Carbureter Return Regulator Plumbing

[skinny z]

As my fuel system development is generally an ongoing affair, I'd like to finalize it once and for all.
Presently I have my system plumbed as illustrated below.

Presently.jpg

The filters are as shown in terms of microns. The pump is an old Holley Blue. The regulator a Holley 12-803BP.
https://www.holley.com/products/fuel_sy ... s/12-803BP

The noise of the Blue pump notwithstanding, what's the disadvantage of the arrangement above? I've a fuel pressure gauge under the cowl hood and pressures are for the most part stable but there are some fluctuations under various conditions that I need to stabilize.

Future plans will be the addition of an SX Performance 18208 in-line pump (Edelbrock and since discontinued) along with revamped supply and return lines. The existing supply is 3/8 steel and the return is -6AN.
Also in the works will be a rework to the plumbing as in the drawing below.

Proposed.jpg

What's the inherent advantage of the new vs the old? Stability? Cooler fuel to the carb at all times?

And a question on the side: Is anyone familiar with SX Performance? There's zero internet presence other than they were absorbed by Edelbrock more than a decade ago. I've got no spec on this pump but it looks to have a very large capacity although output PSI is an unknown.

SX Performance.jpg

Thanks as always.

[prairiehotrodder]

I'm sure you know that the blue pump has a bypass so it doesn't require a return regulator, so you kind of have 2 setups where you only need one. The new fuel pump will likely solve that problem ? I switched to a product engineering pump and return style regulator a few years ago and i really like it. But even that system has a return at the pump and a return at the regulator that uses a jet to restrict the return. Thats what they recomend though. Sorry i couldn't offer more help.

[steve cowan]

As my fuel system development is generally an ongoing affair, I'd like to finalize it once and for all.
Presently I have my system plumbed as illustrated below.


Presently.jpg


The filters are as shown in terms of microns. The pump is an old Holley Blue. The regulator a Holley 12-803BP.
https://www.holley.com/products/fuel_sy ... s/12-803BP

The noise of the Blue pump notwithstanding, what's the disadvantage of the arrangement above? I've a fuel pressure gauge under the cowl hood and pressures are for the most part stable but there are some fluctuations under various conditions that I need to stabilize.

Future plans will be the addition of an SX Performance 18208 in-line pump (Edelbrock and since discontinued) along with revamped supply and return lines. The existing supply is 3/8 steel and the return is -6AN.
Also in the works will be a rework to the plumbing as in the drawing below.



Proposed.jpg


What's the inherent advantage of the new vs the old? Stability? Cooler fuel to the carb at all times?

And a question on the side: Is anyone familiar with SX Performance? There's zero internet presence other than they were absorbed by Edelbrock more than a decade ago. I've got no spec on this pump but it looks to have a very large capacity although output PSI is an unknown.


SX Performance.jpg


Thanks as always.

Kevin,
I set up a fuel system same as your second example, I run a holley 200 gph mechanical fuel pump which has - 10 out of fuel cell, - 10 ball valve fuel shut off then aeromotive filter with stainless filter.- 10 braided to fuel pump.
Out of pump I go - 8 to fuel log at carb then regulator after carb with a - 8 return to fuel cell.
Some people say the return should be bigger than the feed but I have never had a problem.
I have a fuel gauge in the car that works with a autometer dampner set up.
A friend recently put a big block in his Sunday cruiser with the fuel system set up same as your FIRST example and the car ran but was not happy, I got him put regulator after carb and bingo it was a different story.
I figured it was bypassing to much fuel even though gauge said it was OK.

[skinny z]

I'm sure you know that the blue pump has a bypass so it doesn't require a return regulator, so you kind of have 2 setups where you only need one. The new fuel pump will likely solve that problem ? I switched to a product engineering pump and return style regulator a few years ago and i really like it. But even that system has a return at the pump and a return at the regulator that uses a jet to restrict the return. Thats what they recomend though. Sorry i couldn't offer more help.

I appreciate that insight. The issue I've found with the using the Holley Blue is that, although there's a built-in bypass, there's no fuel circulation. Heat soak is a genuine concern especially while waiting in the lanes on a hot summer day. With the bypass regulator, that heat soak is much less of an issue. Another step I'll need to take is some heat shielding where the supply and return pass by the headers.

