acceleration problem related to heat!

[BFS57]

Hello;
Well, it's getting to be summer again (at least here in Florida). The other day I noticed a problem with acceleration when the motor is at 210 degrees!
350, mild cam, Edelbrock performer intake, 1406 carb. This starts out when it reaches 210 degrees, what happens is: First the motor (like some one flipped a switch) while idling starts running a bit rough and looses rpm's. then when I accelerate, easy, it seems alright. but, if I have to step on it, it almost quits!, sounding like it is running out of gas!, If I let off of it and then re-apply, it seems ok.
I'm almost certain it's in the carburetor. When the motor is cold up to and a bit over 190 degrease everything seems fine!
What The Hay! I checked for vacuum leaks, haven't found any obvious things yet. Anyone got a clue!

Bruce

[slocrow]

One word............percolation. I know it's hard to believe but that is my guess. My 32 would scoot fine until is was over 200 and then ........bog off the line and at low (rolling) rpms. I was plagued for two years until I pulled the side curtains. After that no more bog and no more smell of gas in the garage after I'm home from a run. I think it's your underhood temp.
That's my guess anyway....................Frank

[Charlie Chops 1940]

Have you got an insulator block under the carb? That will help. If all else flows put three wooden clothes pins on the gas line...have you changed your antifreeze this year yet?

Charlie

[Dave]

Man I got the insulator and it didnt cure mine and mine its while you have your foot in the radiator about 70 MPH when its hot out.. Any other time its fine. I even changed the hood sides to louvers and it didnt help a bit and the engine temp is 180..Oh well this fun right  Ha Ha Ha ..
Dave

[C9]

What kind of ignition system do you have?

[BFS57]

Hello Again;
At present I am running the Mallory Unilite set up in a chevy distributor fed by a DELCO Coil. I changed the wires and cap out, got them from NAPA. I had vapor lock when I first put the motor in, so I ran my fuel line not close to my motor and insulated it with some oversize rubber hose over the metal fuel line.
If you get on it and it craps out, you can let off and hit it again and it seems to be fine. I have a fan on my waterpump as well as a 2700 CFM electric. Of course this all is in my 57 Chevy.
Giving up any answers yet?
Thanks for the clues so far.

Bruce

[enjenjo]

I think you are on the verge of vapor lock. I have had this same problem, on several cars in the last couple years. I was told that the gasoline has been reformulated for emmisions, and fuel injection, to the point it is too volatile to run well in a carb at high temps.

The cure I have found is using a pusher pump near the tank to keep the fuel in the line under pressure.

[hotrodbob]

if you are not using an electric pump the low pressure from a mechanical pump can contribute to vapor lock in the heat. Or if you have an electric pump to far away from the tank it will cause vapor lock as the pump starts to heat up from working to hard sucking the fuel that far.

I'd also look into getting the engine temp lower.

[Jokester]

Have you checked to make sure the choke is opening?  I had trouble with an electric choke once.

.bjb

[BFS57]

Enjenjo;

The cure I have found is using a pusher pump near the tank to keep the fuel in the line under pressure.[/quote]

OK! sounds like a try to fix! Give me some more info. What kind of pump, how many psi? what else do I need to go with? Regulator? Whatever? I already have a electric wire for pump to the rear of the car via the harness.
Thanks for all the helpful hints so far, all of you knowledgeable guys!

Bruce

[GPster]

The best explanation of fuel perculation i have ever seen was in a book about car wiring. The re-formulation of gasoline is part of it. The pusher electric fuel pump is part of it too. One part of it that sometimes gets missed is the size of the fuel line fron the tank. with a high volumn/pressure fuel pump on the engine it is actually possible to "suck a hole" in the gas in the fuel line. Tight bends in the lines, places near the exhaust, plugged filter in the tank or fuel that is more likely to "percolate" all exaggerate this situation. Sometimes you can feel that the fuel is boiling between the pump and the carb but it could be vaporized before it ever gets to the pump. I'm certainly not trying to tell you this is the only problem. It's just one more thing to add to the list of explanations. GPster

[reborn55]

Sounds like temperature( percolation problem)  Are you running a fan shroud, cooling system in good shape.  Chevy had a similar problem in the mid to late 80's on the Camaro and Monte Carlo SS.  they solved the problem by putting a little fan on the intake near the fuel line.  I would look at any way to bring the temperature down.

[hotrodbob]

What T-Stat are you running? What is normal operating temp.? You gotta get the engine temp down. Fuel problems will persist if the engine runs that hot as the under hood temps will be hotter..... You do have a hood don't ya?

[enjenjo]

Enjenjo;

The cure I have found is using a pusher pump near the tank to keep the fuel in the line under pressure.

OK! sounds like a try to fix! Give me some more info. What kind of pump, how many psi? what else do I need to go with? Regulator? Whatever? I already have a electric wire for pump to the rear of the car via the harness.
Thanks for all the helpful hints so far, all of you knowledgeable guys!

Bruce[/quote]

I am just using a generic electric pump from NAPA. It gives enough pressure on the line to keep it from Vapor locking. I still use the mechanical pump too, just use the electric to boost it. The mechanical will pull fuel through the electric if it;s turned off.

[Mercman1951]

Do you have a heat shield on the carb? Sounds like the fuel may be boiling. I have seen some setups where they bolt on a plate between the carb and intake as a shield...from the factory...an aluminum plate. Is that what you guys are talking about?