[MidnightAuto]

Been off the board a bit, car has been asleep. With that said I am tried of squirting gas in bowl after car sits a week. It’s also killing my starter. So I’m going to adds a pusher pump. Would love feedback on my plan.

So the current setup 1/2 inch fuel line into regulator. Robbmc mech pump, then standard tripower lines. Return vapor line from regulator back to tank.

One constraint- I’m not splicing my existing 1/2 inch steel braided line to insert a pump.

So my idea is to put a Y in the sending unit fuel out side, adding a new line, reduce to 5/16, then pusher pump, then checkvalve. 5/16 line continues up to engine and spliced in with a T on the short line (seen in pick) from fuel block to center carb.


Are there any issues with this approach? Pics attached. Lmk thoughts. Thanks guys

[JLMounce]

You're adding complexity, which is rarely a winning maneuver. If you add an in-tank pump in lieu of your mechanical pump, you can keep your current feed line. Yes you'd need to increase the size of your return line and add a bypass regulator, but it's a much simpler system that helps your car cope with the fact that it needs to run on modern fuels that evaporate quickly.

I think your current plan would work, but has some drawbacks. Specifically what is happening with the fuel in that line after you disengage the pusher pump. You're sending fuel from this line in after your fuel distribution block. Any fuel not delivered to the bowls is going to sit between your check valve and the fuel block, soaking heat from your engine bay with nowhere to go. It won't take much heat to boil that fuel and create vapor in your system. Your mechanical pump now gets to work against that as well.

It's unlikely that a couple extra cranks each time you start up the engine is doing much of anything to the starter. If the car is driven once a week only, that's less starter revolutions than if you drove the car daily, which those starters were designed around.

My advise would be to solve the issue correctly (tank in pump with bypass regulator) or deal with the issue when you want to use the car.

[MidnightAuto]

Thanks for the thoughts. This is the discussion I was hoping for. To answer your question, I guess I thought fuel in that line would not be an issue after the bowl is full. I don’t think the mech pump will be impacted though due to the check valve?

Your approach sounds much cleaner, I’ll have to research in tank pumps. Fillin a Rochester 2g is like 5 seconds at most. They are tiny, so I don’t want to get a 40-80 psi pump for this minor task. I did quickly see an I. Tank pump for carb - it was 600 bucks. That is above my max threshold, for investment in this improvement….

[Jay S]

Would there room to install the tee down on the outlet of the Robbmc pump?

On my cars I don’t run a seperate line. I put the electric pump in series using the same line and use a vane style pump that pushs fuel through the mech pumps, some pumps are harder to pump fuel through, on those it reduces the cranking time to get fuel, but the engine has to crank a little bit. Carters electrics I use a tee and a check valve so the mechanical pump can pull fuel around the electric easier, Holley style van pumps I don’t add a tee, it is all in series. In tank electric is nice, I have a couple of them too.

[tooski]

I have a Holley red as a pusher in series same as Jay S. I use it to fill the bowl and for WOT. The mechanical is a Carter performance 6803. It is supposed to put out 7 psi but only runs at 4.5-5. The Holley does 7 as advertised.

[NeighborsComplaint]

I use a Holley Red pump as a pusher installed in-line just ahead of the tank with no bypass. It feeds my Carter Muscle Car Series mechanical pump. I have it wired through a relay to a toggle under the dash. I use it for startups after prolonged storage and for spirited driving. It draws through just fine with no bypass or check valve and is mounted low enough to self-prime.

[MidnightAuto]

In tank is nice, but looks like I have to modify gas tank.

I had a miserable time making AN lines off the car with a vise, seems like a bridge too far to try on the car as I cant easily remove this line to work on it and splice for an in-line pusher. Sigh.

[MidnightAuto]

And if I put the pusher on the outlet side of the reg, it would not be regulated so seems like I would blow fuel past needle?

[MidnightAuto]

ok all this discussion has given me a modified idea. i think i can put a pusher pump right at the sending unit, and then not have to splice the existing fuel line. I have a little wiggle room where it should fit. So now the question is, ive got a 10AN sending unit, 10AN line all the way to fuel pump. I put the 10AN to future proof for more upgrades later. I would assume its important that I find a pusher pump that has 10AN/1/2 inch ports? any recommendations? low psi of course.

[JLMounce]

I like that idea a bit more, but it too is not without it's pitfalls.

Yes, you would likely want to use a pusher with a -10 inlet and outlet if those are available. The mechanical pump is now going to have to draw fuel through the electric pump. If the current configuration is marginal for your engine power, adding the pump in-line between the tank and the mechanical pump may push you over the edge into not being adequate. That said, with a RobbMC pump and what appears to be a stockish 389, that issue may not present. You can of course run the pump whenever you need it, including in instances like drag racing where you might need the volume.

