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  #21  
Old 09-16-2021, 05:00 PM
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Originally Posted by HWYSTR455 View Post
Does your floor pan have the cutout for the fuel separator?

I ask because once you go to EFI, and you want (and should) to use the EFI tank with in-tank pump, you will be limited to 2 vents on the tank, and one would be needed for a vent/separator return.

What I do is use the 2 vent tubes on the right of the standpipe for vent/return, and let it vent to atmosphere. There's no to little smell this way, and if you wanted to, you could even route one to the charcoal can.

It works good.

If the cap came off the one capped vent on the tank the way you had it, that means psi built up, and you may not have sufficient venting. Just a thought.

EDIT: The EFI tanks technically have a return which enters via the pump assembly to tank fitting. There are 2, small vents on the tank itself.


.
All long gone. All that remained were the 3 rusted through metal vent lines and dry-rotted rubber hose connectors to the mainfold under the car. I had no interest in reinstalling all the missing pieces and just installed the '70 vent provision which was 2 short lengths of hose, a filter, hose clamps and a frame clamp like the one below. I took it a step further and added a length of hose to the open and and ran it up over the tank and alongside the filler neck to get the fumes out from under the car. My '71 had the recess in the frame for the filter end and was predrilled from the factory and also had the square locating tab the bracket.




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Triple Black 1971 GTO. 455 + .040", Block zero decked and align honed. SD Forged rods, forged SpeedPro pistons, crankshaft oil holes chamfered, polished and balanced. 6x-8 heads with 1.77" exhaust valves, bowls blended, port matched and smoothed. Crane 284281 (234/242 @ .050 duration w. .488/.505 lift), Crane Hi-Intensity lifters, Crane 99838 springs & retainers. ProComp RPM clone w. 750 Quick Fuel Slayer, FlowTech headers, TH400 w. Hughes GM25 convertor, 3.55 BOP 10 bolt.
  #22  
Old 09-17-2021, 03:47 AM
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Originally Posted by NeighborsComplaint View Post
It's your pump not mine and I could care less. I assumed by the shape it was also a rotary vane type. You must not have read those instructions too closely because it clearly states it is a diaphragm style pump, not a rotary vane type ... so it can lift. If you understood the instructions, you would recognize mounting as close to the bottom of the tank as possible is the preferred method as it places less strain on the diaphragm. Good on you that it's still working but it wasn't intended as a basement sump pump.
I think you misunderstood something here.
Believe me, I can read an instruction and understand it.

Carter P4070 and P4594 are Carter Universal Rotary Vane Electric Fuel Pumps, they are NOT diaphragm style pump.

https://www.summitracing.com/search?...&keyword=p4070

FWIW

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  #23  
Old 09-17-2021, 08:47 AM
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Originally Posted by steve25 View Post
Do you realize that when the electric pump is not running that the pump is then a great restriction and that if the fuel is hot enough at that point that the difference in pressure can make for vapor lock taking place right there at the pump?
Holley pumps for sure need the fuel "by-pass" circuit (LIKE SOME CARTER FUEL PUMPS OFFER), because the moveable vanes move outward,stick, and then block fuel flow. It only takes one or two sticking vanes to restrict the fuel flow to the mechanical fuel pump. Same deal with any pump that uses Vanes that move outward when the pump is on. Even with the vanes retracted, there is a restriction. The BY-PASS CIRCUIT solves that issue. I use bypass valves with a large "sealing ball" to reduce back flow when the electric pump is on.

As was mentioned, you can buy that bypass system with the pump in some carter pump applications. Not sure of their by-pass flow area.

Tom V.

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  #24  
Old 09-17-2021, 10:24 AM
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Originally Posted by Kenth View Post
I think you misunderstood something here.
Believe me, I can read an instruction and understand it.

Carter P4070 and P4594 are Carter Universal Rotary Vane Electric Fuel Pumps, they are NOT diaphragm style pump.

https://www.summitracing.com/search?...&keyword=p4070

FWIW
I looked at the instructions again and yes, I see they are referring to their mechanical pumps if used in series. With the electric as a pusher, they recommend the stronger diaphragm in the Street/Strip and Strip pumps. Just clumsy wording but I get it.

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  #25  
Old 09-17-2021, 10:47 AM
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Originally Posted by Tom Vaught View Post
Holley pumps for sure need the fuel "by-pass" circuit (LIKE SOME CARTER FUEL PUMPS OFFER), because the moveable vanes move outward,stick, and then block fuel flow. It only takes one or two sticking vanes to restrict the fuel flow to the mechanical fuel pump. Same deal with any pump that uses Vanes that move outward when the pump is on. Even with the vanes retracted, there is a restriction. The BY-PASS CIRCUIT solves that issue. I use bypass valves with a large "sealing ball" to reduce back flow when the electric pump is on.

