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Old 07-01-2014, 01:47 PM
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That looks like a real nice unit! Great find.

I went to a hydroboost unit with an OEM 1.25" bore matching master cylinder for my 6.2L engine swap. Mine had a vacuum power booster, but the diameter was very small and thus boost limited. I also went to a larger master cylinder diameter as I wanted a (more) firm pedal and very short throw on the pedal. I'm super happy. I have way more stopping power than with the vacuum assist (can lock the brakes easy) so it is up to me to properly modulate. Supposedly, the human body modulates braking better with very short and firm push from the leg (vs. lengthier push with softer pedal). My braking confidence is certainly now very high.

This is the cheapest hydroboost unit I've found for an OEM (not rebuilt) unit.
Amazon.com: ACDelco 178-0853 OE Service Power Brake Booster: Automotive Amazon.com: ACDelco 178-0853 OE Service Power Brake Booster: Automotive
- a few months ago when I bought it ... it was $137.XX

From AMAZON, the OEM NEW master cylinder was about $50.
It took some digging in Amazon to find a cheap OEM unit.

Building the lines cost me about $180 with the ends. I used aeroquip power steering lines and ends (they reseal eaton). And a length of lower pressure, but quality return line.
Because of the under floor master mounting, OEM lines won't work. Otherwise, this swap would have been WAY reasonably priced.

Note, the hydroobost install required some fabrication. The mounting plate for the unit I bought had the hole for the mounting bolts offset from the vacuum unit I removed. Three of the four mounting studs matched the master cylinder mounting bracket already in place.
I realized if I cut a large square out of the backing plate I could flip the square and weld it back in, centering the hole within the bracket. It worked a charm. The plate is 3/16" steel and easy to cut and weld.
Since the booster unit can be run in any rotational orientation, I optimized clearance away from the exhaust and welded in new notches to properly index the mounting orientation.

Sorry, but I didn't take any photos of the backing plate after I did my fabrication work. I should have.

The other fab work required me to cut the input shaft and bore out the threaded adjustment sleeve with heim joint which attaches to the brake pedal bell crank as seen in Mike's photos. Once I cut off the end of the booster input shaft, I bored the hole, slipped the sleeve over and welded at the correct overall length (measure the old one first!). I gave myself 1/4" plus / minus on the heim joint threads to optimize the length once installed.

Just an option some may want to explore. If you have power steering and on the order of 1000 psi, the hydroboost unit should work well for you. I think the power steering pump I have is 1200 psi.

Note II, when looking for a unit, look at 3/4 ton trucks or SUVs.

Doug
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