Vapor Lock

67 shadetree mechanic · 05-12-2001, 02:01 PM

Hello,

I'm a new user here and would appreciate some technical advice regarding vapor lock. We recently installed headers on the son's 67 coup. Now its started vapor locking. It didn't do this before. Any advice? The car is a coupe w/289-2v/ps/ac.

Would appreciate any help and Thank You in advance.

\s\

ShadeTree

Fostang · 05-12-2001, 02:44 PM

Vapor lock is pretty much a thing of the past for most people. Vapor lock occurs when the vapor pressure of the fuel is higher than its surroundings. The gasoline in the fuel lines will actually boil creating a vapor of gasoline which a fuel pump can not handle. Today's cars have fuel pumps in the fuel tank where they push the fuel under pressure to the engine. This is wonderful if you own a new car.
In older cars with sucking fuel pumps near the engine, the pressure in the fuel line from the tank is reduced by the fuel pump drawing fuel from a tank at the other end of the car. When this gas starts to get hot, it will actually boil into vapor. Vapor lock is usually the result of high altitude and high temperatures. Vapor lock can occur at any altitude due to excessive heat, but it is more common at higher altitudes because gas at high altitudes vaporizes at a lower temperature. The resulting gas and air mixture can reduce or even stop the flow of gas to your engine.

Symptoms that your car is suffering from vapor lock is a loss of engine power or an engine that will suddenly not start. Vapor lock is most common when you turn off your car on a hot day then try to start it up again a few minutes later. To reduce the chance of vapor lock, avoid running the air conditioner when you don't really need to. At the first signs of power loss, shift your car into neutral and rev the engine slightly. Always use low gear when climbing steep hills.

If your engine has become a victim of vapor lock, here are a few things you can try:

Loosen the gas cap slowly.
Remove the air cleaner cover and hold open the choke flutter valve in the carburetor with a screwdriver. Look out for backfires.
Start the engine, holding the gas pedal all the way to the floor.
If these steps don't work, let the motor cool at least 30 minutes before trying to start the car.
The only thing that truly cures vapor lock is a cool engine.

"As you said modern cars seldom suffer from vapor lock but in addition to the pump location the modern systems operate at a much higher pressure and the systems have bypass regulators. The higher pressures used keeps the fuel from vaporizing and the bypass regulator circulates cooler fuel through the system constantly.

On older cars a bypass regulator can be installed near the carburetor and excess fuel is routed back to the tank and cooler fuel is constantly drawn from the tank. As the fuel does not sit in the fuel line as long it is generally cooler and less prone to vapor lock. Installing an electric pump near the tank in the rear of the car also helps. Installing the pump near the tank pushes the fuel at a pressure of 4 psi or so above atmospheric pressure versus pulling it at a pressure of 4 psi or so to an engine mounted pump ie look up the vapor pressure of gasoline at 10.5 psi versus 18.5 psi (absolute)." Hope this helps try putting thermo wrap around the headers to keep the heat in the tube and out of the engine compartment. Eventually your starter will also start failing so put a heat shield around it to protect it. Headers add power but they add headaches also. I have the ceramic coated ones and still have the heat shield by the starter. Good Luck!

------------------
67'fastback-Edelbrock carb,intake,cam,valve springs.Rhode lifters, CompCam rocker arms, windage tray,cerama coated headers,dual flows with H-pipe, modded c-4,tci stall converter,perma cool electric fan,aluminum water pump,griffen aluminum radiator,accel 8.8 cable,wide cap distriburator,magnetic pick up,v-matic hurst shifter,edelbrock performer nitrous, carter electric fuel pump,ignitor coil,solid motor mounts,magna racing suspension,poly urathane bushings,under rider traction bars, comp. eng. s

Gearhead999 · 05-12-2001, 05:08 PM

Hey Fostang,

Remember the wives tale cure for vapor lock??

Putting those pinch to open wooden clothes pins on the fuel line [metal line] between the pump and carb. When I was younger we use to see it all the time on flathead Fords and other flathead engines. They tend to run alittle on the HOT side.

