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Old 06-26-2010, 10:29 PM
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Default Exhaust manifold porting>>

Alright then, me and a friend were talking about porting and such and started to look around for sounds and such. Ive come to the conclusion, I wanna port my stock manifolds. Mainly for the sound it will give me, and if there is some added power, GREAT!!
But I have some concerns before I do this (im planning on starting this within a week BTW)
With the added flow, will there be any issues with running lean? Or could that just come from intake manifold porting? Is there anything I should know about this other than the porting process itself? I know how the porting is done alone, but Im asking if there is any "secrets" you all know of that would help me out or that I should watch out for or be aware of?
And my last question (I think), what do you guys think of the idea??

Thanks much all
PS, Im dead serious about doing this if you're wondering.
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Old 06-26-2010, 10:42 PM
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Also wanted to ask (even though there is probably no way im gonna do this> ) If I was looking to get some gains out of the porting, I would have to port the heads as well would'nt I??
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Old 06-26-2010, 11:38 PM
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if your un experianced you should really look at a bunch articles and talk with someone who has done it to the same motor but gasket matching is always a quick and easy way to free up alittle airflow
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Old 06-27-2010, 12:04 AM
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Dude, Ive been searching the last 2 hours and cant really find anything too specific. All im getting is its not a huge project and just to have a driving free weekend, is there anything else to it?? I have to belive its that simple. And I can accomplish this by rocking the engine right?? And as far as the porting (or port matching) thats nothing, Ive dont that once before on a cutlass with the rocket 307 I belive it was. Well, started to do it and just sold it to the junk yard.
Like I said, Im really just looking for some good tips and wanting all of your opinions on the whole idea.
And again, its not so much performance im looking for (although that would be cool) as much as Im wanting to get that sound out of it.

And, does anyone know about the crossover? What would the deal be with that? is that diameter large enough where I dont need to do anything?

HAHA! Sorry, I got another "and" I was told by somone (who really doesnt know what hes talkign about most of the time) that all you need to do is match the front manifold, does this seem correct or just plain stupid? I personally am leaning towards stupid, and im wanting to do it even if its not nessesary so i have the satisfaction of another thing done by myself you know?
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Old 06-27-2010, 12:22 AM
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Quote:
Alright then, me and a friend were talking about porting and such and started to look around for sounds and such. Ive come to the conclusion, I wanna port my stock manifolds. Mainly for the sound it will give me, and if there is some added power, GREAT!!
Are you talking about exhaust manifold porting? (I assume because you mention intake manifold porting later) If so, you're not going to drastically change the sound from porting them. Also, I'm not sure how the 3400 manifolds are, but I know virtually no one ports the 3800 manifolds anymore because the front cast iron manifold has a terrible choke point where all 3 runners combine to the crossover, and that is the most restrictive point (its also in an area that you could not port)- so everyone buys PLOGs or headers for the most part.

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With the added flow, will there be any issues with running lean?
Your car won't run lean from doing any porting- you have a MAF sensor which measures how much air comes into the engine. Add mods, and get more flow, and the MAF will see this and compensate. Also, the pcm is able to adjust the fueling outside of the set values with fuel trims to correct and differences (up to a point).

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I know how the porting is done alone, but Im asking if there is any "secrets" you all know of that would help me out or that I should watch out for or be aware of?
And my last question (I think), what do you guys think of the idea??
The bad thing with porting the exhaust manifolds (or even the intakes to a point) is your solid shaft die grinder or dremel bit is only so long, and you have no way of going around curves (and the exhaust manifolds make a steep 90* turn)- so you have no real way of porting once you hit the curve, so you're going to be left with stock manifolds outside of a couple inches in the entrance. If your restriction is later in the manifold like the 3800's, you're not going to gain much.

There is a way to get around that- they have a process called extrude honing where they push this soft clay like material through (it contains abrasives)- and basically ports as it flows through; keeping the porting smooth, and porting around curves and such. The downside is it is expensive.

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If I was looking to get some gains out of the porting, I would have to port the heads as well would'nt I??
Depends what kind of porting you're doing and where the restriction is. IMO, if you were porting the exhaust manifolds, it wouldn't matter if you did the heads for gains since there is already a huge size difference between the exhaust ports and manifold ports. The intake manifold side is much different. If you gasket matched the outlets of the intake manifold, and left the stock head ports- you'd be leaving an overhang of material into the airflow which would hurt airflow.

However, if this is your first time porting- I'd scrap the idea of touching your heads. There is a lot to porting heads- and a lot of stuff you can do to make it flow worse if you don't know what you're doing. The airflow does all kinds of weird things making the turn coming in, and going around the valve- stuff you don't have to consider up in the manifolds.
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Old 06-27-2010, 12:24 AM
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sound from porting? IMHO sound gain will be minimal realistically so will performance gains, with todays technology you may as well go get yourself a set of J/Y heads and get them cnc ported but IMHO not worth the money
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Old 06-27-2010, 12:28 AM
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GREAT! Thanks, yeah, the whole deal I was asking about porting the heads was, I was wondering if I had to do that to see anything, wasnt planning on it.
If I mentioned intake porting, I meant exhaust...OOPS. But awesome, thanks alot.
Do you think it would be better for me to get a set of them from the junk yard to do this with??
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Old 06-27-2010, 12:44 AM
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Another thing, even if there is virtually nothing changed, its somthing I wanna do cause the whole DIY factor (somthing I can say i customized) And cause It will give me a little more expierience. Also, cause I know its gonna change the sound a little at least.
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Old 06-27-2010, 09:47 AM
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Quote:
GREAT! Thanks, yeah, the whole deal I was asking about porting the heads was, I was wondering if I had to do that to see anything, wasnt planning on it.
If I mentioned intake porting, I meant exhaust...OOPS. But awesome, thanks alot.
Do you think it would be better for me to get a set of them from the junk yard to do this with??
The thing about the exhaust ports on the head is you want a difference in size between the head and manifold or header- its called a reversion dam. So you would probably lose power opening it up to the gasket size to match the manifold.

Also, I always recommend getting a junkyard part to practice on. You never know if you might crack through or something- and don't want to ruin your only set.

Are your exhaust manifolds tubular steel or cast iron? The 3800's have a cast iron front and tubular steel rear. You can usually port a lot more in the iron ones because they have more wall thickness. But you need to be careful not to go too deep- remember those manifolds get super hot, and cool pretty fast after- so you've got to think about cracking later on.

Quote:
Another thing, even if there is virtually nothing changed, its somthing I wanna do cause the whole DIY factor (somthing I can say i customized) And cause It will give me a little more expierience. Also, cause I know its gonna change the sound a little at least.
I hate to say it, but I really doubt you'll hear a sound difference. You're not really changing anything that will effect the sound. Headers change the sound because you're changing the way the exhaust pulses come together and interact. Mufflers and resonators change the exhaust sound because they effect the way the sound being canceled or absorbed. But just opening the manifolds at the ends isn't really going to change anything (plus you're not going to be able to change them that much anyways).

Any reason you don't just want to do headers?
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Old 06-27-2010, 10:02 PM
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Don't waste your time porting exhaust manifolds, just get headers and call it a day
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Old 06-27-2010, 10:02 PM
 
 
 
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3800, aware, carlo, cast, choke, customs, exhaust, gasket, intake, iron, laws, manifold, manifolds, matching, monte, point, port, porting, tourists


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