[Evan Purple240]

I have a few questions for you Z-buffs out there in computer land.

I have a e31 head that i want to port and polish, the question is whether this is an effective use of time and money for performance. The motor is modified with a cam, electronic ignition and all the other standard mods i am still running the su carbs too. Porting is the only thing that i kinda forgot to do before assembly. And if anyone can tell me where to remove the bulk of the material from, that would be excellent>!!

Thanks for any input on this subject in advance!
EvanZZZ

 

[Bob H]

Porting is the only thing that i
> kinda forgot to do before assembly. And if
> anyone can tell me where to remove the bulk
> of the material from, that would be

Evan,
The only thing that concerns me is that you say you forgot to do this before assembly. If the head is on the car, it goes without saying, don't touch the head. But we will assume the head is off the car. I would say you will see the most benifit from a simple port matching. If you don't know how that is done, I am going to give a quick explanation.
First, you need the intake gasket. A marker will do for the next part,(shops use a dye). Anyways, take this red or blue marker and mark all around the intake and exhaust ports. now, place the gasket on the head, lining up the bolt holes as it will sit on the head. You will notice that the openings on the gasket are significantly larger than the head. In some areas, the gasket will actually overlap the intake hole. Well, take a scribe,(like a dental pick), and scribe around where the gasket sits. This is to give you a reference for where you should remove material out to. For now, don't worry about the gasket that is overlapping the hole. Take your trusty dremel tool or similar, and start grinding away. The purpose is to get a smooth transition from the intake to the head. So this must be repeated for the intake,(ie put the gasket up to the intake, and scribe where material needs to be removed, after you marked it with your trusty marker.
I wouldn't worry too much about the header, unless you have the stock manifold. With a steel header, it is hard to work with. If it is close, then you should be fine. You can play with it a little, but be careful, that material is not all that thick. If you take a significant amount of metal out of that, they you are creating a hot spot.
Lastly, for the gasket, put it back on the head, and where it overlaps the holes, lightly grind away the gasket material. you may then have to go back and work on the intake manifold again. (the order is up to you).
For extensive porting, don't bother, it is a science that requires a lot of experience to do well. Because if you do it wrong, then you will be worse off then a stock job.
good luck. I would say it is worth your time if the head is in good shape.
-Bob Hanvey

 

[Unknown User]

> Porting is the only thing that i

> Evan,
> The only thing that concerns me is that you
> say you forgot to do this before assembly.
> If the head is on the car, it goes without
> saying, don't touch the head. But we will
> assume the head is off the car. I would say
> you will see the most benifit from a simple
> port matching. If you don't know how that is
> done, I am going to give a quick
> explanation.
> First, you need the intake gasket. A marker
> will do for the next part,(shops use a dye).
> Anyways, take this red or blue marker and
> mark all around the intake and exhaust
> ports. now, place the gasket on the head,
> lining up the bolt holes as it will sit on
> the head. You will notice that the openings
> on the gasket are significantly larger than
> the head. In some areas, the gasket will
> actually overlap the intake hole. Well, take
> a scribe,(like a dental pick), and scribe
> around where the gasket sits. This is to
> give you a reference for where you should
> remove material out to. For now, don't worry
> about the gasket that is overlapping the
> hole. Take your trusty dremel tool or
> similar, and start grinding away. The
> purpose is to get a smooth transition from
> the intake to the head. So this must be
> repeated for the intake,(ie put the gasket
> up to the intake, and scribe where material
> needs to be removed, after you marked it
> with your trusty marker.
> I wouldn't worry too much about the header,
> unless you have the stock manifold. With a
> steel header, it is hard to work with. If it
> is close, then you should be fine. You can
> play with it a little, but be careful, that
> material is not all that thick. If you take
> a significant amount of metal out of that,
> they you are creating a hot spot.
> Lastly, for the gasket, put it back on the
> head, and where it overlaps the holes,
> lightly grind away the gasket material. you
> may then have to go back and work on the
> intake manifold again. (the order is up to
> you).
> For extensive porting, don't bother, it is a
> science that requires a lot of experience to
> do well. Because if you do it wrong, then
> you will be worse off then a stock job.
> good luck. I would say it is worth your time
> if the head is in good shape.
> -Bob Hanvey
Bob, What might be the horsepower increase someone could expect to get from this mod on a non turbo ,and a turbo.

Thanks jason

 

[Unknown User]

Re: intake manifold question for bob

> Bob, What might be the horsepower increase
> someone could expect to get from this mod on
> a non turbo ,and a turbo.

> Thanks jason

Bob,

Sounds like you've done some porting before. Have you ever done an intake manifold? I can get one cheap and would like to at least smooth out the runners. How far can I hog it out? Is it worth the effort? Is there a gain without going to a larger throttle body? What's out there in the way of a larger TB?

I'll have no way to match the intake ports to the manifold outlets because the existing manifold is in place. Does it hurt to have the manifold outlet slightly larger than the port? I figure slightly larger is better than leaving it the way it is. What do you think? Thanks. Simon

 

[Bob H]

Re: intake manifold question for bob

Simon,
Lots of questions. First, yes, there is a way to match a junk manifold to the existing head. Remember, you are matching it all to the gasket. So line up the gasket to your manifold and make the marks. As for hogging it out? just match the transistions. By hogging it out, you are changing the flow characteristics of the manifold, possibly causing some imbalances in flow. Smooth the transistion as far up into thee manifold as you can, but don't take out huge chunks of metal. The goal is to smooth the sides, so it is not so rough.
for serious power, the larger throttle body is the way to go. Motorsport Auto carries one, as well as TWM,(based in california as well). And if you buy a larger throttle body, you have to match it to the intake manifold as well.
And does it hurt to have the manifold outlet slightly larger than the intake port? Yes. If anything, you would rather have the cylinder head be larger than the intake manifold, otherwise it is like a big flat surface to stop incoming air, as opposed to a increase in area.
If you can't take off the head to do some match work when you change manifolds, you are best leaving it the way it is. Think of this analogy. Take a sewer pipe and match it up to a plumbing pipe. Which is the better direction of flow? From the huge sewer into the small plumbing pipe? No, the other way around. So the decision to port should be dependent on the head being removed. But for the most part, it is easy.
-bob hanvey