1932 to 48 Fuel Pressure

[G.M.]

I just googled fuel pressure for1936 Ford and they recommended
below 2.5 lbs. I find that to low and that may account for a lot of
fuel problems posted on this site. I find 3.5 COLD to be a
good setting. As soon as the fuel pump heats up the pressure
will drop below 3 lbs and even lower in hot conditions. Near or
below 2.5 is subject to vapor lock and even more so with corn
gas. Higher pressure keeps the pump full of fuel. G.M.

 

[corvette8n]

I have a stock '41 how do I adjust fuel pump pressure?

 

[Charlie ny]

George,
I certainly respect what you have said here, I'm sure you know that. 3.5
psi is over the border line for me. 3.5 works if the car is sitting but going down the
road can be problematic because of the bouncing and jouncing. This is only my
opinion. An eye lash less than 3 is where I settle on my pumps.
Charlie ny

 

[G.M.]

George,
I certainly respect what you have said here, I'm sure you know that. 3.5
psi is over the border line for me. 3.5 works if the car is sitting but going down the
road can be problematic because of the bouncing and jouncing. This is only my
opinion. An eye lash less than 3 is where I settle on my pumps.
Charlie ny

Charlie, read my post again and digest the pressure/temperature
relation. Time flies but 5 or 6 years ago I did a lengthily heat test
down here in 90 plus outside temps. I blew fans on the pump, made
spacers to raise the pump, insulated aluminum between intake
manifold and pump, insulated the fuel line from the clutch pedal area
to the pump and pump to carb. The fan blowing air down on the pump
was about the only thing that made much of a difference. Even the
fan I used made a difference. Same type square computer fans but
of different RPM's made a difference, the higher RPM fan cooled the
pump better. For the tests I had a thermocoupling hooked to a temp
gauge on the fuel pump. The fan is to bulky and hard to make so not
practical. I even put aluminum heat sinks on the dual exhaust tail
pipes to draw heat away from where the corners of the fuel tank
almost touch the tail pipes. This did help keep the gas in the tank
cooler. Also suggested for going on a trip on hot days that the tank
be filled as you start the trip. This way you get cool fuel out of the
under ground tank. Don't forget the road temperature can be 120
degrees or more which also heats the tank. Refill the tank when it
gets below I;2 tank. Hot pump and fuel lower the pump pressure.
Raising the pressure to 3.5 COLD PUMP solved my problems down
in hot climate. G.M.

 

[flatheadmurre]

Since the only thing setting the pressure on the pump is the spring...why would the pressure drop when it heats up ??
It´s not likely the spring weakens from that kind of heat.
I´m not questioning your observations just curious why and how it happens.
Or are we talking some kind of pressure regulator ?

 

[G.M.]

Since the only thing setting the pressure on the pump is the spring...why would the pressure drop when it heats up ??
It´s not likely the spring weakens from that kind of heat.
I´m not questioning your observations just curious why and how it happens.
Or are we talking some kind of pressure regulator ?

It's very easy to check my pressure findings. Put a pressure gauge
between the fuel pump and carb. This will only be observed if the
engine sets over night so there is no heat on the pump or fuel
system. See what start up pressure is, drive the car for an hour on
a warm day, check and write down the fuel pressures and you will
see the drop I'm talking about. I don't think the spring changes. No
pressure regulator, has to do with fuel and heat. G.M.

 

[Bored&Stroked]

One thing that I find is when the fuel pressure to the carb inlet on a Stromberg is more than about 2.5 lbs, in many cases it will overcome the float's ability to hold the check-valve in place. I usually run a fuel pressure regulator set at about 2 lbs.

 

[scooder]

G.M.
I thought your fuel pump return line setup cured the heat related problems? As it kept the pump cooler? Was this after the New cold pressure setting?
Martin.

 

[G.M.]

