1972 big block vapor lock problem
Le Mans Master
Joined: Jan 2005
Posts: 8,226
Likes: 2
From: Lake Wylie SC
First step that I would do is use an IR gun and read the temperatures of your fuel line from the carb back to the frame rail. See where the heat increases are at and what the nearest source of heat is....... as soon as you hit 140 you are in trouble (fuel boils at 144)
Also sitting fuel is more prone to boil as it stays near the heat source for a longer time (like stopping for gas or in traffic).......... BTW motors with aggressive timing are prone to fuel vapor problems as well as are steel braided fuel lines.
There are a number of thermal barriers available through folks like Jegs
Doug
Also sitting fuel is more prone to boil as it stays near the heat source for a longer time (like stopping for gas or in traffic).......... BTW motors with aggressive timing are prone to fuel vapor problems as well as are steel braided fuel lines.
There are a number of thermal barriers available through folks like Jegs
Doug
Drifting
Joined: Oct 2005
Posts: 1,527
Likes: 148
From: East London/SW Essex UK
First step that I would do is use an IR gun and read the temperatures of your fuel line from the carb back to the frame rail. See where the heat increases are at and what the nearest source of heat is....... as soon as you hit 140 you are in trouble (fuel boils at 144)
Also sitting fuel is more prone to boil as it stays near the heat source for a longer time (like stopping for gas or in traffic).......... BTW motors with aggressive timing are prone to fuel vapor problems as well as are steel braided fuel lines.
There are a number of thermal barriers available through folks like Jegs
Doug
Also sitting fuel is more prone to boil as it stays near the heat source for a longer time (like stopping for gas or in traffic).......... BTW motors with aggressive timing are prone to fuel vapor problems as well as are steel braided fuel lines.
There are a number of thermal barriers available through folks like Jegs
Doug
Le Mans Master
Joined: Jan 2005
Posts: 8,226
Likes: 2
From: Lake Wylie SC
Doug
Drifting
Joined: Oct 2005
Posts: 1,527
Likes: 148
From: East London/SW Essex UK
IMO the logical answer to that would be yes however I am from the older C2 style single line school and I do not have any hands on experience with a dual line...... your analysis seems to make sense to me but I think it would be prudent for you to hear from one who has played with dual fuel line temperatures
Doug
Doug
Le Mans Master
Joined: Jan 2005
Posts: 8,226
Likes: 2
From: Lake Wylie SC
I like your idea of taking temp readings from the fuel line(s). We have just got ourselves a infra-red temp gun for taking some header temps on newly installed 489 engine. I had intended also to take block temp readings to see how accurate in-car gauge is. I will do same with fuel flow and return lines. It will be interesting to compare. Won't be able to do it for some time as I have to get a new radiator.
Usually it is the sidepipe cars that have hot lines before the engine compartment because of the heat getting transferred to the frame that the lines are mounted to.
Are you running a mechanical fuel pump...... if so that is a source of heat getting to the fuel being right next to the block........Some guys switch to electric just to get away from that one point. BTW if your headers are not coated you would do well to find a place near you to get a good alum/ceramic coating job done to them. Mine are coated and by the time I get in the garage and the car up on jack stands all the way around I can grab mine to help pull me around under the car.
Also I would install a heat shield between your carb and intake to keep the heat off the bowls...... do you have heat riser holes in your heads that are not blocked......... if you do not need a choke you can block those and eliminate a lot of heat from getting to the intake.
Also since you are getting a new radiator there is no substitute for a good alum one........ I have a Dewitt's one with a 496 with 11;2 compression and still stay right at whatever thermostat I have in.
Good luck
Doug
Drifting
Joined: Mar 2006
Posts: 1,526
Likes: 2
From: Oak Ridge NC
