Fuel Pressure Regulator Connection & Mounting Edelbrock AVS2

[Some Car Guy]

I thought that factory used a smaller return than the feed. I’ll have to double check.

I would skip the regulator if possible. I doubt you will have issues as the edelbrock pump is supposed to be the same one as one of the carters. I ran the eddy pump with no regulator since it was rated at 6psi and it never gave me an issue so I never checked the psi it put out. Could be different in the era of private equity though.

 

[Geoff 2]

The booster design, venturi position, & emulsion hole positions in the emulsion tubes are determined by the carb company.....& the appropriate fuel level to give the correct mixture strength. Final result of all this is the carb company providing the float level adjustment to provide the correct mixture ratio. If you raise the fuel level via float adjustment, you richen the calibration...& vice versa. You do NOT increase the fuel level in the bowls to maintain mixture ratio. You provide adequately sized n/seats for THAT engine, & a fuel delivery system [ pump & lines etc ] that can deliver enough fuel to the carb with some reserve capacity. D. Vizard claims that a change in fuel level of 0.100" is worth about one main jet size.

 

[68 Sport Satellite]

Still hoping one of you has a good photo of a clean looking regulator install for the AVS2 carb in our cars (bonus for including a Performer RPM intake).

 

[Bird 426]

If you decide to do it before, not after, this is where I mounted mine. One is a return, the other a dead head. At first glance, you don't even see them. Obviously, the orange car isn't together yet.
Good luck!

 

[68 Sport Satellite]

If you decide to do it before, not after, this is where I mounted mine. One is a return, the other a dead head. At first glance, you don't even see them. Obviously, the orange car isn't together yet.
Good luck!

View attachment 1925730

View attachment 1925734

those both look like CLEAN installs. I like that 270 degree fitting! Thanks.
Which car is the deadhead setup and which is the return style? At first glance I suspected the orange car has the return - if so, I would love to see the line connection at the pump that comes from the regulator.

 

[BSB67]

Don’t have a picture with an AVS.

When I’ve done mine, I have found that the Russell and/or Earl’s catalogs helpful in generating ideas with their fitting options. Maybe look there for ideas.

 

[Moparfever65]

Personally I feel you're overthinking this. Just throw the carb on with a single feed and no regulator. I doubt you're running enough HP to run into draining the bowls on a single feed, and mechanical pumps do a great job without an external regulator. Then if you start running into heat soak issues start with a phenolic spacer.

 

[68 Sport Satellite]

Personally I feel you're overthinking this. Just throw the carb on with a single feed and no regulator. I doubt you're running enough HP to run into draining the bowls on a single feed, and mechanical pumps do a great job without an external regulator. Then if you start running into heat soak issues start with a phenolic spacer.

Thanks, I agree my HP is not high enough to drain the fuel bowls with a single feed, but Edelbrock specifically mentions to limit fuel pressure to 5.5 to 6psi max, which has been confirmed by many other users from what I'm reading on reviews. I might get away with no regulator with the Edelbrock AVS2, but I want things optimized, so if I swap in the AVS2 it will get a regulator.

Do you have any experience with the AVS2 you can share?

I'm also not in a hurry. I have little free time and just tinker on this when I can find time once every few months. I really enjoy seeing other owners clean line installs though no matter what I'm working on.

 

[Geoff 2]

You are mistaking the reasoning behind Edelbrock's 6 psi recommendation. Look at a Holley carb with sight plugs in the bowls for fuel level adjustment. Take the old #3310 Holley. It came with #72 pri & #76 sec jets. That was the 'best guess' jetting for a universal carb [ fits anything ] with the fuel level adjusted to dribble out of the sight plug holes. With the H carbs, fuel pressure can be whatever....as long as the fuel level it is adjusted to dribble out the holes...
E carbs do not have this adjustable feature, so a fuel pressure number is provided with a float setting number to provide the correct fuel level for the jets/met rods. Edel has NO IDEA what engine you are putting this carb on & is providing you with a starting point.
If fuel pressure is higher, use the chart in post #7 to increase the float level dimension. And vice versa. I have never found these carbs to be overly sensitive with 50 yrs experience with them. Think about what is happening to the fuel level during.......accelerating hard, braking, cornering, hitting a bump. It is all over the place....

 

[PlymouthMakesIt]

It's not a good idea to put a diaphragm-type fuel pressure regulator on a mechanical pump, it stresses the diaphragm from cycling every time the cam lobe releases the pump spring.

Try drilling the return orifice larger in your fuel filter to relieve more pressure.

If that doesn't work, and your pump is the rebuidlable type, put a weaker spring in it or cut the existing spring.

If you need more fuel flow, an in-tank electric pump with a bypass regulator is the ultimate solution.

 

[SlinktRR]

I think the cleanest look is using AN fittings and braided fuel line. Once you figure out how to cut them, it is so easy to work with. If you are using a pressure regulator then OE appearance is out the window anyways so just use the AN. That 270 degree adapter is an AN type fitting you can get from summit.