G.M.
I thought your fuel pump return line setup cured the heat related problems? As it kept the pump cooler? Was this after the New cold pressure setting?
Martin.

I still have the return line on my 39 convertible and the fuel pressure
runs about 3 lbs. I have a needle valve on the return line. This is
needed if the return line is large enough to run the pump low on
fuel. It took all the testing to figure the return line worked best. I
have other v/8's I drive in both Pa. and down here in Fl. that run
around 3 lbs. I burn non corn gas. A lot of stations now carry it.
They call it recreation fuel. You can Google non corn gas and put in
the state and it gives a list of stations that sell it.

 

[G.M.]

I wanted to add that I later replaced the needle valve in the fuel
return line with a fixed orfice with a .110 hole. If the line is to big
to much fuel is returned and at high speeds the carb runs out of
fuel. The .110 restriction allows me to travel at over 80 MPH if I
want to. Engine don't drop much in RPM's but acts like a governor.
I brazed a 90 degree brass fitting up near the top of the filler pipe
and can look in and see the fuel returning to the tank. The bottle
shown in some of the last posts is a Marvel Mystery oil injection
system if some are wondering what it is. Attached is a picture of
the return line into the filler pipe. What appears to be a second
line is the tail light wires. I think I have more pictures of the pump
with the return line in my other computer at my office will look and
add if I find them. G.M.

Added picture of needle valve in fuel return line before replacing
it with .110 fixed orfice.

 

[G.M.]

One thing that I find is when the fuel pressure to the carb inlet on a Stromberg is more than about 2.5 lbs, in many cases it will overcome the float's ability to hold the check-valve in place. I usually run a fuel pressure regulator set at about 2 lbs.

30 years ago I had all kind of problems with carb needle valves sticking
open or closed. It would work good for a month then start acting up.
I went to a Gross ball valve and I can't recall a problem since. I know
Uncle Max supplies them. He might pop in with his experience with
the ball valves, I think they are being produced in England and not
sure but think they are supplied in the new Stromberg carbs. G.M.

I want to add that you can run the Stromberg with the top off and
watch the fuel level in the carb go up and down as the needle valve
works. With the ball valve you can not see any change in fuel level
as it constantly jiggles leaving in small amounts of fuel. This is
dangerous. G.M.

 

[Bored&Stroked]

Hey GM: Were you getting fuel vapor lock before? Adding a 'return line' reminds me of what we do in many race car setups - so that we don't "dead head" the pump. Also, we typically put a fuel cooler rail in the line - to cool the fuel. I am wondering if all you might need is a fuel cooler rail - and maybe that would get you buy with even a single line.

 

[G.M.]

Hey GM: Were you getting fuel vapor lock before? Adding a 'return line' reminds me of what we do in many race car setups - so that we don't "dead head" the pump. Also, we typically put a fuel cooler rail in the line - to cool the fuel. I am wondering if all you might need is a fuel cooler rail - and maybe that would get you buy with even a single line.

Don't know what a fuel cooler rail is. I didn't do all that testing because
I didn't have VL. It came big time down here in 90 plus temperatures as
soon as corn gas arrived. I really don't know how you would cool the fuel
in these cars without the return line other than the way Mercedes does
it, they use Freon from the air conditioner. G.M.

 

[Lawrie]

We are lucky here in Australia,we can still get non ethanol fuel,recently we were away in our 33,stock fuel pump and carb,towed our caravan in up to 42c and around town runs in 47.5C, engine water temps up to 95 on some hills,no fuel problems, None.
But I have a clean block and radiator,thats made it so.
Lawrie

 

[JSeery]

You can still get non ethanol fuel in the U.S., but it is a state by state deal. In Kansas it is just about everywhere.

 

[Old Henry]

Deleted.

 

[flatford8]

I remember about 45 yrs ago some guys down the road from me had a car they used on the drag strip. It had an aluminum container that had the fuel line coiled thru it. I think they put dry ice in the container.....Mark