[Mart68SS]

Hi all,

I have an original disk break setup on my 69 Chevelle, I would like to replace the 11" brake booster (leaking vacum) with a 9" wihout affecting/changing the rest of my setup. I also want to have more room for my valve covers.

Can i just change from to a 9" booster from the 64-67 chevelle? will it affecting anything negatively? and will it be a direct bolt on installation?

Also if you can, could you suggest the part number i would need?

Thanks for your help

 

[any4xx]

I can’t help with a part number, but if it were me, I’d find one of the double 9” boosters. They pull better than our stock boosters and give you the clearance you seek. Only thing is that you “may” have to lengthen the lines going from your master cylinder to your distribution block.

 

[72mojave]

I'd stick with an 11" if you can. An 11" provides more psi than a single diaphragm 9". I haven't seen a dual diaphragm 9" that is made for A bodies. If you can find one with the correct mounting bracket, it should provide about the same psi as a single diaphragm 11", if you need the space for your valve cover. But your lines would need to be reworked.

https://www.classicperform.com/PDFs/BoosterBrakePressureChart.pdf

 

[69velle]

I agree with above, use a dual 8” if the 11” isn’t working for you. Speedway sells one. Just a heads up, you may need the reduced angle brackets from Detroit speed if you go with the dual setup as it puts the master cylinder closer to the hood.