Of course at that point, the road leads back to the question of why you'd need a mechanical pump at all.

[Jay S]

Originally Posted by MidnightAuto

ok all this discussion has given me a modified idea. i think i can put a pusher pump right at the sending unit, and then not have to splice the existing fuel line. I have a little wiggle room where it should fit. So now the question is, ive got a 10AN sending unit, 10AN line all the way to fuel pump. I put the 10AN to future proof for more upgrades later. I would assume its important that I find a pusher pump that has 10AN/1/2 inch ports? any recommendations? low psi of course.

It would be overkill to use a fuel pump that has AN10 fittings. You’d be better off with AN10 tees and a AN10 check valve that bypasses the electric pump for full flow through the 1/2” line, then plumb in a 5/16” or 3/8” electric pump. Then you have full flow through the AN10 when the electric is shut off.

[OG68]

Originally Posted by JLMounce

You're adding complexity, which is rarely a winning maneuver. If you add an in-tank pump in lieu of your mechanical pump, you can keep your current feed line. Yes you'd need to increase the size of your return line and add a bypass regulator, but it's a much simpler system that helps your car cope with the fact that it needs to run on modern fuels that evaporate quickly.

I think your current plan would work, but has some drawbacks. Specifically what is happening with the fuel in that line after you disengage the pusher pump. You're sending fuel from this line in after your fuel distribution block. Any fuel not delivered to the bowls is going to sit between your check valve and the fuel block, soaking heat from your engine bay with nowhere to go. It won't take much heat to boil that fuel and create vapor in your system. Your mechanical pump now gets to work against that as well.

It's unlikely that a couple extra cranks each time you start up the engine is doing much of anything to the starter. If the car is driven once a week only, that's less starter revolutions than if you drove the car daily, which those starters were designed around.

My advise would be to solve the issue correctly (tank in pump with bypass regulator) or deal with the issue when you want to use the car.

If I can interrupt this thread, is this something that you had in mind?

https://www.summitracing.com/parts/sne-12-303

My thought was to remove the existing mechanical pump and mount a regulator in its place. Would the existing 3/8" feed and 1/4" return lines suffice?
I'm not currently having any operational issues with a 400 HP 400, but In the distant future I may install EFI and replace the QJ, depending on how much worse California gas can get.

[Jay S]

Basic diagram using tees and a check valve. It is not complicated.

[JLMounce]

Originally Posted by OG68

If I can interrupt this thread, is this something that you had in mind?

https://www.summitracing.com/parts/sne-12-303

My thought was to remove the existing mechanical pump and mount a regulator in its place. Would the existing 3/8" feed and 1/4" return lines suffice?
I'm not currently having any operational issues with a 400 HP 400, but In the distant future I may install EFI and replace the QJ, depending on how much worse California gas can get.

Yes, something like that would work. Ideally, you also use a fuel tank with a built in sump, like a Tanks inc unit, but the hydromat equipped pump like you have linked would work as well. Maybe just don't run it much below a 1/4 tank.

In regards to your fuel lines, at 400 hp, the 3/8" line with an in-tank pump will be fine. The 1/4" return line won't be. The problem is that return line is more of a vapor return. It's not mean to pass much physical liquid. What happens when you try to do so is that you build pressure in the return line, which creeps back into the regulator and will add pressure to the carb bowls, or the EFI unit if you go that route. In either case, you end up massively richening the engine to the point where it either runs terribly, or doesn't run at all.

You'll need to plumb at least a 3/8" return line. For a low pressure carburetor setup, it's sometimes necessary to upsize the return larger than the feed.

[67Lemons]

Or you can run a new 1/2” feed line and use the original 3/8” line as the return.

[73ta]

I fought fuel issues for close to 50 years with various pump setups. Went with baffled tank, in tank Walbro 450 pump. 1/2 supply & return lines with a bypass regulator for an 800 cfm quadrajet on my 462" 570 HP Pontiac. Fuel issues gone, forever.

[MarkS57]

Originally Posted by 73ta

I fought fuel issues for close to 50 years with various pump setups. Went with baffled tank, in tank Walbro 450 pump. 1/2 supply & return lines with a bypass regulator for an 800 cfm quadrajet on my 462" 570 HP Pontiac. Fuel issues gone, forever.

Hi 73ta, what regulator did you use for that?

Thanks!

[73ta]

Originally Posted by MarkS57

Hi 73ta, what regulator did you use for that?

Thanks!

Aeromotive bypass regulator.