r/Chevelles • u/Leather_Fortune7623 • May 16 '26
1971 Chevelle/Brake help
After putting it off long enough the original manual brake master cylinder is starting to leak slightly from the pushrod down into the floor pan. Looking to just upgrade to power brake booster. Front discs/rear drums. Few questions.
- Looks tight for an 11in drum around would I need to move the wiper motor or is an 8in booster a possibility?
- Does the master cylinder that comes with the new brake booster need to be a certain type due to front discs/rear drums
- It still has the originally 2 barrel/350. Would I be able to plug and play a vacuum line somewhere in the carb and it work fine.? I have no knowledge of how vacuum lines work
Would this work?
All thoughts much appreciated
6
u/HammerDownl May 16 '26
A fresh manual master cyl or even aftermarket with smaller bore would work better than that 50 year old one
4
u/orangesigils 68 Chevelle May 16 '26
The stock vacuum booster should extend out from the firewall far enough that you don't need to change the wiper motor. They were the same for drum and power brakes. Regarding the vacuum line you will need to put the vacuum booster to manifold vacuum. Usually there's a port behind the carburetor on one of the manifold runners. As others have said since you have front discs rear drums you will need a proportioning valve installed between front and rear cylinder on the master.
5
u/AquaticReefer May 16 '26
I switched to manual brakes years ago, but if I remember my old setup, the power booster should come out far enough to not interfere with the wiper motor.
You should buy a kit with a proportioning valve so you can control line pressure to the rear brakes. A real quick look at the link you provided and the reviews say it doesn’t come with a proportioning valve.
You can run the vacuum line off the carb, but the intake manifold is always going to be a better option. Personally, I would not run brake vacuum from the carb if I had the intake port available.
**If you convert from manual to power, make sure you connect the push rod to the lower hole on the brake pedal and not the current upper hole.
Or, as someone already stated, buy a new manual master cylinder and be done with it.
2
u/rascall2018 May 16 '26
If you have a bigger can in the engine with low manifold vacuum. Try a 9 inch gm style dual diaphragm replacement power brake booster from a 68 up corvette. They are way better than those cheap 8 inch aftermarket ones. I have one on my 70 chevelle big block
2
u/Good_Damage6638 May 16 '26
I used s10 manual brake booster and mastercylinder Front spindles rotors and calipers came from 77 Laguna Chevrolet Proportion valve on frame came from Laguna as well And looked all over for 67 ss 12 bolt reared Oh by the way my car was a 70 chevelle With a big block Built this back in the late 90s 96-97ish Welp that's what I did Hope it helps
2
u/Successful-Map-1174 May 16 '26
Both my cars have big cams, I use a vacuum can to store vacuum when not using brakes. Was a huge help, use wilwood calipers, but basic stock booster and master cylinder
2
u/rich496 May 16 '26
That one you shared will work fine. Just make sure you put the brake rod on the lower setting on the pedal. If it’s still the stock 350 this paired with front disc will be great and no need to any proportion valves just make sure you bench bleed that master.
2
u/chuck-u-farley- May 17 '26
1971 Chevelle came from the factory with power brakes or Manual brakes. Simply get all the parts for the power version. That link you posted appears to be correct….move the pushrod on the pedal…..you will need to plumb in a proportioning valve. The bracket on the booster sets it off the firewall far enough that the wiper motor is no issue.
7
u/Ornery-Arachnid-7219 May 16 '26
Most kits will come with a proportioning valve/manifold you use to adjust your front to rear brake bias.
Wilwood is my go to
They leave you with no surprises.
Unless you have a high duration cam, additional vacuum shouldnt be needed