Forums Migration

Please read this thread

Recent Topics
pool deck paint
by CincyDavid - 07/13/20 06:32 AM
DIY Injector cleaning - What cleaner?
by Spetz - 07/13/20 12:50 AM
Rock Auto promo code
by daves66nova - 07/12/20 11:09 PM
05 Dodge 4.7 L head gasket blown again
by vwmaniaman - 07/12/20 09:44 PM
How come every vehicle’s MPG computer is off?
by OppositeLocK - 07/12/20 09:37 PM
Glock Gen 5 .40 Caliber
by BlueOvalFitter - 07/12/20 08:34 PM
Help me determine if my CVT fluid has been changed
by Dallasmale1970 - 07/12/20 08:01 PM
Hyundais, Hyundais, Hyundais!
by csandste - 07/12/20 07:57 PM
Traveller's (WPP) $10.99 - 5 QT
by Gene K - 07/12/20 07:26 PM
PEAK 10X or Peak Global Lifetime
by pbm - 07/12/20 07:25 PM
Nio stock. How high will it go?
by motor_oil_madman - 07/12/20 05:34 PM
AAP Rotella Gas Truck Clearance
by Sam_Julier - 07/12/20 05:32 PM
Any 47RH Transmission Experts? CTD Ram
by JHZR2 - 07/12/20 04:58 PM
WM Magna1 10w30 gallon $5
by 2strokeNorthstar - 07/12/20 04:55 PM
I found a WWII movie for yinz to watch.
by JimPghPA - 07/12/20 04:45 PM
Jackpoint Jackstand Review
by RamFan - 07/12/20 03:03 PM
Lesabre Brake fluid capacity
by Ihatetochangeoil - 07/12/20 02:56 PM
Newest Members
stepburns, JOLLY300, WheelHorseman, stiguy300, Mark_C
71921 Registered Users
Who's Online Now
49 registered members (avi1777, AndyB, Anthony, AlienBug, 94astro, 7 invisible), 1,132 guests, and 25 spiders.
Key: Admin, Global Mod, Mod
Forum Statistics
Forums67
Topics307,782
Posts5,317,748
Members71,921
Most Online4,538
Jan 20th, 2020
Donate to BITOG
Print Thread
Hop To
Page 1 of 2 1 2
71 Cutlass vapor lock? #5449159 06/08/20 05:06 PM
Joined: Jun 2002
Posts: 13,736
K
Kestas Offline OP
Global Moderator
OP Offline
Global Moderator
K
Joined: Jun 2002
Posts: 13,736
I have a 1971 Cutlass 350 (stock) that I've had for 37 years. I used to drive it regularly until the past 5 years, where I was lucky to take it out once a year. The last time I took it out, I took it for a 15 mile drive. It ran well, but decided to stall out on my driveway and I couldn't put it in the garage. I came back next weekend and the car started up fine.

Yesterday I had a conversation with another classic car owner. He told me that recently gasoline has been reformulated with a lower boiling point and I probably experienced vapor lock. He said the boiling point has been lowered from 175°F to 95°F. This isn't a problem with modern cars that have fuel injection. The fuel is under pressure, which precludes boiling. Is this a thing? The pattern of what i experienced matches this scenario.

This last episode doesn't give me a good feeling about driving my car. I'd feel better if I at least understand what the problem is. I'd like to give my car some more exercise.

Re: 71 Cutlass vapor lock? [Re: Kestas] #5449178 06/08/20 05:44 PM
Joined: Apr 2004
Posts: 1,254
N
nascarnation Offline
Offline
N
Joined: Apr 2004
Posts: 1,254

Re: 71 Cutlass vapor lock? [Re: Kestas] #5449182 06/08/20 06:01 PM
Joined: Dec 2003
Posts: 1,447
W
wings&wheels Offline
Offline
W
Joined: Dec 2003
Posts: 1,447
Starting with vapor lock. Automotive gasoline in most, maybe all states has a higher vapor pressure, (to be over simplified...boils easier) in winter than summer. Summer fuel is the opposite...there are specific times when the switch is made. There is a lot of info out there. Could you have had last year's winter mix fuel in there??

Ethanol is another subject and if you are only driving the car once a year, I'd be concerned about the how good the fuel is in your tank if you are running e10. The ethanol can cause many problems that could be contributing to your problem.

For your car, I would try and run pure gas but if you can only get e10 (like us), I'd use a good treatment/stabilizer. If it were my vehicle I'd use Sta Bil marine and a lead substitute.

Good luck.


'05 Lotus Elise S/C
'85 Land Rover 90 diesel
'74 Triumph TR6
'74 BMW 2002
'72 Land Rover Series III 88"
'99 Porsche 996
'01 Porsche Boxster S (mostly Wife's...)
'19 VW Golf R (Wife's)
Piper Pa28-236


Re: 71 Cutlass vapor lock? [Re: Kestas] #5449183 06/08/20 06:01 PM
Joined: Dec 2005
Posts: 464
J
JohnG Offline
Offline
J
Joined: Dec 2005
Posts: 464
Not sure what military vehicles have to do with your issue, and I'm certain that ethanol has absolutely nothing to do with it, but yes, you might be experiencing vapor lock.

