Electric and Mechanical fuel pump
 

When I got my 67 GTO the previous owner had installed new fuel tank, external electric fuel pump and ran it through the existing mechanical fuel pump, any logic for this? I have heard it does not hurt but don't see benefit and just seems to open possibility for potential leaks.
Any issues with removing mechanical fuel pump? Would need to add regulator and guage but am good with that.

Thanks,
Bob

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Ran my street SD for 30+ yrs that way. The electric pump was low pressure, though. Then the electric pump quit.

My 63 Lemans has had that for better than 22 years now.No regulator,its on a switch,ran it when racing and use to prime when the car sits.Carter street pump on the engine.Tom

My electric pump runs all the time, sdbob, when your electric pump died did car still run with just the mechanical pump?

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With my elect off the mech pump has no problem feeding a 2-4 with a pair of 750s around town,the highways and getting on it once in awhile.The only time I got stranded is when I did not have the mech on the engine and blew a fuse on the elect.Mech went on the next day.FWIW,Tom

Good to know, Thanks!

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Here's what I did. I had a very thirsty 462, ported 6x, Quadrajet intake and carb also ported. It used to run half way decent. I decided to have the stock 1964 B body tank sumped with two outlets. I ran two 3/8" steel lines to a 3/8" tee in the Carter mechanical fuel pump. I also had a 1/4" return line back to the tank to keep the fuel moving.. Wow what a difference! It was like I put a brand new 455 in my car..
The issue with the mechanical pump is feeding it. A guy that designs fuel systems told me to use two 3/8" steel tubing runs instead of one 1/2" run. He said you are pulling not pushing liquid, the rules change....

Interesting, does make sense since you are creating a constant flow of fuel, the restriction at this point would be the feed to the carb, Thanks!

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My GTO has been set up that way since 1967 or so. It goes 12.20s.

My Chevelle is set up that way since about 1978. It goes 9.80s.

I usually drive them around on the mechanical pump and flip the electric pump on for periods of high demand.

K

Cool, you have some fast cars there, Thanks!

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Other than for very high performance cars needing a boost in fuel pressure the main reason to do it is, as was said by a couple of people above, to use the electric pump to fill the float bowls before starting a seldom driven cruise/show car. Otherwise you have to fill them with the mechanical pump by grinding the starter which is hard on the starter and drains the battery. To do this the electric pump can be put on a toggle switch under the dash, and turned off once the float bowls are full which is indicated by a change in tone of the electric pump.

Yes it ran fine. I was surprised when I took electric pump out(conelec pump,spl).pump was junk.

pump
 

Tom, what electric pump did you use? My SD clone would nose over in 4th gear under 6000 but I was running the stock fuel line that came on the 61 Bonneville with tri-power. I did use the same Carter pump you use and it worked great through 1,2,3rd gear and then died at the top of 4th. Thanks, Mike

I ran 1/2 from the elect to the engine pump and 3/8 up to the split and 3/8 to the carbs.Tom

I run the holley red.Tom

Just note that electric pumps do not really produce any suction like a mechanical pump does.
This means that if you feed one off of a stock tank pickup it needs to be mounted at least below the half filled line of the gas tank so that it gets pressure fed .

This also means that you should maintain a half a tank of fuel for the best performance at WOT.

Your problem could be your needles and seats. The standard diameter of the oriface in todays needles and seats is .085-.0935. Standard back in the day was .100. Edelbeock makes them that are .110; part 1466. I don't recall which I put in the carbs I did for you (if those are my carbs that have you falling on your nose?) but I put the .110s in if people tell me they are going racing.

Four .110 needles and seats have a combined area of .038012" and a 3/8" line has an area of .11045" so a 3/8 line will feed a dual quad setup with four .110 needles and seats in the two carbs.

X2 on Post # 17.

Dual quad carbs with 4 needles and seats, Be it Holley or AFB work well as do TRI-Power carbs with .130 needle and seats (Holley).

The Holley Guys have an advantage in that there are fuel bowls with TWO needle and seats in each bowl. So 6 needle and seats on a bad Boy Holley set-up with .110 N&S.

https://www.summitracing.com/parts/q...SABEgJ5TvD_BwE

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Tom V.

Feeling a little inadequate, only trying to feed a single Holley 750 Brawler [emoji3], as always you guys are a wealth of knowledge! Lots of good info on fuel systems, definitely need to go through the one on my car. Thanks!

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One potential drawback would be associated with age of the mechanical pump. As the diaphragm ages, it could possibly crack, and then leak. The electric pusher would then pump fuel into the crankcase. As a maintenance item, occasionally smell the dipstick for presence of fuel. Sounds silly, but I discovered one leaking that way.

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