[skinny z]

As my fuel system development is generally an ongoing affair, I'd like to finalize it once and for all.
Presently I have my system plumbed as illustrated below.


Presently.jpg


The filters are as shown in terms of microns. The pump is an old Holley Blue. The regulator a Holley 12-803BP.
https://www.holley.com/products/fuel_sy ... s/12-803BP

The noise of the Blue pump notwithstanding, what's the disadvantage of the arrangement above? I've a fuel pressure gauge under the cowl hood and pressures are for the most part stable but there are some fluctuations under various conditions that I need to stabilize.

Future plans will be the addition of an SX Performance 18208 in-line pump (Edelbrock and since discontinued) along with revamped supply and return lines. The existing supply is 3/8 steel and the return is -6AN.
Also in the works will be a rework to the plumbing as in the drawing below.



Proposed.jpg


What's the inherent advantage of the new vs the old? Stability? Cooler fuel to the carb at all times?

And a question on the side: Is anyone familiar with SX Performance? There's zero internet presence other than they were absorbed by Edelbrock more than a decade ago. I've got no spec on this pump but it looks to have a very large capacity although output PSI is an unknown.


SX Performance.jpg


Thanks as always.

Kevin,
I set up a fuel system same as your second example, I run a holley 200 gph mechanical fuel pump which has - 10 out of fuel cell, - 10 ball valve fuel shut off then aeromotive filter with stainless filter.- 10 braided to fuel pump.
Out of pump I go - 8 to fuel log at carb then regulator after carb with a - 8 return to fuel cell.
Some people say the return should be bigger than the feed but I have never had a problem.
I have a fuel gauge in the car that works with a autometer dampner set up.
A friend recently put a big block in his Sunday cruiser with the fuel system set up same as your FIRST example and the car ran but was not happy, I got him put regulator after carb and bingo it was a different story.
I figured it was bypassing to much fuel even though gauge said it was OK.

The "different story" is what I hope to achieve.
I should up the inlet to a -8 at a minimum. As for the return, I've tried a few scenarios one of them being the original EFI return line at 5/16ths (car was converted decades ago). That was hugely problematic. Too small a line and quite probably the layout of the parts with the regulator in a poor spot. A quick fix was the -6 line as a return which helped to stabilize things somewhat.
I was a diehard mechanical pump user until I lathed the fuel pump eccentric completely off the the cam. That was a real mess. I converted to an electric arrangement after that.

Fuel Pump Lobe.JPG

Thanks Steve. Always like to hear what you have to say.

[turbo camino]

Running the fuel all the way to the front to get to the regulator before it gets sent back to the tank just adds unnecessary heat. Put the regulator right after the pump outlet, that way the only heat added to the fuel is from the pump itself.

[skinny z]

Running the fuel all the way to the front to get to the regulator before it gets sent back to the tank just adds unnecessary heat. Put the regulator right after the pump outlet, that way the only heat added to the fuel is from the pump itself.

Interesting thought.
But it gets me to thinking about that heat soak from the surroundings with the supply to carb generally static at times. The point of the regulator at the front is to keep all of the fuel circulating past those heat sources where, in my reasoning anyway, it's less likely to be absorbed.

[steve cowan]

As my fuel system development is generally an ongoing affair, I'd like to finalize it once and for all.
Presently I have my system plumbed as illustrated below.


Presently.jpg


The filters are as shown in terms of microns. The pump is an old Holley Blue. The regulator a Holley 12-803BP.
https://www.holley.com/products/fuel_sy ... s/12-803BP

The noise of the Blue pump notwithstanding, what's the disadvantage of the arrangement above? I've a fuel pressure gauge under the cowl hood and pressures are for the most part stable but there are some fluctuations under various conditions that I need to stabilize.

Future plans will be the addition of an SX Performance 18208 in-line pump (Edelbrock and since discontinued) along with revamped supply and return lines. The existing supply is 3/8 steel and the return is -6AN.
Also in the works will be a rework to the plumbing as in the drawing below.



Proposed.jpg


What's the inherent advantage of the new vs the old? Stability? Cooler fuel to the carb at all times?

And a question on the side: Is anyone familiar with SX Performance? There's zero internet presence other than they were absorbed by Edelbrock more than a decade ago. I've got no spec on this pump but it looks to have a very large capacity although output PSI is an unknown.


SX Performance.jpg


Thanks as always.

