Technical Fuel Pressure Regulators and Issues and Options

So I've had a few issues, and having not found much on the topic around here I thought it was deserving enough of a new thread, maybe we can compile information here that others can find in the future when they run across similar issues.

To start with, I'm running a pair of Rochester 2G carbs adapted to an Offenhauser 2 x 4 intake, on a 283 SBC w/ mechanical fuel pump. Some might say no regulator is needed, but without keeping the pressure down below ~5 PSI fuel will pool in the base of the secondary carb and leak past the throttle shaft, creating a mess on the intake. Originally when I installed the system about 18 months ago I had one of these installed in front of the fuel log feeding both carbs:

There are several brands of this style of regulator, but they appear to all be the same. I may be wrong, but my assumption is that they are all made by the same source in China and just have different brand names applied.

Last fall that regulator failed, it started dribbling fuel between the halves of the body. It started slowly, at first just a smell of fuel, it took more than a few days between when I could first smell there was a gas leak, till it developed to where I could see the leak. So I replaced that regulator with another of the same style. I noted that there was an upper limit to the pressure rating, I think it was 9lbs. I didn't think the mechanical pump put out more than that, so I figured I was safe. I should've actually checked it.

So that regulator lasted from last fall until the Friday just before Fathers Day. It failed as I was driving home from the Friday night gatherings up at So Cal Speed Shop and Waldens Speed Shop on LARS weekend. Left me stranded on the side of the road for a bit. This time, it went from from no leak at all to steady stream in a matter of minutes. There was no leakage at all while parked at So Cal Speed, but a couple of miles later I smelled gas, then it was spraying on the windshield about 90 seconds later.

As a temporary fix, to get me home, I removed the regulator and replaced it with a short section of 5/16 fuel hose and a pair of hose clamps. With no regulator in place I checked the pressure, and was getting 9 psi at idle, up >12psi at a fast idle.

So, there was no reason to go back with the same type of regulator as before. Looking around for an option, I found this regulator from Holley, #12-804, adjustable from 1 - 4 PSI.

I've read the info available from Holley, cannot find max fuel pressure. I'm hoping it can take the 12 PSI inlet pressure from the mechanical pump. It does look a bit more sturdy than the previous regulator. With the regulator installed, I adjusted the pressure for just about 4 psi at idle, and I noticed that as I increase the engine speed the fuel pressure drops, to around 1 psi at a fast idle. As I bring the RPMs back to low idle the pressure returns to 4psi. So far I've got maybe less than 100 miles on it, and all seems to be OK, but I haven't pushed it at high speed over prolonged distance yet. Or a long uphill climb. I'm a little concerned that the regulator restricts flow too much, causing it to lose pressure at fast idle. I've got a good hill to test it on near by, I'll get it out there soon to check it out. But other than that, my biggest complaint so far is just visual. The regulator itself is not so attractive, but worse is it's hard to plumb in into the system without it having a rather Rube Goldberg look to it.

Original setup:


New setup:

It's subjective, but I definitely prefer the aesthetics of the round style regulator. One benefit of the new layout is the filter is now at low pressure, which should help the efficiency of the filter, and prevent leaks around the glass bowl.

So, that was a long row to hoe, just to get to this, but does anyone have any experience with this style regulator? How reliable is it? Fuel leaks are no fun! Any problems with fuel supply to the carbs with this regulator (thinking about the drop in pressure at fast idle).

Any other experiences with other brands or types of regulators? Even this one is still on the low price side of things, I found a few that were quite a bit more. The above is ~ $30 USD. There are others available >$100 USD, but they are even more modern looking, not that any of these are traditional, but some are more "modern" looking than others. Like this one ($145):

I'm sure it's a fine unit, just less desirable aesthetics IMO, and kind of over kill for the application.

 

I've been using that little Chrome Holley regulator for 3+ years with no issues. Used it on mechanical as well as electric fuel pump.

 

If you buy a Malpassi regulator, it will be the last one you buy. Infinitely adjustable, built in Italy, l purchased mine on e-bay from a store in England. Received it in a
week. aly

Sent from my 6045O using Tapatalk

 

Malpassi style look and work well. Fuel regulator, pressure gauge and filter in one unit

 

Now I like that! First I heard of these. That looks great, perfect for inside a traditional engine compartment. A little expensive maybe, but if it works well it would be worth it.

I found this technical bulletin, but it does not list max inlet pressure.
https://www.merlinmotorsport.co.uk/files/transfer/technical/doc/filterkingspec.pdf

 

I see they make just a regulator without the filter bowl too:

 

A SBC mechanical fuel pump should not be putting out 9-12psi. 4 to 5 is normal.

 

I am using the Holly on basically the same set up on my nailhead. 5 years and no problems. Using a Car Quest rotary pump, don't know how much press it produces. Have the regulator set at about 3 psi.

 

YOU ARE LUCKY ! I almost burned my car to the ground when that round adjustable Mr Gasket branded POS starting leaking with no notice. Luckily I was driving slow and in my convertible with the top down. I smelled gas and stopped asap and put the fire out with my onboard fire exstinguisher . IMO don't try a third one.

 

It's not a stock pump, but I don't know brand/model. I do know the pressure was 9psi at idle, which rose up to ~12 at fast idle.

 

I had 13 psi on a generic parts store fuel pump. Bought a Carter fuel pump, problem solved with no regulator.

 

I used the regulator you pictured on my 351W with Edelbrock. Been on there for years now. Works good, and I used the side port, to make the 90 degree corner in the fuel line to get from the drivers side fuel pump to the passenger side carb inlet.

 

I dont care what the package says, thats not a regulator, its a restrictor and you will run way too lean at about 90.

 

I think that these figures are low, 6-7 lbs is more normal. I have had one at 9 lbs straight out of the box.

 

Some regulators are bi-pass, and need a return line back to the tank.
I had no success with the Holley, so after much discussion, spent NZ $300 on a fuel-lab non bi-pass regulator, (blocking regulator) only to find it was a bi-pass version, and still had to have a return line.

 

Performance pumps may be higher but the factory recommendation for most Gm V8s is 4.5 to 5.5 psi. Much higher and you will blow the needle off the seat.

 

This is my concern. I haven't had a chance to take it out and test it at high speed yet.

 

I've had this one for a couple of years now and had no problems regulating at 3PSI. Not sure what the upper limit for the inlet pressure is, sorry.

 

I run an Aeromotive #13222. Made for low pressure and has done great.

Sent from my SM-G920P using The H.A.M.B. mobile app

 

Thanks for the info.

Here's more: https://www.aeromotiveinc.com/product/low-pressure-carbureted-regulator/

 

Well I can adjust it and until my "pressure" gauge reads 3lbs.................

 

I'm running 1 of the Holley type you've installed and have been for 4-5 years with no trouble, although I don't entirely trust it as I wonder about it's restrictive aspects.
Couple years ago, Atlanta Motor Speedway had their Annual Motorama and I attended. Weather was piss poor and attendance was way down and when I was out and about I encountered the Edelbrock display and the reps had little to do with such a slack crowd, so the guy I talked to had plenty of time to talk. They had their new line of electric fuel pumps and fuel pressure regulators on display and he was happy to discuss them and all aspects of the subject.
The car I was discussing the setup currently in use was my hiboy '31"A", sbc with 2X4 Edel. carbs, which are very sensitive to excess fuel pressure. Car has pinched frame, and the diaphragm housing of a mech. pump will hit the frame, so I have the low pressure, high volume Carter electric pump and the Holley regulator as pressure is borderline high without a regulator.
His opinion was that I really needed to use a bypass type regulator so as not to put unnecessary strain on the pump when the regulator cut the pressure back by reducing amount of fuel passed on to carbs in order to reduce pressure.
Made sense at the time, but I have to wonder: If you have a carb that will take the higher pressure due to the float design, etc. then the needle and seat is itself blocking the flow of gas when engine is at idle and fuel flow is low. So unless you're running some sort of positive displacement pump like the one on my OT diesel p'up that's a gear type pump and is OEM with bypass regulator, why is a bypass really worth the extra line and stuff?

 

If it was a restrictor , would it not maintain or perhaps even increase the pressure as you wind it down ?
I have used one and the pressure gauge showed a decrease or increase in pressure when adjusted, so are you suggesting that there is minimal flow at increased pressure and maximum flow when dereased pressure.

 

If it was just a restrictor, the pump side of the regulator would see increased pressure and the carb side would see reduced pressure. So you could dial in whatever pressure to the carb that you wanted at an idle, but when you open the throttle and the flow rate through the carb increases, and the restriction in the supply line would cause the pressure on the carb side to decrease. And that is what I'm seeing with the Holley regulator. However, it is not the same as just putting a valve in the line. Believe it or not, I actually tried that while while I was in between pressure regulators. And that operates just as I described above. I could dial in 3 psi pressure to the carb, but when I opened the throttle the pressure fell right off to zero. This Holley regulator acts similarly, but not as bad, so I believe it is more than just a restrictor, it has some amount of pressure regulation ability, but it does lose pressure when the throttle is opened. I still need to get it out to where I can open her up for extended period, just been busy, no chance. (The wife and I did take it out last night to a cruise night, but that was stop & go street lights all the way; and she wouldn't like going 90+ in it anyway)

 

Blues4U, I have the same Holley regulator on my "A" Hiboy roadster with the fairly heavily modified 355cid SBC with 2X4 Edel. carbs I mentioned a bit earlier in this thread. It has spent a little time on the strip and I turn it about 6-6.5K thru the gears with no fuel starvation symptoms. Usually only run the eighth as I have no roll bars and only a lap belt and don't want to get kicked off the track having been warned not to run "too fast" Times have been around 7.60 ET@around 92-93mph. However, once last year when I was having an intermittent ignition problem, I had one run where the thing was running well and almost holding it's own against an "A" Hiboy sedan with a 502 BBC, so I stayed in it long enough to shift to 4th (3.70 gear) after passing eighth marker and then thought better of it, let up and coasted across the quarter at 12.47 ET at something like 111 mph, so it ain't starving for fuel. There was more there, just didn't want to get chastised

 

Thanks d.o.m. for the info.

 

That depends. They make them with several psi ratings. I've had a couple that were 9psi.

I've used the OP's first choice and never had a problem, but I expected to. Maybe I was lucky. The Holley one in the second pic seems to be a good choice. 1-4psi is good for an Edelbrock 600cfm carb, which is what I normally would run.

 

Very few pumps put out that kind of pressure, it is totally unnecessary. I'd just put a decent stock pump on it and do away with regulator. Its a complication when you don't need one.

 

I used the Holly one but as a bypass return regulator connected to a T in the fuel line to divert anything over the set pressure back to the tank. The fuel that goes to the carburetor doesn't go through the regulator that way so no restriction.

 

I ran one with my Weber on my Falcon, until recently, and on several Weber equipped VW's that I have owned over the years.

Rock solid. Not one single issue, ever.