4 barrel intake!

[gestalt1]

check this out:
http://cgi.ebay.com/ebaymotors/PORSCHE-911-CUSTOMS-4-BARREL-INTAKE_W0QQitemZ160039720862QQihZ006QQcategoryZ336 40QQrdZ1QQcmdZViewItem

i've not seen this before. I have no affiliation to the auction, just thought it interesting.
-matt

[masraum]

Ouch. That just seems like a bad idea. I believe we have seen one or two here on the board before, but not that particular version.

[Joe Bob]

WOT Porsche powered sand rails use em....seen a similar set up on Corvairs.

[masraum]

On second thought. Maybe that would be perfect on a laser 917 kit car.

[RarlyL8]

What are the 2 open lines under the carb plate?

[Joe Bob]

Look like oil lines....for warming the plenum?

[Elombard]

I saw that too and meant to start a similar thread, glad you did. What would be the advantages/disadvantages? Tons of info and parts. Heck you could even do one of those TBI set ups for cheap. Seems like you could get the air fuel dialed in pretty good. Big drawback is you still cant use it with big cams.

[A Quiet Boom]

Originally posted by Elombard
..... Heck you could even do one of those TBI set ups for cheap. Seems like you could get the air fuel dialed in pretty good. Big drawback is you still cant use it with big cams.

Funny I was thinking today while looking at my old CIS setup that I could easily fab up a 4bbl plenum. Uh why can't you use big cams? It's done all the time with large plenum 4bbls on V8 engines. The longer runners should help low end torque but might hurt top end. If you think about it it's not that bad an idea, cheap way to go carburated for early and simple conversions. Of course you lose the value of IR setups. What about 3 deuces and no plenum?

Well back to figuring out those 46mm Zenith's.....

[rick-l]

What does the Big rubber coupling between each sides intake manifold do on the DME cars? Do the heads move around relative to each other with stress and heat?

Do the tubes on the above manifold flex?

[EarlyPorsche]

I wonder what it would sound like, might sound really weird. I also don't know what size (CFM) holley I would buy for that. I am guessing around 500cfm would be about it for a 2.2.

[911pcars]

The plenum under the carb is good for more even fuel distribution. The long intake pipes are better for low end torque. However, the fuel source is too far away from the combustion chambers. There will be a huge lag when accelerating until the heavier fuel catches up with the lighter air molecules. IMHO, this setup would run best at WOT.

When cold, the engine will run rough due to poor fuel atomization. The tube around the plenum could be for hot water from a separate water heater. Cold engine also has cold oil, so I don't see the advantage of circulating oil during a startup. Could be the manifold can't atomize fuel very well w/o heat from circulating oil around it.

This would work better if the 4-barrel carb was pressurized with a turbo or supercharger.

Sherwood

[dean]

Originally posted by 911pcars

This would work better if the 4-barrel carb was pressurized with a turbo or supercharger.

Sherwood

No it wouldn't, a gas soaked rag would work better.

[EarlyPorsche]

911pcars, isn't this exactly how all amercian cars are fed with fuel? I dont see where the problem would come from? Also, isn't this manifold going to be just as cold as the stock manifold? I think once the engine is warm this will feed a much cooler air fuel mixture which is a plus as that air gap would probably really help.

[911pcars]

Originally posted by EarlyPorsche
911pcars, isn't this exactly how all amercian cars are fed with fuel? I dont see where the problem would come from? Also, isn't this manifold going to be just as cold as the stock manifold? I think once the engine is warm this will feed a much cooler air fuel mixture which is a plus as that air gap would probably really help.

In theory, that's how all engines work. However, the length of the intake tract from carb to intake valve is the issue. Domestic cars (V-8s, inline 4s and 6s) with carbs usually have a much shorter intake path. The only way this would work is if fuel is injected close to the valve, then the tube only transports air. This is a carburetor that mixes air and fuel at the far end of a tube. The weight of air and fuel is different, and the carb must produce the correct mixture for each cylinder and deliver it on demand. The further away the source of these elements from the combustion chamber, the greater the time lag to supply the correct ratio. In addition, when accelerating, the engine requires an instantaneous gulp of air and more fuel (different A/F ratio). Again, the distance precludes the remote carb in supplying this fast enough.

"Once the engine is warm" is the key. Before that, at startup and before the engine warms up, fuel can't atomize thoroughly due to lack of heat. At steady throttle openings, I see fewer issues with this system.

An engine should run fine once these obstacles are addressed. You could try this out, then let us know how it works.

Sherwood

[Jesset100]

By 1967, the Cross Ram concept was by no means new, Chrysler engineers had developed the "RAM" idea in the early '60's. Equal long tuned runners create a ram effect needed to "pack in" the fuel mixture when using long duration cams on engines with high rpm capabilities.

[Don Z.]

Corvair guys do it all the time.

Corvair guys also bang their heads against the wall because the fuel won't atomize...

Mr. Bernoulli knew that already...

[randywebb]

This was an aftermarket upgrade for VW's - I had one on my '73 Bus. It isn't the greatest - even on a 4 cyl. - but it was lot better than the solexes that VW put on the motors that year.

[scott.k]

Originally Posted by EarlyPorsche

I wonder what it would sound like, might sound really weird. I also don't know what size (CFM) holley I would buy for that. I am guessing around 500cfm would be about it for a 2.2.

not to bring up an old post, but im about to buy a four barrel to put on my car (3.0), and I was wondering what size would be recommended. I was thinking 650 or 700 or 750.

Thanks
Scott

[80-911SC]

I see your in the federation of california ... you do know this wont come close to smog CARB approved right ??? if off road ok but ?? is this for a street car ??

Steve

[mholbrook38]

600cfm would flow plenty for a 3.0 liter. I don't think there is anything smaller but if so, that would probably be better. That intake manifold is a square bore so a Carter AFB or Edlebrock would fit on it. Also some Holley. I've only used Carter/Edlebrock on Mopars in the past.