Fuel system questions

LX Dave

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Jul 2, 2017
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Have some questions for a '84 GT 350 I'm currently building. I want to convert the car to fuel injection. Most likely be a 347 stroker engine to keep stock-like appearance.

Here's what I picked up so far:
-Stock gas tank for fuel injection
-Fuel pump cage assembly
-Walbro 190 lph fuel pump GCA710-2 Link- https://www.summitracing.com/parts/vpn-gca710-2


Here's where I think I'm going to have problems.
I want to keep the dual snorkel air cleaner so I picked out the Holley Sniper fuel injection kit. Link to kit - https://www.summitracing.com/parts/sne-550-511k

Reading through the instructions, it states that I need 50 gph (no problem with current pump), but I need 55-65 psi. Is this pump capable of this? I found only one pressure listing for this pump and it's rated for 45 psi normal operating pressure.

fuel pressure.jpg


The next obstacle is the line size. Stock pressure fitting is 5/16" and return fitting is 1/4". Holley states a minimum of 3/8" feed and return line. They also state you should not have more than 3 psi in the return line or you may run into tuning problems.

Fuel line size.jpg

Is there a way to adapt to that line from the tank fitting?

I'm feeling like this may be a dead end trying to keep the stock air cleaner and having a stock tank with in tank pump.
Anybody have any ideas?
Scrap all my ideas and start over?
I could go with factory injection, but would have to get the harness, computer, etc.... and it would not look right, and I'd loose the air cleaner I like so much.


ETA: Just thought of this too. I could add a sump to the tank I just bought and put a fitting of the correct size in it. Then, cut a disc to fill the stock pump hole and add a fitting to it for a return line. Does that sound better, or not?
 
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90sickfox

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That sounds better. If adding a sump don't just cut a square hole in the tank. Several holes cut with a hole saw work well. They'll act like a baffle. The rating for the pump is tested at the advertised rating of 45psi.

In some stock fuel systems I've noticed as much as 15psi on the return side. I think it has to do with the small 1/4 inch line and the rubber tip on the fuel hanger assembly.

I don't think you'll have an issue with the pump....but the lines are small and the hanger tubes will be a restriction. The best remedy is the sump...with a a1000 pump with pre and after filter.

Most sumps put the return right beside the feed line. Fine for a race car running a quarter at a time. On a street car I don't like that, but with the holley sniper heat soak of the fuel might not be much of an issue. The stock rails sit right on the lower intake and a bunch of heat gets transferred to them. The hated fuel can cavitate causing lean type issues.
 

96pushrod

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The Walbro should be able to sustain the necessary fuel pressure, but will have a lower fuel lph rating at the higher pressure.

They actually make a higher pressure version of the pump, but I wouldn't think you'd need it. http://walbrofuelpumps.com/255lph-walbro-gss342-intank-fuel-pump.html

If you're really hell bent on keeping the air cleaner then you could definitely make it work.

It appears the sniper system comes with the necessary fuel pump though. All you need is the larger feed and return lines and you'd be all set. Seems like a simple option.
 
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LX Dave

Active Member
Jul 2, 2017
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That sounds better. If adding a sump don't just cut a square hole in the tank. Several holes cut with a hole saw work well. They'll act like a baffle. The rating for the pump is tested at the advertised rating of 45psi.

In some stock fuel systems I've noticed as much as 15psi on the return side. I think it has to do with the small 1/4 inch line and the rubber tip on the fuel hanger assembly.

I don't think you'll have an issue with the pump....but the lines are small and the hanger tubes will be a restriction. The best remedy is the sump...with a a1000 pump with pre and after filter.

Most sumps put the return right beside the feed line. Fine for a race car running a quarter at a time. On a street car I don't like that, but with the holley sniper heat soak of the fuel might not be much of an issue. The stock rails sit right on the lower intake and a bunch of heat gets transferred to them. The hated fuel can cavitate causing lean type issues.
That's a great idea with the holes for the sump. If I go that route I'm definitely doing that. I could always run the return line in the bowl that's inside the tank so it won't disrupt the fuel going into the pump.


The Walbro should be able to sustain the necessary fuel pressure, but will have a lower fuel lph rating at the higher pressure.

They actually make a higher pressure version of the pump, but I wouldn't think you'd need it. http://walbrofuelpumps.com/255lph-walbro-gss342-intank-fuel-pump.html

If you're really hell bent on keeping the air cleaner then you could definitely make it work.

It appears the sniper system comes with the necessary fuel pump though. All you need is the larger feed and return lines and you'd be all set. Seems like a simple option.
I would really like to keep the factory air cleaner. Just don't see them around any more.

Maybe I'll look into replacing the lines in the cage with larger ones too. I'd hate to wreck a brand new cage attempting it and it not working.

Got lots to think about. Thanks for the ideas guys.
 

LX Dave

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Jul 2, 2017
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An update for anyone that was kind of following this.

Talked to Holley tech and explained what I was hoping to do. They informed me that the Walbro pump and factory cage assemble is good to go for their system. The only thing I have to do is adapt from 5/16" line to 3/8" line at the fitting on the pump assembly. Also, have to put in a bulkhead fitting in the tank to run a 3/8" return line.

Since I have to install all new fuel lines anyways (old ones were really rusty), not a big deal. And I can get the kit that does not come with a pump and lines, which is a bit cheaper and I can use that money to put towards the fittings and fuel lines I need.

This is working out good as I really wanted to run an in-tank pump.
 
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jrichker

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That sounds better. If adding a sump don't just cut a square hole in the tank. Several holes cut with a hole saw work well. They'll act like a baffle. The rating for the pump is tested at the advertised rating of 45psi.

In some stock fuel systems I've noticed as much as 15psi on the return side. I think it has to do with the small 1/4 inch line and the rubber tip on the fuel hanger assembly.

I don't think you'll have an issue with the pump....but the lines are small and the hanger tubes will be a restriction. The best remedy is the sump...with a a1000 pump with pre and after filter.

Most sumps put the return right beside the feed line. Fine for a race car running a quarter at a time. On a street car I don't like that, but with the holley sniper heat soak of the fuel might not be much of an issue. The stock rails sit right on the lower intake and a bunch of heat gets transferred to them. The hated fuel can cavitate causing lean type issues.
The rubber tip isn't a problem, it will pass more fuel than the pump can put out. The duckbill rubber tip is in fact a one way check valve that keeps fuel in the tank if the car gets turned upside down in an accident. Nice to have I there and working if you are upside down in a burning Mustang....

The 1/4" return line is the problem...
 
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