DIY Intake manifold

[MrHijet]

I have a little side project where I need a custom intake manifold, as I have a non-standard tripple throttle body, which I would like to build on one of my engines.

I am actually not clear where I should start. I have the engine and the throttle body and very limited space between the engine and the (non-removable) firewall.

Because of this, I have to angle the intake manifold, which makes a DIY build even more complex.

My Idea is to build two plates: one facing the cylinderhead and a second plate facing the throttlebody.
Then I could use some easy cuttable material (No idea which could be ideal at the moment) to build a mock up intake to see how much space I have and how it fits under to hood.

Have anyone done something like this ?

Shall I build everything in aluminium, use alum tubes, bend them and let it weld by a professional welder ?

Is there a way to cast them to have "better" bends ?

Any other ideas ?


Cheers,

Daniel

[jfholm]

I had a friend do a mock up once with wood and fiberglass.

I personally would do one out of aluminum plate, tubing etc to match your port configuration. Doing a casting seems to be a big investment of time and money especially if it did not work.

Maybe you could do one out of plaster even and pull a mold off and cast it in fiberglass resin or some plastic resin from one of the sites we have been talking about for the port molds.

John

[Scott H]

[86rocco1]

I've made a few fiberglass items using methods similar to the one Scott described and I'd like to add a couple things. The ordinary polyester resin often used for fiberglass lay-ups also dissolves styrofoam so if you plan to use that, you need to protect the styrofoam from direct contact with the resin. If you use an epoxy resin instead you won't have this problem. Gasoline does indeed dissolve styrofoam but not nearly as well as some other common solvents such as acetone or even brake cleaner with either of these, you'll be able to extract the foam core much more quickly and cleanly than with gasoline.

[jfholm]

Ed,
What about Vinyl Ester resin they are using in some fiberglass bodies now?

John

[86rocco1]

If I'm not mistaken, vinyl ester resins use styrene as their base solvent the same as polyester resins so I'm pretty sure they'd attack the foam too.

FWIW, I used polyester resins on my stuff. I did this mainly because my parts had some tight compound curves which would have made using fiberglass cloth difficult so I used fiberglass mat and the mat I was using is held together using a binder that dissolves in styrene but not in whatever is used as the base solvent of epoxy resin. Had I been able to use fiberglass cloth instead, I may have used epoxy resin and saved myself a bit of work. Instead, I protected my styrofoam plug using thinned out drywall compound over top of the styrofoam and sprayed a few coats of PVA release agent on top of that, it seemed to do the trick nicely. The drywall compound comes off fairly easily if you soak the finished piece in water for a while. If you want to try this, make sure your drywall compound is the premixed stuff not the powder, the powdered stuff will NOT soften up and wash away with water, it's permanent.

[slracer]

I don't have personal experience here but a good friend who has done a lot with fiberglass on model aircraft and others toys says the "blue" insulation foam (urethane) you get at Home Depot, etc does not dissolve in the polyester resins like the "white" (polystyrene?) foam does. There is also some pink stuff floating around, check to see if it is urethane. Either way, it might be worth a look as that stuff is pretty inexpensive. I don't know what dissolves it to get it out however. :p -- Doug

[Scott H]

[86rocco1]

[86rocco1]

[Scott H]

Doug,

This link lists several chemicals that can:

Personally, I would be inclined to stick with polystyrene and use 86rocco's drywall mud method.

The foam board I used had a texture more consistent to the foam available in the hobby stores. IMO, this foam shapes more easily than the expanded foam. I had the best luck using belt and disk sanders loaded with 60 grit abrasives for shaping the foam core. Even so, you will have fits maintaining shape and dimensions. I am sure you will find sanding the drywall mud to be much easier. I am betting 86rocco could give a mini-clinic on the aggravation of shaping foam.

The beauty of his drywall mud solution paves the way for other tricks such as; shape changes using preloaded mud on medical gauze or cheesecloth. Similar to a plaster cast except the mud will dissolve in water faster.

[86rocco1]

The drywall compound is integral to the technique, it not protects the foam, it also allows me to fill in radii, fix mistakes, it can be sanded to nice smooth finish which makes the interior of the finished fiberglass part very nice indeed.

As far as shaping the foam goes, it's always messy, sometimes smelly, definitely not one favourite activities, although it's always sort of satisfying to watch the form slowly emerge. I use a hot wire knife to carve out the rough shapes, the one I've got can be used freehand or table mounted and makes quick work of large pieces of foam. I've got a 3/4" wide belt sander that I use to very good effect. I've also set up, for lack of a better term, a lathe, it's actually just a fixture that spins the work piece while I go at it with the belt sander or whatever.

[86rocco1]

BTW. this was the first thing I made using that technique.

[jfholm]

Ed,
That is really nice! It has had me thinking all day of the many things I can build now. This forum has really been a great source for information. I think I am getting excited again to race as I can do it a lot cheaper now and still have some very nice stuff.
John

[86rocco1]

Thanks John. The rest of the guys we race against all run a Holley carb with the "normal" round filter, we turned a few heads the first time we showed up at the track with that. I guess it didn't hurt that we won the club championship that season. I'm sure I don't deserve it but I'm taking credit for that anyways and a few of the guys have asked me to make them one.