Porting intake

[Geek]

I was looking through the forums, and came across several mentions of porting the intake manifold in order to improve hp. I didn't find any mention of what the best method of doing this is. Is this something that can be done by an amatuer? (I'm fairly handy with tools, but no mech. genuis). I know some of the basics, and I know how to read. Any advice? Good books? Specs and pictures of a ported 1.9 intake manifold ? Any help would be ....well, helpful.

David

[RallyBob]

I wrote a 'how-to' article many years ago for the OANA's newsletter. I believe Charles Goin has a link to a PDF file with my article from his wwwopelmanta.com website. He also at one time had photos of the last intake I ported (I know they were posted somewhere, but can't remember where), which he won at an auction at Carlisle. Ironically, I have neither the article anymore, or any photos of intakes, so I can't personally help.

Bob

[Travis]

http://clubs.hemmings.com/clubsites/...ech/Intake.pdf

-Travis

[kwilford]

I recently tried some of Bob's suggestions on my intake manifold, but I have to admit that it hasn't turned out quite as nice as the pictures. I just concentrated on smoothing out some of the square edges and ensuring that the opening matched the carb. I haven't had the nerve (yet) to try the more radical changes, such as grinding right through the mounting bosses and then welding them up. But I am considering adding the "pent-roof" to the base (to improve low end response by reducing the volume). But I will probably get it professionally welded, as I haven't yet learned the art of aluminum welding with my MIG welder. As for power improvement, I am at least a few months from having it back on the road.

I recently saw pictures somewhere of a CIH engine that had a very nice manifold modification, where he actually cut out the square corners (along side the carb mount) and then MIG welded in angled plates to make the airflow smoother into the side runners. If I can find the picture, I'll post it as well.

I have the .zip file of a bunch of pictures of Bob's (now Charles Goin) intake manifold, but it is too big to post. So here is one select photo (at reduced resolution), and I will see if Gary can post the .zip file somewhere.

[kwilford]

Another Photo

[kwilford]

And another

[kwilford]

And another

[kwilford]

This should do. Look for Bob's signature....

[Gary]

The zip file is now in the downloads section.

[Geek]

Again, thanks. I had a somewhat related question about a dual downdraft setup that is currently for sale on ebay. This is a dual weber 40 downdraft from an Opel Capitan. Is this something that would be worth putting on a stock GT motor, or is this overkill? Would it produce much of a difference over a ported intake with the weber 38? How about the difference between it and a 2.0 litre FI setup? Again, any thoughts would be welcome.

David

[kwilford]

Here are a couple of pictures of the other intake manifold I was mentioning. The whole series can be seen at
http://photos.groups.yahoo.com/group...src=gr&.view=t

Enjoy!

[kwilford]

Note slanted edges of the intake below the carb base.

[kwilford]

And...

[RallyBob]

I usually polish down most items (before buffing) with a dual-action sander, locked out to spin only. They work well at removing 80-90% of the surface blemishes, and you can use progressively finer sandpaper....320 grit works well for the final grit. For the tighter areas, a die grinder with cartridge rolls works awesome, and the final buffing is done with buffing wheels and various compounds.

[kwilford]

Bob,

What do you think of Joe's manifold shown above? Are the angled corners worth the effort?

[RallyBob]

Can't say I've ever flowed an intake with the angled corners. I'd think it would be a bit better with a radiused transition however.
The one key issue to consider is a large angled transition will have far more plenum volume, so I'd consider the 'filler' in the floor of the intake critical, and it would need to be larger than usual to compensate for the increased volume.

[calvin]

I have a set of freshly rebuilt dual forties with cannon intakes. My question on the intakes would polishing them and then adding a brass screens help low end?
c

[RallyBob]

Cannon intakes flow like crap. They're the worst of the sidedraft intakes I've flowed. However, they really respond to being professionally ported. They need to be welded first, on the inner radius just after the mounting flange where the carb mounts. I end up grinding about 3/8" of material away here, and it breaks through the casting. The results are incredible, one person who's using a pair of Cannon intakes I ported gained 500 rpms in top gear at Daytona in his Opel Kadett, with no other changes.

His cylinder head flowed 128 cfm through the bare intake port. With the standard Cannon intake bolted in place, the airflow dropped to 117 cfm. After porting the intakes the airflow increased to 132 cfm, so it actually improved arirflow over the bare port because the intake runner straightens the airflow prior to it entering the port. Opels have turbulent intake ports.

Screen in the intake port? It'll choke down the airflow. Not worth it. Properly sized chokes and a well set-up engine will atomize the air/fuel just fine.

Bob

[calvin]

cannons welded up before blending and reporting

http://briefcase.yahoo.com/pdr1313 look in photo's

[Joe Van Wagnen]

Keith

if your refering to my intake the welder built up the outside more than i asked and it is all solid weld... the inside is radiused just like bob posted in his full race proted intake article

as far as polishing the outside.... i would suggest doing the grinding yourself and taking it to your local polishing place and have them do it.... mine only cost $40 and if you do it yourself it is time consuming and not worth it to me.

The expensive part of getting the manifold ready to port is getting it ready to port by welding.... it is necessary to build a jig to bolt it to to keep the warping to a minimum.... also the easyest way to weld the wedge in the bottom was to cut the bottom out weld the ramp in and then weld the bottom back on. i also had 1/4" alluminum rods installed in the old intake to exaust bolt holes and welded in so i diddnt port into this void (as bob suggested)

both of the mounting surfaces (carb mounting surface and manifold to head surface) warped, i had to have them machined flat again.... this machining also lead to having the bolting suface on the exaust manifold milled down to mach the bolting surface thickness on the intake so everything matched.

[ftl]

Here are some photos of the mods I made to my intake. I went the welded route for the corners, then machined out the whole bottom and made an insert, which was then welded in place. Removing the bottom made the grinding a little easier as well. Since these images were made, I've polished up the exterior of the manifold to make it a bit prettier as well.

[ftl]

Another Image

[ftl]

The third and last angle.

[RallyBob]

Now that's an innovative porting method! I like it.....

Is the plenum insert a solid billet chunk of aluminum?

Very nice!

Bob

[ftl]

Thanks Bob. Now we just have to see how well it works.

I'm not quite sure what billet is, but it started off as a hunk of 1.25" thick aluminum that I found at my friend's machine shop where I was playing at the time. Here is a shot of the intake insert on the milling machine before I made a big pile of filings on the floor. I used the same machine with a smaller bit to take out the bottom of the intake to accept the insert.