Holley fuel regulator adjustment

[Michael Oritt]

I recently purchased a Holley Blue fuel pump to replace the Facet cube I have on my Elva which has an MGA 1500 engine w/two HS6 SU's. The pump came with the 4.5-9 psi regulator which I have plumbed up to the carbs using a Y-block with a pressure guage installed in a 3rd-outlet.

I know that SU's supposedly like 2-4 psi but several folks have told me that they have had good results with this pump/regulator combo and have been able to adjust the regulator's flow down to 4.5 or so psi without any overpressure problems on their SU's, and that the high pressure regulator is better than the 1-4 psi Holley regulator. I hope I have made the right selection here. I'm using AN6 lines from the fuel cell to the regulator with a 3/8" nipple to the block and then 5/16" lines from the Y-block to the carbs,

In any case I am a bit confused by the Holley instructions which state:

"Any change made in fuel pressure will change the fuel bowl float level requirements. A readjustment in fuel bowl levels will be required for proper operation of the fuel system."

Assuming I am able to adjust the pressure down to where it does not overwhelm the needle valves in the float bowls I do not understand why I will need to adjust the float bowl level. I thought that on SU's that is pretty much a fixed thing.

Can someone shed some light here?

 

[Dave Russell]

It "always" takes a bit higher fuel level to shut off a higher pressure. Or put another way, higher pressure tends to sink the floats more which makes the fuel level higher. Don't know if you will have a problem. Try it & see what happens, I guess.
D

 

[blkcorvair]

On a single SU fed simnilar to yours I run 3 psi with no problems so far. 5/16 to carb, no changes to the float adjustment, holley regulator.

 

[aeronca65t]

I've been racing my 1500 on 2 psi.

But I'd probably do as Dave suggests...try it and see if it works.

If you feel that the car is loading up you could always just bring ~One Of These~ along and fit it inline at the track (or even fit it inline ahead of time and set it at Max). Not everyone likes these cheap pressure regulators, but at least it would give you a "Plan B" if you were stuck at the track with severe flooding problems.

From my viewpoint, the floats should not have to be reset if the pressure is correct.

Off Topic: Are you going to New Hampshire with VRG? (or their "field trip" to NJMP on April 5).

 

[Michael Oritt]

Hi Nial and thanks for the info. I have a Holley low pressure regulator available to me as well so hopefully either it at its upper limit or the higher-pressure regulator at its lower limit should work.

I believe I will be going down to VIR for the VSCCA event that weekend. VIR is a four-hour tow for me and I like the course, though I would rather play with the VRG folks.

 

[aeronca65t]

Have fun!

(Man, I *wish* VIR was only a four-hour tow from me!)

 

[Tosh]

Hey aeronca65t,

My 1st post on the MG forum.

Quick question regarding that (cheap) fuel regulator you mentioned.

Is a return line required so as to dump excess fuel/pressure back to the tank?

I ask because I ran one of these regulators for about a week before the diaphragm failed. I should mention that I am running a non stock fuel pump at around 5# pressure level and the exhaust has always had kind of a raw fuel smell to it.

My concern was that the pump was too much for the diaphragm.

I am talking a standard 1800cc 'B' with twin HIF's.

Thoughts??

Apologies, misID'd the forum.

 

[aeronca65t]

Actually, I ran one of those cheap regulators (with a Facet "cube" pump) for over 5 years with no issues. Lots of people have told me they're terrible, but mine was OK.

No return line is needed (at least not with the Facet pump).

But there was a recall on those regulators indicating that there was a batch of bad diagphrams at one point...I got a note in the mail from Summit Racing about the one I'd bought as a spare. These regulators are sold under different brand names but all look the same and, I'm sure, are all built by the same company.

If your regulator failed, it probably allowed full pressure to your carbs...that may have been the raw fuel smell you had (the pump may have been overpowering the floats,causing the car to run rich).

 

[Tosh]

Right.

Mine was NAPA branded and identical to the Summit. I think they are made in England.

