adding a 3" carb cooling fan w/duct for aluminum carb

[Matt Gruber]

back in the 90's the zinc carb would boil too until I added a wood isolator.
.
Now testing a 4011 aluminum carb, even the wood plus cork isolators under the carb to manifold nuts don't stop the heat transfer w/hood closed. But they extend boil time to over 1/2 hr. so it is rarely a problem.(tight space under a 72 vette hood, roomier cars and trucks may not have this problem) Once the fuel boils out it runs like crap until it cools off, not long if there is an open road ahead, but murder in a traffic jam.
So i mocked it up and it looks easier than i thought, and draws way less power, only 0.185 amp. If i forget it is on, it won't kill the battery for days
May test it just hanging the duct near the frame. Better would be to connect it to the '69 vett side duct in the fender.
It actually looks nice, "chrome" dryer duct.
Could be some time until i prove it works, if it does(fan may be too small). First i have to measure the carb temp a few times before, and compare it to after the fan is in. And then I have to drive around for, like a year, to be sure. Maybe then I'll buy a new aluminum carb. If not, I'll rebuild an old zinc spread bore. Or maybe keep the 4011. It is excellent on gas, after re-jetting to #55, and #58 main jets. It cruises even as low as 35 mph thru the annular boosters (about 1500 rpm). There is NO T-slot! Just a .025" pin hole for transition.

[Sandman]

I had a problem with fuel boiling a few yrs back.

I had found the biggest problem with fuel boiling, was in the fuel line to the secondary. Or actually getting hot in the line, but not boiling because it was under pressure, then boiling when it went to the float bowl and was at atmospheric pressure. Kinda like pulling radiator cap off hot engine.
The secondaries are the biggest problem because there isn't fuel flowing to them all the time like the primary line.

To overcome it I made fittings to come out the other side of the bowl(on a centre hung holley bowl) and put a backpressure reg on the outlet line back to the tank.
I used a jet in the fittings so that more would flow past the rear jet than the front.
So then I had fuel continually returning to the tank.

Worked real well for me. Solved the boiling problems, plus car ran better and seemed to make a little more HP as well.

[maxc]

My new Summit 4011 hasn't boiled yet. My hoods not on.
I have t-slots on mine.

[Matt Gruber]

My new Summit 4010 hasn't boiled yet. My hoods not on.
I have t-slots on mine.

maxc,
that's the 750vs right? the larger venturi, 1.375", would have difficulty cruising around town without a T-slot. would have a flat spot until the booster engaged.
.
anybody have the summit 600vs? does it have a T-slot or a pin hole? This could be my choice, due to the quicker responding 1.25" venturi. (and my low cruise speed 40-45 mph around town)
.
Picking a street carb reminds me of picking a street cam. There are downsides to going with a larger size, even tho it costs about the same, bigger is not better on the street, if year 'round drivabilty and good mpg are important. I like being able to drive off on a cold start in winter (Florida) without waiting for it to warm up, for example.
.

sandman- thanks for your story!

[Dodge Freak]

Why not just run a mechanical fan off the engine, it throw lot more air across the engine / carb then a 3" fan would. I run a small 15" flex fan to help out the electric fan in front of the rad

[maxc]

My new Summit 4010 hasn't boiled yet. My hoods not on.
I have t-slots on mine.

maxc,
that's the 750vs right? the larger venturi, 1.375", would have difficulty cruising around town without a T-slot. would have a flat spot until the booster engaged.
.
anybody have the summit 600vs? does it have a T-slot or a pin hole? This could be my choice, due to the quicker responding 1.25" venturi. (and my low cruise speed 40-45 mph around town)
.
Picking a street carb reminds me of picking a street cam. There are downsides to going with a larger size, even tho it costs about the same, bigger is not better on the street, if year 'round drivabilty and good mpg are important. I like being able to drive off on a cold start in winter (Florida) without waiting for it to warm up, for example.
.

sandman- thanks for your story!

750VS Summit carb.

[Matt Gruber]

Why not just run a mechanical fan off the engine, it throw lot more air across the engine

I don't ever run the engine while i'm walking around at a car show. (it DOES have a mechanical fan) Carb doesn't boil until 1/2-1 hour after it is shut off.

[Dodge Freak]

Its the air cleaner and hood trapping the heat, a hood scoop is out - yeah some cars don't look right with them or it cost too much to do it right

[Matt Gruber]

so i put in the fan/duct for a test. Found hole under mud flap in inner fender right over A-arm, just inside tire.
Didn't seal it for this test (too lazy).
Didn't properly wire it either(prove it works first)
Only took a half hour to tie it in.
.
TEST:
drove 10 miles
parked in my garage hood closed 1/2 hour
open hood check carb temp with infrared gun
127-130F
Hot wire fan on
closed hood for 30 more minutes (i looked after 15min and it is working, front bowl under 120F)
more...................soon, test in progress
.
Test over, 30 min hood closed, Front bowl 114F!
Rear 120F. since i have fan flow directed to the front i'm pleased with the result!
Hood up 15 min fan on, front bowl 109F
hood up, fan OFF, another 15min front bowl 114.
So what do you guys think?