As was mentioned, you can buy that bypass system with the pump in some carter pump applications. Not sure of their by-pass flow area.

Tom V.
I could see that possibility. My mechanical pump draws through my Holley vane pump without issue though. I don't drag race the car but on short bursts of WOT, it doesn't run out of fuel with the mechanical pump alone. I do have a dual bowl Holley carb which could possibly compensate with its larger bowl capacity.

Before I installed the Holley pump, I put a reducer on the inlet side and ran some low pressure compressed air through simulating a stream and really didn't note any difference in flow out of the pump vs the supply. Not entirely scientific but a test at least. I just decided to plumb without the bypass and see. It has worked just fine without the bypass.

Perhaps if I were a drag race and running at sustained WOT on a Qjet with limited inlet needle and bowl capacity, I might notice a difference but the current setup has worked just fine since installed. The recent onset of a vapor lock condition was the first time the car ever stumbled. Todays fuel of course continues to evolve.

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  #26  
Old 09-17-2021, 01:26 PM
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Fresh out of body shop from having work done on back of car.

I'd be checking for over-spray (dirt in general) on that vent filter.
And vent hoses for kink or pinch after tank R&R.

Poor vent shows up faster and worse the more gas you have in the tank
Clay

  #27  
Old 09-17-2021, 05:05 PM
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I would keep the mechanical pump and the Quadrajet. Here's the trick to getting them to run strong without one hint of fumes..

Get the gas tank with the three vents at the top front of the tank. Plug the two end vents and connect a 3/8" gas filter to the middle vent port. Make sure the hose has a loop in it and its higher then the tank. Or get a aluminum RCI sumped fuel cell. Mount it in the middle of the trunk, that way you can get gasoline from either side..

Get a vented cap..

Run a 1/4" return line from the supply side of the pump to the carb. I use a tee.. Run the 1/4" tubing line to the tank. If your sending unit top plate has no provisions for the return use one of the plugged vents..

If your running out of gas on the top end, have the stock gas tank sumped for two 3/8" lines. Run another 3/8" line from the tank to the pump connect them both up from the sump to the fuel pump. At the pumps pick up run a tee and connect both 3/8" lines to it from the sump..

This system really works great. I get absolutly no fumes anymore..


Last edited by 389; 09-17-2021 at 05:11 PM.
  #28  
Old 09-17-2021, 06:32 PM
Joe's Garage Joe's Garage is offline
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Quote:
Originally Posted by NeighborsComplaint View Post
I could see that possibility. My mechanical pump draws through my Holley vane pump without issue though. I don't drag race the car but on short bursts of WOT, it doesn't run out of fuel with the mechanical pump alone. I do have a dual bowl Holley carb which could possibly compensate with its larger bowl capacity.

Before I installed the Holley pump, I put a reducer on the inlet side and ran some low pressure compressed air through simulating a stream and really didn't note any difference in flow out of the pump vs the supply. Not entirely scientific but a test at least. I just decided to plumb without the bypass and see. It has worked just fine without the bypass.

Perhaps if I were a drag race and running at sustained WOT on a Qjet with limited inlet needle and bowl capacity, I might notice a difference but the current setup has worked just fine since installed. The recent onset of a vapor lock condition was the first time the car ever stumbled. Todays fuel of course continues to evolve.
Thirty years ago, we installed a Carter high-performance mechanical pump and a Holley blue pump on a 1973 Formula 455. With the qjet, it would sometimes stumble under acceleration if the electric pump was off AND on a long drive on the highway. We would eventually have to turn the electric pump on.

With the Holley 800 spread bore DP, the stumble under acceleration was lessened but, eventually, we had to turn the electric pump on if driving down the highway.

With the Holley the problem was less noticeable under short bursts of acceleration than it was with the qjet, probably, as you noted, due to the larger fuel bowls.

  #29  
Old 09-17-2021, 10:07 PM
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Wow, all these replies and it's really not that hard to make a stock system work and work effectively without the need for added on doodads.

