Probably need hydroboost

Belgian1979vette

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I found out that when going into WOT and subsequently into a hard brake, the pedal went soft. Brakes were bled several times. I'm thinkng now that my electric vacuum pump cannot keep up with the vacuum demand. Engine is also connected thru a one way valve to the vacuum reservoir but at WOT throttle I don't think there will be much vacuum.

So I was thinking about going to hydroboost.

Which sources are best and which kits fit best.
 
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:shocking: U supposed to have a vacuum check valve in the line, stock ones plug into the rubber fitting on the booster, and the 3/8 inner diameter line attaches to the vacum check valve/diode....at WOT or high torque demand, the diode is supposed to keep vacuum in the booster, if the booster loses that stored up vac, it's going to have a piss poor pedal....

I have Hydroboost on my '72....ebay...

:devil:
 
There is somethink not correct....

If your booster loses vacuum, your pedal will be rock solid, not soft !!!!

The only think reduced by poor vacuum is the brake assist, so you will need a very strong leg to stop your car.....

A soft brake pedal can't be caused by a low vacuum in the booster.

Try to verify if the pedal become normal after the second or third time you depress it..... in this case may you have a runout problem in a rotor.
 
There is somethink not correct....

If your booster loses vacuum, your pedal will be rock solid, not soft !!!!

The only think reduced by poor vacuum is the brake assist, so you will need a very strong leg to stop your car.....

A soft brake pedal can't be caused by a low vacuum in the booster.

Try to verify if the pedal become normal after the second or third time you depress it..... in this case may you have a runout problem in a rotor.

Yes it does come back on when I re-applied the brakes after WOT. I only had it happening once. I do not feel any pulsation on the brake pedal. Fronts are still the original rivetted rotors (good condition). I had to shim the rears to work out the runout, which was ok as I remember.
 
That would give too little assist. I think he's losing fluid somehow
 
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.
.....................
I have silicon brake fluid in my 68 and the brakes (manual) are rock hard.
 
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I have done a simplt T return in the 3/8 ID lines, in both the vette and motor home with HB conversions....both work fine, no complaints,

except I starting another thread....


:stirpot:
 
I'm running a pretty radical cam in my Corvette - and it means that you get one assisted stop per stop in stop and go traffic.
The fix, for me, is a vacuum pump (the one that's been sitting on my bench for months) - or I'm going to put a smaller bore master cylinder and eliminate the vacuum brakes altogether
 
:shocking: U supposed to have a vacuum check valve in the line, stock ones plug into the rubber fitting on the booster, and the 3/8 inner diameter line attaches to the vacum check valve/diode....at WOT or high torque demand, the diode is supposed to keep vacuum in the booster, if the booster loses that stored up vac, it's going to have a piss poor pedal....

I have Hydroboost on my '72....ebay...

:devil:

I had the same problem when driving at highway speeds the pedal felt soft. I changes the check valve as you mentioned and the problem went away.:thumbs:
 
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.
.....................
I have silicon brake fluid in my 68 and the brakes (manual) are rock hard.

Be very interested to know the reservoir part number if you have it.


Doug
 
Be very interested to know the reservoir part number if you have it.


Doug

The Hydroboost PS pump I intend to use was, I think used on an Astro Van as original equipment. I searched on RockAuto and couldn't find it. Going out to my garage is not a simple thing, since it's completely full of stuff. Friday I have off and would be willing to try to find it....However.. I did find using Google..

http://www.borgeson.com/xcart/catalog/P_S_Pump_for_HydroBoost_Brake_Applications-p-1716.html

This Borgeson's PS pump for the Hyrdoboost. It has two inlet feeds although not easy to see. It's $166. I think I bought my remanufactured pump from Rock Auto.com for about $90.
 
Here's the part number on the Saginaw PS pump intended to be used on Hydroboost cars.

It's GM 88985365. The AC Delco Number is 36-517048. I bought this on Rockauto and best I can remember, the price was about $90. It's remanufactured, which is no problem, since when you read the below, I dont' intend to use the pump proper anyhow.

It's intended to be used with a compression fit pulley. I want to install a March aluminum pulley for a little bling, so I think a compression fit pulley is not advisable. With an aluminum pulley, I'd prefer a keyed aluminum pulley. This means removing my present keyed pulley pump, removing the ham can (the reservoir) on it and removing the reservoir can on 88985365 and interchanging them so I end up with a PS pump with a keyed pulley and a reservoir can appropriate for the hydroboost. The fun just never ends. Cheers!
 
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