Vapor lock and fuel boiling

[big gear head]

Who is having problems with the current gas with alcohol mixed? My car ran bad for years and left me sitting on the side of the road several times before I figured out what was wrong with it and started using alcohol free gas. I know of several other people who are having problems but don't have access to alcohol free gas. What are the rest of you doing about this? Is there a fuel additive that will take care of it?

[x33rs]

There are things you can do to combat it. We daily drive our classics without issues, using the crappy 91 pump gas we have, with at least 10% ethanol.

For starters I never run any less than the highest octane offered. Lower octane just exaggerates the issue.

I make sure all fuel lines are away from any major source of heat. I find the factory routings to be sufficient. Both the Z and the bird that we daily drive have their factory fuel lines in place.

Proper venting of the fuel system is important and if not vented properly, can sometimes trick one into thinking it's vapor locking.

I also like to use a thick carb gasket (1/4" minimum) to help absorb some of the intake heat. The added benefit is a slight increase in plenum volume. If you want this to be more effective, a 1/4" thick piece of wood is the best heat insulator, with a pair of paper thin gaskets, it's better than the one piece 1/4" thick gasket deal. 1/4" still allows all the factory hook ups without disturbing anything, with the only change that the divorce choke rod needs a bit of adjusting to compensate for the height change.

I always make sure the fuel pump is healthy, some weaker pumps can exhibit a surge issue, or have more trouble pushing/pulling hot fuel.

Lastly, on cars that came with a return style fuel system, I always use it. I see many that are bypassed and the pump dead headed. That keeps the fuel stagnant in the system unless the needle and seat/seats are open.

However even with that said, our Z which is a factory dead head/non return system has never shown any problems with vapor lock, and it's been driven daily for 2 years in the AZ desert heat.

I also make sure the cooling system is up to snuff. I prefer to run cooler thermostats (160-170). The cooler the engine, the cooler everything else is under the hood. Typically our Z runs 185-ish on the hottest summer days when ambient temps approach 110 degrees. It runs cooler during the cooler months obviously, but stays in the 165 range. There is a ton of debate what people feel engine temps should be but the bottom line is, if you want to run a hot stat like a 195, you're going to increase your chances of vapor lock.

I've experimented with blocking the heat cross overs with success but these days, both of our daily drivers are still using their divorce chokes so I have the cross overs open for proper cool weather operation. This hasn't caused any hot start or heat soak issues to date.

Some may suggest to install a pusher pump, which does help fight vapor lock. Frankly I've never found the need for it. I still run the stock mechanical AC pumps on both cars.

Make sure your fuel sock in the tank is in good shape. I run an oversized sock on the cars that is much larger than OEM. I sourced them for a 70's pickup truck and swapped out the smaller units on the cars. Don't recall the part number off hand.

Other little tricks I do is check all OEM brass fittings (if equipped) and I find most internal dimensions are small. I drill them while still leaving enough flare for the fuel line to seal. I also take the shorter metal lines that fit in the cabinet blaster and run glass bead through them at high pressure in both directions in an attempt to extrude hone and soften/enlarge the turns. I've yet to CC one to see if there is a difference, but plan to next time I do one.

It's all just little things in an attempt to help the fuel system.

Of course you can try wrapping things. I tend to not do that because I don't want to disturb the factory appearances.

[big gear head]

I rebuilt a 350 in a '78 Caprice last winter. Everything is completely stock including the emission system. It vapor locks every time it's driven and after it's been shut off and sits for a little while all of the fuel evaporates out of the carburetor. Fuel has to be poured into the carburetor to get it to start again.

I worked on a '55 T Bird a few weeks ago and it vapor locked while idling in the drive way. I had to pour fuel in the carburetor to get it to start again after it cooled off.

I built a 454 for a '85 C10 a few years ago and it vapor locks when driving. It shut off on me a few times before the owner took it home.

My Camaro would shut off on me every time I drove it. When I found out that it was the alcohol in the fuel that was causing it I started running no alcohol fuel and I have no more problems.

