NewbVetteGuy

After evaluating as far as I can tell, pretty much all of the available options for an EFI fuel system for late (78-81) carburated C3s and having found them all lacking in ease of install AND cost, I've decided to just design and build a solution for my 79, with some help from the fine folks @ Corvette Forum, hopefully.


My plan is to use an 82 Fuel Sending Unit, a Walbro in-tank return-style pump, and a Holley hydramat so that I can maintain a clean and constant fuel supply devoid of air.

Requirements are to use the existing fuel tank, avoid having to cut any holes, and to ensure constant and appropriate fuel supply.

I've got a number of initial questions to work through and I'll come back and get moving on this later today, hopefully, but in the mean time here's the Hydramat I'm thinking about using:

https://www.summitracing.com/parts/hly-16-105/overview/


Seriously checkout this Hydramat stuff; it's not cheap but it solves a major problem in a very simple way.




Adam

mrvette

EHEHEH....that was available some ten years ago, I would have done that, but I put an extra fuel tank below and forward of my '72 tank, and the 5 gallons never runs dry....it's a Harbor freight steel air tank rated for 125 psi, welded brackets and bolted in place....not going anywhere unless slammed HARD in the rear, in which the stock tank will kill me first......

OH, edit, I have DPFI at ~40 psi on my car 24 lbs injector rating and a roller 350 engine....

CA_WxMan

If that Walbro pump has an 11mm inlet, like most in-tank pumps do, then you'll probably want to use this version of the Hydramat:
https://www.summitracing.com/parts/hly-16-111/overview/

The one you linked to, P/N 16-105, has 3/8" NPT, which will likely take some type of adapter to connect to your pump.

P/N 16-111 has the 11mm opening to connect directly to most in-tank pumps, just like the OEM pre-filters would have.

lionelhutz

16-111 is the only hydromat that will plug right onto an in-tank pump. That's why I gave that specific p/n in your last thread.

NewbVetteGuy

You guys are awesome! Thanks for the tip!


I was thinking that I would have to put a very small piece of fuel-safe tubing on the 11mm fitting and use a stainless clamp and then another 3/8" NPT fitting and cut the suction tube off so the whole thing would fit properly on the bottom of the gas tank.

I did NOT know that they had a hydramat that would fit right up- no brainer!


Now my question is whether the inside diameter of the 82 sending unit tubes can push 255 LPM or not...


Adam

NewbVetteGuy

I'm looking to do Sequential Multi Port FI with the F.I.R.S.T. fuel injection intake and a crank trigger wheel mounted to the harmonic balancer. -I'd love the tiny extra bit of low end torque and fuel economy improvement. Plus I just like the idea of modern engine tech in my 79 L82 for some reason.

I've been thinking 35lb injectors are probably about right.

Adam

ezobens

That sender should have a 3/8" fuel line which will be plenty for the 255 pump.

NewbVetteGuy

Checked out the Walbro in-tank 255 LPM options; there's 3 different pumps with no real description as to why you'd go with each one.

I'm definitely going to have to give them a call to sort out which model # to get sometime today.


Adam

NewbVetteGuy

This is probably a dumb question but what's the difference between the "sender" that's in the 81 Vette tank and the 82 Vette tank?

I understand that the pump would be different but why would the sender actually be different with a carb vs. EFI?


Adam

NewbVetteGuy

It was a dumb question;

the pictures make things quite obvious: http://www.zip-corvette.com/68-82-c3...nit-meter.html

http://www.zip-corvette.com/68-82-c3...nit-meter.html



Now I've been reading the threads on what it takes to remove the old pump on a 79 with AC.... UGH; not looking forward to THAT...


Adam

NewbVetteGuy

Update: There are 3 in-tank Walbro pumps that might work. I called a Walbro reseller and what they could tell me was that the GSS-340, GSS-341, & GSS-342 are all 255 lph in-tank pumps; the 340 is an 80 PSI pump while the 341 & 342 are 43 PSI models.

They couldn't really tell me what size or type inlet our outlet each one uses, nor which one I would need to work with the 82 sending unit. They've directed me to their Sr. Tech guy Chris who should be able to sort me out (Chris@cyberauto.com).


Hoping to hear back.


Adam

NewbVetteGuy

The plot thickens...

There is a pump model # F20000169; it's a 255 LPH high-pressure pump (80 PSI) that's identical to the GSS340 except that it has a slightly smaller outlet so that it fits the 82 C3's sending unit.


The downside is that as it's essentially the same as the GSS340 except it's 43psi and the inlet side doesn't have an 11mm fitting and won't work with the holley hydramat listed above.

The good news is that they sell a kit; model # 5CA400HP that comes with a much smaller generic "hydramat" / wicking "depth media inlet filter"; it's only 3" x 1" though.


The awesome news is that the kit comes with wiring harness, gaskets, clamps, a small bit of tubing, and the filter media / mini hydramat for $121.93.


This is SOOO much cheaper than the alternatives; I wish they had a larger mat option, but for the price and convenience, I think I'll chance my arm...

https://walbrofuelpumps.com/walbro-5...-pump-kit.html

Adam

Ibanez540r

Good thread Adam. I'm sorting out a similar situation, but for a lot more flow. I need to feed 600+HP on E85 which requires about 30% more fuel then gasoline, and I need to run at 59 psi for my FiTech fuel injection.