Anytime you have winter grade, eg. High RVP gas in your tank, and the temperature gets warmer, there is the possibility that the fuel can boil in the fuel lines near a heat source, such as your engine.
Ambient temps of course would have an impact on this action, as well as routing of the fuel lines near any heat source.

So this is an easy fix. Go exercise your car, and when you get home fill the tank with summer grade fuel. That would be fuel with an RVP (Reid Vapor Pressure) of 9.5 psi or lower.
Winter grade gas is around 15 psi.

Re: 71 Cutlass vapor lock? [Re: Kestas] #5449185 06/08/20 06:02 PM
Joined: Dec 2003
Posts: 1,447
W
wings&wheels Offline
Offline
W
Joined: Dec 2003
Posts: 1,447
Great link nascarnation....very informative. I had started to respond before you had replied.


'05 Lotus Elise S/C
'85 Land Rover 90 diesel
'74 Triumph TR6
'74 BMW 2002
'72 Land Rover Series III 88"
'99 Porsche 996
'01 Porsche Boxster S (mostly Wife's...)
'19 VW Golf R (Wife's)
Piper Pa28-236


Re: 71 Cutlass vapor lock? [Re: Kestas] #5449208 06/08/20 06:46 PM
Joined: Dec 2005
Posts: 464
J
JohnG Offline
Offline
J
Joined: Dec 2005
Posts: 464
BTW, pure ethanol has an RVP of 2 psi.

Re: 71 Cutlass vapor lock? [Re: Kestas] #5449211 06/08/20 06:50 PM
Joined: Oct 2004
Posts: 10,479
B
bullwinkle Offline
Offline
B
Joined: Oct 2004
Posts: 10,479
Originally Posted by Kestas
I have a 1971 Cutlass 350 (stock) that I've had for 37 years. I used to drive it regularly until the past 5 years, where I was lucky to take it out once a year. The last time I took it out, I took it for a 15 mile drive. It ran well, but decided to stall out on my driveway and I couldn't put it in the garage. I came back next weekend and the car started up fine.

Yesterday I had a conversation with another classic car owner. He told me that recently gasoline has been reformulated with a lower boiling point and I probably experienced vapor lock. He said the boiling point has been lowered from 175°F to 95°F. This isn't a problem with modern cars that have fuel injection. The fuel is under pressure, which precludes boiling. Is this a thing? The pattern of what i experienced matches this scenario.

This last episode doesn't give me a good feeling about driving my car. I'd feel better if I at least understand what the problem is. I'd like to give my car some more exercise.

The Bakelite carburetor spacer/isolator is a very good way to lessen this issue by keeping the carb cooler, my brother had to put one on his Jeep's Chevy 283 to keep from boiling the fuel in summer, and the OEM GM fuel filter in the carb fuel inlet likely isn't helping much either. Guessing your Rocket 350 has a Quadrajet? I would make sure your heat riser is opening hot as well (if it has one) to stop the exhaust crossover in the manifold from getting too hot(?)


06 Ram 3500 CTD 4X4(FG Venturi), 89 F-450 7.3, 98 XJ 4.0(XG8A), 05 xB(XG3600), 18 Transit 3.7 (MC), 03 Merc Grand Marquis 4.6 2V(XG2), 11 Express 3500 6.0 (Fram PH10060 for now)
Re: 71 Cutlass vapor lock? [Re: Kestas] #5449217 06/08/20 06:57 PM
Joined: Jun 2003
Posts: 21,105
C
Chris142 Offline
Offline
C
Joined: Jun 2003
Posts: 21,105
Along with what everyone else said. Cars back then often came with an aluminum heat shield/Carb base gasket. They get thrown away by guys that do not understand why they are there. They helped keep the Carburetor cool.You may want to block off the heat crossover in the intake as well. Does the car still have a fuel return line that returns some of the gas from the pump back to the tank?

You can also try the clothes pin trick too. Does the car still have this? this is a chevy version. Olds was simmiliar.

https://www.camarocentral.com/1967_1981_Quadrajet_Carburetor_Pre_Heat_Shield_p/enc-859.htm

Last edited by Chris142; 06/08/20 06:59 PM.

02 Wrangler Napa high milage 10w40
87 F250 Valvoline 15w40
07 fjcruiser Car lube plus 10w30
Z400 castrol T 10w40
Can am Maveric edge 5w40
57 case tractor Chevron sae30
Re: 71 Cutlass vapor lock? [Re: Kestas] #5449218 06/08/20 06:57 PM
Joined: Jan 2013
Posts: 4,086
W
WyrTwister Offline
Offline
W
Joined: Jan 2013
Posts: 4,086
As far as I know , most / all electronic fuel injected gasoline engines have the fuel pump inside the gasoline tank . So , the gasoline is under pressure all the way from the tank to the FI system . Pretty much eliminating vapor lock .