Well I had a 1954 Packard come in my shop last month. The older gentlemen who owned it passed on and his daughter brought it in to get it in running order. It had a flathead inline eight. Well when I pulled up the hood I couldn't believe my eyes. There, in the year 2001, were around 6 or so wooden clothes pins on the fuel line. I started to laugh and my mechanics, all under 40, couldn't figure out what they were there for.

One more on the old Packard. I sent the fuel tank out for cleaning. When the runner came and picked the tank up he asked me what kind of car it came out of. When I said "Packard", he said yeah but who made it. Is is a Ford, Chev, etc.???

Best way I know to fix is insulate and install an electric pump back by the tank so it will push through it.

Fostang · 05-12-2001, 08:38 PM

Actually No I've never heard of that. Sounds pretty darn funny if you ask me. I guess I'm not old enough to have heard that. I'm just trying to gain as much knowlege as I can. Someday I might be able to share it with a son.

------------------
67'fastback-Edelbrock carb,intake,cam,valve springs.Rhode lifters, CompCam rocker arms, windage tray,cerama coated headers,dual flows with H-pipe, modded c-4,tci stall converter,perma cool electric fan,aluminum water pump,griffen aluminum radiator,accel 8.8 cable,wide cap distriburator,magnetic pick up,v-matic hurst shifter,edelbrock performer nitrous, carter electric fuel pump,ignitor coil,solid motor mounts,magna racing suspension,poly urathane bushings,under rider traction bars, comp. eng. s

05-13-2001, 05:19 PM

I've heard about that trick before. I can't remember where or from who I did though. I'm only 16. I got all you oldies beat! Haha...just playin guys...

------------------
'69 Coupe with 351W
=========================
Edelbrock RPM intake, Edelbrock RPM cam, Edelbrock 750 cfm carb, Edelbrock lifters, Edelbrock double roller timing chain, Edelbrock valve springs, Accel coil, Moroso Blue-Max wires, Hedman headers, 2 1/2" pipe, glasspacks, Flex fan, Lakewood traction bars, C4, 3:1 gears, 290hp-stock heads
=========================

Black-Sunshine · 05-13-2001, 08:06 PM

As everyone has already mentioned your problem is probably tied to excessive heat in your fuel line. What they haven't offered you is an EASY solution (if there is one) Check your fuel line in the engine compartment and make sure its sufficiently located away from heat sources. You mentioned that this started after installing new headers. Headers dissipate much more heat than standard exhaust manifolds perhaps you need to wrap your headers with some sort of heat tape to bring down the temperature in the engine compartment.

Ron1 · 05-14-2001, 01:07 AM

I used an aluminum spacer plate under the carb...larger than the carb, to keep heat off the manifold from getting to it. Worked great.

Ron

Tom351 · 05-14-2001, 09:36 AM

Aluminum transfers lots of heat, you are even better off with a phenolic or plastic spacer. I use a 1/4" spacer that I cut out of fiberboard with a jigsaw.

------------------
67 Fastback - Arctic White Pearl paint
351W ,Trick Flow Aluminum Heads, Edelbrock TorkerII, Carter 750 CFM, Comp. Cam 477/510 219/233@.050, Performance Automatic C-4 Trans, 3.55 gears, Front Disc Brakes, 1-1/8" Fr. 3/4" rear sway bars.

My 351W Fastback

vegasmustang · 05-14-2001, 05:37 PM

I live in Vegas and as you all probably know it gets pretty hot here. I remember the clothes pins too and I am only 29. I don't remember where I heard it from either, but when I experienced vapor lock, I tried it and it worked.
----
Just began re-restoring the car I drove in high school. I say re-restoring, because I started...and never finished. The money situation is a little better now, so here we go again!

65 Mustang Coupe w/ 84 5.O. motor.

67 shadetree mechanic · 05-15-2001, 10:20 PM

I've check the fuel lines from end to end. They apear fine (plenty of seperation from hot metal). The car has only driven a few times in the past two years and only once since headers were installed. That day it was indeed hot. The car just died while moving down the road as though it lost spark. It did restart shortly after everything cooled a spell.