I'm also trying to stay with the 82 sender if at all possible. Inline tube said they can CNC bend me a 1/2" line to the corvette specs. My problem is if choking down the pump through the sender then to 1/2" makes sense, or if I should remove the sender lines and use bulkhead fittings. I'm leaning towards the Walbro E85 450LPH pump. Confusing part about that is they rate it for 750HP + but it only has a 3/8" outlet.

If I can pull off using the in-tank I was also considering the hydromat.

NewbVetteGuy

Chris Myer got back to me again; there's two routes I can go:

#1. 5CA400HP https://walbrofuelpumps.com/walbro-5...-pump-kit.html $121.93 + 1982 Corvette sending Unit $100ish ==$221.93

#2 GSS342 255 LPH in tank return Walbro pump, 5CA400HP install kit, Holley Hydramat 16-111, credit for the 1250570 filter that I can't use == $234.69


Option #2 requires "some engineering" to ensure taht the GSS342 can be "appropriately situated in the hanger"; he says the body of the pumps are identical but the difference is that the inlet of the GSS342 is smaller...

I honestly don't even fully understand what part of the sending unit is the hanger or in practical terms how hard this might be to make it hall work. Given that the 79 tank has absolutely no baffles at all, I feel safer not starving the pump in the corners with the larger Holley Hydramat, but I don't really feel confident in my ability to hack something together for #2.


-Anyone think they know what modifications would be required to make #2 work?

Should I give this a try?



Adam

P.S. Ibanez: Email Chris@cyberauto.com your problem and see what he says; he's pretty amazing at this stuff.

Shark Racer

Getting the fuel pump off of my 78 with AC was pretty easy. Hardest part was probably squeezing the hose clamps off and that wasn't really all that bad.

I used an Aeromotive Phantom setup on my car and had to adjust the bracket a few times, ultimately it's about bending and tweaking to get the thing just floating over the surface. I'm not sure if Hydramat is the same story.

You could always do #1, see if you have a problem and go back to #2. I don't know how many people actually drive these cars very hard. I can say if you intend to autocross or do track days you'll very likely starve the pump with #1.

It does look like the Hydramat is pretty forgiving. You just need to get the pump and mat as close to the bottom as possible. I'm looking at pictures of 82 sending units (haven't handled one in person), and as near as I can tell - is it just held on by a hose and clamps?? Seems like that would fatigue the rubber pretty fast. If it isn't, you're going to simply want to attach the mat to the pump somehow and then raise/lower the pump as appropriate on whatever it's attached to until the hydramat skims the bottom surface of the tank. Cut your hose to an appropriate size and clamp to the sending unit.

Good luck!

ezobens

Installing the Walbro pump to the 82' sender is insanely simple.
All you really need to worry about is the inlet side of the pump matching the fitting for the Hydramat. The pump itself is held in by the tension of the fuel hose keeping the pump situated in the mounting ring at the bottom. I've never seen one of these just wander of and fall in the tank if connected securely. If you're worried, you could always strap it to the return tube with a hose clamp or fuel resistant tie wraps but make sure you have an insulator between the pump and the tube or you may have more pump noise that you bargained for.

Here is a pic from Ecklers:




82' Sender with 82' pump installed.

lionelhutz

Just look at the picture of the 82 pickup. There is no hanger or pump mount to modify. The pump is simply held by a piece of hose on the outlet nipple. It really can't get any simpler to setup. Just get the hose the right length that the hydramat sits on the bottom of the tank. You can probably see it through the filler neck. Just make sure you use good in tank submerged in fuel rated hose so it doesn't fail on you.

You could put a piece of rubber around the pump and then use a hose clamp to attach it to the return line if you really wanted to, but it shouldn't be necessary.

I doubt the filter on the cheaper option works like the hydromat. It's likely just a filter that does nothing to help pickup fuel.

Kacyc3

Just saw this, if you haven't purchased a pump you might want to go read this.

http://realstreetperformance.com/Fue...ison-Test.html

NewbVetteGuy

I read it, but it honestly feels a bit like propaganda disguised as a "scientific" test...

The Aeromotive 11142 is a 340lph pump; of course it moves more fuel than a 290lph Denso pump or a 255 lph pump.... That's not a fair comparison by definition. Walbro of course has higher flow pumps, which is what they should have compared to and would have, if they wanted a fair "scientific" test.


They're saying that the $69 Walbro moved 368 lbs/ hour -it's only rated at 255... They said that on a naturally aspirated combo it could support 705 hp, but it's only rated at / marketed at "500+hp". So you get up to 200hp EXTRA? DEAL!


The Walbro far exceeds the flow and hp capacity I need and does it with less amps (almost 1/2 the amps of the Denso) than the other pumps. --I'm running a return system and 90% of the fuel gets pumped and dumped back into the gas tank the bigger I oversize my pump the more capacity and amps I'm wasting.

I REALLY don't need the 958 naturally aspirated HP capacity of the Aeromotive 11142 which costs $172 at Jegs (approaching 3x the cost of the Walbro).


I don't get that test or what it's supposed to "prove"; seems more like poorly thought through propaganda, IMHO.


Adam

Luce

Yea, for the bigger is better crowd. Don't waste money on a bigger pump than you need. All you end up doing is heating your fuel and straining your electrical system more.

I came up with what I think is a slick set up that has worked flawlessly.

I have a surge tank under the hood kept full with the 105ga holley mech pump, then a 255 walbro feeding the engine, and returning to the surge tank. Excess fuel from the mech pump is returned to the tank, keeping the surge tank contents from getting too hot. So far so good.