Vapour lock ???
Thread Starter
Pro
Joined: Nov 2004
Posts: 575
Likes: 0
From: Nice Lake Ontario
Vapour lock ???
What is it?
Where does it occur??
How to cure?
I have a problem with my 69 BB w/Quadrojet
Runs fine on the highway, stays cool at 160*s
BUT when I hit slow traffic or shut it off & restart, I get a serious bucking as in no fuel?? Last night it quit & when I checked carb, it was serious hot to touch & there was no fuel out the squirters when I pumped the throttle. I am going to check fuel pressure tonight but kinda suspect a vapour lock problem. I have a single gasket between iron manifold & carb.
Where does it occur??
How to cure?
I have a problem with my 69 BB w/Quadrojet
Runs fine on the highway, stays cool at 160*s
BUT when I hit slow traffic or shut it off & restart, I get a serious bucking as in no fuel?? Last night it quit & when I checked carb, it was serious hot to touch & there was no fuel out the squirters when I pumped the throttle. I am going to check fuel pressure tonight but kinda suspect a vapour lock problem. I have a single gasket between iron manifold & carb.
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
Been lots of stuff in here on that subject. Basically as I understand it, Vapor lock is a heat issue that has caused the fuel to boil out of the carb and/or fuel line. Some of the fixes for it would be a Return line on the fuel pump to the fuel tank. Insulated fuel line from pump to carb. Thicker isolation gasket under the carb. Carb Heat Shield. Better ventilation underhood.
Lars and some of the other Guru's will no doubt check in on this one
Lars and some of the other Guru's will no doubt check in on this one
Thread Starter
Pro
Joined: Nov 2004
Posts: 575
Likes: 0
From: Nice Lake Ontario
How did the original 60-70s cars get away from it??
Or do I maybe just have not enough or wrong carb base gasket??
I'm using the same base gasket that came on this 454 with this carb just a diff iron manifold.
Geeze I do a search & all I end up with is my own thread !
Or do I maybe just have not enough or wrong carb base gasket??
I'm using the same base gasket that came on this 454 with this carb just a diff iron manifold.
Geeze I do a search & all I end up with is my own thread !
Last edited by sxr6; Aug 1, 2007 at 09:43 AM. Reason: add
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
Most of those cars had bigger engine compartments that got more air flow thru them, kept more of the heat out.
A thicker gasket and/or a heat shield may help you, but insulating the fuel line can't hurt
A thicker gasket and/or a heat shield may help you, but insulating the fuel line can't hurt
Le Mans Master
Joined: May 2006
Posts: 7,708
Likes: 266
From: indy indiana
Been lots of stuff in here on that subject. Basically as I understand it, Vapor lock is a heat issue that has caused the fuel to boil out of the carb and/or fuel line. Some of the fixes for it would be a Return line on the fuel pump to the fuel tank. Insulated fuel line from pump to carb. Thicker isolation gasket under the carb. Carb Heat Shield. Better ventilation underhood.
Lars and some of the other Guru's will no doubt check in on this one
Lars and some of the other Guru's will no doubt check in on this one
Back in the "day" some folks( drag racers) coiled the fuel line thru a coffee can filled with ice. Way back in the day...flathead and early 50s car owners put wooden clothes pins on the fuel lines..that worked a bit,but not great. You might try and see if your fuel line is to close to a heat source. And yes, the return fuel line coupled with an electric fuel pump was the "old,first way" to cure this problem.
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Burning Brakes
Joined: Mar 1999
Posts: 1,047
Likes: 3
From: CA
I still remember riding in my dad 61's Mercury as a kid when vapor lock would cause his car to stop running. And it always seemed to happen on a busy street in chicago. My dad always fixed the car himself (thats how I got started) even though his knowledge of cars was limited...so these were his home grown rememdies...
He would keep a gallon of water in the car and when vapor lock set in he would pour it on the fuel pump. Fuel pumps on 292 merc did more than pump fuel...they also provided vaccum to the wipers (thats another story in itself). I can tell you it worked as it. Maybe it was a bad pump???
But eventually he would pull the thermostat out in the summer and reinstall back in the winter. The car ran cooler in the summer months and this was the best cure for the problem. Vapor lock was never a problem in the winter.
The problem with vapor lock is you dont know at what point in the fuel system it boiling. I suggest you look into all the ideas posted about by forum members. They are all great ideas. But you might also want to check into a high-flow thermostat like from from Mr Gasket. I put one in my car and it really helped wake up my aluminum radiator.
He would keep a gallon of water in the car and when vapor lock set in he would pour it on the fuel pump. Fuel pumps on 292 merc did more than pump fuel...they also provided vaccum to the wipers (thats another story in itself). I can tell you it worked as it. Maybe it was a bad pump???
