Controlling Booster Vacuum - Chevy Impala SS Forum
 
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post #1 of 6 (permalink) Old 01-14-2019, 06:37 PM Thread Starter
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Controlling Booster Vacuum

After the LQ9 swap the vacuum was to low to run the brake booster. So, I added a pump kit. Everything started off good, for about a week. Then noticed pump was running about every minute or so. I checked the line for leaks and found very minimal. Blocking off the vacuum hose with a good vacuum gauge showed that the pump was pulling 26" hg, reset at about 18". Let is sit and pump does not come on and holds vacuum. Reconnect the hose to the booster and leak starts. Checked connector , hose, new booster gasket. Only thing I could come up with is that the booster internal seal leaking. Replaced Booster, it lasted about 3 days. Pulling too much vacuum ? If so how to regulate the vacuum source ? need something , Tried a 2nd switch, SSBC style, same issue.

95 Impala , LQ9/LS3 Swap. BTR Stage 3 with 11.5 comp., DGGM.
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post #2 of 6 (permalink) Old 01-14-2019, 07:09 PM
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I did not like the vacuum pump results, so I installed a hydroboost. If you get the mounting plate from a 95 or older Astro van unit, or a flat one on ebay ($25 and no hunting), and the boost unit from a 2007 (+-) Tahoe, you can use your original master cylinder (the Astro unit has a smaller opening, and will not fit the B body master cylinder). The hose necessary for the boost unit to the steering gear is in another thread about TBI hydroboost installation. It is the same for TBI or LT1 cars. The one from the pump to the hydroboost will be a custom unit, unless you can find one that fits. I used a "Y" to connect both returns to the reservoir. You need a special socket to swap mounting plates. You can install the Hydroboost upside down (with special hoses) to give you more room to work on the engine. You will also have to cut the eye off of your vacuum unit and weld it to the hydroboost unit with a 6 3/8 inch distance from the plate to the center of the eye. Remember to bleed the system

https://www.impalassforum.com/vBulle...l#post12092698

1991 OCC 461 (.030 over 454) BBC, 3.23 posi, flash to pass, drop spindles & springs, Impala rims, Hydroboost, Recaros, MOMO/wood SW w/QR, custom wood shift knob, Pioneer DEH P77DH
1992 OCC now with 5.7 tbi, DEH P77DH
For a parts list, check https://www.impalassforum.com/vBulle...ion-parts.html
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post #3 of 6 (permalink) Old 01-14-2019, 10:15 PM Thread Starter
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had not given the hydroboost a thought. If I cant come up with a relative inexpensive way to control the vacuum source I may give this a try. Already got 250 to 300 tied up in this conversion.
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post #4 of 6 (permalink) Old 01-14-2019, 11:23 PM
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A used hydroboost unit from 2007 Tahoe is about $35-75, hoses $50-120, adapter plate $25, tool for adapter plate $40, misc welding $25.

Since the path has been paved, you should be able to do an install in a day or two. The only glitch is the pressure hose to the Hydroboost unit from the power steering pump. A hydraulic shop can make one if you take one that has two usable ends on it. They can make a hose of the length you measure. The PS pump is on the passenger's side of the engine for an LT1, and the reservoir is on that side as well. You can make your own return line, and T it into the original line.

1991 OCC 461 (.030 over 454) BBC, 3.23 posi, flash to pass, drop spindles & springs, Impala rims, Hydroboost, Recaros, MOMO/wood SW w/QR, custom wood shift knob, Pioneer DEH P77DH
1992 OCC now with 5.7 tbi, DEH P77DH
For a parts list, check https://www.impalassforum.com/vBulle...ion-parts.html
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post #5 of 6 (permalink) Old 01-15-2019, 06:53 AM Thread Starter
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The more Ive thought about this , the more motiviated I get to do it. My LS swap already has the resivoir with the 2nd return, currently capped off.

Local pull a part lists vehicles that have that booster. Have hyd shop that can make the hose. The eye may be an issue as welding is a hit miss around here. Going to do some more digging but Im inclined to go this route.

95 Impala , LQ9/LS3 Swap. BTR Stage 3 with 11.5 comp., DGGM.
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post #6 of 6 (permalink) Old 01-15-2019, 08:24 AM
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If you do it, keep the measurements for the line to the pump, and you may be able to make them for others doing the same install. You might even make hoses for the inverted install as well.

1991 OCC 461 (.030 over 454) BBC, 3.23 posi, flash to pass, drop spindles & springs, Impala rims, Hydroboost, Recaros, MOMO/wood SW w/QR, custom wood shift knob, Pioneer DEH P77DH
1992 OCC now with 5.7 tbi, DEH P77DH
For a parts list, check https://www.impalassforum.com/vBulle...ion-parts.html
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