I've seen several other people who have been having the same problems. Maybe it's the fuel around here that is causing it, but it seem like there should be something that can be added to the fuel to raise the boiling point so that it doesn't do this.

[x33rs]

I see you're in Kentucky? When I lived in Ohio I remember 15-20 years ago there was a big stink about Kentucky switching to reformulated fuel. May have been further back, my memory is fuzzy. Anyway, not sure if that ever happened but you guys are also starting to get into your winter season, and I believe by now the fuel has switched over to the winter blend. So if you're still getting some warm days, that stuff will vapor lock in a heart beat.

I always hated that in Ohio (they did the same thing) because if you have any of those warm days that so often happen in the fall and spring out there, that winter blend fuel is absolutely horrible for vapor lock. It would always bite me in the spring when you get a few odd warm days in March with temps in the 70's, and Ohio wouldn't switch to summer blend until April or May.

[bluel78]

Attended a Studebaker club meeting a while back and this conversation came up. Sounds crazy but a few members were adding diesel fuel, 1/2 gallon to a tank of gas to give the newer fuel some body and lubricant. Tried it in a 80's 454 dually that loved to vapor lock and seemed to help.

[x33rs]

If you have non alcohol fuel that would certainly help. Seems more and more of those are popping up.

Where I'm located, we have one station that carries it, and it was just built last year. The problem though is that it's only available in 87 octane and I can't run that low of octane in our stuff.

I'm not sure what is out there for additives that might help or if there is anything that actually works. The only thing I add to my fuel is a pinch of 2 cycle oil with TCW3 only for some lubricity and cleaning purposes, since the lead is gone. 1 ounce per 5 gallons of gas.

[JKZ27]

The Pure-Gas website shows Casey's General store near Central city sells 91 octane. Might be worth a look.

https://www.pure-gas.org/index.jsp?stateprov=KY

[big gear head]

The Pure-Gas website shows Casey's General store near Central city sells 91 octane. Might be worth a look.

https://www.pure-gas.org/index.jsp?stateprov=KY

That is exactly what I'm running in my car and it runs good on that. I have no more problems, but these other guys don't live in the same town, so they can't get their gas there. I've never heard of the pure gas web sight. I'll have to check it out.

[1967 4K]

I live in central Ky. and run Shell or BP high test in my L78 engine and have never had any issues as being discussed here.
Richard

[JKZ27]

That site has a handy map that helped me find E-free gas near me, mainly for my small engines and ATV stuff. I have been using 93 octane, 10%Ethanol in all my Camaros without issue. My 69 and 79 use stock return style pumps and my 68 is return style EFI, FWIW.

[Steve Shauger]

I drive my cars L78, Z28, L72 regularly spring -summer and fall. Most of the time pump gas and have never had an issue. Only starting issue I had was heat soaked starter solenoids in summer and changed them out to high temp years ago.

[JRSully]

On my 70 L78 Nova, I did reroute the single 3/8 fuel line just a bit higher up on the subframe to keep it further away from the headers. I also run the big and ugly factory carb flange plate under the orig holley, orig fuel pump. NEVER, and I mean even in 90+ degree heat, have I had a problem with fuel supply. FWIW, I did recore the orig radiator to a 4 core and it rarely gets above 180-185, that may be helping.? I typically run 100-100 CAM 2 mixed with a little 93, with the timing all in at 3k, (requires a little more octane)

[Mr. Chevy]

On my 70 L78 Nova motor I had to install the GM heat shield under the Holley Carb also otherwise it would vapor lock and the car would shut down. I also did a 4 core radiator job and run 110 octane race fuel. My temps stay consistent at 180-185 like Jim's.

Rich

[big gear head]

Does anyone know of a fuel additive that will raise the boiling point of the blended fuel?

[x33rs]

Those running cam 2 or any high test 100 octane or 110 octane, will pretty much alleviate any vapor lock issues with it's slower burn rate. That's why I mentioned the higher octane gas you run, the better off you'll be as far as hot start issues and vapor lock.

