bolded

 

Paul, what year tank is that? Is that just a 77-81 style tank with the plastic line removed and then that metal baffle welded in?

Awesome to see interior pictures.
Also, do you know the exact model of that pump? (I could not get my Walbro GSS342 to work with the hanger bracket and cut the hanger bracket off to make mine work; I can see the hangar on yours is intact still.)

Adam

 

If you buy the Walbro GSS342 in-tank pump, it almost perfectly mates up with this Holley Hydramat: https://www.holley.com/products/fuel...s/parts/16-111 (you just have to remove two little plastic "ears" on the bottom of the pump)
-Then as long as you have fuel touching any part of the Hydramat you won't have fuel starvation. It's probably a more expensive solution than fabricating a reservoir ($150), but it's a pretty fast and simple solution to the fuel starvation problem.
(See Paul's pictures earlier in this thread for what the Hydramat looks like in the tank).

I went with the 82 sending unit;

 

Yes, it would go over the pressure setting. I didn't mean install with the regulator, I meant just a loop with a gauge in it. If the pressure is <43psi then you can use the return line you have.

 

it is an aftermarket standard steel tank, my plastic one was leaking, AND I could not modify it for racing.. this tank now has 3 sections running front rear, and the center section has the pump and zig-zag baffle as well as the hydro matt.

The pump supplied by FAST for intake is the one showed in the picture with the holly hydro mat.

The Hydro matt mates up the the FAST pump just fine... as seen in pictures above.

 

Ok good to know, thanks!

I spent all weekend building a shed so I haven't been able to mess with it yet, hopefully get rolling this weekend. For now I just need to figure out the 3/8 hardline to AN -6 connection, and the 5/16 return to AN-6. Once I get time to get under the car and look at the connections I should have a better idea of what I need. I have a tubing bender so I'm thinking I will bend and run new hardline anywhere possible.

 

Ok another question that came up, what should I be using for a pre-filter before my inline pump? I have a good low-micron post filter, but I hear that you should aim for something in the 100 micron range as a pre-filter so that it doesn't cause the pump to have to work hard "sucking"fuel.

I see alot of people saying they use just a cheap inline filter like this:
but it claims it filters down to 10 microns, which according to what I"ve read is too restrictive as a pre-filter.

What are you guys using?

 

Nothing. Straight off the 3/8" sump fitting to the pump.

 

So i'm guessing that means the sock in the tank is enough to stop larger debris.

Swapped my intakes back to my vic jr. single plane last night (was running a performer RPM dual plane, but I hear the single planes work better with throttle body EFI. Plus the RPM was a spreadbore bolt pattern so I would have had to use a carb adapter for the FAST throttle body).

I think I have most of my fuel system figured out. Ended up getting some -6 fuel line and -6 AN fittings for the connections from the factory hardline to the TB, and then from the throttle body to the regulator, and regulator back to factory return line. And then for the short hose connections at the tank I am replacing them with FI rated hose and double clamping, same with the connections from the hardline to fuel pump.

There was some debate over whether the factory return line is 1/4" or 5/16". Weirdly after spending some time googling around it almost seems like it varied on some of the cars, because some people are positive they had 1/4", some say 5/16". I measured mine with a digital caliper and it measures at 0.27", which is technically between 1/4" and 5/16", but closer to 1/4". Weird.

Anyways, planning to run it first with factory return line and see how it does. Worst case scenario, I'll already have the TB return line plumbed down to the hardline at the frame rail, so it would just be a matter of running the hardline back to the tank and then figuring out a larger sump fitting.

 

YES..I would say to sue the sock filter that goes on your fuel pump to stop major debris and it is...as I have read somewhere and been told...that it stops water from passing through it UNLESS it is submersed in water.

I prefer the GM design due to it being tubular and can hold that shape versus some of the ...what I call 'pancake' design sock filters that are really flat and I feel do not really filter well.

The photo below is what go with myself.