But eventually he would pull the thermostat out in the summer and reinstall back in the winter. The car ran cooler in the summer months and this was the best cure for the problem. Vapor lock was never a problem in the winter.
The problem with vapor lock is you dont know at what point in the fuel system it boiling. I suggest you look into all the ideas posted about by forum members. They are all great ideas. But you might also want to check into a high-flow thermostat like from from Mr Gasket. I put one in my car and it really helped wake up my aluminum radiator.
Instructor
Joined: Sep 2004
Posts: 116
Likes: 0
From: Northern California
..
I solved the problem with an electric fuel pump mounted below the gas tank and a 3/8" return line.
Lars post some time back outlined the install.
Additionally, I added a heat shield under the carb.
Good luck.
Lars post some time back outlined the install.
Additionally, I added a heat shield under the carb.
Good luck.
Drifting
Joined: Sep 2006
Posts: 1,986
Likes: 21
From: Columbus MN
My '80 has problems when I run on a hot day, shut off, and go again. It only happens on hot days, so it's reasonable to assume there's a heat problem under the hood. A heat shield has been several times in CF.
Do you have a pic?
Where does it mount?
Any other mods necessary?
Where can I buy one to see if that fixes my high temp problems?
Do you have a pic?
Where does it mount?
Any other mods necessary?
Where can I buy one to see if that fixes my high temp problems?
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
The heat shield for the carb is not complicated, just a sammich of metal and fiber gaskets to isolate the carb from the intake manifold heat soaking and a Shield piece
http://store.summitracing.com/partde...5&autoview=sku
http://store.summitracing.com/partde...5&autoview=sku
Melting Slicks
Joined: Mar 2006
Posts: 3,342
Likes: 7
From: Connecticut
Thats because it's usually spelled vapor
Heres a search with "search thread titles only"
Theres many more with "search entire threads"
http://forums.corvetteforum.com/sear...archid=5700661
Heres a search with "search thread titles only"
Theres many more with "search entire threads"
http://forums.corvetteforum.com/sear...archid=5700661
Drifting
Joined: Sep 2006
Posts: 1,986
Likes: 21
From: Columbus MN
The heat shield for the carb is not complicated, just a sammich of metal and fiber gaskets to isolate the carb from the intake manifold heat soaking and a Shield piece
http://store.summitracing.com/partde...5&autoview=sku
http://store.summitracing.com/partde...5&autoview=sku
Thread Starter
Pro
Joined: Nov 2004
Posts: 575
Likes: 0
From: Nice Lake Ontario
Thats because it's usually spelled vapor
Heres a search with "search thread titles only"
Theres many more with "search entire threads"
http://forums.corvetteforum.com/sear...archid=5700661
Heres a search with "search thread titles only"
Theres many more with "search entire threads"
http://forums.corvetteforum.com/sear...archid=5700661
vapour---vapor
colour---color
I found quite a bit more info clicking on "archive" on the search..thks mdj21
I went & talked to an old street guy & this is basically what he said.
"You can pour water on the fuel pump, you can seach & insulate all lines & pump but there's still a chance if your stuck in trafic it'll re-occur. The best cure-all is to mount a basic electric fuel pump close to the fuel tank...problem solved"
I went to CTC & ordered a basic 4-6 lb pump for $79.
I'll do a follow up once it's in & installed
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
Originally Posted by sxr6
Runs fine on the highway, stays cool at 160*s
BUT ... & there was no fuel out the squirters when I pumped the throttle. I am going to check fuel pressure tonight but kinda suspect a vapour lock problem. I have a single gasket between iron manifold & carb.
BUT ... & there was no fuel out the squirters when I pumped the throttle. I am going to check fuel pressure tonight but kinda suspect a vapour lock problem. I have a single gasket between iron manifold & carb.
Check fuel pressure. You can partially clamp the return hose.
Metal fuel line can have a spring around it as fins for cooling.
Some Q-J have about 1/4 " open insulator/gasket.
Originally Posted by ghoastrider1
Way back in the day...flathead and early 50s car owners put wooden clothes pins on the fuel lines..that worked a bit,but not great.
Racer
Joined: Aug 2003
Posts: 259
Likes: 2
From: Sacramento CA
Do you have one of these, properly plumbed, in front of the passenger side head? If not you might want to put it back like the factory supplied it. It allows cool fuel from the tank to circulate in the supply line.
Last edited by RPOL68; Aug 3, 2007 at 01:02 PM.
Pro
Joined: Aug 2004
Posts: 562
Likes: 1
If you are by chance running on a 10% ethanol blend, the vapor lock is nearly inescapable. An old-timer suggested going to the major fuel suppliers for their 91 or better octane without ethanol during the hot days. I did and it worked like a charm from mid June through mid September. I go back to the 10% in the cooler weather.
