Go back and read my posts, your confused. G.M.
Vapor lock 1 and 2
- Thread starter G.M.
- Start date
Go back and read my posts, your confused. G.M.
In 1957 GMC buses used this same idea in a rear engine bus, had a 248 six with hydramatic would idle on hot days no problem. They had a tee fitting at the carb with return line to tank, used mechanical pump on side of engine. same idea, the tee had a calibrated hole for bypass. This engine was in sideways so no forced air. The plan should work! Laurie
Lawrie
Well-known member
George, I have seen in HQ holden 6 fuel pumps,(these are much the same as the flatheads) there was a real small hole in the top that went between the suction and delivery sides,this was I assume to vent the fuel pressure when the motor was stopped and heat soak got into the pump,these engine also used a stormier carb. Just a thought
Lawrie
Lawrie
ford38v8
Well-known member
George, here we go again. You write something then you forget what you wrote and deny it forever, but then of course everyone is confused but you. Go back and read your own post right here on this thread.
Oh by the way, George, you be sure to take full credit for inventing that fuel return line now, here?
Oh by the way, George, you be sure to take full credit for inventing that fuel return line now, here?
1932 V8
Senior Member
I like the idea of this. It seems like this is the way things are going(or have been but I am out of touch with modern fuel systems) with a return line . I know they are doing this with Holley carbs on high perf engines and of course mechanical fuel injection .
I have a question going back to what I know about how a mechanical fuel injection fuel system works with a mechanical pump that gains pressure with RPM's and has a return line back to the tank to bleed off excess pressure .
So with that said ,How much pressure can the needle & seat handle safely on a Stromberg 97 ??
Lets say it will handle 3 lbs safely , could you get a stock pump to put out 4lbs cold and maybe 3 1/2 lbs hot , then run a return line off the fuel line between the pump and carb/carbs that has a 2 1/2 lb check valve/poppet with a pill (restricting jet ) in it set at .oXX" (would have to do the math) so essentially giving the carb/carbs 2 1/2 lbs at all times with fuel also returning back to the tank to keep the fuel pump cool ???
I am sure there are flaws with this thought but I am liking what you are doing .
I really like the tuning/tinkering/learning/researching part of playing with old Fords in today's modern surroundings. Never a dull moment .
Mike
I have a question going back to what I know about how a mechanical fuel injection fuel system works with a mechanical pump that gains pressure with RPM's and has a return line back to the tank to bleed off excess pressure .
So with that said ,How much pressure can the needle & seat handle safely on a Stromberg 97 ??
Lets say it will handle 3 lbs safely , could you get a stock pump to put out 4lbs cold and maybe 3 1/2 lbs hot , then run a return line off the fuel line between the pump and carb/carbs that has a 2 1/2 lb check valve/poppet with a pill (restricting jet ) in it set at .oXX" (would have to do the math) so essentially giving the carb/carbs 2 1/2 lbs at all times with fuel also returning back to the tank to keep the fuel pump cool ???
I am sure there are flaws with this thought but I am liking what you are doing .
I really like the tuning/tinkering/learning/researching part of playing with old Fords in today's modern surroundings. Never a dull moment .
Mike
ford38v8
Well-known member
Mike, I think you may be somewhat in agreement with GM's check valve theory, so I'll try to blow that theory apart right here.
The pressure required from the pump is simply to be sufficient to replenish the float bowl when the needle valve opens, and to be incapable of blowing past that valve when it closes. The carburetor wants no pressure value beyond that stated.
Adjustment of the bowl level is accomplished with the float, not anything to do with pressure. It is the fully vented float bowl level that is important, to provide a gravity feed to the main jets, no pressure, just gravity.
Beyond that, a check valve is not called for as the needle valve is sufficient to perform its function without the added complication of a check valve.
The pressure required from the pump is simply to be sufficient to replenish the float bowl when the needle valve opens, and to be incapable of blowing past that valve when it closes. The carburetor wants no pressure value beyond that stated.
Adjustment of the bowl level is accomplished with the float, not anything to do with pressure. It is the fully vented float bowl level that is important, to provide a gravity feed to the main jets, no pressure, just gravity.
Beyond that, a check valve is not called for as the needle valve is sufficient to perform its function without the added complication of a check valve.
Surely if you remove the needle valve and use a check valve set at 2 1/2lb or whatever pressure, the float bowl will just overflow and you'd have fuel going allover the place. With out the needle being closed by the float, what is going to stop the fuel at the correct level?
GM, could you please explain this? I've tried to understand your thinking here, but I can't get the check valve bit.
I'm a real believer in the return line from the pump to cool the pump, it's been used on production carburetor engines since late 60's or early 70's wether it be a calibrated hole in a 'T' fitting twix pump and carb or an extra small barn on the pump or return from pressure regulator.
Martin.
GM, could you please explain this? I've tried to understand your thinking here, but I can't get the check valve bit.
I'm a real believer in the return line from the pump to cool the pump, it's been used on production carburetor engines since late 60's or early 70's wether it be a calibrated hole in a 'T' fitting twix pump and carb or an extra small barn on the pump or return from pressure regulator.
