Wtf!!!...so, after striking out with one of the useless Mr. Gasket "dial a flow" type regulators...I went with one of the Holley 12-804 regulators. Supposed to be good for 1-4 psi. It's trying to regulate the fuel pressure from a stock style sbc mechanical fuel pump feeding 3-2G carbs (trying to hold to 2.5psi)...the mechanical pump is delivering around 7 psi. With the Holley regulator installed, the fuel pressure was still drifting anywhere from 0-5.5 psi, so, I bought and installed the rebuild kit. Same result! I've set the pressure to 2.5 psi...next time I look, the gauge could read near zero, re-set to 2.5. Then I'll be driving along, come down to idle in gear and notice that I have the running rich "big cam sound and rough idle"...check the gauge and it 'll be at 4.5 -5 psi. Is there fuel pressure regulator (or brand) that actually does what is intended?
It ain't cheap... https://aeromotiveinc.com/products/...bureted-regulator?_pos=1&_fid=b788f7c52&_ss=c
I had the same issue when I ran that regulator with my tri- power set-up… never really got it corrected.
So you have a SBC with 3 Rochester 2G carbs. I don't understand why you need such low fuel pressure. I drove my 58 Impala for 7 years with 3 Rochester 2G carbs and the stock mechanical pump. I never had a problem with overfueling. There were a lot of GM cars built with 2G carbs and mechanical pumps running 5 - 7 psi and no problems. I think you need to take a good look at the carbs themselves to see why they won't handle the pressure.
I've used Aeromotive fuel components for years and they are high quality. But now I wonder, are your end carburetors correct without the power valves/power pistons/mixture screws? I'm not a 3x2 guy, but I seem to recall for Tri-Power carbs, the end carbs don't affect idle, only the center carburetor has all the stuff, the end carbs are secondaries opened with the throttle linkage.
Strange issue. I run 3 cars at the moment with that 12-804 and they all ork properly including a 3x2 set up. I take it from post #1 you were also having issues with the Mr. Gasket dialamatic reg? Same issue exactly or something else?
I fixed a GTO with a rough over rich idle with one of the MisterGasket round regulators. I never checked the pressure, just turned it down till the fuel quit leaking and took it for a drive. It made a big difference in how the engine responded. Didn't care about the actual pressure, it ran good and idle with out leaking fuel. I believe the pressure needed is directly related to the carb kit needle and seats, they are not what they used to be.
End carbs are properly equipped as outboard dumpers...when the regulator keeps the pressure in the correct range, it works perfectly...8900 miles on the set up. The dialamatic didn't keep a constant fuel pressure also. Very similar.
Do you have a gauge on that input line? The Holley can only handle 7 PSI max, no idea on the dialamatic. That isn't likely, a mechanical pump delivering more then 7 PSI? But if it is, the regulator isn't designed to handle it. I had to step down a high-volume pump with 2 regulators (one with a return line) and the 12-804.
a 12-804 Holley regulator is specified as having a "maximum" input pressure of 7psig. I have had similar problems with a holley regulator wandering around on output pressure. I even had one that was the higher pressure regulator in a 12-804 box. IF you are near the 7paig, you need a dual regulator setup to cut the 7 down to maybe 4 or 5 and then the second regulator to cut that to the 2.5. I am using a Malpasi (sp?) regulator on my flathead to feed two Strombergs and it works well at 2.5. The Malpasi regs have a diaphragm that is attacked by alcohol gas so I dont uses alcohol gas....the alcohol already ate up one of my regulator diaphragms.
Exactly . Should not need a regulator , try lowering your float levels , a '60's 2g should hold 7# without issue .
I don't have a gauge on the pump side of the regulator...the pressure reading I have was done using a temporary gauge to measure the fuel pump early on. Good to know about the possible need for 2 regulators...obviously I need to dig deeper into this. Thanks for the input.
You would think there would be one regulator in the Holley line up that can take high pressure, reduce it to 2-3 PSI, and have a return line, all in one piece. If it exists, I haven't found it, so I do the "step down" thing with 2 regs. 12-841 on the frame rail with return line, reduces line pressure from Walbro in tank pump to 4.5 - 9. (why the hell is that fitting blue?) And the 12-804 I mounted on the back of the blower for the 97s 2.5 PSI. That's a couple hundred dollars in regs but it works. Not saying it is your problem but since you have gone through 2 regulators with the same issue, it very well could be.
I love their products….fantastic reliability …. when younger and dumber I couldn’t afford them….now I look to them first!
The Jalopy Journal
