Intake Manifold Porting - Bad Idea??

[alloydix]

New the e30 world so this might be something that has been solved long ago. My heads have been ported by bavarian engine exchange (the previous owner bought the motor from them) and my intake is completely stock. Would I benefit from porting the intake, or would I lose some of the velocity of the air traveling into the cylinders by enlarging the opening and thus decrease the overall performance. I've looked around for other people who have done this, and some say its not a good idea, and others say only extrude honing works, and others say anything is better than stock, but very few people seem to have done it. So I am really at a loss and don't want to blow money on nothing. I am curies as to what you all think.

[JasonC]

Are you just going to port match the intake to the head?

[alloydix]

That is the idea. Just kind of got the gaskets as close the the head as possible, and will match intake to those (which I also read should not be done buy have no idea why).

[CHIF8008]

matching the gaskets will allow for better flow. that is never bad

[mikeedler]

can't see why that would be a bad idea.

[JasonC]

Go for it if thats all you're going to do. It's pretty easy. Just get the correct bits to do the job.

[alloydix]

well sounds good. I just read some places that you really don't want to increase the overall size of the intake around the injector because then you decrease the velocity of the air going passed the injectors and into the cylinders. Makes sense, yet doesn't. I could see a larger diameter being best with a turbo or something where you are really forcing the air in, but for stock I just am not sure I will notice much (and hopefully not a decrease in performance).

[alloydix]

I was going to have a local shop do it, because I'm hoping they can go farther back up into the the intake, and maybe even smooth some of the casting residue up. Its really rough inside the intake. I saw some guys thread on bimmerforums on a extrude honed intake, and he got up to a 30% increase in flow by smoothing everything.

[JasonC]

but see when smoothing everything out, is an argument of what people will argue about lol. You want the air to tumble. just think of a golf ball. without the dimples how far does it go compaired to a smooth ball?

[alloydix]

haha thats the part that no one argued about. Supposedly if the air will move faster with less turbulence if the inside is not like less than 50 grit roughness. And if the random protrusions are cleaned up the faster the air moves. The faster you get the air to travel before it hits the injectors the better. I really don't know though, school me. I open to all ideas.

[JasonC]

I wouldnt make it completly smooth. I'd leave some ruffness to it. But like you said, "clean it up" I do that to most intakes and heads that i get my hands on anyways. I even did it to my 1.3 in a Festiva i had LOL.

Is there anything else done to this engine besides a port job? Maybe a cam, bigger valves, header, pistons, stroker or anything?

[alloydix]

I doubt I could make it completely smooth, but I'm hoping to clean it up a bit. I'll give a shot tomorrow. Taking it by the shop. And I'll let you know if I notice a difference when its all back together. My biggest difference might be a better vacuum.

[digger]

not worth the effort

[Bearmw]

In my opinion it is only worth port matching if you are doing it yourself and not having to pay a shop to do it. This means having some kind of die grinder and some sanding rolls such as what Eastwood or Harbor freight has. I think the Eastwood porting kit provides 80 grit sanding rolls if I remember. I don't think you need or want to make it too smooth. Also Jim Rowe told me to only go in about 50 mm or so in the runner and make sure you clean it out real good after with a power washer or something.

Doing more than this to the B25 intake gets crazy expensive and for what kind of return?

[nando]

it won't hurt anything, but it's probably not going to make any difference either. at least, it didn't make any difference on my engine.