I'm doing a LS1 brake upgrade on my 84 Z28. 383 big heads & cam, of course vacuum issues with stock brakes. My question is when i convert the front to the LS1 brakes will that be enough to stop the car or will i need to still do something about vacuum. Drums on rear. Any help appreciated!

 

If you have vacuum problems with the OEM brakes you will also have vacuum problems with any other brakes. You need to sort out your issue.

 

what i'm sayng is the cam is is pulling the vacuum from the oem brakes. what i'm asking is when i put the big brakes on it will i still have to do something about vacuum.

 

I understand what you are saying. If you have bad vacuum, LS1 brakes can't overcome that. No brakes can overcome that. You need to fix the problem:

vacuum pump
hydroboost

 

i c what you are saying, which one is best. will a bigger brake booster help.

 

Try adding a extra vac canister from a old Lincoln town car or a Cadillac, ect. That will give you the reserve that you need for your power brakes. You may find a new canister online made to resolve this problem.

 

1 larger canister or two smaller ones, whatever will fit.
Once I made a larger one out of two stock ones.......on another application.

 

Hydra-boost. No vacuum required. Get rid of the huge vacuum booster, and make changing 5 and 7 plugs a bit easier.

 

Curious. How big a cam and what is your idle vacuum?

 

+1 look for a astro van one not to hard to make work and imo look better

 

I guess what I'm angling at is that the OP might not need to go with a hydra-boost arrangement. Perhaps the problem is elsewhere. We've run some pretty hairy cams and managed to produce enough idle vacuum to keep the power brakes happy. Once you get north of about 290 degrees adv duration, you may encounter problems but at 292 we still had between 6-8" vacuum and the booster didn't seem to suffer. We tune these carbs and ignition until we've got it dialed in about as good as it can be. These are street machines too.

 

ssbc makes a brake vacum pump. i had to buy one to feed the brakes of my cammed up 383 the vacum needed.

 

sounds dumb but isuzu box trucks { gm} have a vacuum pump set up with a vacuum switch that would work. 2005-2007 iirc. npr, gmc w3500, gmc w4500

 

James, you have PM.

 

ditch the booster altogether and go with a manual brake setup.. you add lightness and less complexity while freeing up space in the engine compartment..

 

Maybe. But only if you like a nice long pedal.

 

I agree 100% Make your life easy and just install the hydro-boost system!

 

vacuum canister that any place like summit racing sells would be fine. Or they make vacuum pumps to add vacuum but they are loud. Manual brakes are great for a drag setup, but you do lose some braking ability.

 

i loved the manual brakes in my 71 Nova- the fronts were 12" C4 Vette, the rears were the stock drums.. master cylinder was for a 76 Malibu with manual brakes, and i put a Wilwood adjustable prop valve in the rear lines.. the brake pedal felt almost identical to my 94 Caprice 9C1- firm, but not too hard- but with more instantaneous response and better feel. pedal travel wasn't any worse than any power brake equipped car i've ever had (and i've had a LOT of cars..), and the car just squatted down and flat out stopped when i wanted it to..
looking at doing manual LS1 fronts in my 86 Camaro with the same master cylinder i used in the Nova, and might do the matching LS1 rears with a late 60's Corvette manual master cylinder down the road..

 

I didn't say the pedal travel would be worse. I said it would be longer. Personal preference.

If you used a manual brake booster the travel must be longer. Its simple physics. I have never seen a manual master with a bore as large as power masters. Why? Because the pedal effort would be to great.

 

that's why you relocate the pushrod hole on the pedal to change the ratio.. older cars have a hole for power brakes and a hole for manual brakes.

also, the dual piston calipers don't require as much fluid volume to get the same pressure at the pad, so that means less pedal travel, too.. once you put all the pieces together, you wind up with about as much pedal travel and effort with the LS1 brakes and a manual master cylinder as a the stock brakes with the power booster, but with better pedal feel and more stopping power.

 

On a similar note, since we're discussing the possibilities of swapping out master cylinders now, go one step further and also change the brake booster to a dual diaphragm type. Then using the smallest bore master cylinder that still moves the needed amount of fluid for the LS1 caliper (and whatever rears) and it's possible to keep the vacuum assist even in a vehicle with low idle vacuum. This is something that was accomplished in an 81 Monte Carlo with a 4 piston Wilwood front brake upgrade. Idle vacuum was 6" at 750 rpm yet the power brakes feel pretty much as the stockers. did.

 

If you increase the pedal ratio, then your pedal gets even longer with lower effort. If you decrease the pedal ratio, then your pedal gets shorter with higher effort.

I would bet on manual brakes the pedal ratio gets higher to keep effort lower. Again increasing pedal travel.

Finally the number of pistons has nothing to do with the "pressure" (I think you mean force) on the pad. What matters is piston area. The OEM piston area is actually LARGER than almost any other caliper out there including the LS1. The OEM caliper needs less fluid pressure to achieve the same pad force. F=P*A. Either way pad force is quite irrelevant as well. What is important is a normalized brake torque which is driven by the force from the pad to the rotor and lever arm (rotor radius).

See this chart for more info. Right click - view image for larger.