Kevin,
I set up a fuel system same as your second example, I run a holley 200 gph mechanical fuel pump which has - 10 out of fuel cell, - 10 ball valve fuel shut off then aeromotive filter with stainless filter.- 10 braided to fuel pump.
Out of pump I go - 8 to fuel log at carb then regulator after carb with a - 8 return to fuel cell.
Some people say the return should be bigger than the feed but I have never had a problem.
I have a fuel gauge in the car that works with a autometer dampner set up.
A friend recently put a big block in his Sunday cruiser with the fuel system set up same as your FIRST example and the car ran but was not happy, I got him put regulator after carb and bingo it was a different story.
I figured it was bypassing to much fuel even though gauge said it was OK.

The "different story" is what I hope to achieve.
I should up the inlet to a -8 at a minimum. As for the return, I've tried a few scenarios one of them being the original EFI return line at 5/16ths (car was converted decades ago). That was hugely problematic. Too small a line and quite probably the layout of the parts with the regulator in a poor spot. A quick fix was the -6 line as a return which helped to stabilize things somewhat.
I was a diehard mechanical pump user until I lathed the fuel pump eccentric completely off the the cam. That was a real mess. I converted to an electric arrangement after that.


Fuel Pump Lobe.JPG

Thanks Steve. Always like to hear what you have to say.

I have used composite pushrod for a long time now with great success, cast or steel core cam with no issues.

[turbo camino]

It doesn't take all that long for the engine bay heat to raise the temp of all the fuel in the tank. That's why OEMs no longer run the loop all the way to the front, the sooner it can be dumped back into the tank the better.

Fuel temp in the supply line in the engine bay will be higher when it's static, but will be lower once the floats drop and fuel begins flowing compared to one that runs the loop all the way up and all the way back all the time.

[skinny z]

I see what you're saying with regards to sending heated fuel to the tank. Makes sense. That would be along the lines of filter/regulator assembly (that I first saw incorporated on a race car back in my chassis shop days) that was the Corvette offering of the day. That day being 20 years ago. That assembly was right at the tank.

The biggest issue I had, and it always came about in the heat of the day, was the car (and AFR's) nosing over mid-track. Street testing (within reason) without the meltdown of sitting in the staging lanes, never was an issue. On race days, I could modulate engine temps by running the fan with the engine off, cooling the rad and then restart. But the headers were always hot and directly adjacent to the fuel line.
That too me indicated that the supply itself was ok. I didn't have a particularly high fuel demand and even under the g forces of acceleration (which again wasn't all that much in comparison) the limited line size, pump capacity and component arrangement were just acceptable. The nosing over I can only attribute to a gap in delivery due to vapour rather than fuel reaching the carb. I could easily be misdiagnosing the cause altogether which is why I want to make some wholesale changes to the current setup and eliminate any of those variables.
Up size the lines. Add heat shielding. Get rid of the Blue pump (it's noisy as hell). Relocate the regulator to what, by most accounts, is a better place in the line itself.
To actually get to the track this year (after a 9 year hiatus!) is job one. Upgrades and modifications to follow.

[Ishiftem]

You do not want figure three. I’ll give a real life example. My car ran low 11s but wasn’t real responsive to jetting. The car was plumbed like figure three. One day after a pass, someone smarter than me, who we were pitted next to, said the car sounded flat in high gear. His suggestion was check the fuel supply. Now the regulator was set to 5.5 psi and stayed there the whole run. That was with Holley billet pump that put out 11 psi max. I was thinking bigger Pump so I got on the phone with Weldon. I was told my pump was likely sufficient and it was a pressure issue. With it set up like figure three, the entire system only saw 5.5 psi from the pump next to the tank all the way to the carbs. I was told to just put a dead head regulator before the carbs so from the pump to the regulator it would have the full 11 psi and then 5.5 from the regulator to the carbs. So I did it. On the launch the fuel pressure would momentarily drop to zero and immediately recover to 5.5 the rest of the run. The car instantly picked up almost two tenths and became responsive to jetting changes. I then got one of Weldon’s pumps that puts out 27 psi and has a built in bypass that dumps into the tank. I run it set at 15 and that eliminated the momentary drop in pressure on the launch. The fuel system needs pressure to overcome the vehicles acceleration. I can’t explain why the car was slower with the bypass after the regulator because the fuel pressure didn’t waiver. I mean, if the carb saw 5.5 the whole time how could it be starving for fuel? But I was told it was and they were correct! So bypass at the regulator BEFORE the carbs. That way you get increased pressure to push the fuel forward and then bypass the extra like your first figure. Or the best setup is were you have a pump next to the tank with a built in regulator and a bypass that goes directly back to the tank. Say that pump puts out 20 psi but you don’t need all that so you set the pump to 15 and the rest bypasses to the tank. That 15 psi now goes all the way to the bypass regulator before the carbs where it is regulated down to 6-7 psi and the rest runs back to the tank. Cool fuel and sufficient pressure. I know of faster cars that have picked up their 60 ft time by going from 23 psi up to the regulator to 27. If they had the bypass regulator after the carb like figure 3, they would only have 6-7 psi from the pump all the way to the carbs. If going from 23 to 27 psi picks the car up, imagine how hard the car would fall on its face with only 6 or 7. That’s a lot of typing. My thumb is cramping!

