It's been a while since I've posted, hope everyone is doing well. For the most part the truck is working flawlessly, and I just get in and take off... once it starts that is.

There has been one small problem. The fuel evaporates after I shut the engine off and it has been running a while. Modern gas doesn't have the same blend of anti-evaporation additives as it did before the 90's. After shutting off the engine, the carb and fuel lines heat soak and after about 45 minutes to an hour, the gas will completely boil out. I've seen several you-tube videos on how others have attempted to solve this problem as it's common with carburetors across the board. I'm going to try 2 things:
1) an insulative carb spacer shown below. This is an original Ford piece I already had. I believe it came off of an 80's Ford truck, but I can't be sure.

The only downside is I will have to ditch the oil bath breather and use a shallower aftermarket type. The oil bath was already just touching the underside of the hood without adding the spacer.
2) The other addition is the generic "fire sleeve" from Amazon around the fuel line, also seen here. Below is another pic of the sleeve as it wraps around the distributor.

Unfortunately, when I put everything back together, the fuel line leaked at the carb. I swapped carbs thinking I cross threaded it and it leaked in the same place, so I must have distorted the mouth of the flare. It was an aluminum line, so most likely I simply overtightened it.

Has anyone else dealt with this issue? If so, what have you tried? How well did it work?

Some people route the fuel line completely out of the engine bay and back in to keep it away from the heat. In the summer, when the cab and fuel tank get hot enough, the heat will push fuel all the way back to the carb. I hope to at least delay the evaporation process long enough to allow me to stop for dinner and not have trouble starting back up when I'm on a cross country trip.

 

Are the carb bowl floats set to the correct level? Even a really hot engine bay shouldn’t boil out all the fuel from the bowls! I can understand how the fuel lines will heat soak but the engine is starting with fuel that’s already in the bowl. Also...the fuel that’s in the tank shouldn’t be extremely hot either. Believe me, I have dealt with the problem that you are describing.....heat soak and hard starting unless you have time to let everything cool down. It just sounds like something else may be contributing here, as some of your symptoms don’t add up.

 

I had the same problem. I used a 2" thick 4 hole phenolic spacer. Been 6yrs now and no problem with heat soak.

 

In this thread starting at post 20, same problem. Might be some tips.
https://www.ford-trucks.com/forums/1...weeping-2.html

 

The floats are set right. As long as the engine is running, it runs like a top even up a steep mountain grade. If I shut down and re-start before the fuel has evaporated out of the bowls, it starts back up like a new car. I have an aluminum intake which conducts heat much better than cast iron. The FE engine has giant exhaust cross over ports in the heads that introduce a ton of heat to the intake. I am also using an aluminum spacer for the PCV port. Without adequate insulation from the engine, the carb will heat soak. I'm using an Autolite 4100, which again is made out of aluminum not zinc pot metal like a typical Holley. Given enough time, fuel evaporates out of the bowls on virtually all carbureted engines with today's gas (worse with alcohol blends), even all the way down to the fuel pump. Do a search on You-tube for this problem and you will see I'm not alone.

Are you daily driving a carb'ed engine? What engine? Is your intake iron or aluminum? What carb are you running? What type of spacer if any? Are there exhaust port cross overs in the heads and intake? If you have the same arrangement as I do and you have solved this problem on your truck, please share your experience and what you've done to correct it.

In the summer when the cab gets hot enough and after the engine bay has cooled down a bit, the air in the fuel tank expands, pushing gas back up to the carburetor, greatly reducing the time to start. When the ambient temperature is cool however, once the gas boils out, I have to turn the engine over until enough gas is back in the carb for the squirters to squirt. I've even taken the lid off on occasion to refill the bowls so it doesn't make the battery work so hard, and yes the bowls are bone dry. Gas will seek level once the engine bay is cooled off (the next day), but the carb is well above that, so it remains dry.

If I can delay the evaporation long enough to get re-started after a typical hour-long dinner break, I will consider this problem resolved, so I'm hopeful that a couple of simple fixes will be enough. Otherwise, I will have to consider more drastic measures like completely re-routing the fuel line out of the engine bay and removing the intake to block off the exhaust cross overs.

 

Good to hear! I have a 1" phenolic 4 hole spacer to try next, but that was going to require a new fuel line from the fuel pump and there was no way the oil bath breather was going to fit under the hood. Since the oil bath won't fit even with just a 3/8 spacer, and I have to make a new fuel line anyway, that sounds like it just might be the ticket. That will be my next attempt to solve this problem.

I see you're also running an aluminum intake on an FE engine, so that gives me great hope!

 

That's pretty wild that your oil bath won't fit with the 4 barrel cast iron manifold. My buddy has run this combination in his truck since about year 2 that he owned it. He bought it "used" in 1967.

1966 F250 4x4 Custom Cab in Arcadian Blue built at the San Jose plant.
427 side oiler block
428 crankshaft
LeMans rods
428 Police Interceptor aluminum manifold (C7AE)
390/406 cast iron shorty exhaust manifolds
Holley carburetor
Phenoilc spacer
And one very tall air filter





Truck now has approximately 480,000 miles on it. This is the truck that he has owned since 1967 and he's driven it coast to coast many times. No evaporation issues. If you have any questions about this setup that I can't answer I can ask the owner. In the picture above you can probably make out that the radiator has been moved closer to the engine to make room for the A/C condenser in front of it.

