Carb Intake Manifold

[Rocketman]

I've been working a bit on a carb adapter plate, and it's turning out to be a bit of a hassle with the way I'm trying to design it. I'll figure that out I suppose.

On the other hand, the carb intake manifold appears to be a small and fairly simple piece (at first glance) I don't own a festiva (yet) & I'm not super familiar with carbureted cars so bear with me. What's the purpose of all the water passages running beneath the manifold? Looks like one side goes to a the heater core, what are the two threaded bosses on the back for?

Being that the runner passages are a very simple design casting-wise, it gets me thinkin about making a whole manifold with a Weber flange. (or whatever flange)

So, thinking out loud, what could make the manifold better, and would it be worth it? Keep in mind the water passages and EGR stuff would likely all have to be deleted, or added in afterwards separately. Larger runners? Different runner design? (4 into one plenum? instead of 4>2>1?) Trying to think single-plane here as dual planes, or passages crossing each other gets real tricky real quick

Thoughts? Worth it? Spend my time on something else? lol

[bravekozak]

Patterns are expensive. Especially if you make an aluminum matchplate. You would also need two patterns for the cores. Not worth it. There aren't enough carbies left in North America to waste big bucks on patterns. I still believe that aluminum welding and machining wider bosses is the way to go, rather than change the throttle linkage geometry by installing an adapter. I personally prefer cars with no computer control.

[Rocketman]

I have my own "backyard" foundry that I am running full time now as my source of income. This includes all the woodworking tools to make the patterns & coreboxes, the equipment to mold & cast the part, a pair of metal lathes and a milling machine to massage the casting into a usable piece. Aluminum matchplate is not necessary, wood patterns & tooling plastic coreboxes would suffice here

[sasquatch]

I would love to learn how to do my own castings... it looks like a lot of fun

[FestYboy]

in this case, a 4-1 (or more correctly a 1-4) would be more desireable than our current setup. we need longer runners that are larger for better torque down low and better breathing up top.

the water passages are for de-icing perposes and to run those 2 pesky thermo-vac switches on the bottom. i suspect it would be wise in this case to at least keep a loop in the intake for the de-icing, but i don't see a reason for anything else aside for a place to mount our EGR (just in case there's a visiual inspection).

[blkfordsedan]

You can look on-line and find numerous sources for info on intake manifold design. There is a relatively formula used by Chrysler back in the old days that will calculate the runner length needed to target specific and multiple RPM ranges. It's based on the wave pulses bouncing back and forth in the runners and timing them with respect to the valve opening. The effect happens at multiple RPM occasions. The optimum length is from valve seat to carb, so you would have to measure the length of the port in the head. There are also formulas on runner diameter with respect to RPM and plenum volume.

[bravekozak]

I threw all of that theory out the window when I designed my GM 2.8 V-6 manifold. I thought the factory runners were optimized. Wrong thought.
I just went to my local speed shop and had it flow tested on a Superflow 500. I had to just grab a die grinder and grind it out myself and keep retesting. The pattern shop was useless with this.
The difference was night and day. I went for as big a flow as possible. MacPherson Off-Road Racing in Arizona liked it. It was better than any modification that they tried to do on the factory intake manifold. Dyno proven. I have the authenticated graphs.

[blkfordsedan]

Total air flow will always improve with bigger, straighter ports, but it's all relative to the application. Usually the OEM is a compromise between many factors, but sometimes the OEM is spot-on. The Ford 4.6 PI intake is a good example. There are several aftermarket intakes that offer some gain in the 5000+ rpm range, but almost all give up HP and torque below 5000 or at least don't add anything in the normal driving range. I would say it would be hard to NOT improve on the Festy carb intake with just a simple design. I would probably do a simple single open plenum and make the ports big enough to match a B6 head and taper down to the B3 port size at the flange..but leave enough meat there to be able to port match a B6 head. Equal runner length and volume, a carb base big enough to be able to machine to accept a Weber or maybe even an old Ford 2v carb. The more simple the design, the easier it will be to cast.

[bravekozak]

If the computer isn't required, a lot of vacuum fittings and bosses could be eliminated from the manifold (including EGR). However, a third core would still be necessary for prevention of icing on the butterflies during cold weather starts.

[mattdickmeyer]

I have a carb & EFI intake that will be ready for production soon. I have months invested in design & development with 43hrs of flow bench time. Nothing will top this GUARANTEED!

[blueoval]

do you have any pics or info on it? thanks

[drddan]

I have a carb & EFI intake that will be ready for production soon. I have months invested in design & development with 43hrs of flow bench time. Nothing will top this GUARANTEED!

....and I am awaiting these to come to fruitation!

[mattdickmeyer]

I am no longer sharing any info or pictures mid development of my work. I have found out that some people are copying or (atempting to copy my products). This is frustrating as bring quality perfomance parts to market cost thousands! I will post pics of finished products soon.

[zoe60]

Let me know when these manifolds go into production. I would love to get one for my B6.

[mattdickmeyer]

After thorough testing, and i'm completly satisfied with the results i will let every one know when available.