Vapor lock and fuel boiling

[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
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]

Originally Posted by 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.

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.