Martin.
expavr
Well-known member
Aeromotive makes a decent fuel pressure regulator 3-60 psi with a by pass port that you can plug a fuel return line into. Cost $135.00. No need to reinvent the wheel if you decide to install a fuel return line. These regulators are designed to be used on high performance engines which may be overkill on our street driven flatheads, but its use along with a fuel return line might be worth the effort if vapor lock becomes a serious problem. Les Williams
flatmotor40
Well-known member
Well mine will be a little hard to start after you let it sit for 15 min after riding around for 10 miles or so and you have to grind and when it fires it like it is rich and loaded up.Went and put reg gas without 10% in it and really made no difference.Did the same thing after that run.But shut it off and wait a minute or so and it fires before it turns over 1 rev.Have 1"micarter(spell) under the 2 97's.Electric pump only at 2 1/2 lbs.This has just started in the last few months.Drive it every week all year so it doesn't sit very long unless it rains
Old Henry
Well-known member
You have hit the nail right on the head. Although the return line may help avoid vapor lock while the engine is running, that is not the most frequent problem with vapor lock. It is after a hot engine has sat out in the sun for 10 minutes. The return line has no benefit then, neither does a carb spacer. The engine heat and the sun beating down on the hood just heats everything, including the carb, fuel lines, and fuel pump, above boiling temperature and you have vapor lock no matter how many return lines or spacers you have. I was actually going to install a return line and bought all of the materials to do so until I figured this out. The only solution to this problem is to either open the hood every time you stop, install a fan that comes on when the engine is turned off to blow air from outside the engine compartment into it to cool it, or install an electric fuel pump to prime everything and refill the carburetor that has boiled out like I did.
BILL WZOREK
Well-known member
Henry:
How long have you been around these cars , & use those two words together may be a foopaa !!!!!
Old Henry
Well-known member
Had to look up "foopa".* Hadn't seen that before. You are right on there. I certainly do have some of that.
*foopa
"An area of fat usually found on the bellies of older women who do not exercise, it can also be found rarely in some men and younger women who don't get exercise. It is located above the hip and is located dead center of the body usually above waistline, making one appear to be bloated or enormously fat."
(I'm thinking your use of "foopa" may have been a faux pas.
)
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1952henry
Well-known member
Faux pasHad to look up "foopa".* Hadn't seen that before. You are right on there. I certainly do have some of that.
*foopa
"An area of fat usually found on the bellies of older women who do not exercise, it can also be found rarely in some men and younger women who don't get exercise. It is located above the hip and is located dead center of the body usually above waistline, making one appear to be bloated or enormously fat."
(I'm thinking your use of "foopa" may have been a fopaux.
And, when said person is wearing tight pants and a tight shirt, these now visible fat pockets are called "muffin tops".
1932 V8
Senior Member
Nobody is talking about removing the needle and seat . I am not sure where this got derailed but that has never been said by GM or myself.
All that this discussion is about is keeping fuel flowing through the fuel pump at all times to keep it cooler while still having at least 2- 2 1/2lbs of pressure at the carb/carbs to keep them from starving at higher RPM's.
That's it .
Old Henry : question for you : If the under hood temps are a concern then wouldn't it be to our advantage to start with the carb/carbs cooler ( with the spacers) and the fuel pump cooler ( with a return line ) ????
So instead of shutting off the engine with a fuel pump at 135 deg and then it rising to lets say 8 deg , we would start with a fuel pump at 125 deg and then it will rise the same 8 deg so ending up at 133 deg which is still under what GM proved to be the vapor lock point under the hood of his 39 Deluxe .
In theory that would solve the vapor lock for restarting the car in hot weather.
(My numbers are all just examples to explain what I am saying except GM's 135 deg that was proven in his situation )
All that this discussion is about is keeping fuel flowing through the fuel pump at all times to keep it cooler while still having at least 2- 2 1/2lbs of pressure at the carb/carbs to keep them from starving at higher RPM's.
That's it .
Old Henry : question for you : If the under hood temps are a concern then wouldn't it be to our advantage to start with the carb/carbs cooler ( with the spacers) and the fuel pump cooler ( with a return line ) ????
So instead of shutting off the engine with a fuel pump at 135 deg and then it rising to lets say 8 deg , we would start with a fuel pump at 125 deg and then it will rise the same 8 deg so ending up at 133 deg which is still under what GM proved to be the vapor lock point under the hood of his 39 Deluxe .
In theory that would solve the vapor lock for restarting the car in hot weather.
(My numbers are all just examples to explain what I am saying except GM's 135 deg that was proven in his situation )
Old Henry
Well-known member
You might be right but I highly doubt it. You're talking about less than 6 oz of cooler fuel in the carb, pump, and fuel lines against 600 lbs of steel that's 180-190°. I don't think it would take long to melt 6 oz. of frozen water under that hood sitting out in the sun in 10-15 minutes much less heat that much fuel from 125° to above boiling temperature under the same circumstances. Just my thoughts.
Old Henry
Well-known member
G.M.'s statement in post #12: "An exact check valve at 2 1/2 lbs could eliminate the needle valve."
That's what the discussion has been trying to "debunk".
Old Henry
Well-known member
Not sure where you got that definition. From Wikipedia: A faux pas (/ˌfoʊˈpɑː/ plural: faux pas /ˌfoʊˈpɑːz/) is a socially awkward or tactless act, especially one that violates accepted social norms, standard customs, or the rules of etiquette.[
I think that's the word Bill and I were meaning to use. Unfortunately, we're both spelling challenged.
