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LS-1 MGBGT aka PROJECT GINSU

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JMA Avatar
JMA Silver Member John Anderson
Donvale, Victoria, Australia   AUS
You need to be careful not to overboost unless you intend plumbing in ABS.

There is an alternative to a large diameter and that is going dual diaphragm, the pictures are a GM 7" dual diaphragm booster which on unmodified sheetmetal is a tight fit. Apart from enlarging the pedal box holes and shortening the threaded section for the pedal clevis, that booster bolts straight in. Another option is to use a remote booster but that can look somewhat inelegant.

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IMG_0324.JPG

nonracer Gold Member Steve Codianni
AZ, USA   USA
In reply to # 3877324 by JMA You need to be careful not to overboost unless you intend plumbing in ABS.
Quote:
I don’t want to hijack this thread but can you explain how you can “ Overboost “ ?
I’ve never heard that term used before

NOHOME P P
O, ON, Canada   CAN
1967 MG MGB GT "Maggie (GT From Hell)"
In reply to # 3877482 by nonracer
In reply to # 3877324 by JMA You need to be careful not to overboost unless you intend plumbing in ABS.
Quote:
I don’t want to hijack this thread but can you explain how you can “ Overboost “ ?
I’ve never heard that term used before

Imagine for a second that your brake pedal was a toggle switch with an OFF or ON position and nothing in the middle. That would be overboost. Or what Citroen used to call normal brakes!



Pete

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mgbgts Avatar
mgbgts Rob Meier
Johnstown Ohio, USA   USA
I hate overboosted brakes (like just about any American car from the 60's and 70's) and the soft pedal feel of the late B's isn't any better to me, That's why I said I considered going with manual brakes, but I'm going to try to set up power brakes but with less boost and more feed back through the pedal. I have some research to do yet to get what I want (the BMW's booster is HUGE, so that's a no go) whatever I end up with will be under 8" in dia. as there just isn't room for anything bigger. If I can't get a set up I like I may revert to manual. Luckily I have time to figure out a plan, as there is still a long way to go before the brakes can be finalized and tested. Meanwhile I tossed in a stock late MGB booster for a test fit as anything I end up with likely won't be noticeably bigger (and I had it on hand) Right now I'm figuring on using the BMW master cyl. and I have to take bore size, pedal leverage, booster leverage and all that into consideration to hopefully find something that works well.

nonracer Gold Member Steve Codianni
AZ, USA   USA
So what you guys are referring to as "overboosting" is simply extremely easy leg effort ? Since the assist doesn't have anything to do with output pressure I was little confused with the term overboosting .
I would think if having an adjustable pedal ratio you would be able to change the "feel" of the brakes in either a power assist or manual system . Different MC bore sizes should have some effect on this also but it would be trial and error to get it perfect .

slightly modified Avatar
slightly modified Silver Member Chuck Royer
Hayward, CA, USA   USA
1964 MG MGB "SLIGHTLY MODIFIED"
I truly love the feel of my manual (1" dual master cylinder) 4 wheel disc brakes on my SBC MGB, easy to modulate, harder you push faster you stop and easy to feel the onset of lockup (11" discs all around with proportioning valve).-----------------Chuck P.S my "B" is reasonably high powered (500hp) and I need reassuring brakes.

Jim Blackwood Avatar
Jim Blackwood * BlownMGB-V8
Gunpowder Rd, Florence, KY, USA   USA
What was the application for that GM dual diaphragm unit?

Jim

rficalora Avatar
rficalora ROB FICALORA
Willis, TX, USA   USA
1976 MG MGB V8 Conversion "MG MUTT"
For what it's worth, I used a chrome bumper pedal box and no brake booster on my car and have been happy with the feel of the brakes. I'm using a Mazda master (with Isuzu Trooper resorvior to fit in the indentation on the firewall). Like Chuck, I have disc brakes on all 4 corners.

Note that the pedal box opening size and shape are a little different between CB and RB so worth deciding before finished with mods and paint.



Edited 1 time(s). Last edit at 2019-01-20 12:32 PM by rficalora.

Jim Stabe Avatar
San Diego, CA, USA   USA
Here's a universal one on Amazon

https://www.amazon.com/Diaphragm-Power-Brake-Booster-Universal/dp/B01CGRQ6AM

These guys seem to have every configuration you could want





Jim

"If you want me to agree with you then we would both be wrong"

'66 MGB widened 11" with supercharged LT1 Chevy and 6 speed, C4 Corvette suspension
Pictures here Part 1 http://forum.britishv8.org/read.php?13,7581
Continued in Part 2 http://forum.britishv8.org/read.php?13,22422
Continued in Part 3 http://forum.britishv8.org/read.php?13,33108
Continued in Part 4 http://forum.britishv8.org/read.php?13,40751
Continued in Part 5 http://forum.britishv8.org/read.php?13,48698,48698#msg-48698
Continued in Part 6 http://forum.britishv8.org/read.php?13,61672

nonracer Gold Member Steve Codianni
AZ, USA   USA
I've never had good luck with the 7" single or dual diaphragm boosters even with engines that made a lot of vacuum . I have a good luck with the 8" dual though .

slightly modified Avatar
slightly modified Silver Member Chuck Royer
Hayward, CA, USA   USA
1964 MG MGB "SLIGHTLY MODIFIED"
Per my advocacy for manual brakes, I have a long duration .600" lift solid roller cam in my SBC (limited vacuum--LOL)

Jim Blackwood Avatar
Jim Blackwood * BlownMGB-V8
Gunpowder Rd, Florence, KY, USA   USA
The Roadmaster has very good brakes and good pedal feel with a 15/16" MC and no booster. It uses early Dodge Dart front calipers and Jag XJ6 rear calipers.

Jim

NOHOME P P
O, ON, Canada   CAN
1967 MG MGB GT "Maggie (GT From Hell)"
I suspect there is more to brake pedal "feel" or "Bite" than just boost level. Caliper and pad design also factor in to the equation.

For what it is worth, MGB brakes, while adequate, have always felt very wooden to me. The car does stop, but there has never been a feeling that the pads are digging into the rotor with any enthusiasm, just clamping hard. If that makes any sense?

Pete

V8MGBV8 Avatar
V8MGBV8 Carl Floyd
Kingsport, TN, USA   USA
Yeah, I'm not a fan of MGB brakes, either.

mgbgts Avatar
mgbgts Rob Meier
Johnstown Ohio, USA   USA
I plan on essentially using the full braking system from the donor BMW (except the booster as it's quite large in diameter and won't even come close to fitting anywhere near the brake pedal) and substituting a booster that will fit if I can. I may look into what master cyl the BMW guys are using when they want manual brakes an track cars as an option ( if any are doing that)

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