Regulator is nice but not absolutely necessary for an AVS. I would mount to the firewall run braided hose and call it done.

 

[BSB67]

I think the cleanest look is using AN fittings and braided fuel line. Once you figure out how to cut them, it is so easy to work with. If you are using a pressure regulator then OE appearance is out the window anyways so just use the AN. That 270 degree adapter is an AN type fitting you can get from summit.

Regulator is nice but not absolutely necessary for an AVS. I would mount to the firewall run braided hose and call it done.

That why I suggested the catalogs. My regulator sits under my air cleaner. I used braided lines and AN fittings, but on a Holley.

 

[68 Sport Satellite]

I emailed Aeromotive (the company who makes the Fuel Pressure Regulator) and one of the guys there got back to me a week later with some very good info.
He said it's recommended with a return style fuel pressure regulator to mount it AFTER the carb, whether with mechanical pump or electric pump. This prevents fuel starvation and maintains more consistent fuel pressure. The regulator pressurizes the system. The return line when used with a return style regulator mounted after the carb should be larger than the fuel supply line, with actual return line size depending on fuel pump GPH flow rating as well as the length of return line.

If no regulator is used, as with the 3 nipple fuel filter I have installed BEFORE the carb - this filter has the small .060" return line orifice (instead of a larger 1/4", 3/8", or 1/2" return) because otherwise since the filter is before the carb, fuel starvation can result. So what's the purpose of that 3 nipple return filter - it's not to return fuel with free flow as in the return regulator return line, but rather it's a vapor return line. Both styles of return can help with vapor lock. However, I'm not sure if the 3 nipple filter with it's .060" vapor return are really doing much to help keep fuel cooler like the larger return lines do.

I also read up more on those 3 nipple fuel filters and I'm reading that since it's a vapor return port, the return nipple should be facing up or it won't be that effective. Makes sense.

I'm still figuring things out, but this was a big clarification for me, but it seems so obvious to me now...
Hope this helps the rest of you

 

[Geoff 2]

With a return style [ bypass ] reg, there is no ' after the carb'. What you have: a fuel line that goes to the pump, then in a loop that returns to the tank. Somewhere in that loop is the reg. It has a port on it for the carb.
Basically the pump is pumping fuel to the tank in a loop, & the engine takes what it needs from the loop.

 

[SlinktRR]

Maybe, but i doubt it makes much difference on a street car.

If you mount the regulator to the firewall you can plumb with AN in different configurations and test

I use a holley regulator and the holley cartridge fuel filter on a six pack before the carbs and it works great with the stock return line. Engine makes 600 horsepower. I haven't had vapor lock since I had an AVS 650 on a 383 with no regulator and return line plugged.

 

[68 Sport Satellite]

With a return style [ bypass ] reg, there is no ' after the carb'. What you have: a fuel line that goes to the pump, then in a loop that returns to the tank. Somewhere in that loop is the reg. It has a port on it for the carb.
Basically the pump is pumping fuel to the tank in a loop, & the engine takes what it needs from the loop.

For example sake, I'll describe how I will do if I'm keeping my Holley style carb that's in there now instead of the AVS2. I've got a fuel log with dual outlet's on the side that connect to the carb and a port on each end of the fuel log (one is currently plugged and one is feeding the fuel log). Here's how I'm going to plumb it now:

Fuel Tank -> Carter mechanical fuel pump -> Wix fuel filter -> fuel log front of car end inlet -> fuel log dual outlets connected to carb -> fuel log firewall end outlet connected to Aeromotive fuel pressure regulator inlet -> Aeromotive fuel pressure regulator return outlet back to fuel tank (will require a 1/2" return line).

I think Aeromotive used the terms Before and After the carb to differentiate between the fuel hitting the regulator before the fuel sees the carb vs hitting the carb fuel log first before it sees the regulator. In both cases, the carb sees the same set pressure, but if the fuel hits the carb first before the regulator then the fuel pressure remains much more stable. That's how they explained it to me.

 

[68 Sport Satellite]

Maybe, but i doubt it makes much difference on a street car.

If you mount the regulator to the firewall you can plumb with AN in different configurations and test

I use a holley regulator and the holley cartridge fuel filter on a six pack before the carbs and it works great with the stock return line. Engine makes 600 horsepower. I haven't had vapor lock since I had an AVS 650 on a 383 with no regulator and return line plugged.

that's awesome. Is the fuel pressure dead steady or does the needle bounce some?
Prior to this a few years ago I had my 1/4" return line with Quickfuel carb and regulator before carb and the pressure needle bounced around a lot (with mechanical pump). Hoping moving the regulator to the other end of the fuel log and increasing the return line size will make it more steady as well as keep the high ethanol fuel cooler so I have easier hot starts and better throttle response (the Aeromotive rep said I can expect both).

The more I've dug into this, the less confident I've become in swapping over to the AVS2. I think for now I'm keeping my Quickfuel on there and getting the regulator and return line sorted first.