I've raced my Formula for 25 years, and daily drive it, with the stock Q-jet and stock fuel system in place. Have gone as quick as 12.76 at 106 with a stock 400 RAIII....PS legal. Just 91 octane pump gas at any chain store, no hint of fuel starvation, no hot start issues, no vapor lock, and it gets pretty darn hot here in Arizona. Really all the fuel system needs is a well thought out stock setup and a tank that is vented properly.
I have some tricks in the carb with a larger needle/seat, a marine style filter in the carb which is basically a screen, and the brass fitting opened up as far as I can without affecting the flare nut seal, all in an attempt to keep the carb fed.
Stock AC Delco large body fuel pump with factory return line. My 70 Formula is California built so it has the Charcoal cannister system. I vent the tank as intended through this system, all hooked up and functioning.
The steel lines I run glass bead through them at high pressure as an attempt to extrude hone the lines, a trick I learned from the PS racers to possibly increase flow but it does in fact increase capacity, I've CC'd a couple lines after the process. Again all in an attempt to keep the engine fed with fuel.
I've never bothered to block the heat cross over because I do daily drive the car and prefer the divorce choke to work.

It's really just simple tricks like that, doesn't take anything really special. It does have it's limitations however. I've gone as quick as low 12's at 108 mph in another car with similar fuel system setup before I kind of hit a wall with it, and that car weighs 4100 lbs so the stock fuel system could possibly go 11's in a lighter car.

None of that really matters though as the OP is going EFI anyway. As long as you put together a solid fuel system to support it with a pump in the tank you'll enjoy that EFI.

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  #30  
Old 09-17-2021, 10:08 PM
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If you want to run a Mechanical Fuel Pump, the mod that Ken Crocie did years ago,
where he married a 6 valve mechanical Chevy pump to a Pontiac Upper Housing would be
something to consider. I have seen two of those modded pumps and they worked well.

Then you can add the electric pump of your choice for any fuel supply that is needed for top end blasts.

I have run as quick as 11.55 at 117 with my bucket of bolts and good tires in the quarter. Engine was a good engine with a very good
camshaft/ Wilson Manifold ported heads.

Tom V.

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  #31  
Old 09-17-2021, 10:17 PM
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Yeah that would never pass pure stock tech though.

What I'm doing is attempting (and succeeding) in making the stock system feed the engine while maintaining stock appearance and components to comply with the rules.

Those guys have gotten even better with it now than when I was more involved with it.

But the real point of that post was to show that the stock system, can and will work just fine for most any 13 second street car on the forum here, and is capable of working well into the 12's with a little prep.

PS. Another tip I did was run a very large sock on the fuel pickup in the tank. I think it was for a truck application. I was picking them up at the dealer at the time. I've gone as far on another car to solder in a 1/2" pickup on the sending unit.

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Last edited by Formulajones; 09-17-2021 at 10:26 PM.
  #32  
Old 09-18-2021, 02:10 PM
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Originally Posted by Formulajones View Post
None of that really matters though as the OP is going EFI anyway. As long as you put together a solid fuel system to support it with a pump in the tank you'll enjoy that EFI.

That is absolutely right.

Just an update. When I placed the order for the Holley Sniper Tank w. in-tank 255Lph pump and sending unit through the eBay Holley store (smoking deal at $395 incl. shipping) the delivery est was Sep 10.

When it didn't show up, I checked their store and found all listings removed and a notice "This seller is away until Tue, Sep 21. Expect a delay in delivery until they return." I'll just have to wait and see. Seems too late in the year for vacation shutdown, maybe closed for inventory, whatever. Hopefully the order doesn't get cancelled for no stock, then I'm on to plan B.

Just a quick question about an alternative if for any reason my Holley order goes south. I see Spectra offers a Canadian-made tank, in-tank pump and sender assembly with a welded neck for only $359 (free Prime delivery). Performance specs are the same as the Holley, though the Hollley kit includes a Tanks, Inc. powdered coated w. separate pump and sending unit. I went with the Holley based on quality as I never really considered Spectra a quality brand.

Anyone have experience with one (Spectra)?


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  #33  
Old 09-18-2021, 02:16 PM
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I've used Spectra tanks for years (non EFI) for factory replacement stuff. That's what most all the parts houses sell as repo tanks for the classic cars. Comes from Canada.

Good tanks, never had an issue with any of them.

Have not tried their EFI tanks as I always go straight to Tanks Inc. for the in tank fuel pump stuff. The Tanks Inc tanks appear to be a little different visually so I don't believe they are Spectra tanks. Tanks Inc also sends their tanks powder coated which is really nice. It doesn't stain or peel and stays looking good for a long time.

I wouldn't be afraid to try a Spectra EFI tank though, I just haven't had the temptation. I do know the Tanks Inc EFI tanks are baffled and work well. Don't know of the Spectra EFI tanks are baffled the same.

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