The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - 47-59 HydroBoost / LS GM Type II Pump Connections

1project2many · 01-24-2022, 01:04 PM

Here is an O ring fitting:

Here is an inverted flare fitting:

Here is a special (and cool) part designed to transform the first fitting into the second.

The nut in the picture you posted appears to be designed for an "O" ring fitting. This fitting relies heavily on the end of the line being formed and sized correctly. The flat flange in the tubing which acts as an O-ring backer must be in good shape, not cracked or bent. The O-ring must be the correct size, both ID and OD, and should not be tapered or "squished." The nut on the PS line should have a flat, squared surface which applies pressure evenly to the backer. This way the backing flange is not distorted when the nut is tightened. Many people misunderstand these fittings and try all sorts of wrong fixes when the fitting leaks. It is possible that Ogre is correct, the tubing you have is using an inverted flare nut on an O ring end. It definitely looks like your tube has a home-grown fix in the form of a larger O-ring at the top of the nut. The adapter on the RH side of the photo next to the section of tubing would work perfectly. The O-ring on the end of the fitting is the only one needed to seal the connection. The large O ring on the nut on the LH side of the photo is not needed.

I would not use a flare fitting in an O-ring pump nut. It might work and it might be fine. But my experience working on vehicles with mix-n-match fittings is that it is likely to develop a leak when you least want one.

There are *many* variations on the pressure and flow regulators on stock GM pumps. There are also two different methods of installing HB on OE GM vehicles. IME when the HB is in series with the steering gear there is a significant but very brief reduction in steering assist if you simulate a panic stop at the brake pedal. IME when the HB is in parallel with the steering gear the steering system is less affected by braking. In order to plumb HB in parallel you would not want flow restriction.

Cooler should be in the return line before the steering box. Best if it is after the steering box and HB and before pump. I usually put PS coolers in front of the radiator but they can be found in OE applications under the core support. I agree with Ogre... It won't hurt but it's probably not necessary unless you are building a vehicle that will carve corners and use brakes hard and often.

01-24-2022, 01:04 PM	#18
1project2many Registered User Join Date: Mar 2012 Location: Lakes Region NH Posts: 3,158	Re: HydroBoost / LS GM Type II Pump Connections Here is an O ring fitting: Here is an inverted flare fitting: Here is a special (and cool) part designed to transform the first fitting into the second. The nut in the picture you posted appears to be designed for an "O" ring fitting. This fitting relies heavily on the end of the line being formed and sized correctly. The flat flange in the tubing which acts as an O-ring backer must be in good shape, not cracked or bent. The O-ring must be the correct size, both ID and OD, and should not be tapered or "squished." The nut on the PS line should have a flat, squared surface which applies pressure evenly to the backer. This way the backing flange is not distorted when the nut is tightened. Many people misunderstand these fittings and try all sorts of wrong fixes when the fitting leaks. It is possible that Ogre is correct, the tubing you have is using an inverted flare nut on an O ring end. It definitely looks like your tube has a home-grown fix in the form of a larger O-ring at the top of the nut. The adapter on the RH side of the photo next to the section of tubing would work perfectly. The O-ring on the end of the fitting is the only one needed to seal the connection. The large O ring on the nut on the LH side of the photo is not needed. I would not use a flare fitting in an O-ring pump nut. It might work and it might be fine. But my experience working on vehicles with mix-n-match fittings is that it is likely to develop a leak when you least want one. There are many variations on the pressure and flow regulators on stock GM pumps. There are also two different methods of installing HB on OE GM vehicles. IME when the HB is in series with the steering gear there is a significant but very brief reduction in steering assist if you simulate a panic stop at the brake pedal. IME when the HB is in parallel with the steering gear the steering system is less affected by braking. In order to plumb HB in parallel you would not want flow restriction. Cooler should be in the return line before the steering box. Best if it is after the steering box and HB and before pump. I usually put PS coolers in front of the radiator but they can be found in OE applications under the core support. I agree with Ogre... It won't hurt but it's probably not necessary unless you are building a vehicle that will carve corners and use brakes hard and often. Last edited by 1project2many; 01-24-2022 at 01:14 PM.