I'm assuming it was vapor lock but could be another problem. Like I said, the car has benn garaged (in-work) for about 2 years now. Maybe I'm just chasing a ghost.

I appreciate your advice but would like to understand the vapor lock a little better. Sounded like you were describing a sudden lost in fuel pressure due boiling fuel within the fuel lines or in the carb bowl or did I misinterpret what your saying?

Would appreciate any/all responses about this subject.

BTW, I'm also aware the cloths pin trick on old Ford flatheads. My pop has had a few of those back in his hayday.

Thank You!

shovelnose · 05-16-2001, 01:55 AM

Put a clear filter in and look in it right after the car has been driven good and hot. You will see the rolling bubbles.

A plastic spacer plate, 1/4" gasket, block heat cross-over in the intake, insulate the fuel lines near anything hot, fresh air, remove insulation on the hood, heat sheild for the carb, return line. Any of the above will help.

If you ever drained your coolant and didn't bleed the system, you will probably not have heat in the car and the engine will over heat. This is another form a vapourlock. The air pocket gets trapped and coolant can't flow past it under pressure.

------------------
82 Mercury Capri 302.
Comp. Cams
Tremec 3550
3.73's
12.8@106 N/AKevin's Capri

Gearhead999 · 05-18-2001, 10:01 PM

I personally run a wooden spacer, about 3/8 inch, under my dual AFB's. I made it out of a scrap piece of mahogany from my wooden Chris-Craft boat.

Works great, keeps the heat from the carbs.

05-12-2001, 02:01 PM	#1
67 shadetree mechanic Registered Member Join Date: May 2001 Location: Fort Worth Texas Posts: 4	Vapor Lock Hello, I'm a new user here and would appreciate some technical advice regarding vapor lock. We recently installed headers on the son's 67 coup. Now its started vapor locking. It didn't do this before. Any advice? The car is a coupe w/289-2v/ps/ac. Would appreciate any help and Thank You in advance. \s\ ShadeTree

05-12-2001, 02:44 PM	#2
Fostang Registered Member Join Date: Feb 2001 Location: Stockton, Ca Posts: 599	Vapor lock is pretty much a thing of the past for most people. Vapor lock occurs when the vapor pressure of the fuel is higher than its surroundings. The gasoline in the fuel lines will actually boil creating a vapor of gasoline which a fuel pump can not handle. Today's cars have fuel pumps in the fuel tank where they push the fuel under pressure to the engine. This is wonderful if you own a new car. In older cars with sucking fuel pumps near the engine, the pressure in the fuel line from the tank is reduced by the fuel pump drawing fuel from a tank at the other end of the car. When this gas starts to get hot, it will actually boil into vapor. Vapor lock is usually the result of high altitude and high temperatures. Vapor lock can occur at any altitude due to excessive heat, but it is more common at higher altitudes because gas at high altitudes vaporizes at a lower temperature. The resulting gas and air mixture can reduce or even stop the flow of gas to your engine. Symptoms that your car is suffering from vapor lock is a loss of engine power or an engine that will suddenly not start. Vapor lock is most common when you turn off your car on a hot day then try to start it up again a few minutes later. To reduce the chance of vapor lock, avoid running the air conditioner when you don't really need to. At the first signs of power loss, shift your car into neutral and rev the engine slightly. Always use low gear when climbing steep hills. If your engine has become a victim of vapor lock, here are a few things you can try: Loosen the gas cap slowly. Remove the air cleaner cover and hold open the choke flutter valve in the carburetor with a screwdriver. Look out for backfires. Start the engine, holding the gas pedal all the way to the floor. If these steps don't work, let the motor cool at least 30 minutes before trying to start the car. The only thing that truly cures vapor lock is a cool engine. "As you said modern cars seldom suffer from vapor lock but in addition to the pump location the modern systems operate at a much higher pressure and the systems have bypass regulators. The higher pressures used keeps the fuel from vaporizing and the bypass regulator circulates cooler fuel through the system constantly. On older cars a bypass regulator can be installed near the carburetor and excess fuel is routed back to the tank and cooler fuel is constantly drawn from the tank. As the fuel does not sit in the fuel line as long it is generally cooler and less prone to vapor lock. Installing an electric pump near the tank in the rear of the car also helps. Installing the pump near the tank pushes the fuel at a pressure of 4 psi or so above atmospheric pressure versus pulling it at a pressure of 4 psi or so to an engine mounted pump ie look up the vapor pressure of gasoline at 10.5 psi versus 18.5 psi (absolute)." Hope this helps try putting thermo wrap around the headers to keep the heat in the tube and out of the engine compartment. Eventually your starter will also start failing so put a heat shield around it to protect it. Headers add power but they add headaches also. I have the ceramic coated ones and still have the heat shield by the starter. Good Luck! ------------------ 67'fastback-Edelbrock carb,intake,cam,valve springs.Rhode lifters, CompCam rocker arms, windage tray,cerama coated headers,dual flows with H-pipe, modded c-4,tci stall converter,perma cool electric fan,aluminum water pump,griffen aluminum radiator,accel 8.8 cable,wide cap distriburator,magnetic pick up,v-matic hurst shifter,edelbrock performer nitrous, carter electric fuel pump,ignitor coil,solid motor mounts,magna racing suspension,poly urathane bushings,under rider traction bars, comp. eng. s

05-12-2001, 05:08 PM	#3
Gearhead999 Registered Member Join Date: Sep 1998 Location: Oviedo, FL Posts: 992	Hey Fostang, Remember the wives tale cure for vapor lock?? Putting those pinch to open wooden clothes pins on the fuel line [metal line] between the pump and carb. When I was younger we use to see it all the time on flathead Fords and other flathead engines. They tend to run alittle on the HOT side. Well I had a 1954 Packard come in my shop last month. The older gentlemen who owned it passed on and his daughter brought it in to get it in running order. It had a flathead inline eight. Well when I pulled up the hood I couldn't believe my eyes. There, in the year 2001, were around 6 or so wooden clothes pins on the fuel line. I started to laugh and my mechanics, all under 40, couldn't figure out what they were there for. One more on the old Packard. I sent the fuel tank out for cleaning. When the runner came and picked the tank up he asked me what kind of car it came out of. When I said "Packard", he said yeah but who made it. Is is a Ford, Chev, etc.??? Best way I know to fix is insulate and install an electric pump back by the tank so it will push through it.

05-12-2001, 08:38 PM	#4
Fostang Registered Member Join Date: Feb 2001 Location: Stockton, Ca Posts: 599	Actually No I've never heard of that. Sounds pretty darn funny if you ask me. I guess I'm not old enough to have heard that. I'm just trying to gain as much knowlege as I can. Someday I might be able to share it with a son. ------------------ 67'fastback-Edelbrock carb,intake,cam,valve springs.Rhode lifters, CompCam rocker arms, windage tray,cerama coated headers,dual flows with H-pipe, modded c-4,tci stall converter,perma cool electric fan,aluminum water pump,griffen aluminum radiator,accel 8.8 cable,wide cap distriburator,magnetic pick up,v-matic hurst shifter,edelbrock performer nitrous, carter electric fuel pump,ignitor coil,solid motor mounts,magna racing suspension,poly urathane bushings,under rider traction bars, comp. eng. s

05-13-2001, 05:19 PM	#5
BennyBoy Guest Posts: n/a	I've heard about that trick before. I can't remember where or from who I did though. I'm only 16. I got all you oldies beat! Haha...just playin guys... ------------------ '69 Coupe with 351W ========================= Edelbrock RPM intake, Edelbrock RPM cam, Edelbrock 750 cfm carb, Edelbrock lifters, Edelbrock double roller timing chain, Edelbrock valve springs, Accel coil, Moroso Blue-Max wires, Hedman headers, 2 1/2" pipe, glasspacks, Flex fan, Lakewood traction bars, C4, 3:1 gears, 290hp-stock heads =========================

05-13-2001, 08:06 PM	#6
Black-Sunshine Registered Member Join Date: Dec 2000 Location: Laguna Niguel Ca Posts: 46	As everyone has already mentioned your problem is probably tied to excessive heat in your fuel line. What they haven't offered you is an EASY solution (if there is one) Check your fuel line in the engine compartment and make sure its sufficiently located away from heat sources. You mentioned that this started after installing new headers. Headers dissipate much more heat than standard exhaust manifolds perhaps you need to wrap your headers with some sort of heat tape to bring down the temperature in the engine compartment.

