The Stovebolt Site Forums The Parking Lot Big Bolts hydroboost

So , I want to install a hydroboost out of a mid nineties chevy 3500 into my coe. I converted from original 50's drum brakes to chevy 3500 disks. (See griggs what to do topic) The issue i have is my coe does not have power steering. Can one run a hydroboost just by using a power steering pump? The truck presently has a hydrovac, but that only works with one bowl master cylinders. I probably can buy a regular booster set up but don't know if they are right for a two ton truck.
Thanks in advance
chris
51 chevy coe

Yes, you can use a hydroboost unit with just a power steering pump.

I don't see any reason the 3500 unit wouldn't be adequate for your truck.

Your 51 is probably lighter and designed to go much slower than what a modern 1 ton truck.

Here's some good hydroboost articles.

http://www.gmfullsize.com/forum/showthread.php?t=156800
http://classicbroncos.com/hydroboost.shtml
http://bangshift.com/general-news/t...-on-your-classic-gm-muscle-car-or-truck/

I have not done it yet but I do plan to use a hydrobooster and no power steering pump. It has been done before.
One piece of advice I've seen on the matter is to use a high pressure hose and appropriate fittings for the return to reservoir, this is the line that would have gone to the PS gearbox. You also have a 3/8 hose return from the hydrobooster, it goes to a nipple on the reservoir just as usual.

I will use a GM type II pump also called a Saganaw TC pump. They make a lot of versions of that pump and some lower flow and lower pressure, and or a fitting or valve can be swapped to reduce pressure. I'm thinking low flow and pressure is what I'd needed but still need to do some research and or ask some of the aftermarket/performance hydrobooster dealers.

Grigg

The low pressure output from the hydroboost would go back to the PS resevoir. It only flows when you're braking. The high pressure output line which goes to the power steering gear box could be T tapped into the same line, but I'm wondering if it would be better served to run it through before heading back to the PS resevoir.

I also am wondering if slightly restricting the high pressure return would be beneficial to prevent starving the hydroboost of fluid under hard braking. Just a thought.

No, no restriction of any kind is needed or desirable. That is important enough that even a T in the line can cause hydroboost trouble due to the flow interruption/restriction at that junction.

Hydroboost only needs and uses pressure when you press the brake pedal. Otherwise fluid flows in and out uninterrupted, and then on to the PS gear box where it also flows straight through unless turning the wheel.
So without a PS gear box the "high pressure" line exiting the booster should go unrestricted back to the reservoir.
Then as is the usual practice for a hydrobooster its return line goes absolutely unrestricted back to the reservoir, NOT a T with anything else.

Griggs & Whitedog
Thanks for the info. This gives me a direction to work with. So I need to get a part number and then I have to figure out what size brake lines to use throughout the whole system.
Any recommendations as all the calipers are single piston? I can get the part numbers for the calipers.
Chris

Griggs,
Will you be mounting the hydroboost on the firewall or below the floor boards where the orig master cylinder resides?
Chris

I like under the floor, looks better and looks original, and I think less work.

Good plan on brake line sizes is to use what the vehicle you pulled the brakes from used. In your case a P30 or 3500HD chassis. I believe they were 1/4" from MC to proportioning valve. From there two different 3/16" lines to each front. To the rear a 1/4" and I forget if 3/16" or 1/4" on the axle to each side?
All this you can find by looking at one in the parking lot, or perhaps a friend has one complete you can scope out.

I re-read my last post, and it looks like I need to re-write. I was going to say, "I'm wondering if it would be better served to run it through a PS cooler before going back to pump."

Now, I'm in a dilemna with my project. My PS pump only has one high pressure out, and one return, which is molded into a plastic housing.

I'm going have to rethink How I'm doing things now.

Swap the reservoir for a more useful one or a remote and very likely have to add the "high pressure" return fitting.

I don't see that the pump and fluid will be doing much work without an actual PS gear box so heat should not be an issue.
If you did want a cooler or filter or any other possible restriction it would go on the "high pressure" return.
The return hose from thehydrbooster only returns spoon fulls of fluid after pressing the brake.

Could a check valve be added? Then they could be T-d together on the return side of the pump.

I don't see how