Dual Diaphragm vs. Single Brake Booster Opinions

[curtish57]

Hey All,

I think my booster is going out on my 70, I still have stopping power without any real issue but when I am holding pressure on the pedal for any length of time, like coming to a stop or holding the car at a light, the brake pedal will slowly sink to the floor. I don't lose any braking power and if I release it I have the pedal again right at the top but if I hold it it will sink. I have the original 11" setup but I think I want to go with something like these: 

https://www.summitracing.com/parts/sum-760241/make/chevrolet/model/monte-carlo/year/1970

https://www.summitracing.com/parts/rsd-g81310971/make/chevrolet/model/monte-carlo/year/1970

 

Does anyone have experience with these units in particular or any other relatively affordable upgrades? Is it worth it to go from single to dual diaphragm? 

Thank you. 

[cny first gen 71]

Sounds like master cylinder going bad. To test booster with car shut off pump the pedal up until it's hard then start car with your foot on pedal it should drop down a little bit.  If you hold very light pressure on pedal like you say maybe sitting at a light if it fades it's probably master cylinder,  if you hold more pressure it probably won't fade. Rear seal is probably starting to seap. If you change it use only NEW master cylinder not rebuilt. 

[420ponies]

I "had to install" a dual diaphragm booster just to clear my valve covers. I also installed rear disc brakes, so this may not matter much. I have very good brakes as I can tell from stock ( dual disc master cylinder and proportional valve ) .You need to remember that these cars were sub par for braking back in the day, even with disc brakes. The setup was from  Leeds Brakes , give them a call and they can help you out with all your questions, I promise. Worked for me.

[MC-71]

Go to NAPA

[BobW]

I installed a Hydroboost system. I can now lock up the brakes on this 2 ton barge! Can you?

Not cheap, but effective and safe.