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#21
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Triple Black 1971 GTO |
#22
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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 |
#23
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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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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#24
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Triple Black 1971 GTO |
#25
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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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Triple Black 1971 GTO |
#26
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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
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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
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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
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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. |
The Following User Says Thank You to Formulajones For This Useful Post: | ||
#30
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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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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#31
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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. Last edited by Formulajones; 09-17-2021 at 10:26 PM. |
#32
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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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Triple Black 1971 GTO |
#33
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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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