05-14-2001, 01:07 AM	#7
Ron1 Registered Member Join Date: Sep 1999 Location: Vancouver, WA USA Posts: 439	I used an aluminum spacer plate under the carb...larger than the carb, to keep heat off the manifold from getting to it. Worked great. Ron

05-14-2001, 09:36 AM	#8
Tom351 Registered Member Join Date: Oct 2000 Location: Atlanta,GA,USA Posts: 278	Aluminum transfers lots of heat, you are even better off with a phenolic or plastic spacer. I use a 1/4" spacer that I cut out of fiberboard with a jigsaw. ------------------ 67 Fastback - Arctic White Pearl paint 351W ,Trick Flow Aluminum Heads, Edelbrock TorkerII, Carter 750 CFM, Comp. Cam 477/510 219/233@.050, Performance Automatic C-4 Trans, 3.55 gears, Front Disc Brakes, 1-1/8" Fr. 3/4" rear sway bars. My 351W Fastback

05-14-2001, 05:37 PM	#9
vegasmustang Registered Member Join Date: May 2001 Location: las vegas Posts: 6	I live in Vegas and as you all probably know it gets pretty hot here. I remember the clothes pins too and I am only 29. I don't remember where I heard it from either, but when I experienced vapor lock, I tried it and it worked. ---- Just began re-restoring the car I drove in high school. I say re-restoring, because I started...and never finished. The money situation is a little better now, so here we go again! 65 Mustang Coupe w/ 84 5.O. motor.

05-15-2001, 10:20 PM	#10
67 shadetree mechanic Registered Member Join Date: May 2001 Location: Fort Worth Texas Posts: 4	I've check the fuel lines from end to end. They apear fine (plenty of seperation from hot metal). The car has only driven a few times in the past two years and only once since headers were installed. That day it was indeed hot. The car just died while moving down the road as though it lost spark. It did restart shortly after everything cooled a spell. I'm assuming it was vapor lock but could be another problem. Like I said, the car has benn garaged (in-work) for about 2 years now. Maybe I'm just chasing a ghost. I appreciate your advice but would like to understand the vapor lock a little better. Sounded like you were describing a sudden lost in fuel pressure due boiling fuel within the fuel lines or in the carb bowl or did I misinterpret what your saying? Would appreciate any/all responses about this subject. BTW, I'm also aware the cloths pin trick on old Ford flatheads. My pop has had a few of those back in his hayday. Thank You!

05-16-2001, 01:55 AM	#11
shovelnose Registered Member Join Date: Oct 2000 Location: Ontario, Canada Posts: 234	Put a clear filter in and look in it right after the car has been driven good and hot. You will see the rolling bubbles. A plastic spacer plate, 1/4" gasket, block heat cross-over in the intake, insulate the fuel lines near anything hot, fresh air, remove insulation on the hood, heat sheild for the carb, return line. Any of the above will help. If you ever drained your coolant and didn't bleed the system, you will probably not have heat in the car and the engine will over heat. This is another form a vapourlock. The air pocket gets trapped and coolant can't flow past it under pressure. ------------------ 82 Mercury Capri 302. Comp. Cams Tremec 3550 3.73's 12.8@106 N/AKevin's Capri

05-18-2001, 10:01 PM	#12
Gearhead999 Registered Member Join Date: Sep 1998 Location: Oviedo, FL Posts: 992	I personally run a wooden spacer, about 3/8 inch, under my dual AFB's. I made it out of a scrap piece of mahogany from my wooden Chris-Craft boat. Works great, keeps the heat from the carbs.