Understood. The AN fittings and expense comment had to do with getting the loop/return as close to an actual flow through as possible, by putting the regulator 'after' the secondary bowl feed, to make the LEAST out of a dead head situation.
Still pleading ignorance with the 'look at' statement. 'Looking at' the Holley and Mallory regulators I see they are not the same, but do NOT 'see' how that makes the latter gooder than than the former. I would suppose a $200 regulator to be 'better' than a <$100 regulator and could also suppose that 'better' to mean it is faster and more consistent...but I don't know why. The less expensive is likely not a real regulator at all, but simply a restrictive device.
What Holley did is copy what everyone else was doing before a real bypass regulator was brought to market.
Look at the Holley dead head regulator. The fuel comes in the bottom and goes out through the sides. Long ago, we took those very regulators and ran the fuel IN through the OUT passage and the RETURN fuel went back to the tank through the INLET side of the regulator.
It wasn’t the best way to do it (I eventually junked that regulator and used a #8 Enderle bypass valve with different sized jets to control return fuel and that was a far better option than running the fuel backwards through the dead head regulator as a bypass...keep in mind Holley said there was no way ANY car, street/strip or drag race that needed a bypass and once again, Holley was wrong. It’s easier on the pump and the fuel pressure is stable) but it’s what we had.
Now look at the “bypass” regulator from Holley I posted. It does exactly what I said we were doing with the dead head regulator because it is in fact, a dead head regulator that you run the fuel backwards through. Just a bad way to do it.
So what I’m trying to get you to understand is that Holley “bypass” regulator is really just a dolled up dead head regulator.
If you look at the Mallory, Aeromotive or any other reputable brand, you will see it’s not a dead head regulator that runs the fuel backwards through it.
The way Holley does it with those regulators you’ll see pressure creep (especially if you have a pump that is capable of feed say...500 honest HP in a car with bite) and worse you’ll see (its easy to spot if you data log but you can tell if you don’t because the car will have a bog at the hit you can’t tune out) the pressure drop to almost zero as the load is applied at the hit. When that happens, you go dead lean and the engine has a stumble.
Then, you use the big blue pump cam and 45 squirters and open the power valve up an inch below transbrake vacuum or an inch below vacuum while the engine is on the two step. And yet, the bog is still there.
That’s a sure sign the pump is too small, the regulator is not up to the task or both.
Looking at the two pictures I posted you should be able to see the way the fuel moves through the regulator, bypass or dead head. It’s the cheap way to do it. And it can cause issues.
That’s why I tell everyone to buy something other than the Holley regulators, dead head or bypass. Buy once, cry once.