Your 1971 mode 350 engine likely has a n engine driven mechanical gas pump . Which creates a pressure lower than atmospheric pressure , at the gas line , going to the gas tank . This reduced pressure can cause the gas to boil ( vapor lock ) . Excessive heat ( gas line routed too close to exhaust system ) can make this situation worse .

As has been suggested , using pure gas may help . Rerouting or insulating part of the gas line may help .

A solution that was sometimes used back in the day was to install a generic electric fuel pump under the vehicle , near the gas tank . There by , the gas would be under pressure , the rest of the way to the engine . Unlikely to boil / vapor lock .


Wyr
God bless
Re: 71 Cutlass vapor lock? [Re: Kestas] #5449220 06/08/20 07:01 PM
Joined: Aug 2009
Posts: 2,636
G
Gasbuggy Offline
Offline
G
Joined: Aug 2009
Posts: 2,636
can anyone confirm if the boiling point change is factual?


Cadillac CTS-V 6.2L 10w30PP
Volvo P1800 Euro L
76 Mercedes 300D Rotella T4
Series III Land Rover VWB
02 Yukon 10w30 PP
01 P71 M1 EP-HM 0W20
95 Accord - 386k. Mobil 2 RIP
Re: 71 Cutlass vapor lock? [Re: Kestas] #5449224 06/08/20 07:10 PM
Joined: Jun 2012
Posts: 2,612
O
oldhp Offline
Offline
O
Joined: Jun 2012
Posts: 2,612
Like other's have said make sure you got summer gas. If close to a pure gas station, use that kind of gas for the old critters we all have. If your car is stock then I'll bet it has that HUGE factory air cleaner that traps heat like all get out. Maybe think of putting on a smaller 10" open chrome ( +12 HP : ) that won't trap the engine heat at the carb. Check under the car and make sure the gas line is not around any exhaust pipes. If it is you can wrap the exhaust pipe or make a heat shield for the gas line. Another helpful option is. Is there any drag race or circle track race tracks around you? I'm sure you could buy some fuel from there. You could mix in 5-8 gals race gas with your gas. It helps. If it stalls spray some carb cleaner into the carb, that will tell you for sure if it's vapor lock. Good Luck..................Vapor lock can a pain in the rear!!!!

Last edited by oldhp; 06/08/20 07:11 PM.

"None of us are getting out here alive...drink that beer...eat that pizza...drive that Hot Rod"
"When others cut you down, remember where they came from."
"I don't run...........I just quietly wait"
Re: 71 Cutlass vapor lock? [Re: Gasbuggy] #5449233 06/08/20 07:23 PM
Joined: Jun 2003
Posts: 35,802
E
eljefino Offline
Offline
E
Joined: Jun 2003
Posts: 35,802
Originally Posted by Gasbuggy
can anyone confirm if the boiling point change is factual?


Not as OP describes it.

It will boil at a partial vacuum at warm-ish temps and it will be worse with winter-grade RVP fuel.

There's also a chance that the evap emissions are primitive or non-existent, and that the year-old gas has already evaporated off the better parts. That should make it less likely to vapor lock, but more likely to run poorly.

"They" generally try to have fuel that evaporates as slowly as possible while still starting an engine to help with ground level smog emissions. There's butane (?) in winter gas that isn't allowed in summer gas for this reason, and since they have to get rid of it, summer gas costs more. This would also help avoid vapor lock.

Re: 71 Cutlass vapor lock? [Re: JohnG] #5449245 06/08/20 07:44 PM
Joined: Apr 2004
Posts: 1,254
N
nascarnation Offline
Offline
N
Joined: Apr 2004
Posts: 1,254
Originally Posted by JohnG
Not sure what military vehicles have to do with your issue,

The military vehicle in the link has a Chevy 235 gasoline fueled six banger, typical of the old iron affected by this stuff. He was having the problem during parades in hot weather.

Re: 71 Cutlass vapor lock? [Re: JohnG] #5449249 06/08/20 07:49 PM
Joined: Apr 2004
Posts: 1,254
N
nascarnation Offline
Offline
N
Joined: Apr 2004
Posts: 1,254
Originally Posted by JohnG
I'm certain that ethanol has absolutely nothing to do with it.

Tell that to the general aviation guys.....

https://generalaviationnews.com/2011/06/26/vapor-lock-ethanol-and-ultralights-2/

Re: 71 Cutlass vapor lock? [Re: Kestas] #5449260 06/08/20 07:56 PM
Joined: May 2010
Posts: 11,621
S
spasm3 Online Happy
Online Happy
S
Joined: May 2010
Posts: 11,621
Could be vapor lock , but check for spark when it won't start. Just to make sure its not the coil. An ignition coil can work cold and not when hot.


13 elantra 84k 5w30 synpwr
03 chevy avalanche 83k synpwr 5w30
17 mazda cx-5 19000 miles m1 0w30
Page 1 of 2 1 2
Previous Thread
Index
Next Thread

BOB IS THE OIL GUY® Powered by UBB.threads™