bigvette1

I have read the merits and the negatives of "gasket matching the runners" of an intake manifold to the gasket or head port size. One line is they are smaller to increase the air flow rate into the head. Another says no make them bigger - then the air flow dumps inequaly to the heads.

Does anyone have experience in this area? Sure would like some advice before I turn on the grinder. :thumbs:

69stingray

I have no advice. I would suggest looking at the two things:

1. John Lingenfelter's book on how to build a small block Chevy. Excellent book and does have a chapter on porting, I think.

2. Look at http://www.extrudehone.com, they "port" intake manifolds and cylinder heads using an abrasive material (which is a liquid, just like air) that removes material as it flow though the head/intake manifold. Never tried it, only read about it. I think it is on the $ side.

[Modified by 69stingray, 11:32 AM 1/11/2003]


[Modified by 69stingray, 11:33 AM 1/11/2003]

flynhi

I've done this a couple of times and I've been surprised at how much the heads and intake manifold are mismatched. I don't know that port matching dramatically increases airflow but it just makes sense that a smooth transition from one to the other will decrease turbulence and increase airflow somewhat.
It's easy to do in a couple of hours with a grinder and an abrasive kit from Eastwood.

The Money Pit

The purpose of the intake is to provide a path for fuel and air to flow between the carb and the cylinder head,ulimately the cylinder. The smoother the "pipe",the more flow potential. Just like a kink in the garden hose slows down the water,a transition between the head and intake will impede the flow.
I did mine by hand with a variety of files,and used the intake gasket as a template for the port,and blending the intake ports as far into the port as I could reach. Aluminum is soft and wil file quite easily. I would not recommend a grinder here. Once it's gone,you can't put it back.

john's '81 mouse

For a relatively mild horsepower/street driven machine, not run a lot above 6,000 to 7,000 rpms, everything I've read says don't bother.............in fact, a number of authors suggest you can do more harm than good..........turbulance in the intake runners is a good thing and this turbulance keeps the gasoline in an atomized state, also a good thing.

73 LS-4

I personally spend most of my porting time smoothing angles rather then enlarging, the important thing is to be consistent port to port. Which intake are you currently working with, I did some work with my L-36 intake before instalation if that's the intake your working with I can give some pointers.

:cheers:
Pat Kunz

bigvette1

Pat, any advice from practical work is appreciated. I am really working on a stock manifold for a 73 LS-4. I am keeping the stock for hood clearance and to maintain the EGR required in this state. May not be working but it is there. The heads are the 049's that have been worked over well. Porting, valves etc.

I figure if the manifold is opened up with the reworked heads I should see a fairly good gain.

Let me know either here or drop me an e-mail.

adam

I'm somewhat confused as well...

I've read that if you want to do it, you need to torque the intake to the head
after painting both the gasket and head with different colors. Where they
combine (ex. red + blue = purple) you match from there. It went on to say
that you should glue the gasket to the head so it doesn't move from then on...

I'm surprised that nobody suggests making the intake port smaller to be like a
venturi to speed up the charge through the port...

No facts, just question.

Twin_Turbo

:skep:

Ken73

:withstupid:

NHvette

The extruded honing is more like playdough consistency - with abrasive
particles in the compound. By forcing it through the passageways, it 'sands'
the insides of the intake runners. A little bit to get it smooth - more to open
it up. Neat stuff - but I read that it's pricey, too.

A pic from their website:


:seeya


[Modified by NHvette, 1:41 PM 1/14/2003]

bigvette1

From Adam
Quote - I'm surprised that nobody suggests making the intake port smaller to be like a venturi to speed up the charge through the port...

No facts, just question.

Is this not the theory of the Edelbrock Torker II single plane that seems to get a lot of bad press? The theory seems solid - speed up the flow and it acts like a ram effect into the heads.
I don't want a Torker II discussion, just a comment from memory of previous posts. Thanks.

NHvette

Prices: AL manifold: 365 cast iron: 525
AL heads: 750 cast iron: 995
exhaust manifolds: 500




[Modified by NHvette, 1:52 PM 1/14/2003]

73 LS-4

Jim,

I dragged out my old LS-4 intake to take a look at it, forgot how heavy that thing is :eek: Anyway I'd start with removing all the casting flash that I could, some ports will have more then others, just try to make them all equally smooth, the thing here is you don't want to make the runners like mirrors since some texture will help keep the fuel in suspension, so just smooth out the really rough stuff is all I'm talking abot here. Now you'll see that you have two different runner designs on there the ones that come in from real low and curve up and the ones that come high and curve down. It looks to me like your worst two runners would be the front two low ones, these ports almost would be aimed at the roof of the head port when bolted up rather then the valve since they come in at such a low angle and try to make that curve to the head (the L-36 is a tad taller so it's not near as bad there). So I would probably try and remove a little material at the bottom of those ports to decrease my angle into the head ports. The 049 heads have pretty good sized intake ports so a little bit larger on the intake won't mismatch, had a hard time getting my intake gaskets to stay out of the head ports so they are almost as big as the gasket holes anyway. The other ports on the intake aren't that bad just a little cleanup work would help. If I was you I'd try to stay with the stock contours of the ports and only enlarge them slightly so that your still smaller then the head ports by a little bit. the two worst runners I described before I wouldn't touch the top of those runners at all or it may make the problem worse there, just the bottoms of those, jhust be sure not to lower them too much. Another trick that I normally like to do is when I'm pretty much happy with my work is to go to the opening of each runner and just cut a small 45 degree angle on the edge of each port to remove that sharp edge at the end, my reasoning behind this is when you bolt the intake up you'll have the smaller intake ports bolted the the larger head ports and that slight cut there should make an easier transition for the air between the intake and head, in other words it creates a tad less room for an eddy(sp?) to develop. I hope I was of some help. Too bad they check for EGR there, the L-36 is a nice upgrade and it's still short enough to use the cowl induction setup with the 73's (It's about a 1/4" taller) plus it's about a 1/3 the weight.

:cheers:
Pat Kunz

69stingray

That is a little pricey. Neat process. Does anyone know anyone who has used it?

And yes, air is liquid. The "putty" flows more little a liquid then a solid, I think. The concept is the putty would remove the restrictive areas just as the intake air would see it.

sb69coupe

:confused: Dude, I thought air is a gas? It's compressible, right? Do you mean that air FLOWS like a liquid or something?

69stingray

OK, OK, OK, :crazy: , you guys caught me. Air is a gas, technically. Yes, meant to say it flows like a liquid, and so does the "putty". So I guess I was trying to say the gas (air) and the solid (putty) flow like a liquid. :thumbs: , giving the inside of a intake manifold and/or cylinder the proper shape and smoothness. Back to your discusion on porting..... :leaving: