The Stovebolt Site Forums The Shop Area Engine Shop dropping float height in carter webers, 56 235 motor

I live in Arizona where it gets to over 100 degrees. I have replaced the old Rochester carb with a pair of Tom Langdons dual carbs. Last summer the heat soak is a real problem. Even at long stop lights the engine starts to overload. Has anyone dropped the float height and by how much to help remedy this problem? I have even made a double heat shield to run under the carbs to deflect some of the exhaust heat.
Thanks Sharon

The cure for heat soak is heat insulating spacers under carbs, electric fuel pumps and routing of fuel lines. Heat soak is a fuel leaning condition. My understanding of 'overloading' is quite different than a lean condition.
Could you give us a better description of what's going on with your 235 so we might better understand.

Do they appear wet at the throttle shafts after the engine has been shut off for a few minutes?

One precaution- - - -lowering the float will also create a lean condition over pretty much the entire mixture range, and will most likely cause a flat spot in the transition from idle to midrange RPM. Ideally, the float level needs to be just barely below the level of the venturi so it only needs a little extra airflow above idle to start the fuel flow in the main metering circuit.
Jerry

Heat soak is the fuel boiling in the carb fuel bowl. It usually comes after shutdown but like in a severe case like Sharons it even does it at idle. It is a flooding condition. It is not the same thing as vapor lock where the fuel boils in the lines & blocks the flow of gas to the carb causing hard starting & stalling after it runs a short distance. About the only way to solve heat soak is insulators & shields.

Fuel boiling in the carb bowl is a flooding condition. Does the fuel expand and get pushed into the throat of the carb? Don't understand exactly. Would you explain please. Thanks.

Yes the fuel does boil out of the carbs and down the intake. After some driving on a warmed up motor if you stop at a store for 20 - 30 minutes and come out to start the truck you have to give it extra throttle to keep it idling. It wont even idle on its own. You can smell the raw fuel out the exhaust. You have to keep the RPMs above 1500 for 20 to 30 seconds before it clears its throat and will idle on its own. On a 5 minute stop this wont happen. That's why I thought dropping the float level just a hair might help. I had an old MGA that did the same thing every summer.
I have insulator blocks under both carbs and have built a heat shield from 2 layers of aluminum with 1/2" spacing between them. Even put fiberglass insulation in the air gap. I hope this info helps you guys.
Thanks Sharon

Are your dual carbs the Carter-Webers (Ford 740s)?

What intake manifold are you using?

I had them on my 261 with a Fenton intake and they were no problem starting at anytime. They were just weak at high RPM.

Just had a thought. I might use an electric fan on the radiator and take off the 4 blade fan. Have the fan run when the engine temp gets hot and keep running after you turn the motor off. Say keep running for 10 to 15 minutes. This would blow air across the carbs cooling them down and lowering the engine temp also. I know some of the foreign cars I worked on would do this just to lower the engine temp. Maybe use a timer relay or temp relay to shut the fan off. How does this sound instead of lowering the floats?
Sharon

tclederman,Tim,
The carb set up I got from Tom Langdon and I think intake also .I cant see the name on the intake because of the aluminum shield I made to keep the exhaust heat down. They are 2 barrel progressive carbs. I would need to find the invoice to see exact numbers for you. I wish I could take pics and post them to show the set up under the carbs. How do you do this. You need some kind of account right?

The intake is a Fenton and the carbs are 32/36 electric choke carter/weber DGVE's.

Maybe a fuel bypass / regulator to send fuel back to the tank when it swells up from heat in the line. Or a simple fuel regulator to lower the pressure down to 3 psi, the floats should be able to hold that and not flood the engine. Low pressure is how I cured my three Rochester's from doing the same thing.

You probably have a nice fuel line setup, but for a test, you place two 1/4 turn shut off valve right before each carburetor inlet. Shut them off after a long hot drive and see if the problem really is in the carb or is in the whole fuel system leading up the carbs.

Might try that. Sounds like a possible solution. That's thinking out of the box.

Thanks Sharon

http://s50.photobucket.com/ Pic of carb shield

I got into photobucket and I think it worked. This should be a pic of the aluminum shield I made to keep excess heat off carbs. I'm going to check fuel pressure now to see if I need a regulator. Thanks for the help you all.

Sharon
Will let you know how it all works out.

Sharon,

That is the link to the main photobucket homepage - not to your account (and, not to the specific photo in your account).

Photobucket is a PITA. Nonetheless, there are limited alternatives for free hosting sites.

Get you photo in your display, try to right-click on your photo and "display in new tab". If that works, copy the address/link for that displayed photo and post that link here.

The PITA for pics is the reason I and sure others don't do it. I would love it if this forum would allow photos to be attached to questions and answers like over on the AACA site.
Sorry, just wishful thinking. 🤔

http://s50.photobucket.com/user/tdanella/media/20170213_144744_zpspnzdpokz.jpg.html?o=0

does this display the picture?

Yes

It does not remedy the problems for me - too many ads that hang-up my computer.

There are no ads if you just give the address of the photo (and, the photo displays almost instantly).

I'll try harder next time. The fuel pressure on a stone cold motor is 3 1/2 lbs. Maybe it's higher when it gets really hot I don't know. Guess I'll look into a fuel pressure regulator.

how much fuel pressure should I be running on this motor?

thanks Sharon

I know nothing about these specific carburetors; were they mine, I would be calling the company that sold them.

With that in mind, a few general comments:

It would seem you have two different issues, both caused by excessive heat. For the difficult starting from 5 minutes to an hour after shutdown, try this link:

http://www.thecarburetorshop.com/Troubleshooting.htm#Hardstarthot

The issue of loading up at stop lights may be somewhat difficult to solve. If you have a manual transmission, the best "fix" may be periodically "blipping" the throttle until you leave the light. However, as Joe mentioned, an electric fuel pump at the tank, and a return line at the carburetor going back and dumping into the tank MIGHT help, as this will continually shunt hot fuel back to the tank for cooler fuel. However, at idle, the fuel useage may be so small as to not make a difference. What is probably happening is the fuel in the carburetor bowls are perculating through the bowl vent and into the main venturi area, creating an artificially overrich condition. Blipping the throttle will help to alleviate this condition.

As to the fuel pressure question, I would defer that to the company selling the carbs.

Jon.

Those carbs are not the 32/36 Webber units. Thoes are the ford 32/32 motorcraft 740 units also sold by Tom. I had a slight fuel issue but it was fully fixed after I moved my lines. I ran mine right above the exhaust like you but then moved them up and out of the way and my issue went 100% away.

My fuel line location

Hey wolffcub, I see you added the fuel pressure regulator and gauge. How much pressure are you running to the carbs? Very clean setup with those braided lines also. Thanks for the great answer.

Sharon

I was running a electric pump so i used it then but ended going back to the manual pump. Now the regulator is fully open and not doing anything but i kept it because it has a filter attached below it. The manual pump puts out about 7psi.

My pump puts out 3 1/2 lbs when cold. Seems to be enough to run at freeway speeds. I'll try your setup, thanks