I should mention that the 'failed' diaphragm allowed fuel to drench the area around the driver side fender wall so there was no mistaking what and when it failed.

Thank you.

Keep on.

 

[Michael Oritt]

Go here in the MGA Guru site for two articles on regulators and failures/recalls

https://mgaguru.com/mgtech/fuel/fp202.htm,
https://chicagolandmgclub.com/driveline00/0604/jasw.html

 

[Simon TR4a]

I use an electrical impeller pump, the low pressure Holley regulator and a Holley pressure gauge.

To reduce the pressure to 21/2 psi you loosen the threaded screw then tighten the locking nut. This is the opposite of what seems intuitive.
I have not adjusted float levels on my carbs. Before investing in the gauge I had too much pressure, very rich at low revs, and too lean at higher speeds or throttle openings.
Hope this helps!

 

[JerryB]

the round fuel pressure regulator talked about above is known as the Alondra or C.R. or Purolator regulator among other names as this design has been sold to many companies over the years. It has raised pressure numbers and a rotating adjusting wheel. Being polite, it is a piece of crap. One reason is the numbers have no correlation to actual pressure. The below Holley regulator is inexpensive and reliable. If you throw dirt/crud in the gas downline to ANY pump or regulator the will die....USE A 30 micron FILTER before the pump and regulator.

The Holley regulator part number:
12-803 will regulate 4.5 to 9psi
12-804 will regulate 1 to 4 psi

the difference in the two is the internal regulating spring. The regulators are identical except for the spring.
There is a Holley repair kit for these regulators that includes BOTH springs and a diaphragm (Holley #12-807) . These regulators have three 3/8 FPT ports, 1 inlet and two outlets. Use one outlet to attach a pressure guage and the other outlet port to the carburetors. You are flying BLIND if you DO NOT USE a pressure GUAGE!

These regulators will support 250 hp. They are non-bypassing. A bypass is only needed for very high fuel flow or injectors.


"""""""""""""""overpressure problems on their SU's, and that the high pressure regulator is better than the 1-4 psi Holley regulator. I hope I have made the right selection here. """""""""""

WRONG selection. SU carbs want about 2 to 2.8 psi...anything over that will collapse the floats or wont let the needle and seat meter fuel in the bowl properly.



""""""""""""" "Any change made in fuel pressure will change the fuel bowl float level requirements. A readjustment in fuel bowl levels will be required for proper operation of the fuel system." """"""

Thats correct. Increased pressure MIGHT raise the fuel level depending on the carb internal design of the n. & s and float. 1/2 psi wont change things.....keep in mind that all this Holley stuff is used mainly with fuel pressures of 6 to 9 psi.....one or two # difference and you should always recheck fuel levels in the bowls.



""""""""""""""""On a single SU fed simnilar to yours I run 3 psi with no problems so far. 5/16 to carb, no changes to the float adjustment, holley regulator."""""""""""

a 5/16" i.d. line will flow 200 hp no sweat. No need to run bigger or spend more $$$.

 

[Michael Oritt]

I installed the Holley Blue pump and Holley low pressure (1-4 psi) regulator and pulled larger lines--3/8 versus 5/16--from the cell up to the regulator and through a Y-divider (with fuel pressure gauge mounted on it), then 5/16 up to the HS6's.

After completing plumbing and wiring today I fired it off and adjusted the regulator to 3 psi at fast idle, then repeatedly revved to 5K. The fuel pressure stayed constant, the EGT guages looked even and there was no overflow from the bowls so I think I am good to go, or at least start.

Best--Michael Oritt
Elva Courier

 

[Tosh]

Gonna install the Holley 12-804 as per the previous discussion(s). The rebuildability factor is a +.

JerryB's observations regarding the the Alondra or C.R. or Purolator or NAPA (or whatever) not being particularly trustworthy confirm my suspicions and it appears a replacement diaphragm for that unit is as rare as hen's teeth.

Keep on.