Top Tier stations have seemed to be the best for me, even though their gas still has ethanol, it's a more refined fuel and the ethanol content seems more consistent. Usually costs a bit more than the generic stations. Here's a site for Top Tier stations. Just click on the locater at the top of the screen to look for Top Tier stations in your area..

https://www.toptiergas.com

To touch on the consistent ethanol comment. Several years back I was testing ethanol at a few local stations with those cheap ethanol kits you buy on ebay. I'm a fanatic tuner and was curious what I was putting in the tank, since ethanol affects the air fuel ratio needed. I found some stations had as much as 17% ethanol so it wasn't very consistent from one tank to the next. I don't know if they monitor this more closely these days but interesting none the less.

As far as additives Big Bear, I really don't know of anything that actually does what it says at raising the boiling point, or octane level. There are fixes in a bottle that people claim work :dunno:
I've just preferred to avoid that scenario. Since we daily drive them I just want to fill up the tank and go type of thing. So I spend a lot of time on the fuel system, engine temps, and the tune, to make sure it doesn't give me issues with the crappy gas we have these days.

The only thing I do add that I mentioned earlier, is 2 cycle engine oil with TCW3. Just to give the gas some lubricity, and has cleaning properties. Good for the valves, guides, rings, etc... Doesn't do anything for octane or vapor lock issues though.

[x33rs]

Playing with resizing some pictures. Don't know if this will work or not. But anyway, this is my wife's Z that she daily drives. I've made no attempt to move or insulate any of the factory lines.
I do run a 1/4" thick base plate gasket to help with heat (probably can't see in the picture), and I still have the heat cross over open so the divorce choke works, but I haven't found the need for any type of heat shield under the carb. I was open to that option if a problem existed, but it's driven fine for the last 2 years without.
I was a little concerned with vapor lock since this is our only daily driver that uses a dead head fuel system. Everything else here is a return style. But it's proved to be a trouble free driver. It's a true 11:1 compression and runs fantastic on the 91 pump we have here.

[big gear head]

I was putting Shell gas in my Camaro and thought that it was the thing to do. Didn't have much trouble with the local Shell station, but I took a road trip to Somerset and had to get gas before heading home. I found a Shell station there and filled it up. I didn't even get out of town before it vapor locked and I was sitting on the side of the road. It did it 2 more times before I got home. The alcohol free gas at the local Casey's works well.

The '78 Caprice has the thick gasket under the Q Jet carb, but still vapor locks every time he drives it. All of the fuel lines are original. The guy who owns the car is blaming me for the vapor lock issues. I've told him to get better gas in it, but he thinks that there is nothing wrong with the gas. He says that he didn't have any problems with it when he was driving the car 3 years ago. He's telling people that I messed up his carburetor. This is why I'm trying to find some fix for the fuel that he has in the car now.

[Mr70]

Has he tried putting some Race Gas in it?
Click here and on FUEL FINDER in the top right corner,then enter his zip code to find the nearest Sunoco station by him.>https://www.sunocoracefuels.com/

[x33rs]

I was putting Shell gas in my Camaro and thought that it was the thing to do. Didn't have much trouble with the local Shell station, but I took a road trip to Somerset and had to get gas before heading home. I found a Shell station there and filled it up. I didn't even get out of town before it vapor locked and I was sitting on the side of the road. It did it 2 more times before I got home. The alcohol free gas at the local Casey's works well.

The '78 Caprice has the thick gasket under the Q Jet carb, but still vapor locks every time he drives it. All of the fuel lines are original. The guy who owns the car is blaming me for the vapor lock issues. I've told him to get better gas in it, but he thinks that there is nothing wrong with the gas. He says that he didn't have any problems with it when he was driving the car 3 years ago. He's telling people that I messed up his carburetor. This is why I'm trying to find some fix for the fuel that he has in the car now.


That's unfortunate you're getting blamed for something that isn't your doing. It sounds like he has a lack of understanding the real underlying issue, and from your explanations here, it appears that different stations certainly have an effect on the outcome.

A case like that as you described, I'd try exactly what Mr70 stated, and get some race gas in the tank to see if the symptoms disappear.

[big gear head]

I haven't been able to get him to do anything. He has parked the car and blames me because it won't run.