DUB

 

By sump I mean the fuel sump welded onto the bottom of the tank. No sock. It's been that way for years now.

The sock should stop enough debris though. That's all the factory pumps have for a filter.

 

Not having taken apart new style fuel pump for a C5,C6 or C7as of yet to see if GM implemented a filter inside the pumps construction. Logic would dictate that some form of filtration is there due to making sure any significant debris does not ruin the pump. Because assuming that each and every gas stations has perfect filters coming off of the tank in the ground is kind of ridiculous. Like I have heard. You do not want to get gas when they are filling up the in ground tanks due to they are stirring up the stuff that is in them.

I can say that the C4 Corvettes have that filter sock I posted a photo of on the fuel pump and also has a yellowish-white sump bonded to the bottom of the plastic liner in the fuel tank..

Whether you cut open your tank to install a sump set-up or attach it to the sending unit like I have seen. I feel it is wise to take that step so the pump is always drawing fuel from a reservoir that is not effected by you accelerating or making turns while driving.

DUB

 

By any chance does anyone on here have the FAST Rpm module tach adapter thing ? Part # is 170637.

I bought the EFI used and the previous owner had an MSD ignition and didnt need it (the FAST EZ system requires a really clean tach signal, so you have to either use the tach adapter with an HEI, or use a CDI ignition) and didnt have it. So I either need to find one to buy cheaply (costs nearly $100 new, so I'm hoping someone has it and doesnt need it ) or figure out a cheap CD ignition.

 

I took a minute and took a part a sending unit for a C5 and there is filter sock inside it. The round white housing is the sump also. The red arrow is pointing to the filter sock.




DUB

 

Ok so I'm getting mixed answers on this after doing some research, so I just want to make absolutely sure: you are saying if I am using an external fuel pump, I ONLY need the post filter, no pre filter (since the sock in the tank will filter enough)?

I see most people saying use a 100 micron pre filter, and I see some saying you can use any 3/8" pre filter since it is not under pressure before the pump.

 

Conceptually you don't want to use an overly restrictive filter before the pump. It will inhibit flow. I would say the latter are correct in their reasoning.

 

I haven't used anything to filter before the pump for years now, so I would think you'd be just fine with the sock in the tank.

As I pointed out last time, the factory (GM) has always only uses a sock on EFI pumps, so it's not as big a problem as some people worry about.

You could check that the sock is in good condition and not collapsed around the pipe so it restricts flow.

 

Obviously the sock will do fine due to seeing the sending unit I posted a photo of out of a C5.

As for the filter AFTER your fuel pump....and knowing that you are using fuel injectors. What do they recommend as the micron value for a fuel filter??? They are selling you this set-up ...so they should know what to put in it so you are compliant and the system will last.

When I run into issue like this like I have in the past I call a company like WIX and have them look up what the filter is and the micron value for that fuel filer replacement for a C5 for example and then C4 and see if the micron values changed or stayed consistent.

100 microns AFTER the fuel pump seems to be fine for fuel injectors but call and find out for yourself. If I am not mistaken the fuel filter for a C4 is above 100 microns.

DUB

 

I saw the picture of the C5 sending unit, and I appreciate the research! But is the C5 sending unit the same as the C3? I guess I was wondering what the relevance is.

 

Ok I took my fuel sending unit out. FYI, on my 79 I was able to remove it without dropping the tank by removing the fuel door and rubber cover, and then finagling the sending unit out of the fuel door hole.

Plan is to remove the 1/4" return line fitting, and use a 3/8" 90 degree fitting with a hose barb on one end (top) and NPT threaded bottom end. Then I can thread on a lenth of 3/8" flared line to put the return below the fuel level.

Then I will just attach my current 3/8" feed line to the new 3/8" hose barb (return line) and run a new 3/8" feed line. I figure this is the best solution for me since I would have to cut the stock feed line anyway to install the fuel pump and filter, so I might as well leave it in tact and run a new length of hardline. Hopefully getting that done tonight!