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First, a BIGthank you to all the posted threads on this topic, I have been trying to use all your ideas and hints and knowledge in my project,,, so this is what i have come up with for my '75, Let me know if I have forgotten anything,,, I'm hoping to install this in the tank this week,,,,,,,teddy
ONE major thing to consider......WHEN GM installs fuel pumps in a fuel tank...the pick-up screen is installed in a reservoir that will always have fuel in it so when the car is making turn or accelerating/decelerating..the fuel (when low) does not slosh and cause the fuel pump to suck in air.
I have seen some members who actually built a reservoir to the sending unit and it has holes in it so fuel can SLOWLY flowing to it but not be able to flow out...and yet these holes...when the fuel is low...will be able to keep up with the volume that the fuel pump is requiring.
LASTLY...the fuel hose that you used to join the fuel pump to the sending unit...you might want to call the manufacturer of THAT hose and ask them to what it is rated in PSI. I believe most 3/8" fuel hose is rated to 50 psi...and when I am doing fuel system modifications....I get the bio-fuel hose that is rated to something like 220 psi. I get it at O'Reillys and I am sure others may have it and what I get has green writing on it.
Thanks DUB, I'm taking Holley's view that with using the HydraMat, an additional reservoir or sump is not necessary, ( check their website on this product, I want to believe them, hope I'm not too naive, ),,,, As for the in tank hose, very few hoses are constructed for in-tank submersible environment, that I was able to find, most have inside lining for fuel, but not the exterior of the hose, this Gates hose [ part # 27093 ] is made and rated for this application (high pressure - 100 psi. per their specs.)
Thanks carriljc, my goal was to keep my original sending unit, and this 75 has a large opening that allowed for the additions i made,
I am venting using original charcoal can, this original tank has two vent lines, one venting open area where fuel is, and another venting the area between the bladder and the steel tank, and I'm using the old return fuel port as a third vent port, all three tied to the original venting system, Richard454, I'll post a pic of the lines befor I install the tank in the car,,,,,I'm also pondering the idea of a inertia switch, but I'm thinking the ECM should shut fuel pump off if their is no crank signal, in the event of a wreck, ,,,,,Nice looking job Richard454
It's cool that you have that big access hole on yours...
I had to work with the smaller gas tank hole on my 68. The good thing is that I can take it out from the top. I mention the canister pump only in case you have problems with that "mat" system. Hopefully you do not have problems and it works well for you.
Originally Posted by 60 SHARK
Thanks DUB, I'm taking Holley's view that with using the HydraMat, an additional reservoir or sump is not necessary, ( check their website on this product, I want to believe them, hope I'm not too naive, ),,,, As for the in tank hose, very few hoses are constructed for in-tank submersible environment, that I was able to find, most have inside lining for fuel, but not the exterior of the hose, this Gates hose [ part # 27093 ] is made and rated for this application (high pressure - 100 psi. per their specs.)
Thanks carriljc, my goal was to keep my original sending unit, and this 75 has a large opening that allowed for the additions i made,
Thanks for your good thoughts,,,
Last edited by carriljc; Jun 1, 2017 at 11:27 PM.
Reason: eidt: "I CAN take it out from the top"
I did notice carrilijc that you did not drop your tank to do your upgrade, I'm sure it was tedious, looks like you had good success,,,i am hoping the best with Holley. Years ago I had a 1968, but back then I never thought about EFI. Maybe I can wrap up the tank part of my project today,,,,,thanks for all the thoughts.
Thanks DUB, I'm taking Holley's view that with using the HydraMat, an additional reservoir or sump is not necessary, ( check their website on this product, I want to believe them, hope I'm not too naive, ),,,, As for the in tank hose, very few hoses are constructed for in-tank submersible environment, that I was able to find, most have inside lining for fuel, but not the exterior of the hose, this Gates hose [ part # 27093 ] is made and rated for this application (high pressure - 100 psi. per their specs.)
