Remote carburetor?

[Eric]

I'm working on a project where I am converting a fuel injected motor to carburetion. I'm wondering about the practicality of mounting the carb (sidedraft) on the fenderwall away from the intake manifold and connecting the two with a flexible coupling.
If both the fuel and the air/fuel mix is warmed, am I likely to have any driveability issues?

[Pinhead]

You would want to heat your manifold at least to coolant temp. The other thing is, throttle response will suffer due to the lag time between throttle tip-in and the air actually getting into the engine.

Having said that, I like the idea. Manifold heat and internal texture should help with fuel vaporization. You'll want to run pretty small pipe, though, to keep internal velocity high which will keep more of the fuel from dropping out of suspension.

[Eric]

Thanks for your input Pinhead.
The manifold will be heated by coolant and the fuel/air mix will run through a section of copper pipe that will have an outer jacket that will be coolant heated as well. The aluminum intake will be filled with steel screen and the inner section of copper pipe will be filled with copper scrub pads. Internal surfaces will be roughed up too.
I hear you about the inner diameter of the pipe wanting to be kept small to maintain velocity but with all the restriction of the screen I figure it's best to go no smaller than carb throat diameter.
I think you're right about poor throttle response, I just hope that it will be driveable.

[Pinhead]

I think having scrub pads inside the pipe will be bad for two reasons: Air restriction and Fuel condensation. Condensation being the worst of the two for mileage, IMO. But it will prove to be an interesting experiment.

[Eric]

And it looks something like this-
http://cedarman.webs.com/apps/photos/al ... id=9473686

[Pinhead]

How's it running? That definitely looks interesting!

My only complaint would be the sharp "elbows" causing fuel to drop out of suspension, and dry flow manifolds usually don't do well for air-fuel mix...

Results??

[Eric]

I haven't driven it yet, I need to sort out vacuum leaks, fuel pressure issues, etc. But running in the driveway it purrs like a kitten!
The manifold is a throttle body injection unit, so it's really not a "dry" manifold.
I don't think fuel dropping out of suspension will be a problem as the manifold is full of steel screen rolls a la Don Kendon.
The couplings on each end of the heat exchanger are transparent so it's interesting to see the flow of liquid gasoline leaving the carb but after passing through the exchanger it's dry.
You were right about the pot scrubbers- too restrictive, I pulled them out.

[daves66nova]

Have you driven it yet?

[Eric]

No, I haven't. After everything else was sorted out I found that it would lean out badly at higher rpms.
I spoke with two different guys that are experts on Zenith Stromberg carburetors (which is what that car has now got on it) they both told me that there is no way that carb would flow enough fuel to feed that engine.
I was advised to go with a 1.75" S.U. carb which is what I'm now looking for.
I'll update as soon as it's on.

[threepiston]

Well, the smaller the carb, the harder it sucks on the venturi. It may restrict the air, but as long as it flows enough fuel, you will be ok even if running a 1bbl on a Caddy 500.... Don't be afraid to enlarge jets, as brass can be soldered and re drilled..... Air bleeds play a huge role too, after the main has been sorted.

A torch tip cleaner is how I got my hybrid huge engined mower to run good. A little here, rev, a little there, rev, repeat....

Cutting a coil or two off your vacuum spring will make the fuel come sooner too (under the "dashpot") at WOT....