I forget where I bought my Hydrobeast. I think it was Vette Brake Products.
It was very difficult to install...this is with the front dash of the car missing. I ultimately removed the entire steering column to make installation easier. Getting a socket wrench with extensions and u-joints ultimately got the job done. I did rebuild the entire clutch and brake mechanism since I was working in the area.
...People complain that the Hydrobeast is too sensitive. This is nothwithstanding that it was original equipment on GM vehicles where users had no idea that they had a hydraulic boosted brake MC instead of a vacuum assisted MC. In OEM applications, it didn't have an overly aggressive braking. From what I've read, the Hydrobeast must not have any..no..resistance in it's return hydraulic line. The instructions for the Hydrobeast may show a T junction to feed low/no pressure oil back to the PS pump. The factory did not use this plumbing. The PS pump 'reservoir;" i.e. the small Danish ham can, had a special return fitting just for the Hydrobeast, this was in addition to the return fitting for the PS. The Hydrobeast return line was strategically located so the hydraulic fluid could flow back into the can without restriction. I bought one of these PS reservoirs. Maybe the box its in has the GM part number. This is for the 70. The MC is from Stainless Steel Brake Corporation...it's a billet aluminum MC. I've never driven the 70 yet.
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I have silicon brake fluid in my 68 and the brakes (manual) are rock hard.