Thanks carriljc, my goal was to keep my original sending unit, and this 75 has a large opening that allowed for the additions i made,
Thanks for your good thoughts,,,
I am glad that you looked into this and verified that your rubber hose as going to be able to not only handle the pressure you need and is also submersible in fuel.
First, a BIGthank you to all the posted threads on this topic, I have been trying to use all your ideas and hints and knowledge in my project,,, so this is what i have come up with for my '75,
Let me know if I have forgotten anything,,, I'm hoping to install this in the tank this week,,,,,,,teddy
]
Looks good , maybe you might want to tie the two wires to the bracket so they wont move around at the connections .
Thanks bazza77, I just finished up in the garage , I did what I could,,,,the pump unit needs to go into the tank befor the sending unit, then attach them after the sending unit is rotated into place,,, tight fit but not impossible, I got it all in tonight, I'll post pix later, of time all wired and plumed,,,
ONE major thing to consider......WHEN GM installs fuel pumps in a fuel tank...the pick-up screen is installed in a reservoir that will always have fuel in it so when the car is making turn or accelerating/decelerating..the fuel (when low) does not slosh and cause the fuel pump to suck in air.
My own personal experience with this (but on a different car, a '98 Firebird) is the sock that comes with the aftermarket pump (such as the one shown in the above pics) is usually sufficient to hold the fuel during hard cornering/acceleration. How I know is I replaced my intank pump with an aftermarket pump, the sock came off during installation (and I didn't know it). But the pump was still submerged in gas. I kept running out of fuel! Especially during hard acceleration. I pulled the pump assembly back out to find the sock had come off, put it back on (right) and it's been great ever since. Intank pump, although a major PITA to install, is well worth it in the end.
Last edited by htown81vette; May 31, 2017 at 09:45 PM.
I hope that "mat" works. I used to have a Holley Pro-Jection, with an external fuel pump, and if I was less than 1/4 tank, then I would lose fuel pressure whenever I took a sharp corner.
No problems such as that with my in-tank canister pump. It's been wonderful for years.
My fuel tank is vented via the fill cap.
This is the last look at it before I installed the tank, I hope this explains what I did, my goal was, not to put any new penetrations in the tank, and if the sender goes bad, i only have to modify the new one to accept these parts easily, It just took me some time thinking it through 20 times befor i actually did it, lol, I'll keep updates coming as i progress, Thanks for your thoughts,,,, teddy
[QUOTE=60 SHARK;1594839247]First, a BIGthank you to all the posted threads on this topic, I have been trying to use all your ideas and hints and knowledge in my project,,, so this is what i have come up with for my '75, Let me know if I have forgotten anything,,, I'm hoping to install this in the tank this week,,,,,,,teddy
Walbro pump ( @ 80 psi.-210 lph.=50 gph.)
Holly - HydraMat Fuel Reservoir System
Gates - Submersible high pressure fuel line
Delphi connectors
EARLS - AN fittings
other parts, DIY from stuff in my garage
[/QUO
I love what you did here! It's exactly what I thought would need to happen. Thank you for the pics and for reaching out! It's truly appreciated!
So,, it has been several years now that i have installed my DIY in tank fuel pump system.
. It is still working awesom! I see others lately pondering doing the same,, so i thought i would give a up date..
The only hick-up i had,,, was my own falt. I initially wired up my pump backwards,, ( i had no fuel pressure ). I traced everything out and readily found my mistake. Then the car fired right up. 👍.
The Holley Hydramat is working perfectly,, as advertised. I even thought one time my gas guage failed,, i thought i had recently filled up,,, guess i had not. But i was able to drive many many miles on 'E' ,, hard right and left turns and agressive starts and stops,, then it just quit.?.?.?. OH, I WAS OUT OF FUEL,,🤷,, LOL,LOL,.. I looked in tank, and not a drop or wet spot. That mat sucked it dry,,,👍😁👍. [ My guage was actually still working 👈 🤪 ]
I hope this helps others pondering doing the same. Its not too dificult. AND, very cost effective compaired to "buying a aftermarket unit".
for new EFI , your thoughts on in-tank pump DIY
