Since I brought my car back from the dead for the 2nd time, I've always been annoyed buy the percolation of this ethanol gas, there is no non ethanol gas sold around here. Every time after a hot soak the gas would boil off and flood the manifold and empty the carb bowls. I did the following to try and stop this from happening mostly learned from you guys on here, wire open the heat riser, block the carb heat, install a heat shield, install a heat spacer.. All seem to help a bit but not all the way. It still took 3 or 4 cranks before it would fire. After 4 the wife started opening her purse looking for her AAA card.

This week I added a muffin fan to the outside ot the radiator frame to blow cold air on to the carb.


I used the existing cold air duct that goes to the heater box. By removing the end that goes to the heater box and routing it to the carb, now when I shut off the engine I can turn on this fan and blow cool air on the carb . Today I made a 10 mile run stopped at a restaurant turned on the fan and went in for an hour and a half, typically after this same routine it would take 4 cranks to fire. today started right away. when i drove home and put it in the garage the engine temp was approaching 200, shut it off , turned on the fan and let it sit for half an hour started on the first crank.

fan located on the outside of the rad shell, was able to get in there without removing the hood, had to insert from in front and then put up in place...


Cold air duct heading to carb


Going to carb

At the carb

One cable tie to hold in place.... snip this and the duct will go right back on the heater box...
The next part will be to move the switch inside the cab so I won't have to lift the hood to turn on and off. This might work for you, it took about 2 hours total to get working, hiding the wires might take longer if you're into showing..

Good luck fighting the battle of crappy gas..
Dave

 

Very innovative Dave.
Here in the hotter climes the ethanol gas can be a real nightmare.

 

I have tried all the same remedies you have and had the same results on my 64/327/300. Exact starting problems with heat soak as well. Since my C2 has no heater intake tube, I wonder if just mounting the fan on my heat shield and directing it toward the carb float bowl would have the same effect or whether bringing in the outside air is the key to it all. Dave

 

My original plan was to just get a couple of L brackets and mount the fan on the heat shield...it meant that the air cleaner wasn't going to fit correctly.. Drawing air in thru the rad meant that air would be at least 180 degrees, which wouldn't cool too much, that's when I thought that the outside would be best.. the heater box duct is way bigger than needs to be just to keep the carb cool. I think a 2 inch duct would do just fine and look less obstrusive. Taking air anywhere around the wheel well would be another area to look to mount the fan...

Also no original parts were harmed to make this mod...

Good luck...

 

A marine engine compartment exhaust fan will work, also. Check marine supply houses.

 

i used a old pc fan in my 72. pulls air from the a-frame area into 3" duct to carb. switch under dash- BUT i only needed it w/aluminum carb. so last 5 yrs it just sits there.

 

I looked at the marine fans and they are interesting, they have the duct flanges making it easy to connect to... BUT they draw 2.5 amps vs 100ma for the muffin fan, so leaving it on for a long time is no problem....

 

Well you just ruined my idea for a carburetor intercooler system. I envisioned a cooling plate between the carb and intake with it plumbed to a mini radiator (with optional water spray) and thermostatically controlled electric cooling fan, integral Li-ion battery and roof mounted solar panel.

 

you're going to have to keep it under $20 and 2 hrs of work... and we're going to need pictures....

 

I had the same problem with my holley and big block. you could hear it sizzling when I shut the engine off and the carb was too hot to touch.
a 1/4 inch 30$ phenolic carb spacer/insulator and a 160 degree thermostat solved it all. carb was then always cool to the touch.
see jegs or summit....

 

Yea I have a 1/4 inch insulator under the big *** aluminum heat shield in picture 4, you can also see the nylon washers under the studs, I also have insulation on the fuel line from the fuel pump. I think I will remove the washers and the aluminum heat shield and see how it works just with the fan...

 

This week I took off the big *** aluminum heat shield and the nylon washers, did the same 10 mile run to a restaurant and let it sit for an hour and a half with the fan running.... started on the first crank. brought it home parked it in the garage for 2 hours with the fan running, this time it started on the last step of the choke....so it had cooled down the choke spring which is right beside where the air is coming out...

For me this is a simple inexpensive way to overcome the percolation problem...

 

Interesting solution. How much does it draw down the battery with the fan running for 1.5 or 2 hours?

Live well,

SJW

 

The fan I used is a computer muffin fan and only draws 100ma, it puts out around 120cfm, which seems enough to keep the carb cool...
Could probably run it all day and still start the car...

Dave

 

Dave, I just installed the same fan that you did on my '57 FI. Works like a charm! I gave some kids rides a few days ago on a 90 degree afternoon with no fuel perc problems. I couldn't have done that before. Thanks!

So many threads on the CF about hot engine running problems seem related to fuel percolation, or other problems exacerbated by percolation. This fan cost me $16. I had everything else that I needed.

 

Yep, that could run for hours. Thanks for the reply.

Live well,

SJW

 

Todd, glad to hear this worked for you, especially on your FI, was wondering if it would help since its so different to a carb. Heat soak with ethanol gas makes it a challenge in a Corvette. Having a 500 lb cast iron engine at 200 degrees and a pair of cast iron manifolds at 400 degrees all radiating heat in still air with fiberglass(insulation) everywhere and no metal to absorb all that heat, oh, and the big air cleaner stops the hot air from rising even with the hood cracked open… Having air moving past the carb and moving it out from under the air cleaner certainly makes a big difference and made the car a pleasure to drive again….

Glad it helped

Dave

 

What about in a C2 where you don’t have the fresh air pipe to work with? It doesn’t seem like just moving the air around would help. I don’t have perc problems driving it’s just when I stop for even a few minutes-it’s flooded!

OOPS, I see someone already posed a C2 question, but I guess there isn’t a satisfactory solution with out some non stock equipment. Mine has the fuelie air intake in the radiator support, but a duct would really look out of place.

 

Old school. Leave the hood unlatched. Allows for more hot air escaping the engine bay.

 

I might start with getting the fan and hang it anywhere that allows the air to blow past the carb with or without some duct work, you should be able to get fresh air from around the chassis.

Good Luck...