Doing a vacuum swap, dual or single diaphragm booster?

[short_dustin]

I'm about to buy the parts from a local parts store to convert my turbo buick to vacuum brakes and there are two boosters. One that's deeper into the engine bay that's a dual diaphragm and a thinner looking one that's a single diaphragm. I personally think the single looks a little cleaner since it doesn't stick out so far. Is there a big difference in performance or durability?

I'll buy the better one if it's worth it, I was just wondering if it made any difference.

Thanks,

 

[~JM~]

I asked this same question several months back. The response was to use a dual-diaphram. I ordered the M/C & Booster from a 1987 Monte Carlo.

Here are a few threads on brakes. http://turbobuick.com/forums/threads/hydroboost-or-vacuum.369756/#post-2947082

Good luck
~JM~

 

[87turbot-type]

Dual

 

[novaderrik]

the big dual diaphragm 12" booster from a late 80's Caprice would be the way to go..

 

[big reazon]

x2 I bought the bigger caprice booster for my project.

 

[~JM~]

the big dual diaphragm 12" booster from a late 80's Caprice would be the way to go..

How is the fit with this booster? Any pics?

What are the benefits over the smaller one? The smaller dual diaphram booster looks almost like it belongs there on the firewall.

Thanks
~JM~

 

[big reazon]

bigger booster holds more vacuum for better braking

 

[novaderrik]

How is the fit with this booster? Any pics?

What are the benefits over the smaller one? The smaller dual diaphram booster looks almost like it belongs there on the firewall.

Thanks
~JM~

i don't know of any pics, but it's something i picked up on over on the www.montecarloss.com board a couple of years ago.

as to the benefits- you get twice as much assist from 2 diaphragms as you get with one, and a bigger diaphragm means more assist..
calculate the surface area of 2 12" diaphragms and compare that to the surface area of a single 10" diaphragm or dual 8" diaphragms and you will see the benefits..

 

[big reazon]

the caprice is dual 10.75 fyi.
gbody dual is 9
gbody singe is 10.75
If you have found a 12" unit send me a link please.

 

[turbotim231]

don't make mistake i made. tried the single from monte carlo, had to swap it out for the dual (didn't do my homework)

 

[novaderrik]

the caprice is dual 10.75 fyi.
gbody dual is 9
gbody singe is 10.75
If you have found a 12" unit send me a link please.

i only ever saw it referred to as a dual 12" booster. never had a need to look any deeper than that. but yeah, you're right- NAPA only shows it as 10.75" for a late 80's/early 90's Caprice.
that's what you get for trusting those shifty Monte Carlo SS guys..

but still- that's a LOT of booster..

 

[big reazon]

Yeah it is a lot of booster was going to go for the 12 if it was available lol

 

[GN owner]

I am assuming that the bigger Caprice vacuum booster assy will bolt right up to the GN firewall and the GN master cylinder? I am seriously thinking of upgrading to the Caprice booster but I would like to know of any problems that I will encounter if I do upgrade from the 8 in dual diaphram to the Caprice unit.

Thank you in advance for any amplifying information!

 

[big reazon]

Direct swap with proof
http://www.montecarloss.com/community/ubbthreads.php?ubb=showflat&Number=757283#Post757283

 

[GN owner]

Big,

Thank you for the link!

 

[big reazon]

No problem. Make sure you properly bleed your master cylinder if you are replacing it also bleeding the master cylinder itself makes a world of difference. Let us know how you like it once you get it done so that others will use this mod also.

 

[~JM~]

Wish I'd seen this sooner. Just finished swapping the brakes for the smaller dual diaphram unit.

Anyone know if the various cables, etc. will clear the big booster?

~JM~

 

[big reazon]

yep will clear

 

[jmd]

One of my cars had a single; the other a dual. Never noticed a difference when they had the same brake on each. So I question the "twice the assist" bit.

The Orca 91-96 B/D bodies have an offset pushrod on the booster. Stick to the 90-down for the booster.
Their master cylinders are non-matching thread for the line fittings too.

 

[big reazon]

Yeah the twice as much assist is a bit excessive but every little bit helps. I agree with 90 and down booster. I also recommend they stay with the g body master cylinder it has a smaller bore which will get you more pressure the caprice has a bigger bore that will get you more volume.