it might work for you. if it doesnt, you are not that much worse off then , are you...