Go Back   The Ford Barn > General Discussion > Early V8 (1932-53)

Sponsored Links (Register now to hide all advertisements)

Reply
 
Thread Tools Display Modes
Old 09-08-2017, 06:17 AM   #1
Charlie ny
Senior Member
 
Join Date: May 2010
Posts: 2,510
Default 2 1/2 psi fuel pressure

I've had a few requests for 2 1/2 psi fuel pump springs. To my knowledge
there is not a spring available that fits this criteria. In my opinion many
things can effect pump pressure not the least of which is hard to detect
wear in the components. My average success rate with achieving 2 1/2
psi the first time with a rebuild is less than 50%. After an unsuccessful test
I will install a slightly weaker or stiffer spring depending on the the pressure
readings or failing that the lever or base....I never really know. Can't beat
real world testing.
Charlie ny
Charlie ny is offline   Reply With Quote
Old 09-08-2017, 06:39 AM   #2
trainguy
Senior Member
 
trainguy's Avatar
 
Join Date: May 2010
Location: Lehighton Pa
Posts: 1,085
Default Re: 2 1/2 psi fuel pressure

Your post makes me wonder if the springs are constant from spring to spring or manufacturer to manufacturer?
trainguy is offline   Reply With Quote
Sponsored Links (Register now to hide all advertisements)
Old 09-08-2017, 01:19 PM   #3
Charlie ny
Senior Member
 
Join Date: May 2010
Posts: 2,510
Default Re: 2 1/2 psi fuel pressure

Phil,
Part of the answer is the number of times the pump has been rebuilt and by whom.
Bases and bowls from Holley, AC, B, and off shore bases and bowls get mixed. Then
the slotted type of arm vs the bushed type of arm adds to the challenge....it's all
good however once the needle settles on 2 1/4 to 2 3/4 psi.
Spring consistancy in my experience is vague, different number of coils, slightly different diameters, varying heights....etc etc.
Charlie ny
Charlie ny is offline   Reply With Quote
Old 09-08-2017, 02:55 PM   #4
Tinker
Senior Member
 
Tinker's Avatar
 
Join Date: May 2010
Location: MN/FL
Posts: 5,711
Default Re: 2 1/2 psi fuel pressure

Charlie, what are your thoughts on putting an extra gasket under the pump to lower pressure?
Tinker is offline   Reply With Quote
Old 09-08-2017, 04:20 PM   #5
Charlie ny
Senior Member
 
Join Date: May 2010
Posts: 2,510
Default Re: 2 1/2 psi fuel pressure

I've tried that with limited success, those gaskets are pretty thin. I admit trying this
but it bit me in the behind, I'll spare the details. It's easier in the long run to work
within the confines of the pump.......thank heaven for patient customers.
Charlie ny
Charlie ny is offline   Reply With Quote
Old 09-08-2017, 04:59 PM   #6
drolston
Senior Member
 
drolston's Avatar
 
Join Date: Jun 2014
Location: Williamsburg, VA
Posts: 1,072
Default Re: 2 1/2 psi fuel pressure

Sponsored Links (Register now to hide all advertisements)
Quote:
Originally Posted by Tinker View Post
Charlie, what are your thoughts on putting an extra gasket under the pump to lower pressure?
Raising the pump would lower the stroke and therefore the volume capacity of the pump, but the effect on pressure at the no/low flow condition is complicated. No-flow pressure is not really determined by the strength of the valve springs, but by the flexibility of the pump diaphragm versus the volume of the pump stroke. If fuel outflow is blocked by the carb float valve, the only place for the fuel in the pump chamber to go when the center of the diaphragm is pushed up by the pump rod is for the outer part of the diaphragm to "balloon" down a little. Because the pump volume for each stroke is pretty low (maybe a tablespoon?), it is not much of a stretch for the diaphragm.

Because the pump diaphragm up stroke (pressurizing) is on the down stroke of the push rod, the strength of down spring of the pump lever would theoretically limit pump pressure. That spring also keeps the pump push rod from floating off of the cam at high rpm. I am guessing that the Ford engineers have that spring just high enough to avoid that problem. Interesting physics problem for this winter. I will report back.