[skinny z]

That 15 psi now goes all the way to the bypass regulator before the carbs where it is regulated down to 6-7 psi and the rest runs back to the tank. Cool fuel and sufficient pressure. I know of faster cars that have picked up their 60 ft time by going from 23 psi up to the regulator to 27. If they had the bypass regulator after the carb like figure 3, they would only have 6-7 psi from the pump all the way to the carbs.

What you're describing is how I'm running my fueling now.
Pump at the back with about 14 PSI maximum output (although I suspect the old and ancient Holley Blue pump may be somewhat less). This then makes it's way at that pressure to a frame rail mounted carbureted by-pass regulator (near where a mechanical SBC fuel pump would normally be) where the pressure is adjusted to a 6 PSI output to the carb. The line from the regulator to the carb would be a deadhead as it ends there. So two lines from tank to regulator. One supply and one return.
Fuel pressure was somewhat unpredictable although I'll admit that it's been so long since any meaningful full throttle runs have been that I can't recall how or what the anomalies were. If my memory is correct, the last few passes made saw the fuel pressure drop at the top end. That could be an indicator of something more than where the components are placed though. (I mentioned the old pump in use.)

Since this new engine/transmission/converter combination is all new and untested, I'll be proceeding with what I have, which for the record would be figure 2 above and go from there. If I read your account correctly, this is also your arrangement correct?

[rebelrouser]

I always used a fuel pump that had a return built into the pump with a short return hose going back to the tank from the pump, and a dead head regulator, that way you get around some of the heat being added to your fuel in the tank. The holley blue pump is tried and true, and I have never needed to use a return style regulator with one of those pumps, the regulator they send with one of those pumps from holley is a deadhead style regulator. By using the pump with a return back at the tank you can set the pressure in the line to the regulator, I like around 20psi. My drag car wqas making between 700 and 800 HP over the years so a holley blue was just not big enough. I think the main thing no matter what set up you decuide to go with is to test the results with a flow test. I cut and pasted this cheat sheet, I used to give it to my students and to customers after I built an engine for them.

[skinny z]

The issue I had with the dead head regulator I was running was that the fuel in the line that passes by the headers, trans and other heat sources would get heat soaked when the engine was idling or sitting with the ignition off. It would manifest itself at about half track with a nose over, a corresponding drop in fuel pressure and then recovery. At least this is what I attributed the problem to as it was only in the heat of the day while waiting in the lanes for the next pass. Never a street issue.
This is what prompted me to at first use a mechanical pump with a return line, then an electric pump with a bypass regulator at the engine. This kept the fuel circulating although it seems that it too would add heat to the fuel via the gas tank.

Once having sorted this entirely new engine and transmission package, the fuel system will need addressing.
I'll put that cheat sheet to good use too.

EDIT: Quick question. The cells in the chart represent what exactly? Pounds of fuel per hour?

[dannobee]

Running the fuel all the way to the front to get to the regulator before it gets sent back to the tank just adds unnecessary heat. Put the regulator right after the pump outlet, that way the only heat added to the fuel is from the pump itself.

Even a stock eliminator car will pull enough g's to stall out a low pressure fuel system on launch. The fuel just kinda stalls in the line on hard acceleration.

He really needs to have the regulator near or at the carb, with at least 20 psi of fuel pressure up to the regulator.


Edit: Pretty much what Ishiftem said. It's THAT critical on a drag car.