Additional equipment.

Air Conditioning
Power Steering
Very very rare Warn overdrive that bolts to the back of the NP435
PTO Winch

The air conditioning blower has always been mounted under the jumper seat between the two Bostom Viking T-Bar suspension seats. The handle just in front of that is for the overdrive. He has 16 forward gear combinations and 4 in reverse. Very trick truck. He added the second set of shocks front and rear back in the day when he used to be part of the 4x4 Rescue Council here in WA.

 

I'm using an Edelbrock Performer, not a stock cast iron intake (see pics below). I hated to lose the stock appearance of the oil bath, but I hadn't opened the hood in over a year. Drivability trumps looks at this point.

I decided to skip the 3/8 insulation gasket and go straight to the 1" phenolic spacer. At this point form follows function since I had to give up the oil bath anyway.

Not a fan of the 70's chrome look, but the drop base provides a lot of hood clearance. I could easily run a 4" filter (it's 3" now), but unless I install headers, there's not much point. Once I start going down the performance rabbit hole, it's hard to stop.

The good news is that I was able to dial in the "new" modified 4100 with manual choke fairly quickly as this requires swapping out the primary throttle shaft. The bad news is the gas now leaks out of the splice where I used a rubber hose to attach the two sections of fuel line. Before I can drive again, I'll have to make new lines with a bubble flare at the ends of each line, but that's for another day.

 

That should work. Keep in mind that spacers almost always lean the mixture at higher RPM, and you might need to go up a couple of jet sizes. All my experience with that is on Holley 4150's the 4100 might behave differently. I do know that other than not having any power valve protection the 4100 is one of the best driving around street carbs out there.

 

The 4100 behaves very much like a Holley and I was already running a little on the lean side, so when I get around to working on it again (too hot right now) I'll up the main jets a couple of sizes. Thanks for reminding me!

 

To add to this post someone said something about the intake manifold exh cross over that heats the intake & crab.
Because we dont drive our truck in winter it would be wise to block off this cross over.
Also dont know if your motors use a heating plate between the carb & intake that hot water runs thru to also heat the carb.
Both of the above should be blocked off / removed to keep from heating the intake / carb.

"I" also dont think it is boiling ALL the fuel out of the carb bowl.
The heat is "boiling / heating" the fuel in the bowl(s) and the vapors from this are pushed up the vent and being heavier that air it goes down the carb intake.
This then "floods" the motor and why the hard restart when hot.
When it dose restart dose it act like it was flooded till it clears out?
This is what I dont think all the fuel boils out of the carb bowl.

I have a 300 six in my 81 F100 and because I use my truck all year round, it can get into the low 20's, I run a hot water heating plate on the factory log intake manifold. From the factory the intake & Exh manifolds are bolted together with a valve that sends hot exh to heat the intake manifold.
Because of the hot water plate it dose heat the intake & carb so I have a little issue with hot start too.

Just my .02
Dave ----

 

Is your 1" phenolic an open style or 4-hole style?
A 4-hole style would lessen the plenum area and possibly possibly eliminate the need to up the jet size.
If you really want to keep the oil bath, you might consider installing an electric fuel pump inline, out of the way and view, such as under the truck, and switch it on to pump up before hitting the key.

BarnieTrk

 

Wasn't using a stock style heated spacer. I'm not going to pull the intake off to block the crossovers, but if I had it to do over again, definitely that is the thing to do.

Very possible that this is indeed what is happening after an hour stop when hot. The solution however is the same; prevent the carb from overheating.

Glad to get everyone's input. I asked for help and I believe I have a solution, so thanks to all who contributed.

 

I have seen some truck motors use the heater plate and why I brought it up as it is a easy thing to do to help keep from heating the carb.
Oh I hear you on not pulling the intake just to block off the crossover but if you do pull it down the road to block it off,

If it dose not help you at this time it may help others when doing a search for "hot restart".
Dave ----

 

This is to follow up on how the 1" plastic spacer worked out... or more accurately, how it didn't work out. The Autolite 4100 requires a unique dedicated design spacer. A Holley spacer resulted in both vacuum and fuel leaks and made it impossible to set the idle properly. Given that, I went back to my original plan of using an 80's Ford insulating spacer between the aluminum Autolite spacer with PCV port and the intake.

In attempting to make a new fuel line, I broke my Eastwood flaring tool. The tube must have been made out of 4340 chromemoly steel or perhaps way thicker than it should have been, IDK. I ordered a Mastercool hydraulic hand pump kit as a replacement from Amazon. Big mistake. It arrived with 5 pieces missing, and naturally one of those was one of the 5/16ths die halves that I needed. I returned it immediately and after talking to Mastercool, I ordered a universal kit from Toolpan.com. It's a very nice kit that allows flares on a much shorter radius tube as the dies are half as long as the Eastwood dies.

As far as the evaporating gas out of the carb goes, even with the 1" plastic spacer the results were less than spectacular on a 50-minute re-start when hot test. Considering the cost, time and amount of work I went through in order to attempt a fix, I may have been better off just living with what I had. It's better, but not by a huge margin, and I lost the use of my oil bath breather in the process. The Holley chrome bling just doesn't come close to the cool factor of an oil bath under the hood. Since it behaves differently depending on weather, I'm going to leave the insulating spacer in for a year to evaluate. If I can't justify the changes, I'll revert back to the oil bath.