I recommend keeping the pump at full stroke and using a pressure regulator. Grosse type float valves have worked well for me to over 4 psi.
drolston is offline   Reply With Quote
Old 09-08-2017, 05:17 PM   #7
uncle max
Senior Member
 
uncle max's Avatar
 
Join Date: May 2010
Location: SLC Utah
Posts: 772
Default Re: 2 1/2 psi fuel pressure

Charlie, or anyone else...
I have a pal who does any imaginable spring in any quantity, from medical pacemakers to mine elevator springs and anything in between.
He supplies all my choke return springs, accelerator fulcrum springs and throttle speed springs, all heat-treated 302 stainless.
Don't laugh, but he has a degree in Spring Engineering.
Have a peek at his website: www.springworksutah.com
If you'd like a quote, just send me a sample and/or a good description. Everything is CNC and kept in a file, so if I go back for more in 10 years, I get the same thing... Did I mention he did the valve springs for the recent restoration of the Mormon Meteor?
Quote:
Originally Posted by Charlie ny View Post
I've had a few requests for 2 1/2 psi fuel pump springs. To my knowledge
there is not a spring available that fits this criteria. In my opinion many
things can effect pump pressure not the least of which is hard to detect
wear in the components. My average success rate with achieving 2 1/2
psi the first time with a rebuild is less than 50%. After an unsuccessful test
I will install a slightly weaker or stiffer spring depending on the the pressure
readings or failing that the lever or base....I never really know. Can't beat
real world testing.
Charlie ny
__________________
RIP Tyler... My Son, Helper & Best Friend.
Feb '78 to Father's Day '10.
www.97-express.com ~ info@97-express.com
uncle max is offline   Reply With Quote
Old 09-08-2017, 05:28 PM   #8
Charlie ny
Senior Member
 
Join Date: May 2010
Posts: 2,510
Default Re: 2 1/2 psi fuel pressure

d,
Good points. The flex in the diaphragm is in the picture. While developing my own diaphragm I tried lots of materials and thicknesses, a single piece of .062 material
behaved way different than what I ended up with........which is two pieces of .031
material. The material by the way is military grade viton.
Keep us posted on what you come up with this winter.
Regulators are great but it's possible to go with full stroke and stay within
the comfort range of our little carbs.
Charlie ny
Charlie ny is offline   Reply With Quote
Old 09-08-2017, 06:35 PM   #9
Tinker
Senior Member
 
Tinker's Avatar
 
Join Date: May 2010
Location: MN/FL
Posts: 5,711
Default Re: 2 1/2 psi fuel pressure

Quote:
Originally Posted by drolston View Post
I recommend keeping the pump at full stroke and using a pressure regulator. Grosse type float valves have worked well for me to over 4 psi.
I've gone through the pressure regulator route and wasn't satisfied with them.
Plus I personally prefer the look of just the pump. Thanks

Charlie thanks for your response. It's appreciated.
Tinker is offline   Reply With Quote
Old 09-09-2017, 06:11 AM   #10
B_man_Al
Senior Member
 
B_man_Al's Avatar
 
Join Date: Feb 2011
Location: Ottawa ON Canada
Posts: 301
Default Re: 2 1/2 psi fuel pressure

I know this is a little off topic, but I have been using the Airtek electric pump for several years now, located at the back of my model B. I had the same excessive pressure problems overrunning the carb float. Rather than add a regulator, I put 2 Tee's at the inlet and outlet of the pump and a bypass hose with a very small orifice inserted in the hose to limit the amount of pressure out of the pump. I don't remember the orifice size but was about .02 to .04 if I remember. I used a solder plug and drilled it out till I got the pressure I wanted. Its around 1-2 PSI now, down from the 5 or so.
B_man_Al is offline   Reply With Quote
Old 09-09-2017, 06:43 AM   #11
Charlie ny
Senior Member
 
Join Date: May 2010
Posts: 2,510
Default Re: 2 1/2 psi fuel pressure

Max,
Thank you for the intro to Spring Works !
Charlie ny
Charlie ny is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Sponsored Links (Register now to hide all advertisements)


All times are GMT -5. The time now is 06:40 PM.