[Dodge Freak]

That seems pretty cool but why only a 10 min drive, after 10 mins you should had drove it hard for 10 - 15 more mins, that would have heated up everything more - like the trans

My carbs get too hot to touch on a 90 degree day after parking for 30 mins in the garage. Takes 5 to 10 seconds to fire it up, I start cranking and then open the gas a little and pretty soon if fires and I rev it high for few seconds. Sometimes it will idle rough but doesn't stall I take right off to cool things off

I have a high torque mini starter, cranks the engine over pretty quickly, once it fires you gun the engine for a bit

Maybe your gasoline is junk down there

[F-BIRD'88]

I would think a auxillary electric fan on the rad and a auxiliary inline water pump in line in the heater hose circuit to move the water would be much more effective as you would be attacking the heat/hot soak problem right at the source. The carb and whole engine will cool down a whole lot faster.
Much easier to package it under hood with much better results. Run it for about 15 minutes at after shut down, on a timer.

Hot soaked carb: Start it up and rev the engine to about 2000+ rpm for a minute or so before driving.
This will get fresh cooler fuel (from the fuel tank) into the carb, lines and mech pump, which will cool it.

Normalizing the temp hot soaked engine/carb temp is no different than warming it up on a cold winter morning
before driving off.
Run it... @ at high idle speed. Some things are just better when kept simple.

[Matt Gruber]

That seems pretty cool but why only a 10 min drive, after 10 mins you should had drove it hard for 10 - 15 more mins, that would have heated up everything more - like the trans

My carbs get too hot to touch on a 90 degree day after parking for 30 mins in the garage. Takes 5 to 10 seconds to fire it up, I start cranking and then open the gas a little and pretty soon if fires and I rev it high for few seconds. Sometimes it will idle rough but doesn't stall I take right off to cool things off

Dodge
I'd say we are in agreement(except it was 20 minutes with red lights and traffic).
It was just a "proof of concept" test.
When i drive 22 miles 1 way to the tire store, after an hour or so there, if it starts instantly and runs great after that, i'm convinced. will file patent and get rich
FBIRD
i'm sure there are other ways. i had the fan and duct left over from another project and total weight is only ~1 lb. and i also have a 4.5" fan (only cost $5.99) if more air is needed.
There is no elec fan at the radiator to try.
Easier to package? this looks great and was the easiest thing i ever installed.
.
Car guys,
allelectronics.com has switches, LED's etc, and a nice fan for $3.50 part # CF-407 .3 amp, more power than mine.
Home Depot has nice chrome accordian style duct cheap. Don't put up with carb boiling! Gas boils out of carb into intake, drips into cyl's, washes oil off cyl walls, shortens engine life. can dilute oil with gas.
and the obvious, it wastes gas!

[Bob Hollinshead]

I had a problem with fuel boiling a few yrs back.

I had found the biggest problem with fuel boiling, was in the fuel line to the secondary. Or actually getting hot in the line, but not boiling because it was under pressure, then boiling when it went to the float bowl and was at atmospheric pressure. Kinda like pulling radiator cap off hot engine.
The secondaries are the biggest problem because there isn't fuel flowing to them all the time like the primary line.

To overcome it I made fittings to come out the other side of the bowl(on a centre hung holley bowl) and put a backpressure reg on the outlet line back to the tank.
I used a jet in the fittings so that more would flow past the rear jet than the front.
So then I had fuel continually returning to the tank.

Worked real well for me. Solved the boiling problems, plus car ran better and seemed to make a little more HP as well.

I like that idea! With an electric pump and a thermostatically controlled switch it could also cool it down more when shut down.

[Matt Gruber]

Bob
i had a 2nd elec return pump on my 61 in '94.
i 1st tried draining the bowls at shut off.
Then, at re-start i'd run both pumps to cool it down.
i found the acc pump vapor locked and it was hard to start!
VERY HARD TO START
Plus all the add'l fuel plumbing created multiple leak sources, a fire hazard anytime anything leaks, and more fuel sources in a crash.
My bowl return is long abandoned.
I can't recommend anything with more fuel lines.
Too dangerous
Now that there is a safer method, why anybody would plumb more fuel lines over a small fan is beyond me.

[F-BIRD'88]

If you don't have this heat shield, get one.
http://www.holley.com/108-70.asp

You can make your own for a few $'s. Paint it WHITE.