Hot carburetor problems?

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Hot carburetor problems?

Postby deronmoped » Mon Jun 01, 2009 5:04 pm

So I'm having a too hot of fuel related problems.

1) Starting after running it and letting the car sit for a while requires running the starter for extended periods.

2) Sitting at stop lights and the engine starts to idle really rough, all most wants to die and I need to step on the gas a little to keep it running fairly smoothly.

3) Not sure if this is related, but when I get into boost, sometimes the engine backfires through the carburetor, I should document this better so I know if it does it all the time when it's only hot.

So one of the problems I have is with a lot of under hood exhaust components, 2-manifolds, 2-turbine housings and downpipes off the turbines.

Here is what I have to try to keep the heat from causing problems.

1) 1/2" carburetor insulator.

2) Heat shields around the 2-turbines and part of the 2-downpipes.

3) Electric fuel pump back at the tank.

4) Fuel filter not in the engine compartment.

Anyone know at what temperature things get out of hand for fuel? I mean what is a safe under hood temperature?

Has anyone had similar problems and what worked for them?

Thanks, Deron.
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Re: Hot carburetor problems?

Postby cjbiagi » Mon Jun 01, 2009 6:31 pm

Fuel can boil at a fairly low temp as I recall, 150-180 degrees. I had a similar problem and I made a recirculating system that returns the fuel back to the fuel tank so it doesn't just sit there in the fuel line/filter too long. This was done on BB Vettes as I recall and is also done on some later cars. Anyway, short of that I would try using some heat insulation wrap on the fuel lines and see if that helps.The entire line in the engine compartment should be wrapped . Also look under the car to see if the fuel line is close to any exhaust components.
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Re: Hot carburetor problems?

Postby deronmoped » Tue Jun 02, 2009 12:09 pm

Yeah, I thinking I will get a bypass regulator to replace my deadhead regulator. That should help while the car is running.

Insulation is the fix for a lot of things.

If all else fails, I may even add a thermostatically controlled small fan that runs while the engine is still hot and sitting. There is just no way for the heat to get out of the engine compartment after the engine is turned off.

Deron.
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Re: Hot carburetor problems?

Postby monza75tc » Tue Jun 02, 2009 9:55 pm

If the fuel lines are too warm, you could do like I had to do on my ole Merc flathead.....attach a couple of wooden clip on clothes pins to the fuel line. Funny...well it doesn't look the nicest, but it works.
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Re: Hot carburetor problems?

Postby deronmoped » Wed Jun 03, 2009 2:28 am

It's got to be tough to keep the fuel cool.

The air that is coming into the engine compartment is pretty hot considering it just went through a hot radiator. Then you have all the radiant heat. Makes you realize one big reason the auto makers went with fuel injection, keep the gas under high pressure till you need to use it.

Heat shields will block some of the radiant heat and insulation will slow the hot air from getting at the fuel. I'm probably going to have to incorporate as many of these measures as I can to get things under control.

Deron.
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Re: Hot carburetor problems?

Postby AusRs » Wed Jun 03, 2009 4:55 am

even on my Monza i had to insulate the fuel lines as fuel was boiling :( the hole in the hood has helped out an amazing amount ,would recommend it
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Re: Hot carburetor problems?

Postby deronmoped » Wed Jun 03, 2009 12:29 pm

What hole, do you have a scoop or cowl induction?

Yeah, these cars have no way to get the heat out, the engine compartment is built like a oven. All of a sudden those louvers, holes, open engine compartments start to make a lot of sense. I have been thinking of some way to get the heat out, not a easy fix if you plan on keeping the stock look.

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Re: Hot carburetor problems?

Postby chevyart » Thu Jun 04, 2009 10:57 pm

the factory 409 cars from 63 and 64 had return lines to the tank to prevent this from happening. this problem was also caused the stock fuel mpump used to cook as it is in the block and always drawing heat. this usually doesent happen with electric pumps . anoth ttrick from the truckers is to get a fuel filter with an in and out fitting and a third fitting (out and rout it right back ti the stock fuel line just before the fuel pump. this drains the gas when you shut off the hot engine and also circulates it a little more chevy art
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Re: Hot carburetor problems?

Postby AusRs » Fri Jun 05, 2009 9:01 am

deronmoped wrote:What hole, do you have a scoop or cowl induction?
.

Yes i made a hood scoop .works wonders getting heat out
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Re: Hot carburetor problems?

Postby deronmoped » Tue Jun 09, 2009 2:59 am

So I have been working away at it.

Decided to try one thing at a time to see when I could stop making things that would lower the fuel temperature.

The first thing I did was make a custom heat shield for the carb. This went between the manifold and carb. It should help block radiant heat from coming off the manifold. I made it as large as possible, mounted my fuel regulator on top of it to block heat from getting to it too. Well I drove the car today, it was not a hot day so the test is inconclusive, but when I went to start the car after everything being heat soaked, I was surprised as it started real easy. I usually have to crank the starter for like 10 seconds. I was not expecting this much of a improvement, but I still need a really hot day to see if this will be enough of a fix.

I still plan to insulate the fuel line in a couple more places.

I probably not get the bypass regulator, as that is expensive and time consuming to install.

I though about going to a electric fan. That would give me the option of having the fan run while the engine was stopped, controlled by a thermostat of timer. The things I did not like about a electric fan were, it does not circulate air all the time, the stock fan and fan clutch are pretty hard to beat in the cooling department and the added cost.

Deron.
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Re: Hot carburetor problems?

Postby cjbiagi » Tue Jun 09, 2009 6:46 am

You don't need a bypass regulator, I just use a fuel filter that has a small orfice and extra fitting designed to return fuel to the tank. I use my original vapor recovery line as a return or you can run another line back to the tank. I can get a pic of the filter or get you one if needed.
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Re: Hot carburetor problems?

Postby BillPappy » Tue Jun 09, 2009 8:29 am

Clyde

Did ya do anything with the Now Gas return line. Where it enters the tank? I was looking at that a few weeks ago. thinking about the samething.
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Re: Hot carburetor problems?

Postby chevyart » Wed Jun 10, 2009 1:31 am

do like clyde said bu you dont have to go all the way back with a return line. just loop it back into the in fuel line in front of a mechanical fuel pump(if you are using one. if not then use the return line to the top of tankchevy art
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Re: Hot carburetor problems?

Postby deronmoped » Wed Jun 10, 2009 1:43 am

I was reading about doing that and they were recommending no larger then a .060 orifice in the return line. You would want to make sure that where the line dumps into the tank that it is immersed in gas or you may hear noise. Also if you use a existing line to return the fuel, that may have been a vent line, you want to make sure you have some way of getting air into the tank.

Now of course what you are trying to do will need to address the problem. A bypass/return line will not take care of a heat soaked carb, it will help a little while the engine is running, but not while it is off. A overheated carb will be the worst when it is using the least amount of fuel, idling or with the engine off and you try a restart.

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