Intake manifold match porting.

[flemcadiddlehopper]

I am in the middle of a 2110 build, that many of you have been answering questions for me.
The question this time regards match porting. I understand it and the needs for it and have a good pic that illustrates where it is needed.

My question actually has more to do with the opening of the port and the opening of the manifold. If the manifold runner was opened into the the adjacent runner just above the head (say, about an inch) and the head opening was smoothed and radiused, would each cylinder (per head) be able to draw from both carb barrels (similar to a balance tube) and would it not help with the lean issues associated with every second cylinder to fire in the sequence? Kinda like a Syamese port with no control valve.
Has this been done?

gordo.

[modok]

no, that would CREATE " lean issues associated with every second cylinder to fire in the sequence"

IR carbs always run equal, there is no "issue"

If you had kadrons then it would be an issue, but looks like IDFs to me

[flemcadiddlehopper]

It wouldn't help the top end a bit, as it does on a Variable runner intake manifold? Or do I just need to stop thinking all V8ish?

gordo.

[modok]

It is used on v-8 only for supercharged apps

Do you have a supercharger?

You have some of the best carbs in the world, just get em tuned in and they are as good as EFI

[flemcadiddlehopper]

I'm just always looking for something that most don't do, Although it is usually for good reasons. ...Yes, if everyone else jumped off the bridge ,I would too.

gordo.

[mark tucker]

the "IR" system is hard to beat,it smooths out rough cams, has extreamly good throtel responce.it's hard to beat if it is tuned right.But if you feel the need to make it run like crap go ahead and grind away,but before you do, think on this.in that aera it might be kinda hard to weld inside the 2 runners to fix what has been effed up.a better soultion if you still have to try it is to drill&tap the outer walls and 1/2"run a tube/hose from 1 side to the other side of each intake, then you can just plug the hole when you get your answer.other wize just port them and forget about it.or if the droping of 1&2 is your disired affect just sell the idf's &put on a set of kdogs,solerplex's,weblers,brosouls, or what ever single throat crabs you can find. good luck,have fun&dont get hurt
funny I didnt see you in the watter behind me??

[66brm]

[modok]

huh, yep

[flemcadiddlehopper]

you guys kill me ...I get it, bad idea.... it is tough to know what is just old school because that is the way it has always been done from the sixties on, or if it really is the right thing because other options have been tried and proven not to be as effective.
I am sure there was some poor German old guy sitting at home whining to his fat ugly wife, that he invented direct injection for VW back in the sixties, and that all the other engineers laughed at him and told him there was nothing better than this tiny little solex.

So....has it been tried? What where the results?

Gordo.

[modok]

Yes it has been tried. Nobody's ever reported any kind of benefit, most likey it must run so awful they never speak if it again.
THere are some plenum type manifolds made for IDF/ida type carbs, you may be able to find some, never seen anybody actually claim they work well but they do exist. Connecting the two sides below the carbs would have superior results far as HP and torque, if you DO want to connect them
http://www.thesamba.com/vw/classifieds/detail.php?id=913554



On kadron or stock manifolds, sometimes it is good to have a SMALL passage between them, that acts as a damper. Since the runners are already connected upstream it does not really change the signal to the carb.

[spencerfvee]

back in the 1970s not real sure on this guys but i think it was C.B that sold heads that were cut out about 1/2 " into the intake port on the head . and they cut 1/2 " into the stock vw end castings. the heads were for the mini stock class. for dirt track racing . back then the rules said only single port intake manifolds could be used lol i think C.B. was trying to get around the rules . from what i understand it only worked best at high RPMs . not soon after that the rules were changed so you could run dual port heads . spencerfvee

[Eric Hodges]

The reason the IR-type carbs work so well is the basic design. I recall from some ancient Weber documentation that the carbs are designed to be 'pulse' carburetors. That is, they are designed to respond quickly to a gulp of air, meter and mix it correctly, then stop. If you make it respond too continuously, it will not work right. Review some threads on the progressive, it has been tried with difficulty and anguish.

Regards.
_________________
'74 Super, worn, becoming DD

[flemcadiddlehopper]

Actually the carbs were designed to deal with the pulsing of the intake air. When carbs are flow tested on a flow bench, it is not pulsed. The emulsion tube design acts as an air brake to stop the flow of gas quickly. The IR intake was also designed around the pulsing of air. When the intake valve closes the intake mixture has to stop suddenly (which it doesn't do well) but the inertia of the air keeps it moving to pile up against the valve, building pressure until the valve opens again. In effect it has a two stoke feel to the intake as it "comes on pipe". Intake and exhaust all work together in a set rpm range of the tuned pipe length.
To get away from that on pipe feel and tuned range and have a flatter torque curve the engine generally is de-tuned. Enter small carbs and restrictive exhaust. The engine does not produce as much power but is smooth running and not over stressed.
My thoughts on why I thought this may be effective has to do with air/fuel mixture swirl effect. The air/fuel coming directly down the one runner has a straight shot at the intake port and is fast moving, if the air/fuel mixture that was joining it from the other intake runner just had the brakes put on it would spill int the other side at a different speed there by tumbling the mixture more as it heads into the engine.
They have used this style of intake as a centre section on single carb application of DRLAs. I am sure that somewhere there as been an article produced where it was tried on dual carbs, but there are 50 years of articles to search through, that is why I ask you guys.

Tanks for all the input, Gordo.

[spencerfvee]

allso i must ask you . then why does a single port head work so well. it has a open plenum that feed fuel to both intake valves . could it be because it has a single intake manifold .feeding fuel to the head . i see right now on thesamba think it was clyde berg has a dual carb weber intake manifolds for sale .that were made into a open plenum manifold . spencerfvee . i just went to clydes adds to get a picture of the intake manifolds he must have sold them there gone spencerfvee

[JustBuggy]

[flemcadiddlehopper]

Yes those are ugly and not what i had in mind at all. The opening I am talking about is where the two manifold runners join together just before entering the head. In fact I was just looking through an old book with lots of seventies hot rod VW stuff in it, HP Books, How to Hotrod a VW Engine, and it had a picture of an intake manifold that had the rough cut-out that I was thinking of. Not a word was mentioned about it because they were explaining intake locating dowels. But there it is.

now if it was opened up a bit more and smoothed out it would be how i envisioned it.

Gordo.

[modok]

what purpose would it have? every hole needs a purpose

[Glenn]

[66brm]

I've never refered to it as a purpose before but whatever floats your boat
_________________
Aust. RHD 66 Type 1
Aust. RHD 57 Type 1 Oval

[JustBuggy]

Steve Martins "The Jerk" comes to mind here .....