Steering, Suspension, & Brakes

tips, technology, tools and techniques related to non-driveline mechanical components

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Jim Stabe
Jim Stabe
San Diego, Ca
(715 posts)

Registered:
02/28/2009 10:01AM

Main British Car:
1966 MGB Roadster 350 LT1 Chevy

authors avatar
Re: Power Brake Boosters
Posted by: Jim Stabe
Date: March 17, 2019 10:32AM

I ran across this on the internet this morning. [brakepower.com]


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5777 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Power Brake Boosters
Posted by: BlownMGB-V8
Date: March 17, 2019 12:10PM

The booster itself is a vacuum canister, and should hold enough for one or two boosted applications, maybe more depending on how hard you hit the pedal. An aux canister will add more uses between. You can base the size on the booster itself.

Jim


MGBV8
Carl Floyd
Kingsport, TN
(3677 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Power Brake Boosters
Posted by: MGBV8
Date: March 17, 2019 12:43PM

Yeah, a reserve canister is not going to help an engine with low vacuum to begin with. I guess that means using an electric vacuum pump, like Bill suggested.

Here is a Brake Bias calculator to go with the one Jim S. posted.

[www.tceperformanceproducts.com]


Jim Stabe
Jim Stabe
San Diego, Ca
(715 posts)

Registered:
02/28/2009 10:01AM

Main British Car:
1966 MGB Roadster 350 LT1 Chevy

authors avatar
Re: Power Brake Boosters
Posted by: Jim Stabe
Date: March 17, 2019 02:09PM

This is the calculator I used to design my brake system. It is an Excel spreadsheet so I couldn't post mine on this site but you can download it - it is the attachment in the first post. I like this one because it takes center of gravity height into account as weight is transferred during a stop. It came out pretty much on the money for my car.
[locostusa.com]


88v8
Ivor Duarte
Gloucestershire UK
(645 posts)

Registered:
02/11/2010 04:29AM

Main British Car:
1974 Land Rover Lightweight V8

Re: Power Brake Boosters
Posted by: 88v8
Date: March 17, 2019 02:58PM

My TR6 with its big cam, made 7" at idle. And it does matter, because if you're tootling down the high street at pretty much idle, that's how much vacuum you have when some pedestrian walks out in front of you.
So I fitted an electric vac pump and a vacuum switch, gave me 19".

Worked well for the five years I ran the car.

Ivor


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5777 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Power Brake Boosters
Posted by: BlownMGB-V8
Date: March 18, 2019 10:06PM

Thanks for the link on that spreadsheet. After inputting values it is obvious from the results that I have a problem in the front calipers. Must be some stuck pistons, blockages, or something. Didn't think it was working the way it should.

Jim


MGBV8
Carl Floyd
Kingsport, TN
(3677 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Power Brake Boosters
Posted by: MGBV8
Date: April 10, 2019 09:40AM

Finally went out & measured the vacuum on my engine. Warmed up, it pulls 17" with an occasional dip to 16". When I reve the engine to 2500rpm or so & let off, it jumps to 21". That seems pretty normal at my altitude of 1450'.

The MGC, over the years, had a number of different booster ratios available ranging from 1.6 to 3.0. Rather than changing my booster to something else, I would like to source a stock size booster with a higher boost ratio. If, there is such a thing.

Hmm....
Quote:
IMHO the PBR VH40 units, either in dual NA spec or solo EU, AU configuration, are state of the art direct replacements for the OEM calibration of the Girling MKIIB units. I have only spent a little time going through some barely legible spec information to conclude the VH40 PBRs have about a 30% more effective boost than the OEM Girlings which compare nearly equally to the larger Lockheed substitutes. -Robert Kirk
[www.mgexp.com]




MGBV8
Carl Floyd
Kingsport, TN
(3677 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Power Brake Boosters
Posted by: MGBV8
Date: April 11, 2019 02:49PM

Nevermind, the PBR VH40 boosters are remote only.


mgb260
Jim Nichols
Sequim,WA
(1966 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Power Brake Boosters
Posted by: mgb260
Date: April 11, 2019 04:43PM

Carl, I saw a picture recently of a dual diaphram street rod booster in a MGB but can't find it now.


MGBV8
Carl Floyd
Kingsport, TN
(3677 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Power Brake Boosters
Posted by: MGBV8
Date: April 11, 2019 09:12PM

On this thread, Jim? ;)

Mike Stemp posted some pics of his on page one. Seems the way to go.


mgb260
Jim Nichols
Sequim,WA
(1966 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Power Brake Boosters
Posted by: mgb260
Date: April 12, 2019 01:09AM

Carl, Yep, that is the one. I looked everywhere except page one on this thread. Speedway has them:

[www.speedwaymotors.com]



Edited 1 time(s). Last edit at 04/12/2019 01:11AM by mgb260.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5777 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Power Brake Boosters
Posted by: BlownMGB-V8
Date: April 12, 2019 09:08AM

Helpful video on that link too. Not too long.

So to be clear, the advantage of the dual diaphragm is that it doubles the pressure applied to the M/C? (for the same booster diameter)

Jim


MGBV8
Carl Floyd
Kingsport, TN
(3677 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Power Brake Boosters
Posted by: MGBV8
Date: April 12, 2019 09:54AM

I don't think it doubles, Jim. Just eyeballing the 7" dual booster, the front diaphragm looks to be a good bit smaller than the rear.

Not much info out there on actual booster ratios. Did find this on Ebay:

"A 7" Dual booster gives you 27% more stopping power than a 7" single"

I think the MGB booster is a 6", so a 7" dual booster should be quite an improvement.



Edited 2 time(s). Last edit at 04/13/2019 11:45AM by MGBV8.


88v8
Ivor Duarte
Gloucestershire UK
(645 posts)

Registered:
02/11/2010 04:29AM

Main British Car:
1974 Land Rover Lightweight V8

Re: Power Brake Boosters
Posted by: 88v8
Date: April 25, 2019 04:19AM

Well, I'll tell ylou something about boosters you probably already know; they can leak.

The Bendix Hydro Vac on my Rambler had 56 years in service, it was working, but I thought it was time for a refresh, so I sent it for rebuild.
On return, they mentioned that it had a big vacuum leak and on their test rig it didn't work at all.
Now, their test rig doesn't have a 327 vacuum pump, so it was working on my car.
And even with the engine off, it held some vacuum.

But as I now realise, it wasn't working very well. The brakes now are a lot sharper.

And, I've had an intermittent problerm where the engine won't idle. Happened after a long run when it was thoroughly hot. Couldn't find any cause, thought it was bad petrol.
And. it used to pink on acceleration even though the timing is correct,.

Now, both those problems have gone.
Cause? I guess, the vacuum leak.

The more stuff you have, the more there is to go wrong.

Ivor



Edited 1 time(s). Last edit at 04/25/2019 04:20AM by 88v8.
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